Appendix H. Trail Maps

#

Visitor Center Refuge Headquarters Newark

North Shoreline Trail

Marshlands Road

No Name Trail

Newark Slough Trail

§ ̈¦880

UV84

84

Dumbarton Bridge

Jarvis

Willow

Legend

Trails

No Dogs

Dogs Allowed

No Dogs, No Bicycling

Unit Name

Newark

Mowry

Don Edwards San Francisco Bay National Wildlife Refuge - Newark Unit Trails

Alameda County, California

 U.S. Fish & Wildlife Service

H-1
Marshlands Road

Tidelands Trail

Upland Connector

Newark Slough Trail

La Riviere Marsh Trail

Newark Slough Trail / Tidelands Trail

Quarry Trail

Pumphouse Trail

Tidelands Trail

Visitor Center

Refuge Headquarters

Legend

Trails

No Dogs

Dogs Allowed

No Bicycling, No Dogs

Parking

Trail Shifted

Don Edwards San Francisco Bay National Wildlife Refuge - Newark Unit Trails Inset

Alameda County, California

 U.S. Fish & Wildlife Service

H-2
#

Visitor Center Refuge Headquarters Newark

Newark Slough Trail

880 § ̈¦

UV84

Dumbarton Bridge

Legend

No Dogs

Dogs Allowed

No Dogs, No Bicycling

Unit Name

Newark

Mowry

Alviso

Don Edwards San Francisco Bay National Wildlife Refuge - Trails in the Mowry Unit

Alameda County, California

 U.S. Fish & Wildlife Service

Warms Springs Trail

H-3
Environmental Education Center

Alviso Slough Trail

Moffet Bay Trail

Mallard Slough Trail

Alviso Slough Trail Alviso Slough Trail

880 § ̈¦

£¤101

UV237

UV85

UV262

UV237

Milpitas Alviso

237

Legend

No Dogs Unit Name

Mowry

Alviso

Don Edwards San Francisco Bay National Wildlife Refuge - Trails in the Alviso Unit

Santa Clara County, California

 U.S. Fish & Wildlife Service

Warm Springs Trail

Stevens Creek East Trail

H-4
H-5
#

#

#

Atherton

Redwood City

East Palo Alto

Bay Trail

SF2

Trail

Ravenswood Trail

Nob les Trail

£¤101

UV82

UV84

UV84

El Camino Real

Willow

Woodside

Bayfront

Dumbarton Bridge

Marsh

Marsh

Legend

No Dogs Unit Name

Newark

West Bay

Don Edwards San Francisco Bay National Wildlife Refuge - Trails in the West Bay Unit

San Mateo County, California

 U.S. Fish & Wildlife Service

Faber-Laumeister Trail

H-6
Appendix I. Mammalian Predator Management Plan

DON EDWARDS SAN FRANCISCO BAY NATIONAL WILDLIFE REFUGE 

PREDATOR MANAGEMENT PLAN

TABLE OF CONTENTS

Overview and background .............................................................................................................. 1

Threats to the California Clapper Rail ............................................................................................ 3

Overview of Mammalian Predation and Clapper Rails Numbers ............................................... 4

Relevance to Refuge Purpose and Goals ........................................................................................ 7

Draft Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California ............. 7

Mammalian Predator Management Plan ......................................................................................... 7

Trapping, Shooting, And Toxicants ............................................................................................ 8

Predator Barriers ......................................................................................................................... 9

Mammalian Predators ................................................................................................................... 10

Red Fox ..................................................................................................................................... 10

Raccoon ..................................................................................................................................... 12

Rats ........................................................................................................................................... 13

Striped Skunks .......................................................................................................................... 13

Feral cats ................................................................................................................................... 14

Gray fox .................................................................................................................................... 14

Virginia opossum ...................................................................................................................... 14

Non-target Terrestrial Predators ................................................................................................ 15

Consultation and coordination with others ................................................................................... 15

Contact information: Cheryl Strong, Wildlife Biologist, Don Edwards San Francisco Bay 

National Wildlife Refuge, U.S. Fish and Wildlife Service, cheryl_strong@fws.gov.

1) OVERVIEW AND BACKGROUND

During this century, habitat loss and other impacts have caused the near extinction of the California 

clapper rail (Rallus longirostris obsoletus) and the salt marsh harvest mouse (Reithrodontomys raviventris) 

throughout their ranges. Entirely dependent for their survival on very limited and dwindling estuarine 

habitat, habitat loss and degradation, contaminants, and increased predation levels threaten their existence. 

Both species nest, rear young, and forage within the Don Edwards San Francisco Bay National Wildlife 

Refuge (Refuge, Figure 1).

Intensive predation by non-native and urban-subsidized mammals (e.g., rats (Rattus spp.), foxes, opossums 

(Didelphis virginiana), and raccoons (Procyon lotor)), has been identified as a major factor that limits the 

reproductive success of the endangered California clapper rail. Although we do not have information on 

predation levels of salt marsh harvest mice, they are also assumed to be negatively impacted by these same 

predators, and are therefore incorporated into this document.

The U.S. Fish and Wildlife Service (Service) proposes to increase the endangered California clapper rail 

population to a Refuge goal of 1.2 rails/ha during the breeding or nonbreeding season, the endangered salt 

I-1 
marsh harvest mouse populations, the threatened western snowy plover (to a Recovery Unit goal of 1.0 

chicks fledged per adult male) and other sensitive waterbird populations and nesting success by conducting 

selective predator (rats, red fox (Vulpes vulpes), gray fox (Urocyon cinereoargenteus), raccoons , striped 

skunks (Mephitis mephitis), opossum, and feral cats (Felis spp.) management at selected locations on and 

adjacent to the Refuge. This will produce a small-scale reduction in the local population of some terrestrial 

predatory species in localized areas. The purpose of the proposed action is to maximize endangered 

species' chances for survival both at the Refuge and throughout their ranges. Management actions will be 

designed to minimize lethal actions and disruption to wildlife. The need for action stems from an 

immediate and serious threat to the survival of the endangered species due to predation. 

The major Refuge purpose is to provide secure habitat (e.g., nesting, feeding, and resting areas) for

endangered species and migratory birds. The overall objective of the predator management program will be 

to provide that secure habitat by selectively controlling and reducing the detrimental impacts of large 

populations of selected predators. Management of the selected predators is essential to protect and 

maintain breeding populations of clapper rails, salt marsh harvest mice, western snowy plovers, and 

colonial nesting birds, such as Caspian terns and Forster's terns. 

In spite of all that has been altered in the bay, it is still one of the most important wetland migration areas 

for shorebirds and other waterbirds between Alaska and Peru. On April 16-18, 1988, PRBO Conservation 

Science (PRBO) conducted a shorebird census of San Pablo and San Francisco bays. Observers counted 

838,000 shorebirds of 28 species. Given the potential for some error, PRBO estimates that between 

600,000 and 1,200,000 shorebirds were present on the weekend count. The Observatory conducted a 

second springtime shorebird survey in April 1989, and observed over 930,000 shorebirds along the tidal 

mudflats and adjacent wetland areas. A 2006-2008 November high tide roost count of shorebirds 

throughout San Francisco and San Pablo Bays was about 300,000 (Pitkin and Wood 2011). The majority 

of these birds were concentrated in south bay. In April of 1990, San Francisco Bay National Wildlife 

Refuge was designated as a Hemispheric Shorebird Reserve because of the wildlife values this protected 

habitat provides for shorebird populations.

The Refuge and the San Francisco Bay Bird Observatory (SFBBO), with the assistance of many 

experienced ornithologists and veteran birders, compiled a checklist entitled Birds of San Francisco Bay 

and San Pablo Bay National Wildlife Refuges. This list, which includes 281 species, underscores the 

importance of the San Francisco Bay area as bird habitat and emphasizes the great diversity of birdlife that 

occurs in the bay. It includes all species that are found in San Francisco Bay and the Delta. It does not 

include all species that can be found in nearby upland habitats.

The bay area provides habitat for 47 species of mammals. The salt marsh harvest mouse is an endangered 

species that requires tidal and non-tidal wetlands around the bay for survival (USFWS 1984). The salt 

marsh wandering shrew, which the Service has been petitioned to list as an endangered species, also 

inhabits some areas around the bay. The most important marine mammal associated with wetlands within 

the project boundary is the harbor seal. This species uses tidal salt marshes and mudflats for breeding and 

hauling-out grounds. The largest haul-out sites in San Francisco Bay are located in the south bay. Other 

mammals common to the area are raccoon, brush rabbit, big brown bat, Mexican free-tailed bat, gray fox, 

and California ground squirrel. 

San Francisco Bay waters, with the proper control of pollutants, have the potential to support a substantial 

fishery in the bay area. Salt marshes and shallow water areas provide for larval, young, juvenile, and adult 

fishes and shellfishes such as shiner perch, top smelt, staghorn sculpin, halibut, striped bass, clams, crabs, 

mussels, and bay shrimp. Important commercial and sport fishes that utilize deepwater habitats include 

northern anchovy, starry flounder, striped bass, king salmon, sturgeon, and American shad. 

I-2 
2) THREATS TO THE CALIFORNIA CLAPPER RAIL

The California clapper rail became endangered due to habitat loss and degradation and over-hunting. 

Over-harvesting by commercial and sport hunting initially contributed to the depletion of the rail 

population (USFWS 1984). A historic newspaper account from the San Mateo Leader on October 23, 

1897, referred to at least 5,000 rails killed in the San Francisco Bay area during a one-week period in 

1897. Similar accounts between 1890 and 1910 note individual hunters killing 30 to 50 rails a day. After 

the enactment of the Migratory Bird Treaty Act in 1913, rails regained much of their abundance in the 

remaining San Francisco Bay marshes (Bryant 1915, Grinnell and Miller 1944). However, urbanization 

has led to the eventual diking of most salt marshes of San Francisco Bay, largely for the purposes of salt 

harvesting, agriculture, and commercial development. Over 90% of the original clapper rail tidal marsh 

habitat has been lost. 

Today, major threats to the survival of the California clapper rail include the historic loss of habitat, marsh 

conversion, the potential impact of contaminants, and increased predation. To maximize acquisition 

efforts in a region where land prices are very high, the Service is pursuing cooperative purchases with the 

California Department of Fish and Game and other entities. In addition large-scale restoration projects 

such as the South Bay Salt Pond Restoration Project will begin to reverse the trends of habitat loss. Despite 

an aggressive land acquisition program, and active restoration of tidal salt marsh, recovery will be a slow 

process. Based on the progress of similar projects, it may take 10 to 20 years or more to recreate healthy 

salt marsh which would support California clapper rails.

In the extreme southern reaches of San Francisco Bay, tidal salt marsh has been converted to more 

brackish marshes by the freshwater influence of treated sewage effluent. This conversion has greatly 

reduced habitat value to endangered species, including the California clapper rail and salt marsh harvest 

mouse. The Service has worked closely with the regulatory agencies to prevent future tidal marsh 

conversions and to develop suitable compensation for past conversions.

The Service has investigated the occurrence and potential impacts of contaminants on clapper rails. In a 

Refuge study, Lonzarich et al. (1990) found elevated levels of mercury and selenium in clapper rail eggs. 

Organochlorine (pesticide) residues were low and had decreased by 2 to 3-fold since 1975. 

A new 3-year study examining potential effects of contaminants in rails began in spring 1991. Biologists 

investigated factors affecting breeding populations, nest success, movement, and survival in selected 

Refuge marshes. “Flooding was a minor factor, reducing the number of eggs available to hatch by only 

2.3%. Contamination appeared to adversely affect California clapper rail reproductive success. Predation 

on eggs was a major factor affecting nest success, reducing productivity by a third” (Schwarzbach et al 

2006).

One of the primary reasons for the declining population is low annual recruitment of young. Predation of 

eggs by rats, raccoons, and red foxes, and the predation of adults by red foxes were identified as the 

primary causes. Other sensitive waterbirds and ground nesting species, including Caspian terns (Sterna

caspia), Forster's terns (Sterna forsteri), and the Federally threatened western snowy plovers (Charadrius

alexandrinus nivosus) are also being affected.

I-3 
Figure 1. Land status map of the Don Edwards San Francisco Bay National Wildlife Refuge. 

Overview of Mammalian Predation and Clapper Rails Numbers 

Refuge studies of clapper rail populations during the breeding season have shown that clapper rails have 

been subjected to high levels of nest predation by rats, red fox, and raccoons (Harvey 1988, Foerster et al. 

1990). In addition, the results of winter high tide surveys for clapper rails indicate the population declined 

severely from the early to mid-1980s (Harvey 1988, Foerster 1989). The decline accelerated in the late1980's coinciding with the arrival of the red fox (Harvey 1988, Foerster 1989, Foerster et al. 1990). From 

a population estimate of approximately 1,500 in the early to mid-1980's, biologists estimated the 

population of California clapper rails in early 1991 may have been less than 500 individuals (Albertson 

I-4 
and Evens 2000, but the population increased from the mid- to late-90s to an estimated 1,040 to 1,264 

individuals (Albertson and Evens 2000). A study conducted from 2005 to 2008 estimated the population 

at 1,403 to 1,448 individuals (Liu et al 2009). 

Clapper rail numbers have not declined uniformly throughout the south bay where the majority of the 

population is concentrated (Liu et al 2009). Based on winter population surveys, numbers have remained 

relatively stable in some of the marshes of Palo Alto, on the west side of the Bay. However, rail numbers 

elsewhere have declined precipitously, particularly in the east side of the south bay in some of the marshes 

supporting the largest subpopulations of rails. The timing and locations of these declines coincide closely 

with the arrival, occurrence, and relative abundance of the red fox. For example, prior to 1986 red foxes 

had never been seen in the salt marshes of San Francisco Bay during winter high tide rail surveys. By the 

winter of 1990-1991, biologists counted 6-8 individual foxes in Mowry and Dumbarton marshes while 

conducting rail surveys (Figure 2).

Biologists at the Refuge conducted nighttime spotlight surveys for terrestrial predators within the Refuge 

during the spring and summer of 1989 and during the spring of 1990. The decline in the rail population is 

associated with the direct increase in the number of predator sightings during both the breeding season and 

the non-breeding season (i.e., during winter high tide surveys). 

The Service has determined that the red fox is a problem predator of California clapper rails on the Refuge. 

This is based on Refuge studies, predator surveys, and documentation of incidents where red fox visitation 

and predation is evidenced, in combination with known red fox foraging patterns and numerous sightings 

throughout the Refuge. In addition, rat and raccoon depredation of rail nests has been verified in 

Dumbarton and Mowry marshes (Foerster et al., 1990). Biologists have observed red foxes, rats, and 

raccoons foraging in Refuge marshes including Dumbarton, Mowry, and Ideal marshes during all tidal 

conditions, including the peak of extreme winter high tides when rails are very vulnerable to predation. 

Gray foxes (Urocyon cinereoargenteus) appear to have increased on the Refuge in recent years due to 

numerous sightings documented in 2010-2011. A gray fox was caught on camera depredating a western 

snowy plover nest at Eden Landing Ecological Reserve north of the Refuge (Robinson-Nilsen, et al. 2010). 

As a defense against predators, clapper rails tend to freeze, depending on their coloration and surrounding 

dense vegetation for camouflage. Such avoidance behavior appears to work adequately in the presence of 

coyotes with which clapper rails have evolved and coexisted since long before Europeans' arrival in the 

area (USFWS and U.S. Navy 1990). This coexistence is evidenced in southern California by the presence 

of light-footed clapper rails in good numbers in the salt marsh of Upper Newport Bay and Mugu Lagoon, 

where coyotes are present and red foxes are virtually non-existent (USFWS and U.S. Navy 1990). Foxes 

are skilled and efficient predators which rely heavily on ambush techniques for hunting. They are known 

to surplus kill, i.e., kill and cache prey even when not hungry (A. Sargeant, USFWS, pers. comm.), and 

they have an affinity for eggs which they also cache for future consumption (Kruuk 1964,; Timbergen 

1965; A. Sargeant, USFWS, pers. comm.). Clapper rails, which have been known to posture and defend 

their nests from predators, may easily fall prey to a red fox seeking eggs. Because eggs may be preferred, 

the adult rail may or may not be eaten after being killed. Defense mechanisms evolved over time by the 

clapper rail do not appear to be well-suited or effective for defense against newly confronted red fox 

predation techniques.

There have been no direct observations of red foxes killing or carrying dead California clapper rails on the 

Refuge. This is not surprising because (1) clapper rails are secretive in nature, few in number, and sparsely 

distributed on the Refuge; (2) visibility in the marsh is limited by dense vegetation and minimal human 

access; (3) observation opportunities by skilled biological observers are infrequent; and (4) the vast 

I-5 
majority of fox activity occurs under the cover of darkness. Additionally, obtaining direct and verifiable 

evidence of red fox predation on clapper rails is difficult because red fox prey items are very difficult to 

retrieve. Red foxes tend to consume prey away from the capture location in the field and may carry it to 

well-concealed dens where it is almost completely devoured (Sargeant 1978, Sargeant et al. 1984). 

In April 1990, Refuge biologists discovered active red fox dens at the edge of Dumbarton Marsh and in the 

adjacent Audubon Marsh. They found three California clapper rail carcasses along with a variety of other 

birds, including mostly waterbirds, at the dens. Red foxes were seen foraging in and along Dumbarton 

Marsh more frequently in 1990 than in previous years (USFWS, unpubl. data). Furthermore, rail numbers 

declined by more than 50% in Dumbarton Marsh from January 1990 to January 1991 (Figure 2). 

Severe declines were documented in Mowry Marsh (marshes on the north and south sides of Mowry 

Slough, and north to Newark Slough), located immediately south of Dumbarton Marsh (Figure 1). This 

marsh traditionally has supported a large subpopulation of rails, second only to Dumbarton Marsh. Harvey 

(1987) estimated that 140-160 rails resided there in the early to mid-1980s. Winter surveys in 1989-1990 

produced a total of 70 rails. Surveys conducted during the following winter (1990-1991) indicated that 

numbers had dropped by 29%, to 50 birds. Numbers of predators, particularly red foxes, have increased 

greatly in Mowry Marsh during the same period.

Ideal Marsh is the next salt marsh north of Dumbarton Marsh (Figure 1). It is separated from Dumbarton 

by a series of active salt ponds, roads, and levees. As many as 80 rails had previously been found in winter 

surveys in this 138 acre tidal salt marsh. In the early 1980's the breeding population was estimated at 19 

rail pairs (Harvey 1988). Surveys conducted more recently indicate that only a few rails remain (peak of 2-

3 found during both breeding and nonbreeding season surveys), although the marsh is comprised of tidal 

salt marsh, dominated by pickleweed and cordgrass. The highest numbers of predators have been observed 

in this marsh during nighttime spotlight surveys conducted from 1989 to 1991, including red foxes, feral 

cats, raccoons, and skunks. Many of these predators may be moving into Ideal Marsh from the nearby 

Coyote Hills Regional Park, where sightings of red foxes and raccoons are frequent (I. Bletz, pers. comm.). 

Numerous levees provide pathways from such areas directly to Ideal Marsh.

 

Refuge staff and personnel from the San Francisco Bay Bird Observatory survey nesting colonies of 

waterbirds annually. In 1990, surveys revealed severe impacts by red foxes on a major Caspian tern 

(Sterna caspia) colony on a levee between salt ponds M4 and M5, southeast of Mowry Slough. As many 

as 650 adults have used the area for nesting, which has been monitored since 1981. It was one of only five 

Caspian tern nesting colonies along the central and northern California coast, all of which are in San 

Francisco Bay, totaling 2818 birds in 1988-1989 (Carter et al. 1990). In early May 1990, red foxes 

destroyed all Caspian tern nests at this colony. Refuge biologists observed cached (buried) eggs and fox 

tracks in, and leading to and from, the colony. The terns attempted to re-nest over the next month but the 

eggs were repeatedly taken by the red foxes. Subsequently, the colony was abandoned and has not 

returned as of 2012. Two to three red foxes were regularly observed on the levee near the colony during 

nighttime spotlight surveys. 

A mammalian predator management program, targeting the red fox, has been conducted at the Seal Beach 

National Wildlife Refuge since 1986. The program was initiated in response to an increase in red foxes 

and a decrease in the nesting success and population size of the endangered California least tern (Sterna 

antillarum browni) and the endangered light-footed clapper rail (Rallus longirostris levipes). The predator 

management program has successfully reduced the number of red foxes and increased the nesting success 

and population sizes of the two endangered species (USFWS and U.S. Navy 1990). In 1986, light-footed 

clapper rail breeding numbers had fallen to 10. Predator management was initiated that year and by 1991, 

I-6 
rail numbers had increased to 69, an all-time high for that area since monitoring began in 1979 (C. 

Houghton, pers. comm.).

A mammalian predator management program, also targeting the red fox has been conducted on Don 

Edwards since 1993. With predator management, the California clapper rail population increased to an 

estimated population at 1,403 to 1,448 individuals in 2005-2008 (Liu et al 2009). This plan has been 

amended to include problem individuals of grey fox and opossums. 

Predation is a natural part of a healthy, functioning ecosystem. There are many native predators that 

potentially could or do prey on California clapper rails, salt marsh harvest mice, and ground-nesting 

migratory birds. However, this is a selective small-scale effort to reduce intensive predation in localized 

areas by specific, predators implicated in population declines of endangered species and migratory birds.

In addition to non-native predators, many “suburban native predators” such as raccoons, opossums, foxes, 

and skunks, that exploit garbage and other human food sources are subsidized in an urban area such as the 

south bay and can reach unnaturally high density, outcompeting and preying on other native species 

(Crooks and Soulé 1999).

3) RELEVANCE TO REFUGE PURPOSE AND GOALS 

The Refuge was established in 1974 for its “particular value in carrying out the national migratory bird 

management program,” and one of the Refuge’s three stated goals is to protect and enhance endangered 

species populations and their habitats. Listed species have benefited from the management of mammalian 

predators since 1993, and monitoring results suggest that continued management of selected mammalian

predators is necessary to protect and maintain clapper rails, harvest mice and snowy plover breeding 

populations. This plan has direct bearing on the Refuge’s ability to fulfill its purpose and goals.

Draft Recovery Plan for Tidal Marsh Ecosystems of Northern and Central 

California

The Service released a Draft Recovery Plan for Tidal Marsh Ecosystems of Northern and Central 

California in 2009 (USFWS 2009). This recovery plan is an expansion and revision of the California 

Clapper Rail and Salt Marsh Harvest Mouse Recovery Plan (USFWS 1984). The recovery plan also 

encompasses four other threatened and endangered plant species, and 11 species of concern that occur in a 

variety of tidal marsh habitats. The recovery plan identifies goals, objectives, criteria, and actions needed 

to recover all focal threatened and endangered species so they can be delisted. The implementation of the 

predator management plan is consistent with the objectives outlined in the Recovery Plan.

4) MAMMALIAN PREDATOR MANAGEMENT PLAN

The existing Refuge predator management program utilizing a combination of barriers, trapping, and 

shooting will continue. Lethal controls would only be used when necessary, and as humanely and 

selectively as possible. This plan is consistent with Refuge and Service goals to increase the populations 

of the endangered California clapper rail and the salt marsh harvest mouse, the threatened western snowy 

plovers, and other sensitive waterbird populations, by reducing predation levels through selective predator 

management within selected locations on and adjacent to the Refuge. 

Emphasis would be focused on the removal of rats, red foxes, feral cats, skunks, opossums, and raccoons 

from areas of highest value to endangered species and colonial nesting birds. Individual grey foxes would 

be removed in the event that they were determined to be a problem predator in the area where they were 

I-7 
captured, but would not be routinely removed. The use of several capture and removal techniques would 

allow flexibility in the program and should maximize the effectiveness while minimizing associated costs. 

Predator barriers would be installed in selected locations as appropriate. The installation and maintenance 

of physical barriers would continue for as long as the predators threaten the wildlife populations in the 

area. The trapping or shooting portion would continue for a 5-year period or until rail densities reach a 

Refuge goal of 1.2 rails/ha as measured over a two-year period during the breeding or nonbreeding season. 

 

All activities are conducted by Refuge staff under the direction of the Refuge biologist. In addition, the 

Refuge manager may authorize other trained personnel (e.g., U.S. Department of Agriculture -Wildlife 

Services) to conduct the animal removal efforts. All activities will occur on Refuge property, however, 

predator management on adjacent properties may be conducted given the approval of the appropriate 

landowner. Most activities will be conducted away from areas that are in close association with urban 

developments or areas with high public use. 

Trapping, Shooting, And Toxicants 

Padded Leg Hold Traps

Non-lethal, padded leg hold traps can be an effective technique on all target species when properly set 

(Timm 1983). The greatest advantage of this method is that it allows the release, generally uninjured, of 

non-target species. Traps would be set near areas of high value to endangered species and migratory birds. 

In addition, trapping would occur along levees and boardwalks (i.e., predator pathways) leading to the 

high value areas. Adjacent non-refuge lands may be trapped with the approval of the landowner. Because 

most captures occur at night, traps would be set and checked in the evening and checked and closed at 

sunrise. Upon capture, all target predators would immediately be euthanized by the most humane means 

possible that are approved for use. Euthanization would occur by either injection with a commercially 

available euthanizing solution as approved by the USDA, Wildlife Services or by shooting. 

Although not without controversy, euthanasia is a widely accepted form of putting surplus animals to death 

(USFWS and U.S. Navy 1990). Zoos, animal welfare clinics, animal control facilities, and veterinarians 

all utilize euthanizing techniques, particularly lethal injection. Steve Graham, Director of the Detroit Zoo, 

estimated that over 19 million dogs and cats are humanely put to death, i.e., euthanized, each year in the 

United States (Cassel in USFWS and U.S. Navy 1990). Zoos in Detroit, Michigan, and Sacramento, 

California and elsewhere around the country, euthanize surplus animals to control populations because 

there is often no acceptable place to relocate them (Blum, Cassel, and Barbiers in USFWS and U.S. Navy 

1990). Deceased animals would be disposed of by cremation or burial. Non-target animals would be 

released.

The California Department of Fish and Game prohibits the release of non-native species into the wild in 

California without Fish and Game Commission approval. The Service concurs that it is inappropriate to 

release potentially destructive species into the wild. Transport of any wild animal within the state requires 

permits from the California Department of Fish and Game.

Disadvantages of padded leg hold traps include that they are time consuming to set, sets are ruined by rain 

or standing water, non-target animals may be captured, animals may become trap-wise, and traps must be 

checked frequently since live animals are held. These traps are not appropriate for rats and feral animals. 

Removing live animals from these traps can be hazardous.

Predator Calling/Shooting

I-8 
Authorized personnel would use shotguns and rifles to shoot selected predators. Predator attractant calls 

such as tape recordings, reed-type calls, or other distress calls would be utilized as appropriate. 

Opportunistic shooting of target predators would occur in areas away from public use. These methods 

would only be used in areas of high value to endangered species and migratory birds. The advantages of 

this technique are that shooting is effective, humane, inexpensive in terms of cost and maintenance, and 

would pose little threat to humans or non-target species. This would be the most selective method of 

predator removal. The main disadvantage is the limited shooting range in some areas that are in close 

proximity to urban development. 

Live Traps

Whenever possible, live "box-type" traps would be set in areas near endangered species and migratory bird 

habitats. The primary advantage of live traps is the ability to release non-target animals. All live traps 

would be checked daily and target predators would be humanely dispatched. Disadvantages include their 

limited effectiveness for some species and/or individuals, the repetitive monitoring efforts required because 

of live animals, and their large size which makes them unwieldy in certain conditions. 

Predator Barriers

This plan would involve the use of barriers such as water, fences, or other structures that would physically 

limit predator movements. The construction of strategically located levee breaks or water barriers would 

create an impasse for some terrestrial predators. Similarly, an artificial fence may prevent some predator 

movements into sensitive areas. Fencing or breaks in the levees must not adversely affect endangered 

species, which it is intended to protect, and must be compatible with other management operations.

Figure 2 contains a conceptualized drawing of a predator fence. The fences may be constructed from 

locally available materials such as vinyl-coated chain link fence, 1" galvanized poultry netting, or tensar 

polygrid netting. The fences would be supported by 4" x 4" wooden posts. The top two feet of the fence 

would be directed at a 45 degree angle to deter climbing. A commercially available perching deterrent 

would be attached to the tops of all posts to deter predatory birds. An underground barrier may be 

included with each fence. 

The Shorelands Corporation, a private development corporation, has developed and field tested a barrier 

fence in former salt ponds, proposed to be used in conjunction with the development of a horse racing 

facility in the Baumberg Tract, (Letter to the Refuge from Mr. John Thorpe, President, Shorelands 

Corporation, dated August 6, 1990). These former salt ponds are located north of the Refuge, on the east 

side of South San Francisco Bay. The Shorelands Corporation estimated that it would cost approximately 

$1,500,000 for the erection of the predator barrier and the installation of public access control structures. 

Electric fences also may have limited application in some situations. Electric fencing has been used, with 

limited success, to protect California least tern colonies in southern California (M. Silbernagle, USFWS, 

pers. comm.). However, because of the configuration of the remaining tidal salt marshes and the numerous 

levees leading to the marshes, the installation and maintenance of electric fences would be very labor 

intensive and costly in this high salinity environment. The electric fences may conflict with the authorized 

access needs of Cargill Salt. 

Disadvantages of the barriers include a limited effectiveness on animals that can swim, dig, climb, or move 

across mudflats, an increased number of perch sites for avian predators, limitation of areas that can be 

barricaded because of the physical topography, high installation and maintenance costs, and limitations on 

breaching or blocking levees because of an existing management agreement with Cargill Salt. 

I-9 
FIGURE 2. Example of a predator barrier fence.

5) MAMMALIAN PREDATORS

Red Fox

Red foxes are the most widely distributed carnivores in the world. Two populations of red foxes, one 

which is native, the other introduced, occur in California (Gould 1980). The Sierra Nevada red fox 

(Vulpes vulpes necator) is native to the Sierra Nevada Mountains in California. This subspecies occurs 

from Siskiyou County south to Tulare County (Gray 1977, Hall 1981), generally at elevations between 

5,000 and 8,400 feet. The Sierra Nevada red fox is listed as threatened by the State of California.

The other subspecies of red fox was introduced into California by hunters or escaped from commercial fox 

farms (Sleeper 1987) and probably descended from stock introduced from Iowa or Minnesota (Roest 

1977). Those occurring in the nearby Sacramento Valley are most like red foxes (V. v. regalis) from the 

northern Great Plains. These alien red foxes now occur in the Sacramento Valley, southern California, and 

parts of coastal central and northern California. 

 

Prior to late 1986, red foxes had not been observed on the Refuge. Red foxes have been observed in most 

parts of the south bay and in all habitat types. There have been reports of active dens in several south bay 

locations since 1987. Dens have been located in grassy uplands, levee banks, and salt marshes among 

other habitat types. The rapid range expansion of the red fox may be related to its ability to adapt to 

urbanization and the absence of a higher order predator (e.g., coyote) in the area. 

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Worldwide reports of red fox abundance vary from a few individuals in many square miles to over 70 red 

foxes per square mile (Voigt 1987). The highest reported populations have been in an urban area in Great 

Britain (Voigt 1987). In North America, a breeding density of about two adults per square mile is 

considered a relatively high population (Sargeant et al. 1984, Voigt 1987). Red fox litter sizes vary from 1 

to 10 pups, but average 4 to 7 pups (Samuel and Nelson 1982).

Red fox populations are made up of family groups, usually consisting of a mated pair and offspring 

(Sargeant 1972, Voigt 1987). Red fox family groups tend to occupy discrete contiguous territories, 

ranging in size from 1 to 8 square miles, but generally less than 5 square miles (Sargeant 1972, Sargeant et 

al. 1987, Voigt 1987). Territory size is a function of population size. Territories as small as 25 acres have 

been recorded in extraordinarily high fox populations in Great Britain (Voigt and MacDonald 1984).

Adult red foxes tend to remain in the same territory for life (Voigt 1987, A.B. Sargeant, USFWS, pers. 

comm.). Most juvenile males and young females disperse from the parent territories (Storm et al. 1976, 

Voigt 1987). Dispersal distances are shorter where territories are small, and consequently, population 

densities are greater (Voigt 1987). Dispersal distances range from less than 10 miles to over 50 miles 

(Storm et al. 1976, Voigt 1987). Populations grow rapidly in areas where red fox survival is high and 

dispersal is blocked or inhibited by water or urban barriers (e.g., people, highway traffic, buildings). 

Dispersal of young red foxes to and from the Refuge is undoubtedly influenced by major roads and flood 

control channels.

Red foxes are generally nocturnal (Ables 1975), but are often seen during the daytime. Although adult red 

foxes maintain strong social bonds, they tend to be individualistic in their movements and behavior 

(Sargeant 1972, Voigt 1987). Adult red foxes tend to travel several miles throughout their territories daily 

(Sargeant 1972, Voigt 1987). These extensive movements occur even if food is readily available at sites 

known to the red foxes (A.B. Sargeant, USFWS, pers. comm.). Such daily movements are needed to 

maintain territory and maximize prey capture opportunities throughout the territory. Thus, as a result of 

their extensive movement, the likelihood of encounters between red foxes and ground nesting birds 

increases as red fox abundance increases.

Red foxes require a considerable amount of food to survive. Eighty-seven percent of the ingested energy is 

used for body maintenance (Vogtsberger and Barrett 1973). Prey consumption by red foxes fed whole 

prey averaged 5.0 pounds/week for individual adults and 3.0 and 4.2 pounds/week for individual pups at 

ages of 5-8 weeks and 9-12 weeks, respectively (Sargeant 1978). Sargeant (1978) estimated a typical 

family of two adults and five pups would require 317 pounds of prey during the 12-week period after 

whelping.

Red foxes are versatile, highly efficient predators, but they are also capable scavengers (Voigt 1987, A.B. 

Sargeant, USFWS, unpubl. data). The red fox is known to surplus kill (i.e., kill more prey than it can 

consume), sometimes on a large scale (MacDonald 1976). Red foxes have diverse food habits, eating 

mammals, birds, bird eggs, amphibians, reptiles, fishes, insects, worms, refuse, plants, and other items 

(Ables 1975, Samuel and Nelson 1982, Sargeant et al. 1984, Voigt 1987, A.B Sargeant, USFWS, unpubl. 

data). There are many cases of ground nesting bird populations being extirpated or sharply reduced by 

introduced foxes (Blokpoel 1971, Kadlec 1971, Johnson and Sargeant 1977, Drieslein and Bennett 1979, 

Maccarone and Montevecchi 1981, Petersen 1982, Southern et al. 1985).

Red foxes generally consume mid-size or small prey (e.g., ground squirrels, voles, mice, small birds) in 

entirety and frequently remove prey from the site of capture before eating it (Sargeant 1978). Food 

caching of day-old chicks by a 6-week-old red fox was observed by MacDonald (1976). Ducks, and 

perhaps other prey, generally do not struggle when captured by red foxes (Sargeant and Eberhardt 1975F). 

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For these reasons it is common for there to be little or no evidence of predation at sites where prey are 

captured.

Red foxes have a strong attraction for eggs and will take and cache large numbers (Kruuk 1964, 

Timbergen 1965, A.B. Sargeant USFWS, unpubl. data). Typically a red fox takes all eggs from a nest, one 

at a time, and discreetly caches each egg nearby (Timbergen 1965, A.B. Sargeant, USFWS, unpubl. data). 

Cached prey items are well concealed and difficult to find by humans. Generally, no eggs are eaten at the 

site (A.B. Sargeant, USFWS, unpubl. data). This type of egg predation by red foxes is characterized by 

little or no nest disturbance. In instances where eggs are difficult to take from nests, a red fox may use its 

paws to pull eggs out, resulting in some nest disturbance. When eating eggs, red foxes consume little 

eggshell (A.B. Sargeant, USFWS, unpubl. data). For this reason, and because of their tendency to cache 

eggs, examination of fecal material, stomach contents, and food remains at dens reveals little about the 

amount of egg predation by red foxes. Considering these factors, it is extremely difficult to document the 

magnitude of red fox egg predation.

Matt Klope (U.S. Navy, unpubl. data) found that the diet of red foxes at Point Mugu Lagoon in southern 

California varied seasonally and consisted primarily of a large number of birds. He also documented red 

fox predation on California least tern nests. Gary Page (PRBO, pers. comm.) documented the extensive 

loss of snowy plover nests to red foxes at the Salinas River National Wildlife Refuge and many other areas 

along Monterey Bay. Feeney (1991) conducted a snowy plover study in and around the Baumberg Tract 

(former salt ponds in the south bay). She found evidence of red fox predation on a snowy plover nest and 

observed red fox stalking snowy plover chicks. She observed red foxes taking shorebirds, including an 

American avocet and dowitcher. Of 29 red fox scat samples examined during this study, 83% by volume 

was comprised of feathers and avian bones, indicating that the diet of red foxes in the Baumberg salt ponds 

may consist primarily of birds (Feeney 1991). Meckstroth et al. (2007) found that bird species were the 

most frequent prey found in the stomachs of red foxes from South Bay (61%), whereas small rodents were 

most frequent for red foxes from Monterey County (62%).

Due to the implementation of the original mammalian predator management plan on the Refuge, reports 

and trappings of red fox have decreased by ~2010 (B. Popper, pers. comm.). However, they can still be a 

predator of concern at a local level and in many of the wetland habitats of greatest importance to 

endangered California clapper rails, salt marsh harvest mice, and colonial ground nesting birds. Biologists 

have regularly observed red foxes foraging at night and during the day in tidal salt marshes and along salt 

pond levees. They have seen foxes swimming in tidal salt marshes and in salt ponds. Moreover, red foxes 

have been observed stalking small mammals in the refuge tidal marshes during extreme high tides (J.E. 

Takekawa, pers. comm.). Red foxes are known carriers of a variety of important diseases, presenting a 

significant public health concern. Viral diseases such as rabies, canine distemper, and infectious canine 

hepatitis may infect red foxes and be transmitted to native canids (e.g., coyote, kit fox, gray fox) and to 

dogs. Of the viral diseases, rabies is a significant threat to human health. Red foxes may host bacterial 

diseases, such as leptospirosis, which can infect dogs and humans. Parasites, such as Echinococeus 

multilocularis, canine heartworm, and sarcoptic scabies, may be transmitted to other canids by red foxes. 

The transmission of these diseases and parasites by expanding populations of alien red foxes would be 

detrimental to other canids (D. Jessup, CDFG, pers. comm.).

Raccoon 

The raccoon is one of the most widely distributed carnivores throughout California and the United States. 

Raccoons den in a variety of areas including hollow trees, ground burrows, brushpiles, abandoned 

buildings, dense marsh vegetation, haystacks, and rock crevices (e.g., riprap along levees). This mainly 

nocturnal, native mammal is an efficient and opportunistic hunter, displaying omnivorous feeding habits. 

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The raccoon's diverse diet includes crayfish, fish, small mammals, birds, eggs and young of ground-nesting 

birds, insects, fruit, nuts, and berries (Jameson and Peters 1988). 

Raccoons breed mainly in early spring, but matings may occur from December through June. The 

gestation period is about 63 days. Most litters are born in April or May, but some late litters may appear in 

the summer. One litter, averaging 3 to 5 young, is raised per year. Young raccoons are weaned sometime 

between 2 to 4 months of age. Raccoon populations consist of a high proportion of young animals, with 

1/2 to 3/4 of fall populations normally being composed of animals less than one year of age. They may 

live as long as 12 years in the wild. Family groups of raccoons usually remain together for the first year 

and the young den for the winter with the adult female. The family then gradually separates during the 

following spring and the young become independent.

Prior to 1988, raccoons had not been reported as regular inhabitants in many of the salt marshes of South

San Francisco Bay. Foerster et al. (1990) identified raccoons as a major clapper rail egg predator in the 

salt marshes of the San Francisco Bay NWR. Raccoons have also been observed in the salt marshes during 

the nighttime spotlight surveys conducted by refuge biologists. Snowy plover nests in the Crescent Pond 

Unit of the Refuge have also been lost to foraging raccoons.

Rats

The Norway rat (Rattus norvegicus) is a stocky burrowing rodent, unintentionally introduced to North 

America by settlers who arrived on ships from Europe. Norway rats are now found throughout the 

contiguous 48 states. Norway rats burrow to make nests under buildings and other structures, beneath 

concrete slabs and rock piles, along stream banks and the bay edge, in garbage dumps and any other 

locations where suitable food, water, and cover are available.

Norway rats will eat nearly any type of available food, including cereal grains, meats, fish, eggs, nuts, and 

fruit. They are mainly nocturnal, although when populations are high, some individuals may be active 

during the daylight hours. The average female rat has 4 to 6 litters per year and may successfully wean 20 

or more offspring annually. Litters of 6 to 12 young are born 21 to 23 days after conception. Young rats 

are capable of eating solid food at 2 1/2 to 3 weeks. They become completely independent at about 3 to 4 

weeks and reach reproductive maturity at 3 months of age.

Rats have been identified as clapper rail egg predators by several investigators (DeGroot 1927, Applegarth 

1938, Harvey 1988, Foerster et al. 1990). They swim readily and biologists at San Francisco Bay NWR 

regularly observe rats in the salt marshes during the highest winter tides.

Striped Skunks 

The striped skunk (Mephitis mephitis) occurs over most of the continental United States and is a common 

resident in portions of the Refuge. Striped skunks are seen regularly by refuge staff during morning and 

evening hours. Skunks usually nest and rear young in an underground burrow, under debris or buildings. 

From 4 to 10 young are born in a litter, usually during the spring. Young are independent by early fall.

The normal home range of the skunk is an area 1/2 to 1 1/2 miles in diameter. During the breeding season 

a male may travel 4 to 5 miles each night. Striped skunks are omnivorous and their diet includes fruits, 

berries, insects, small reptiles, small mammals, carrion, and eggs (Seymour 1968). They are one of the 

most important predators of duck eggs in the Prairie Pothole region of the northern Great Plains (Johnson 

et al. 1989). 

I-13
Skunks have been observed in tidal salt marshes, along salt pond levees, and in upland habitats on the 

refuge. Meckstroth et al. (2003) found striped skunks to be the most common predators found in tidal 

marsh adjacent to urban areas.

Feral cats

Feral cats include domestic cats that have reverted to living in the wild and descendants of domestic cats 

that breed and live in the wild. Feral cats are predators of small mammals, birds, reptiles, and insects 

(McMurray and Sperry 1941). Predation by cats may affect endangered and other bird populations in at 

least two ways: 1) by direct predation on birds and their eggs, and 2) by reducing available alternative prey, 

causing other predators to shift to other species including those that are endangered. Mammals usually 

constitute the most important category of prey, while birds contribute as much as 19 percent (Eberhard 

1954) to 25 percent (Hubbs 1951) of the stomach contents of feral cats. The importance of birds in the 

diet of feral cats has been found to vary seasonally. Hubbs (1951) found that birds constituted 25% of the 

annual diet of feral cats in the Sacramento Valley, but increased seasonally to a high of 70% in June. Most 

domestic cats appear to be opportunistic hunters. Churcher and Lawton (1989) found that the diets of 

foraging feral cats consisted of 65 percent small mammals and 35 percent birds. They calculated that at 

least 20 million birds are killed annually by cats in Britain, and concluded that domestic cats may be a 

major predator of small birds and mammals in urban and suburban environments. Cats are also reported to 

regularly prey on larger animals including rabbits, pheasants, and ducks (Hubbs 1951, Liberg 1984) and 

bird eggs (Hubbs 1951). Moreover, feral cats have been known to kill adult light-footed clapper rails 

(Zembal and Massey 1988, M. Weitzel, USFWS, pers. comm.). In recent years (~2008-2010) three radiotagged clapper rails have been found dead outside of feral cat feeding stations in the South Bay (C. 

Overton, USGS, pers. comm.)

Refuge biologists have frequently observed feral cats foraging in salt marshes, including during the peak of 

extreme winter high tides, foraging along salt pond levees, and wading at the edge of tidal sloughs. These 

feral cats are wild and bear little resemblance to domestic pets. The total effect of feral cats on California 

clapper rails, salt marsh harvest mice, and other wildlife is unknown at this time. The handling of feral

animals on Federal lands is governed by parts of 50 CFR 26, 28, and 30.

Gray fox 

Gray foxes (Urocyon cinereoargenteus) are native predators in the local ecosystem. Diet of the gray fox 

consists of small rodents, small birds, berries, insects, and fungi. Gray fox have recently been observed 

foraging in dry salt ponds and along levees and were captured on video depredating a western snowy 

plover nest (Robinson-Nilsen et al. 2010). Perhaps due to the successful removal of many of the red fox in 

the area, reports of gray foxes have been increasing in the South Bay, including on the Refuge. In the event 

that an individual gray fox is determined to be a problem predator, this fox will be removed from sensitive 

habitat.

Virginia opossum 

Virginia opossum (Didelphis virginiana) was introduced to California from the east coast and has become 

well established throughout the state. These nocturnal marsupials are omnivorous and readily fee don birds 

and their eggs as well as small mammals. Like raccoons, opossums can become numerous in areas where 

food is supplemented by human food resources, and are a concern in marshes and adjacent to housing and 

business developments (B. Popper, USDA, pers comm.).

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Non-target Terrestrial Predators

Other potential terrestrial predators on the Refuge include California ground squirrel (Spermophilus 

beecheyi), and roof rats (Rattus rattus). These species are non-target species and will be released if 

trapped. 

6) CONSULTATION AND COORDINATION WITH OTHERS 

In January 1990, a meeting was held at San Francisco Bay NWR to discuss the predator situation 

(emphasis on the red fox) and possible methods for addressing the situation. The meeting was attended by 

the Santa Clara Valley Audubon Society, California Dept. of Fish and Game, East Bay Regional Parks 

District, Golden Gate Audubon Society, Save San Francisco Bay, and San Francisco Bay Bird 

Observatory. The group discussed the need for action, including the development of the original 

mammalian predator management plan and environmental assessment. Further meetings were held later in 

the year with the Humane Society of the United States, the Humane Society of Santa Clara Valley, Ohlone 

Humane Society, and Peninsula Humane Society. 

Resolutions in support of predator management to protect the California clapper rail were passed by The 

Western Section of the Wildlife Society (an organization of professional wildlife biologists) and the 

American Ornithologists' Union. 

The Service has coordinated development of the plan with the California Department of Fish and Game. 

Following are California Fish and Game Code sections that relate to control of predatory mammals, 

including the introduced red foxes.

Section 2118: Prohibits the importation, transport, possession, or release of live wild animals in 

California, except under a revocable, nontransferable permit.

 

Sections 4000-4012: Defines trapping provisions for fur-bearing mammals.

Sections 4150-4154: Defines nongame mammals and control of depredators.

Sections 4180-4181: Defines provisions for controlling depredating mammals and the use of leghold traps.

7) LITERATURE CITED 

Ables, E.D. 1975. Ecology of the red fox in North America. Pages 216-236 in M.W. Fox, ed., The wild 

canids-- their systematics, behavioral ecology and evolution. Van Nostrand Reinhold Company, New 

York.

Albertson, J.D., and J.G. Evens. 2000. California Clapper Rail. Pages 332-341 in Baylands Ecosystem 

Species and Community Profiles: Life Histories and Environmental Requirements of Key Plants, Fish and 

Wildlife (P.R. Olofson, Ed.). San Francisco Bay Area Wetlands Ecosystem Goals Project, San Francisco 

Bay Regional Water Quality Control Board, Oakland, California.

I-15
Applegarth, J.H. 1938. The ecology of the California clapper rail on the south arm of San Francisco Bay. 

M.S. Thesis, Stanford University, California.

Blokpoel, H. 1971. Fox predation on a bird island. The Blue Jay. 29(1):32-34.

Bryant, H.C. 1915. California clapper rail breeds in Alameda salt marshes. Calif. Fish and Game 

1(4):192.

Carter, H.R., D.L. Jaques, G.J. McChesney, C.S. Strong, M.S. Parker, and J.E. Takekawa. 1990. 

Breeding populations of seabirds on the northern and central California coasts in 1989 and 1990. Tech. 

Rpt. prepared by the USFWS and funded by the Pacific Outer Continental Shelf Region of the Minerals 

Management Service, U.S. Department of the Interior, Washington, D.C., under Inter-agency Agreement 

No. 14-12-001-30456. October 1990. 443 pp. 

Churcher, P.B., and J.H. Lawton. 1989. Beware of well-fed felines. Natural History. July 1989.

Crooks K.R., M.E. Soule. 1999. Mesopredator release and avifaunal extinctions in a fragmented 

system.Nature 400:563–566

DeGroot, D.S. 1927. The California clapper rail: its nesting habits, enemies, and habitat. Condor 

29(6):259-270.

Drieslein, R.L. and A.J. Bennett. 1979. Red fox predation on greater sandhill crane chicks. Wilson Bull. 

91(1):132-133.

Eberhard, T. 1954. Food habits of Pennsylvania house cats. J. Wildl. Manage. 18(2):284-286.

Feeney, L.R. 1991. Snowy plovers and their habitat at the Baumberg are and Oliver salt ponds, Hayward, 

California. Draft tech. rpt prepared for the City of Hayward. 162 pp.

Foerster, K.S. 1989. Summary of the California clapper rail winter populations in the San Francisco Bay 

National Wildlife Refuge - November 1988 to January 1989. Tech. Rpt. prepared for the San Francisco 

Bay National Wildlife Refuge. Newark, California. 17 pp. 

Foerster, K.S., J.E. Takekawa, and J.D. Albertson. 1990. Breeding density, nesting habitat, and predators 

of the California clapper rail. Tech. Rpt. # SFBNWR-11640-90-1 prepared for San Francisco Bay National 

Wildlife Refuge. Newark, California. 43 pp. + appendix. 

Gould, G.I., Jr. 1980. Status of the red fox in California. California Dept. Fish and Game, Nongame 

Wildl. Invest., Job I-8, Progress Report.

Gray, R.L. 1977. Extension of red fox distribution in California. California Fish and Game 63:58.

Grinnell, J. and A.H. Miller. 1944. The distribution of the birds of California. Pac. Coast Avifauna 27.

Hall, E.R. 1981. The mammals of North America, Vol. 2. John Wiley and Sons, New York.

Harvey, T.E. 1987. The California clapper rail: biology, present status, and future trends. Presentation at 

Amer. Ornith. Union meeting.

I-16
Harvey, T.E. 1988. Breeding biology of the California clapper rail in south San Francisco Bay. Trans. 

West. Sect. Wildl. Soc. 24:98-104.

Hubbs, E.L. 1951. Food habits of feral house cats in the Sacramento Valley. Calif. Dept. of Fish and 

Game 37:177-189.

Jameson E.W., Jr., and H.J. Peters. 1988. California Mammals. California Natural History guides: 52. 

University of California Press. Berkeley. 403 pp.

Johnson D.H. and A.B. Sargeant. 1977. Impact of red fox predation on the sex ratio of prairie mallards. 

U.S. Fish and Wildlife Service. Wildlife Research Report 6. Washington, D.C.

Johnson, D.H., A.B. Sargeant, and R.J. Greenwood. 1989. Importance of individual species of predators 

on nesting success of ducks in the Canadian Prairie Pothole Region. Can. J. Zool. 67:291-297.

Kadlec, J.A. 1971. Effects of introducing foxes and raccoons on herring gull colonies. J. Wildl. Manage. 

35(4):625-636.

Kruuk, H. 1964. Predator and anti-predator behaviour of the black-headed gull (Larus ridibundus L.). 

Behaviour Supplement 11, 129 pp. + 22 figures.

Liberg, O. 1984. Food habits and prey impact by feral and house-based domestic cats in a rural area in 

southern Sweden. J. Mammal. 65(3):424-432.

Liu, L., Wood, J., Nur, N., Stralberg, D., and M. Herzog. 2009. California Clapper Rail (Rallus longirostris

obsoletus) Population monitoring: 2005-2008

Lonzarich, D.G, T.E. Harvey, and J.E. Takekawa. 1990. Trace element and organochlorine levels in 

California clapper rail eggs. Draft Manuscript. San Francisco Bay National Wildlife Refuge. 

Maccarone, A.D., and W.A. Montevecchi. 1981. Predation and caching of seabirds by red foxes (Vulpes 

vulpes) on Baccalieu Island, Newfoundland. Canadian Field-Naturalist 95(3):352-353.

MacDonald, D.W. 1976. Food caching by red foxes and some other carnivores. J. Tierpsychol. 42:170-

185.

McMurray, F.B. and C.C. Sperry. 1941. Food of feral house cats in Oklahoma, a program report. J. 

Mammal. 22:185-190.

Meckstroth, A., and A.K. Miles. 2003. Predator of nesting waterbirds in an urban environment. Final 

Report. Moffett Federal Airfield, NASA Ames Research Center, Mountainview, California. 49 pages.

Meckstroth, A. M., Miles, A. K. and Chandra, S. 2007. Diets of Introduced Predators Using Stable 

Isotopes and Stomach Contents. The Journal of Wildlife Management, 71: 2387–2392. doi: 10.2193/2005-

527

Petersen. M.R. 1982. Predation on seabirds by red foxes at Shaiak Island, Alaska. Canadian FieldNaturalist 96(1):41-45.

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Pitkin, M. and J. Wood. (Editors). 2011. The State of the Birds, San Francisco Bay.PRBO Conservation 

Science and the San Francisco Bay Joint Venture.

Robinson-Nilsen, C., J. Demers, and C. Strong. 2010. Western Snowy Plover Numbers, Nesting Success, 

Fledging Success and Avian Predator Surveys in the San Francisco Bay, 2010. Unpublished Report. San 

Francisco Bay Bird Observatory, Milpitas, CA.

Roest, A.E. 1977. Taxonomic status of the red fox in California. Calif. Dept. Fish and Game. Nongame 

Wildlife Investigations, Job II-1.3. 14 pp. 

Samuel, D.E., and B.B. Nelson. 1982. Foxes. Pages 475-490 in J.A. Chapman and G.A. Feldhamer eds., 

Wild mammals of North America. The Johns Hopkins University Press, Baltimore.

Sargeant, A.B. 1972. Red fox spatial characteristics in relation to waterfowl predation. J. Wildl. Manage. 

36:225-236. 

Sargeant, A.B. 1978. Red fox prey demands and implications to prairie duck production. J. Wildl. 

Manage. 42(3):520-527.

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(Vulpes). Am. Midl. Nat. 94:108-119.

Sargeant, A.B., S.H. Allen, and R.T. Eberhardt. 1984. Red fox predation on breeding ducks in mid 

continent North America. Wildl. Monogr. 89.

Sargeant, A.B., S.H. Allen, and J.O. Hastings. 1987. Spatial relations between sympatric coyotes and red 

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Contamination on Reproductive Success of California Clapper Rails (Rallus longirostris obsoletus) in San 

Francisco Bay. The Auk , 123:45-60. 

Seymour, G. 1968. Furbearers of California. Calif. Dept. of Fish and Game, Sacramento, CA.

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Trabuco Canyon, California.

Southern, W.E., S.R. Patton, L.K. Southern, and L.A. Hanners. 1985. Effects of nine years of fox 

predation on two species of breeding gulls. The Auk 102:827-833.

Storm, G.L., R.D. Andrews, R.L. Phillips, R.A. Bishop, D.B. Sniff, and J.R. Tester. 1976. Morphology, 

reproduction, dispersal, and mortality of Midwestern red fox populations. Wildl. Monogr. 49:1-82.

Timbergen, N. 1965. On the food caches of red foxes (Vulpes vulpes L.). Zeitschrift Fuer 

Tierpsychologie 22:119-149. (In German, English translation at the Northern Prairie Wildlife Research 

Center - U.S. Fish and Wildlife Service).

Timm, R.M. (Editor) 1983. Prevention and Control of Wildlife Damage. Univ. of Nebraska Press. 

Lincoln, Nebraska.

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U.S. Fish and Wildlife Service. 1984. The salt marsh harvest mouse/California clapper rail recovery plan. 

Region 1, Portland, Oregon. 141 pp. 

U.S. Fish and Wildlife Service. 2009. Draft Recovery Plan for Tidal Marsh Ecosystems of 

Northern and Central California. Sacramento, California. xviii + 636 pp.

U.S. Fish and Wildlife Service and U.S. Navy. 1990. Final Environmental Impact Statement. 

Endangered Species Management and Protection Plan. Naval Weapons Station - Seal Beach and Seal 

Beach National Wildlife Refuge. Region 1, Portland, Oregon.

Vogtsberger, L.M., and G.W. Barrett. 1973. Bioenergetics of captive red foxes. J. Wildl. Manage. 

37(4):495-500.

Voigt, D.R. 1987. Red Fox. Pages 379-392 in M. Novak, J. Baker, M. Obard, B. Malloch, eds., Wild 

Furbearer Management and Conservation in North America. Ministry of Natural Resources, Ontario, 

Canada.

Voigt, D.R., and D.W. MacDonald. 1984. Variation in the spatial and social behaviour of the red fox, 

Vulpes vulpes. Acta Zool. Fenn. 171:261-265.

Zembal, R., and B.W. Massey. 1988. Light-footed clapper rail census and study, 1988. Calif. Dept of 

Fish and Game Report., FG 7609. 29 pp.

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Appendix J. Avian Predator Management Plan

Avian Predator Management Plan

Don Edwards San Francisco Bay NWR, USFWS

J-1 

DON EDWARDS NATIONAL WILDLIFE REFUGE

AVIAN PREDATOR MANAGEMENT PLAN

1) OVERVIEW ........................................................................................................................... 1

2) BACKGROUND .................................................................................................................... 2

Western Snowy Plover ................................................................................................................ 2

California Least Tern .................................................................................................................. 3

California Clapper Rail ............................................................................................................... 4

Salt Marsh Harvest Mouse .......................................................................................................... 5

Existing predator management efforts in the South San Francisco Bay and adjacent areas ...... 6

Salinas River National Wildlife Refuge and the Monterey Bay area ...................................... 6

Alameda National Wildlife Refuge (proposed; Dept. of the Navy property) .......................... 7

Eden Landing Ecological Reserve (California Dept. of Fish and Game) .............................. 8

3) AVIAN PREDATOR MANAGEMENT PLAN .................................................................... 8

4) GOALS OF THE AVIAN PREDATOR MANAGEMENT PLAN ..................................... 10

a) Steps to Achieve Goals ..................................................................................................... 11

Conduct avian predator management plan........................................................................... 11

b) Monitoring and Coordination ........................................................................................... 11

c) Species Specific Protocols ................................................................................................ 12

Common ravens and American crows .................................................................................. 12

California gulls ..................................................................................................................... 13

Red-tailed hawks and northern harriers ............................................................................... 15

Other species ......................................................................................................................... 16

5) RELEVANCE TO REFUGE PURPOSE AND GOALS ..................................................... 18

6) JUSTIFICATION ................................................................................................................. 19

7) COLLABORATORS AND CONTACTS ............................................................................ 19

8) REFERENCES ..................................................................................................................... 19

9) ACKNOWLEDGEMENTS .................................................................................................. 25

Contact information: Cheryl Strong, Wildlife Biologist, Don Edwards San Francisco Bay 

National Wildlife Refuge, U.S. Fish and Wildlife Service, cheryl_strong@fws.gov.

1) OVERVIEW 

In conjunction with its existing mammalian predator management plan and other wildlife

and habitat management plans, the U.S. Fish and Wildlife Service (Service) proposes to 

implement an avian predator management plan at the Don Edwards San Francisco Bay 

National Wildlife Refuge (Refuge) and adjacent lands. The goal of the plan is to increase the 

production of the Refuge’s population of western snowy plovers (Charadrius alexandrinus 

nivosus, federally listed as threatened) and California least tern (Sternula antillarum browni, 

federally listed as endangered) by selectively removing problem avian predators that pose a 

threat to snowy plover and least tern adults, chicks, or eggs. The plan will also benefit the

federally endangered salt marsh harvest mouse (Reithrodontomys raviventris) and California 

clapper rail (Rallus longirostris obsoletus) and other locally nesting bird species.
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Removal and deterrence of avian predators will be accomplished by various methods including 

hazing, relocation, or lethal control. Target predators include California gulls 

(Laruscalifornicus), northern harriers (Circus cyaneus), red-tailed hawks (Buteo jamaicensis), 

common ravens (Corvus corax) and American crows (Corvus brachyrhynchos). Other 

potential, but less likely target species include peregrine falcons (Falco peregrinus), American 

kestrels (Falco sparverius), merlins (Falco columbarius), loggerhead shrikes (Lanius 

ludovicianus), Cooper’s hawks (Accipiter cooperii), sharp-shinned hawks (Accipiter striatus), 

great-horned owls (Bubo virginianus), barn owls (Tyto alba), and burrowing owls (Athene 

cunicularia).

The development of an overall predator management plan to address the full suite of avian and 

mammalian predators has been recommended and endorsed by independent researchers. For 

example, Shuford (2008) recommended that the revised plan place particular emphasize on 

species of predators, such as the California gull and common raven, which have greatly 

increased in the South Bay in recent decades (Ackerman et al. 2006, National Audubon 

Society 2002, Strong et al. 2004a).

2) BACKGROUND 

Western Snowy Plover

The Pacific coast population of the snowy plover breeds primarily on coastal beaches over a 

range that extends from southern Washington to southern Baja California. In 1993, the species 

was listed as threatened under the federal Endangered Species Act throughout this range. 

Threats to the snowy plover include habitat loss and human disturbance of nesting grounds. 

Snowy plovers also suffer from low reproductive success due to high predation levels, often 

due to artificially inflated predator numbers in a human-modified landscape (USFWS 2007). 

Significant loss of breeding habitat in southern California has made the state’s remaining 

breeding areas crucial to maintaining a stable snowy plover population. Along the Pacific 

Coast, the San Francisco Bay (Bay) is the northernmost area supporting over 100 breeding 

snowy plovers (Page et al. 2000). Historic salt evaporator ponds provide all known nesting 

habitat for snowy plovers in the Bay area. Recovery goals call for 500 breeding snowy plovers 

in the entire Bay area and 1.0 fledged chick per male. The area included in the South Bay Salt

Pond Restoration Project (of which the Refuge is a part) will manage habitat for 250 breeding 

snowy plovers (USFWS 2007, USFWS and CDFG 2007). Restoration efforts of the South 

Bay Salt Pond Restoration Project will decrease the area of dry, seasonal pannes available for 

nesting snowy plovers (USFWS and CDFG 2007). This smaller footprint will concentrate 

snowy plover nests, thus increasing the need for effective avian predator management and 

more intensive snowy plover habitat management.

Region-wide, snowy plover avian nest predators include American crows, common ravens, 

gulls, northern harriers, falcons, owls, and herons (USFWS 2007). Locally, documented 

predators of concern are California gulls, northern harriers, common ravens, and red-tailed 

hawks (Robinson- Nilsen et al. 2010). Nest success in the South Bay has decreased from ~84% 

in 2004 and 2005 to 58% in 2006, 49.4% in 2007, 54% in 2008, 59% in 2009 and 41% in 2010 

due mostly to predation (Robinson-Nilsen et al. 2010). Because there is usually no sign of 
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predation other than missing eggs at depredated nests, we have traditionally had no way of 

identifying predators. However, as of August 2009, the San Francisco Bay Bird Observatory 

(SFBBO) has documented predations using a nest camera set up on snowy plover nests in the 

South Bay. Nest cameras have identified red-tailed hawks, northern harriers, common ravens, 

and California gulls as nest predators along with a single instance each of gray fox (Urocyon 

cinereoargenteus) and ruddy turnstone (Arenaria interpres); Robinson-Nilsen et al. 2010).

In 2008, a flock of California gulls roosting in an area with snowy plover nests corresponded to

a wave of predation on nests and the disappearance of snowy plover chicks (Robinson et al. 

2008). 

Robinson et al. (2007) documented a harrier taking a snowy plover nest on one occasion and a 

chick in another. Northern harriers have been suspected of contributing significantly to a zero 

fledge rate at the Salinas River NWR in 1999 as observations of harriers at the Salinas Refuge 

coincided with periods of snowy plover chick loss (USFWS 2007). Removal of targeted 

individual northern harriers corresponded in timing to an increase in nesting success at 

California Dept. of Fish and Game’s Eden Landing Ecological Reserve that is also part of the 

South Bay Salt Pond Restoration Project area (Robinson et al. 2007).

California Least Tern

The historic breeding range of the least tern extended along the southern California coast 

between Santa Barbara and San Diego, with some nesting sites documented as far north as 

the San Francisco Bay and as far south as southern Baja California. Today, the breeding 

range is limited to San Francisco Bay and a few areas along the coast from San Luis Obispo 

County to San Diego County. The least tern population has declined due to human 

encroachment and destruction of nesting habitat. Human disturbance related to dredging 

and development have reduced nesting habitat on beaches and mudflats. Due to a lack of 

beach for nesting, many remaining least tern colonies now nest on more terrestrial areas 

away from the ocean, making them more vulnerable to predation by mammals and avian 

species that are well-suited to a human-modified landscape. The least tern’s fishing grounds 

have also been severely impacted by dredging, development and pollution (USFWS 1980). 

Depending on the year, there are 3-6 least tern colonies in the San Francisco Bay, with 

Alameda Point the largest colony with >300 breeding pairs in 2009 (USFWS unpub data); 

only two other Bay area colonies had >20 breeding pairs (Marschalek 2008). Service 

recovery goals call for the establishment of four colonies in the Bay area with at least 20 

breeding pairs and 1.0 fledged chick per pair (USFWS 1980). Restoration efforts of the 

South Bay Salt Pond Restoration Project will increase the number of islands available for 

nesting least terns in the South Bay. These islands may also be used by competing species, 

including California gulls, increasing the need for effective avian predator management.

Marschalek (2008) reported 39 and Marschalek (2009) reported 45 species as possible, 

suspected, or documented predators of least terns. The most reported predators were avian 

species. The most common avian predators were gulls, peregrine falcons, common ravens, 

great blue herons (Ardea herodias), American kestrels, as well as burrowing owls and great 

horned owls. 
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At the Alameda colony, fencing and predator management limit predation, particularly in 

respect to mammals. In 2006, common ravens and gulls were suspected to have taken 2-10 

eggs and burrowing owls took at least 26 adults and 15 chicks (Euing 2007). In 2007, four 

verified kills were made by red-tailed hawks, peregrine falcons and northern harriers, and 25 

other verified kills by unknown avian predators (USFWS, unpublished data). In 2008, 

peregrine falcons, northern harriers, red-tailed hawks, common ravens, American crows, and 

logger-head shrikes were documented predators on eggs, chicks or adults (Marschalek 2009). 

In 2009, local nesting families of peregrine falcons and red-tailed hawks continued to 

depredate eggs, chicks, and adults at Alameda Point. American crows also depredated eggs 

at this colony, while California gulls, American kestrels and Cooper’s hawks were also seen 

in the vicinity of the colony. In 2012, one male American kestrel was responsible for the 

loss of over 200 chicks within the colony (USFWS, unpublished data). In addition, a newly 

re- established California gull colony was present near the least tern colony in 2010 although 

no fledglings were produced presumably due to predation by western gulls (Larus 

occidentalis, USFWS, unpub. data). 

Least tern nests in a newly establishing colony in Eden Landing Ecological Reserve in 2008 

were depredated after a large number of California gulls roosted in the immediate area 

(Robinson et al. 2008). In 2009, a northern harrier was caught on camera depredating a newly 

hatched least tern nest (Robinson-Nilsen et al. 2009).

Least terns at Hayward Regional Shoreline abandoned a newly established colony in 2005 and 

again in 2006 after California gulls established a roosting site on an adjacent island and 

depredated the least tern colony (Riensche 2007). The following year, least terns established 

15 nests, but only fledged four young after an increase of gulls on an adjacent island. Active 

predator management in 2007 and 2008 allowed least terns to produce 49 and 70 fledglings 

respectively (Schacter et al. 2008). In 2009, this colony had 80 least tern nests, producing ~65 

fledglings with very active predator management (D. Riensche, pers. comm.). Avian predators 

on this colony included California gulls, peregrine falcons, and American crows with northern 

harriers, red- tailed hawks, and common ravens suspected as predators (Marschalek 2009).

California Clapper Rail

California clapper rails were historically abundant in all tidal salt and brackish marshes in the 

San Francisco Bay area (Cohen 1895), as well as in the larger tidal estuaries from Marin to 

San Luis Obispo counties. California clapper rails are now restricted almost entirely to the 

marshes of the San Francisco Bay Estuary where the only known breeding populations occur, 

where they exist in disjunct populations (USFWS 2009 and references listed therein). The 

breeding period of the California clapper rail extends from late February or early March into 

August. Clapper rails require an intricate network of sloughs to provide invertebrates and 

escape routes from predators, particularly for flightless young (Taylor 1894, Adams 1900, 

DeGroot 1927, Evens and Page 1983, Foerster et al. 1990, Evens and Collins 1992). The small 

natural berms along tidal channels provide elevated nesting substrate with relatively tall 

vegetation, such as Grindelia stricta (gumplant). 
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According to the Draft Recovery Plan for Tidal Marsh Ecosystems of Northern and Central 

California (USFWS 2009), predation pressures on clapper rails must be reduced in order to 

downlist the California clapper rail to threatened status. Thus they recommend that a predator 

management plan be developed and implemented at all sites with significant predation issues.

Reproductive success of the California clapper rail is low, with hatching success estimated at 

19-43% (Harvey 1988, Foerster et al. 1990, USFWS unpub. data). Predation was reported to 

account for a third of the lost eggs. Known avian predators on clapper rails and their eggs 

include great blue herons, red-tailed hawks, peregrine falcons, northern harriers, barn owls, 

great horned owls, short-eared owls (Asio flammeus), and common ravens. Numbers of native 

avian species (common ravens, American crows, California gulls) have increased above 

historical levels due to the increased availability of human food resources and nesting 

opportunities associated with the human activities. Other species, such as the northern harrier, 

can no longer forage in upland habitats due to urban development and their foraging activities 

are concentrated in wetland areas USFWS 2009 and references listed therein). 

Common ravens, peregrine falcons, and red-tailed hawks nest in electrical towers and 

buildings and forage in nearby marshes. The peregrine falcon has increased locally in recent 

years as a result of peregrine falcon recovery actions. Hunting intensity and efficiency by 

avian predators is increased by electric power transmission lines, towers, and boardwalks, 

many of which cross through tidal marshes and provide otherwise-limited hunting perches 

(USFWS 2009). These predation impacts are greatly intensified by a decrease in high marsh 

and high tide cover in marshes (Sibley 1955, Evens and Page 1986). 

Salt Marsh Harvest Mouse

The salt marsh harvest mouse is generally restricted to saline or saline/brackish areas in the 

San Francisco Bay, San Pablo Bay, and Suisun Bay area. No historical records exist of its 

abundance or distribution in the estuary to use as a baseline, however the salt marsh harvest 

mouse probably occupied most of the pickleweed-dominated marshes and high marsh zones 

of San Francisco Bay, San Pablo Bay, and the Suisun Marsh prior to the significant marsh 

reclamation of the 1840s. Habitat loss leading to fragmentation of the populations, non-native 

species invasions, and insufficient escape habitat are major threats to this species. In the South 

Bay, this species is currently limited to existing fringe tidal marshes and diked marshes. 

Larger populations likely exist in the few, larger marshes that remain in the South Bay (for 

example: Calaveras Point Marsh, Bair Island, Greco Island, Mowry Slough, and other 

sites)(USFWS 2009 and references listed therein). 

Although little is known about predation impacts to salt marsh harvest mice, predation related 

to flooding is an important factor (Johnston 1957, Fisler 1965, USFWS 2009). During high 

winter tides great blue herons, great egrets (Ardea alba), snowy egrets (Egretta thula), ringbilled gulls, California gulls, northern harriers, white-tailed kites (Elanus caeruleus), 

American kestrels, short-eared owls and other avian predators can be seen taking small 

mammals from the upper edges and flooded areas of marshes. Clapper rails also occasionally 

take small mammals (Terres 1980, Josselyn 1983, Meanley 1985). Salt marsh harvest mice 

depend on dense vegetation cover for predator protection. Flooded vegetation exposes mice 
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and other small mammals to predation. Unnatural predation is thought to exist in some 

marshes where salt marsh harvest mice are concentrated into narrow pickleweed zones due to 

surrounding habitat loss (USFWS 2009). 

Existing predator management efforts in the South San Francisco Bay and 

adjacent areas

The Refuge’s mammalian predator management plan was written in 1991, in response to low 

reproductive success rates of the California clapper rail as well as other ground nesting 

species, including snowy plovers. It integrates a variety of techniques, including the removal 

of mammalian predators, primarily non-native red foxes (Vulpes vulpes), feral cats (Felis 

catus), skunks (Mephitis mephitis), and raccoons (Procyon lotor) by USDA Wildlife Services 

and the installation of predator barriers such as fencing or water (USFWS 1991). 

Currently, USDA Wildlife Services implements avian predator management at Salinas River 

National Wildlife Refuge in the Monterey Bay area (USFWS 2002), at Eden Landing 

Ecological Reserve, an important snowy plover breeding site in the South San Francisco Bay 

(CDFG 2000) and at the Alameda least tern colony for the Dept. of the Navy (Euing 2007). 

Avian predator removal in other areas provides us with insight into the efficacy of such plans 

on the reproductive success of snowy plovers and least terns.

Salinas River National Wildlife Refuge and the Monterey Bay area

The Salinas River National Wildlife Refuge implemented an experimental avian predator 

management plan in 1999. After implementation, snowy plover nesting success increased to an 

all-time high of 70%. Based on the results of the 3-year experimental plan at the Salinas River 

NWR and surrounding Monterey Bay areas, the Service and its cooperators concluded that 

avian predation was adversely affecting snowy plover reproductive success at the three study 

sites, and that removal of problem avian predators was an effective strategy for reducing

predation-related mortality and increasing fledge rates. Avian predators at Salinas River NWR 

include northern harriers, red-tailed hawks, common ravens, American crows, American 

kestrels, and loggerhead shrikes. The avian predator management plan is now incorporated into 

the Salinas River NWR Comprehensive Conservation Plan.

Salinas River NWR avian predator management is concentrated immediately prior to and 

during the snowy plover breeding season (March–September). Management strategies are

implemented on the Refuge and on adjacent public or private properties with consent of the 

landowner. Individual non-corvid predators determined to be a threat to snowy plovers are

trapped, banded, and relocated (>150 miles away) as possible. A combination of live-trapping 

techniques are used, including bal-chatri traps, dho gaza nets, bow nets, net launchers with bait, 

pole traps, pigeon/starling harnesses, padded jaw-leg holds, cage traps and lures. Hazing or 

lethal control is used on rare occasions when necessary, for example, when repeated trapping 

attempts have failed and there is an immediate threat to snowy plovers. The decision to 

lethally remove an avian predator is determined on a case-by-case basis, and based on the 

degree of threat, the breeding phase of the snowy plovers, professional judgment of the 

situation, and knowledge regarding the species involved. Lethal methods include euthanasia 
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and shooting, and are implemented as humanely and selectively as possible. If a problem raven 

or crow is found on the Refuge, it is controlled lethally. 

Additional measures to discourage avian predator use of snowy plover breeding areas include 

attaching spikes to signs and removing abandoned posts which serve as perches. Salinas River

NWR and its cooperators continue to monitor snowy plovers to determine hatch and fledge rates 

as well as adult survivorship and population size. In addition, avian predators on the Refuge and 

adjacent lands are monitored, recording species observed and their behavior and habits (USFWS 

2002). 

Alameda National Wildlife Refuge (proposed; Dept. of the Navy property) 

Predation is the major cause of breeding failure at most least tern colony sites in California. Due 

to the limited availability of suitable nesting habitat and the colonial nature of terns, breeding 

least terns tend to concentrate in high numbers, making them especially vulnerable to predators.

Avian predator management on Alameda maintains high least tern breeding success and is 

conducted on adjacent properties in cooperation with the Navy. Avian predators at Alameda 

include northern harriers, red-tailed hawk, common ravens, American crows, American kestrels, 

peregrine falcons, logger-headed shrikes, barn owls, great horned owls, and burrowing owls.

Discouraging avian predators from the area by preventative measures is the first option. 

Tarmac areas are maintained free of vegetation to discourage predators, to provide least tern 

roosting habitat, and to maintain unobstructed views needed for predator detection by least

terns. Adjacent areas are mowed to maintain vegetation height below six inches during least

tern nesting season in order to attract avian predators away from the least tern colony. 

Power poles and other structures (e.g. fences, buildings, poles) have been removed or 

modified that provide predator perches. Buildings and other potential habitat are inspected for 

nesting predators before least tern nesting season and predator nests that are close to the 

colony are removed. The use of outside lighting is restricted near the colony site to prevent 

attraction of predators to the area at night. 

Nonlethal methods are used whenever possible, including box-type traps, soft-catch padded 

leghold traps, hazing, egg oiling, Bal-chatri traps, pole traps, Dho gazo nets, bow nets, pigeon 

harnesses, effigies, and lures. Avian predators that pose an immediate threat to the least tern 

colony and cannot be humanely live-trapped will be taken by humane lethal methods, which 

may involve shooting or euthanasia. The decision to lethally remove an avian predator is

determined on a case-by-case basis, after taking into account the degree of threat, breeding 

phase of the terns, type of predator, resident versus migratory status of predator, and 

professional knowledge of the situation and species involved. 

Peregrine falcons that depredate the tern colony or cause impacts to tern productivity are hazed 

and/or removed according to the special protocols developed by the Santa Cruz Predatory Bird 

Research Group. American kestrels are live-trapped and removed. Northern harriers and redtailed hawks may be hazed, live-trapped and removed, lethally removed, have their eggs oiled, 
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or young relocated where their proximity is determined not to threaten the colony. Active 

burrowing owl burrows are monitored for signs of least tern predation. 

Any gull nests on the least tern colony site are removed. Individual gulls that become 

predators on terns or threaten the colony are lethally removed. Avian predator presence and 

activities are monitored prior to and during the nesting season (USFWS 1999). In 2010, the 

Service and SFBBO added artificial eggs to California gull nests on paved areas adjacent to 

the least tern colony to reduce clutch size. However, this colony was unsuccessful due to 

western gull predation, thus the results of this experiment is unknown. Plans to oil California 

gull eggs in 2011 were postponed as the colony failed to return to nest. 

Eden Landing Ecological Reserve (California Dept. of Fish and Game)

CDFG conducts predator management to reduce predation of the federally listed California 

clapper rail, western snowy plover, salt marsh harvest mouse, and species of concern in the Eden 

Landing Ecological Reserve (which is a part of the South Bay Salt Pond Restoration Project).

As part of their predator management, avian predators such as corvids and other predators 

determined necessary are removed by trapping, capture or shooting. Avian predator presence and 

activities are monitored prior to and during the nesting season by SFBBO. Landscape changes 

have been made to reduce the number of perches in the area as well as the placement of oyster 

shells on the pond bottoms to provide camouflage for snowy plover nests and chicks (RobinsonNilsen et al. 2009). 

3) AVIAN PREDATOR MANAGEMENT PLAN 

In order to increase reproductive success of listed species, the Refuge, in cooperation with the 

SFBBO and USDA Wildlife Services, propose an avian predator removal plan on the Refuge 

and lands adjacent to the Refuge beginning in 2013. The purpose of the plan is to document 

the effects of avian predator removals and deterrents on the nesting success of snowy 

plovers, least terns and other nesting species, and to assess the efficacy of removing avian

predators in the region. 

Avian predator management may occur year-round but will be concentrated immediately prior 

to and during the breeding season (March–September). Management strategies included in this 

plan will be implemented within the Refuge, and with the consent of the appropriate agency or 

landowner, on adjacent public and private properties. Under the avian predator management 

plan, the Refuge and its cooperators will continue to monitor snowy plovers and least terns to 

determine reproductive success rates as well as population size. Clapper rail numbers will 

continue to be assessed per standardized methods (see http://www.prbo.org/cms/663#clra). In 

addition, avian predators on the Refuge and adjacent lands will be monitored; information 

recorded will include species observed and their behavior and habits.

Only permitted and authorized agencies or individuals will implement predator management 

actions; all activities will be conducted in a humane manner, under the direction of the Refuge 

and in close coordination with SFBBO or other qualified organization. Management actions 
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will be carried out by USDA Wildlife Services, or other such qualified agencies or individuals. 

Refuge personnel and their cooperators may assist with efforts. Non-lethal techniques will be 

used whenever possible, including hazing, trap and release, and the use of effigies and emetics. 

There is a long history of trapping raptors safely and releasing them for research and 

rehabilitation around the world. We only use traps that have been approved in a Migratory 

Bird permit issued by the Migratory Bird Division of the Service. Biologists will observe any 

birds captured by trapping methods prior to release to insure the bird is healthy and 

uninjured. All birds are banded prior to release to monitor birds in case they return. 

The decision to lethally remove an avian predator will be determined on a case-by-case

basis, and will be based on the degree of threat, the breeding phase of the snowy plovers and

least terns, professional judgment of the situation, and knowledge regarding the species 

involved. Lethal methods may include trapping, euthanasia and shooting, and will be 

implemented as humanely and selectively as possible. Shooting will be conducted only by 

personnel trained and certified in firearm safety. In order to avoid human safety hazards, 

shooting will take place only when members of the public are not in the area. 

Control of mammalian predators will continue as described in Appendix I. 

The Refuge and its cooperators will continue to explore avian predator management 

alternatives that will protect the snowy plover, clapper rail, harvest mouse and least tern while 

minimizing disturbance to native avian predators. There is particular interest in developing 

management techniques that would permit problem predators to remain on the Refuge but 

would prevent them from hunting in nesting areas, such as the use of larger oyster shell plots to 

provide camouflage to nesting snowy plovers. Additional measures to discourage avian 

predator use of listed species habitats will include continuing to attach metal spikes to signs on 

the Refuge and removing abandoned posts on the Refuge, both of which serve as perching 

sites. Other potential plans include creating snowy plover and least tern nesting habitat farther 

from nesting habitat of northern harriers, and the removal of nests (active and inactive) from 

power towers to preclude corvid and red-tailed hawks from nesting. To reduce the suitability of 

nesting substrate for California gulls, the Refuge may attempt to smooth existing levees and 

remove vegetation and woody debris in target areas (Blokpoel and Tessier 1992). The Refuge may 

also explore the use of emetics to reduce the appeal of bird eggs to corvids, raptors and gulls in a 

method known as conditioned taste aversion (Avery et al. 1995).

Our overall tiered approach to working with avian predators on endangered and threatened species is 

outlined below. 

1. Remove perches from area before nesting season begins. Modify levees to preclude 

California gulls from nesting (i.e. by removing boards and smoothing levees). 

2. Remove existing nests on power towers and other structures before raptors and 

ravens begin using them for the season. 

3. Place dummy eggs with an emetic in an effort to condition resident avian predators 

to avoid predation on eggs. 

4. If nesting on towers or other structures has begun, oil eggs to prevent hatching (most 

raptors, excluding sensitive species-see below) or remove nests and eggs (ravens). If 
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chicks are present, place raptor chicks in a wildlife rehabilitation facility; remove 

ravens. 

5. Trap and release adult raptors if individuals are hunting in the nesting area of 

endangered and threatened species. All trapped birds will be banded to determine if 

and when they return to the area. 

6. Lethally remove adults if all other methods fail to protect endangered and threatened 

species. 

4) GOALS OF THE AVIAN PREDATOR MANAGEMENT PLAN

The goals of the avian predator management plan are to: 

o Maintain a 3-year average population of 125 breeding snowy plovers on the Refuge. 

This number will be included in the management of 250 snowy plovers as part of the 

South Bay Salt Pond Restoration Project, in addition to the snowy plovers that use the 

Eden Landing Ecological Reserve. 

o Maintain a 3-year average productivity of at least 1.0 fledged chick per snowy 

plover male. 

o Establish a colony of 20 breeding least tern adults on at least one colony on the 

Refuge, after restoration of islands in ponds of the South Bay Salt Pond 

Restoration Project.

o Maintain a 3-year average productivity of at least 1.0 fledged chick per least tern 

breeding pair.

o Thru predator monitoring, reduce predation pressure on California clapper rails to a 

level below at which it negatively affects long-term population persistence for 5 

consecutive years.

o Reduce individual problem avian predators in localized areas. Problem predators are

defined as individuals of species known to prey on listed species which are exhibiting 

hunting behavior in nesting areas.

The plan is being developed to support the Refuge’s management objective of recovering 

and maintaining a stable snowy plover population; the numerical targets reflect the best 

available data on the numbers of individuals necessary for a self-sustaining snowy plover 

population. With the implementation of the South Bay Salt Pond Restoration Project, the 

Refuge will be creating least tern nesting habitat; this predator management plan would 

protect any least tern colonies that are attempting to establish in these new areas on the 

Refuge (USFWS and CDFG 2007). In addition, depredation of California clapper rail and 

salt marsh harvest mice by avian predators would be reduced, as identified in the Draft 

Marsh Recovery Plan (USFWS 2009). 

The avian predator management plan is designed to operate in concert with existing 

management efforts, including the Eden Landing Ecological Reserve predator management 

plan (CDFG 2000) and efforts by the Navy at Alameda Point (Euing 2007). 
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a) Steps to Achieve Goals

Conduct avian predator management plan

 Determine if removal of avian predators results in increased snowy plover hatch 

and fledge rates.

 Determine if removal of avian predators results in the successful establishment of 

one or more least tern colonies on the Refuge in suitable restored habitat.

 Determine the effects of removing avian predators on the avian predator population 

dynamic in the area where the removal occurred (ie. did another avian predator 

move into the area? If so, did it become an effective predator?).

 Compare before and after predator management plan data to identify a positive 

correlation between avian predator removal and nesting success and/or colony 

establishment. 

SFBBO and the Refuge will monitor snowy plovers to determine hatch and fledge rates, as well 

as population size in the South Bay. SFBBO will also monitor avian predators at these

locations. They will record what avian predator species are using these sites and note their

behavior. Nest monitoring of other nesting species such as American avocets (Recurvirostra 

americana) and Forster’s terns (Sterna forsteri) by SFBBO and USGS will also provide 

information on the efficacy of this plan. 

Criteria to continue with avian predator management:

• An increase in snowy plover hatch rate.

• The establishment of one successful least tern colony in suitable restored habitat. 

• An increase in the hatch rate of adjacent nesting species such as avocets and terns 

in the event that more data are required than can be collected from snowy plovers.

• An increase in numbers of Clapper rails or salt marsh harvest mice in selected 

marshes.

 

b) Monitoring and Coordination

SFBBO is the primary snowy plover and avian predator monitor for Eden Landing Ecological 

Reserve and the Refuge. Christina Donehower is currently the Science Coordinator and is 

responsible for documenting avian predator presence both by direct monitoring and in 

compiling data submitted to SFBBO by volunteers and field crews.

Cheryl Strong, Refuge, is responsible for overseeing the snowy plover project at the Refuge 

and is the main contact for the South Bay Salt Pond Restoration Project. She will be contacted 
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by SFBBO or USDA Wildlife Services regarding predator management efforts on the Refuge. 

Rachel Tertes or Joy Albertson, Refuge biologist and supervisory biologist for the Refuge 

complex, respectively, are secondary contacts. Eric Mruz, the Refuge Manager, can be 

contacted if others are not available.

Brian Popper is wildlife biologist for USDA Wildlife Services and supervises the predator 

removal efforts in the South Bay. John Krause is the wildlife biologist and manager of the 

Eden Landing Ecological Reserve (CDFG). 

c) Species Specific Protocols

Common ravens and American crows

Numbers of American crows and common ravens (corvids) have increased in the San 

Francisco Bay and central California coast over the past several decades, and are positively 

associated with human population density (Marzluff and Angell 2005). Crows and ravens have 

increased in the Bay area (National Audubon Society 2002) and are becoming increasingly 

significant as nest predators on snowy plovers. Along the Pacific Coast, nest predation by 

corvids is a major cause of nest failures (Leibezet and George 2002). Of 63 nests in 2005 in 

Oregon, corvid predation accounted for 22 nest failures, by comparison with 14 failures due to

mammalian or unknown predators (Lauten et al. 2006). In Santa Barbara, American crows 

were the most frequent predator on snowy plover nests and on experimentally placed quail

eggs (Lafferty et al. 2006). At Point Reyes ravens have consistently been the most significant 

nest predator, accounting for 69% of predation events over five years and destroying ~50% of 

all nests (Hickey et al. 1995). In northern California, ravens are the single most significant 

predator limiting snowy plover reproduction (USFWS 2007). Snowy plovers in Point Reyes 

National Seashore declined 32% from 1986-2000 largely because of nest predation by ravens 

(Point Reyes National Seashore, unpub. data). In 2007, a common raven was seen taking a 

snowy plover nest in the South Bay and in 2009, SFBBO filmed a raven depredating a plover 

nest with a nest camera (Robinson et al. 2007 and Robinson-Nilsen et al. 2009). While current 

hazing efforts at local landfills may also help to reduce the number of ravens in the South Bay 

in the long-term, more immediate, targeted action is warranted. Potential methods to control 

corvids include: 

1. Behavioral modification including the use of effigies and distress calls on site to 

deter use of the immediate area. This method was used successfully at the Refuge’s 

Environmental Education Center in 2008 by USDA Wildlife Services to deter crow 

use of a newly-seeded restoration area. Plastic effigies were placed on the site and 

hawk and/or owl calls were played when the crow flocks were present in order to 

get them to mob. After mobbing, crow distress calls were played. The flock of

crows eventually landed in nearby trees and then flew away from the site. While the 

effigies remained on the site, the crows did not return. However, they did return 

once the effigies were removed. 

2. Lethal control of corvids hunting over endangered species habitats, including the 

use of traps and calls as allowable by law.
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3. Removal of nests in PG&E towers or other structures near nesting colonies of 

snowy plovers and least terns or over tidal marsh. This has been done successfully 

in the past in the Eden Landing area in cooperation with USDA Wildlife Services 

and PG&E.

4. Use of conditioned taste aversion to “teach” local corvids that eggs are not 

palatable. This is a non-lethal method that has been used successfully in resident 

populations and may help to reduce the predation pressure on nesting terns and 

plovers. 

California gulls

California gulls are common in the South Bay where three large and various small breeding 

colonies exist. California gull colonies have been growing at an exponential rate in the South 

Bay, from <200 in 1982 to over 49,000 in 2009 (Figure 1; Strong et al. 2004a, RobinsonNilsen et al 2009). At snowy plover nesting sites, observations of California gulls coincided 

with periods of snowy plover chick and nest loss and least tern nest loss in 2008 (Robinson et 

al. 2008). In 2008, the Refuge created nesting habitat by drawing down water in Alviso pond 

A12. While this was successful in creating nesting habitat for American avocets and Forster’s 

terns and at least one snowy plover pair, an influx of California gulls into the pond in June 

reduced nesting success and very few birds nested here the following year (USGS, unpub 

data). Ackerman et al. (2006) documented California gulls as an important predator of 

shorebird eggs in the South Bay, and a major predator of American avocet chicks. Avian 

predators accounted for 46% and mammalian predators for 54% of egg loss in avocets. 

California gulls were responsible for 33% of avian predation and 15% of total nest predation of 

avocets documented by cameras (Ackerman et al. 2006).

California gulls are also important predators of snowy plover nests in the interior at Mono Lake 

(Page et al. 1983). 

During winter surveys of California clapper rails at extreme high tides, biologists have seen 

gulls, mainly California and ring-billed (Larus delawarensis), foraging in salt marshes in 

groups of usually 10–50 individuals and taking rodents, including harvest mice (Joy Albertson 

pers. comm.) adding to the effect of mammalian predation pressure on harvest mice. 

While current hazing efforts at local landfills may help to reduce the number of California gulls 

nesting in the South Bay in the long-term (SFBBO unpub data), more immediate, targeted action 

is required to protect resources in the short term. California gulls pose an increasing threat to 

breeding snowy plovers and other ground-nesting birds because they not only depredate nests

and chicks, but can also take over and trample nesting habitat and crush eggs (see references in 

USFWS 2007). The South Bay Salt Pond Restoration Project displaced California gulls from 

their current largest nesting colony in 2010 (pond A6), adding more displacement pressure on 

other nesting species (Shuford 2008) and subsequently other nearby colonies grew in size. 

Increases in non-breeding California gulls along Coastal California and the first recorded 

breeding of this species on the Farallon National Wildlife Refuge in 2008 add to this concern 
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Nest

over displacement and predation in the region (G. Page, PRBO and G, McChesney, USFWS, 

pers. comm.). 

Figure 1. Numbers of nesting California gulls in the South San Francisco Bay, 1982-2008.

50000

40000

30000

20000

10000

0 

1984 1988 1992 1996 2000 2004 2008

Year 

The goal for the California gull population is to limit the spread of new colonies into 

sensitive areas and remove “specialist” individuals that learn to prey on eggs and nests. 

Potential methods to control California gulls include: 

1. Non-lethal control (using vehicle harassment, use of noise makers, lasers, 

starter pistols, arm waving and shouting, and pyrotechnics where feasible).

2. Locating nests and oiling of eggs where individuals pose the highest threat to 

snowy plovers or least terns and marsh species. The destruction of nests or eggs has 

been used frequently to control gulls by reducing attendance of adults at colonies 

and suppressing breeding success. Treatment of intact eggs (such as by oiling) to 

prevent hatching generally keeps gulls from relaying in the same season if the 

adults continue to incubate. However, this method is resource intensive and may 

not be effective in the long-term (Shuford 2008 and references therein).

3. Lethal removal of “specialist” gulls that hunt over endangered species habitats, 

eating eggs and/or young (Guillemette and Brousseau 2001). Shooting adult gulls 

has had limited success in controlling population numbers, but can be effective 

when it selectively targets specific problem gulls (such as chick- specialists). 

Shooting can also be effective when it focuses on removal of relatively few 

individuals nesting on small islands (Shuford 2008 and references therein).

4. To reduce the suitability of nesting substrate for California gulls in certain areas, 

the Refuge will work to smooth levee surfaces, remove vegetation and woody 
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debris and grade levees to remove irregularities. Early-season use of heavy 

equipment to frequently grade, disk, or drag a boom over flat areas has proven 

effective in preventing ring-billed gulls from building their nests (Blokpoel and 

Tessier 1992). 

5. To reduce the availability of food, the Refuge has been working with local 

landfills. The largest landfill (Newby Island; City of San Jose 2007) is currently 

undertaking intensive gull abatement procedures to limit foraging on the landfill. 

In addition, preliminary efforts to create a covered area where food waste will be 

composted may help to reduce available anthropogenic food waste to gulls at 

Newby Island (R. King, pers. comm.). To be effective overall, it is crucial that 

intensive gull abatement programs be concurrently and continuously operational at 

all of the large landfills located adjacent to the South bay (Tri-Cities and Newby 

Island), and possibly also at landfills in other areas around the Bay. Given the 

gulls’ tendency to habituate to any harassment techniques these will need to be 

varied and monitored over time to ensure their effectiveness (Shuford 2008 and 

references therein).

Red-tailed hawks and northern harriers

Red-tailed hawks nest in power towers and other structures around the South Bay, often adjacent 

to endangered species habitats. USGS nest camera data have found that red-tailed hawks were 

the most frequent nest predators on American avocets and black-necked stilts (Himantopus 

mexicanus) (23% of all predation events on avocets; Ackerman et al 2006). SFBBO has also 

captured red-tailed hawks on camera depredating snowy plover nests (Robinson-Nilsen et al. 

2009). Red-tailed hawks appear to have increased slightly overall in the Bay area according to 

Christmas Bird Count results, particularly in the more urban count circles of the Bay area 

(National Audubon Society 2002). 

Northern harriers are listed as a species of special concern in California, largely due to 

moderately reduced numbers within California caused by habitat loss, and the potential for 

human-induced threats to moderately reduce the population over the next 20 years (Davis 

and Niemela 2008). However, in the Bay area Audubon Christmas Bird Count data from 

1955 to 2002 indicates that numbers of harriers counted per party hour from two local counts 

adjacent to the South Bay plover nesting habitat have increased (the Hayward-Fremont and 

Palo Alto counts; National Audubon Society 2002 summarized in Strong et al. 2004b). In 

addition, Breeding Bird Survey indices show a slight increase in harriers, 1968-2007 (Sauer 

et al. 2008). Although both of these data sets must be interpreted with caution, mammalian 

predator management and wetland restoration in the Bay area may currently be benefiting

this marsh-nesting species.

Development has limited upland habitats where northern harriers can forage. The increase in 

tidal marsh due to the South Bay Salt Pond Restoration Project will increase the amount of 

nesting habitat for northern harriers, but may also increase the tidal marsh prey base for this 

species (such as voles and other mammals that use tidal marsh). Thus as the restoration project 

progresses, northern harriers may rely less on hunting over some endangered species habitats. 
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Potential methods to control red-tailed hawks and northern harriers include: 

1. Non-lethal control (using vehicle harassment, use of noise makers, arm 

waving and shouting, and pyrotechnics where feasible). 

2. Finding of nests and oiling of eggs in selected areas where individuals 

pose the highest threat to endangered species. 

3. Use of conditioned taste aversion to “teach” local raptors that eggs are not 

palatable. This is a non-lethal method that has been used successfully in resident 

populations and may help to reduce the predation pressure on nesting terns and 

plovers. 

4. Removal of nests in PG&E towers near endangered species habitats. 

5. Trap and relocate problem individuals of this species. 

6. Lethal control of individuals hunting over endangered species habitats will be 

considered as a last resort. 

Other species

Peregrine falcons, American kestrels, great-horned owls, barn owls, burrowing owls, loggerhead 

shrike, merlin, cooper’s hawks, and sharp-shinned hawks.

While these species are not considered to be an immediate threat to the persistence of 

endangered species in the Bay area, there is a potential for individuals of these species to 

become specialists that hunt over nesting areas, eating eggs and/or chicks. Individuals of 

these species will be dealt with on a case-by-case basis, and only removed if deemed to be a 

serious threat to a listed species.

We will harass (using vehicle harassment, use of noise makers, arm waving and shouting, and 

pyrotechnics) or lethally remove any predator listed above documented hunting over 

endangered species habitats. Specific protocols for certain special status predators are

outlined below.

Peregrine falcons 

Peregrine falcons have recently been delisted from the U.S. Federal List of Endangered and 

Threatened Wildlife. Due to their current listing as a Federal Bird of Conservation Concern, 

more specific protocols are given for peregrines. In recent years, a family of peregrine falcons 

have nested on the Bay Bridge adjacent to the Alameda Point least tern colony and appear to 

have become specialists that hunt over nesting colonies, eating eggs and/or chicks. However, as 

with all species listed above, individuals will be controlled on a case-by-case basis, and only if 

deemed to be a serious threat to a listed species.

Deter peregrine falcon from nesting area 
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1. USDA Wildlife Services will coordinate observation time to determine if 

peregrine falcon is a regular visitor of the area, and if the bird visits on a schedule. 

2. If peregrine falcon is a first-time or regular visitor, USDA Wildlife Services will use 

a variety of methods as appropriate to harass but not harm peregrine falcon. These

methods may include vehicle harassment, use of noise makers, arm waving and 

shouting, and pyrotechnics. 

Trapping peregrine falcons 

1. Trapping will be used as a last resort. The decision to trap will be made on a case-bycase basis, after evaluating such things as nesting phenology, size of colony, percent 

of terns present, and any additional factors deemed pertinent.

2. SFBBO or another qualified individual may need to observe peregrine falcon 

to determine status, such as breeding adult, fledgling, floating adults.

3. USDA Wildlife Services will have the lead to capture peregrine falcon using 

approved methods, determined by State and Federal permits. SFBBO or another 

qualified individual may assist.

4. USDA Wildlife Services will inform Refuge before trapping attempt and keep them 

informed of progression of trapping. Refuge or other qualified individual will pick 

up trapped peregrine falcon within one day of trapping. 

5. Refuge will take the lead in banding and releasing any bird caught under these protocols. 

SFBBO or another qualified individual may assist with banding, transport and release 

of the peregrine falcon at a distance from the Refuge, such as Goose Lake or Salton 

Sea in California. Landowners’ permission will be obtained for release sites.

6. Peregrine falcons will not be held in captivity for more than 2 days, unless

peregrine falcon requires rehabilitation for injuries, etc. All peregrines will be 

color-banded per regulations before release.

American kestrels

Although considered stable over most of its North American range, American kestrels have 

declined in the Bay area according to Christmas Bird Count data from the past fifty years, 

likely due to increased urbanization and lack of cavity sites for nesting (National Audubon 

Society 2002, Smallwood and Bird 2002).

Because of local concern for this species, the Refuge will relocate, rather than lethally remove 

individual “problem” kestrels on a case-by-case basis. This was done in 2009 and 2012 with a 

male kestrel from the Alameda area; Wildlife Services captured these birds and released them 

out of the area (B. Popper, pers. comm.). If that is not possible, an individual may be lethally 

removed.

Great horned owls 
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This species appears to adapt remarkably well to habitat change as long as nest sites are 

available (Houston et al. 1998). Although not well-covered in these types of surveys, great 

horned owls appear to have declined in the Bay area according to Christmas Bird Count data 

from the past fifty years (National Audubon Society 2002). Great horned owls are suspected 

predators at snowy plover nesting sites in Oregon (Lauten et al. 2008) and are known to predate 

piping plovers, including adults (Murphy et al. 2003). Great horned owl tracks were found next 

to a near-fledgling least tern at Seal Beach in 2009 (C. Collins, pers comm).

Management recommendations in Houston at al. 1998 indicate that individuals that prey on 

endangered species may need to be removed. If individuals are seen perched near the colony 

they will be harassed away from the sites. If owl predation is confirmed, then attempts will be 

made to locate the nesting and/or roosting site of the individual and it will be live-trapped and 

released off site. If that is not possible, it may be lethally removed. 

Burrowing owls

Burrowing owls are listed as a species of special concern in California and as a Federal Bird of 

Conservation Concern due to moderately reduced numbers within the state caused by habitat 

loss and the potential for human-induced threats to greatly reduce the population over the next 

20 years (Gervais et al. 2008). Burrowing owls have increased on Breeding Bird Survey routes 

in California 1968-2006 (Sauer et al. 2008), but this may be largely due to increased numbers in 

agricultural areas especially the Imperial Valley in southern California (Gervais et al. 2008). In 

the Bay area, this species is declining and indeed has been extirpated from some locations 

(Klute et al. 2003 and references listed therein). Because of concern for this species, the Refuge 

will relocate, rather than lethally remove individual “problem” owls on a case by case basis. 

This has worked successfully in the past, where burrowing owls have been removed from the 

Farallons National Wildlife Refuge where they were predating ashy storm-petrel adults and 

chicks (Oceanodroma homochroa, J. Albertson, pers. comm.). Reduction of burrowing owl 

predation is one of the key management recommendations for ashy storm-petrels on the 

Farallons National Wildlife Refuge (Carter et al. 2008). The ashy storm petrel is also designated 

a species of special concern in California and as a Federal Bird of Conservation Concern and is 

recognized by the IUCN as Endangered (Carter et al. 2008, Birdlife International 2004). One 

burrowing owl was also removed from Alameda Point where in 2006, the owl took ~26 least 

tern adults and 15 chicks (Euing 2007). In both cases, burrowing owls were successfully 

relocated.

5) RELEVANCE TO REFUGE PURPOSE AND GOALS 

The Refuge was established in 1974 for its “particular value in carrying out the national 

migratory bird management program,” and one of the Refuge’s three stated goals is to protect 

and enhance endangered species populations and their habitats. Listed species have benefited 

from the management of mammalian predators since 1993, but recent monitoring results suggest 

that management of selected avian predators is also necessary to protect and maintain clapper 

rails, harvest mice and snowy plover breeding populations as well as potential least tern 

nesting colonies that may establish on the Refuge as part of the South Bay Salt Pond 

Restoration Project. The new plan has direct bearing on the Refuge’s ability to fulfill its purpose 

and goals.
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6) JUSTIFICATION 

The avian predator management plan will result in localized reductions in numbers of some 

avian predator species around the Refuge. In most years, an estimated 2–10 individuals per 

species, or fewer will be affected, and impacts on individual birds will be minimized by the use 

of humane and selective techniques. Populations of avian predators using grassland and 

riparian habitats will not be affected.

Without effective predator management, losses of chicks and adults of the Clapper rail, snowy 

plover, least terns and loss of salt marsh harvest mice will continue to threaten the recovery of 

these listed species. With management, including avian predator management, the Refuge 

snowy plover population is expected, at a minimum, to maintain its current size of 

approximately 125 breeding adults. Snowy plover reproductive success is expected to increase 

to 1.0 fledglings per male per year. With the avian predator management plan, we may be able 

to establish at least one least tern colony of 20 adults, with a fledging success rate of 1.0 

fledglings per pair per year in the South Bay on newly created habitat as part of the South Bay 

Salt Pond Restoration Project. Numbers of tidal marsh dependent species should also increase 

due to both predator management and restoration efforts. 

7) COLLABORATORS AND CONTACTS

This plan will be implemented in cooperation with the following agencies and organizations. 

U.S. Fish and Wildlife Service, San Francisco Bay NWR Complex 

Cheryl Strong, 510-557-1271; cheryl_strong@fws.gov 

Joy Albertson, 510-792-0222; joy_albertson@fws.gov 

Rachel Tertes, 510-792-0222; Rachel_tertes@fws.gov

Eric Mruz, 510-792-0222; eric_mruz@fws.gov

U.S. Fish and Wildlife Service, Migratory Bird Office, Region 8 

Jennifer Brown, 916-978-6183, Jennifer_c_brown@fws.gov 

Marie Strassburger, 916-414-6727; marie_strassburger@fws.gov

San Francisco Bay Bird Observatory (SFBBO)

Christina Donehower; 408-946-6548; cdonehower@sfbbo.org

California Department of Fish and Game (CDFG); Eden Landing Ecological Reserve 

John Krause, 415-454-8050; jkrause@dfg.ca.gov

U.S. Department of Agriculture, Wildlife Services (USDA Wildlife Services)

Brian Popper, 510-219-4944; brian.j.popper@aphis.usda.gov

8) REFERENCES
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Marschalek, D.A. 2009. California least tern breeding survey, 2008 season. California

Department of Fish and Game, Wildlife Branch, Nongame Wildlife Program Report, 2009- 

02. Sacramento, CA. 23 pp. + app. 

 

Marzluff, J.M. & Angell, T. 2005. In the Company of Crows and Ravens. Yale University Press, 

New Haven, Connecticut.

Meanley, B. 1985. The marsh hen: A natural history of the clapper rail of the Atlantic coast salt 

marsh. Tidewater Publ., Centreville, MD. 

Murphy, R.K., I.M.G. Michaud, D.R.C. Prescott, J.S. Ivan, B.J. Anderson, and M.L. FrenchPombier. 2003. Predation on Adult Piping Plovers at Predator Exclosure Cages. Waterbirds 

26:150-155. 

National Audubon Society. 2002. The Christmas Bird Count Historical Results [Online]. 
Avian Predator Management Plan

Don Edwards San Francisco Bay NWR, USFWS

J-23 

Available http://www.audubon.org/bird/cbc; accessed 15 November 2004 and 1 September 

2009. 

Page, G. W., L. E. Stenzel, D. W. Winkler, and C. W. Swarth. 1983. Spacing out at Mono Lake: 

Breeding success, nest density and predation in the Snowy Plover. Auk 100:13–24. 

Page, G.W., Hickey, C.M., and L.E. Stenzel. 2000. Western Snowy Plover. In Baylands 

Ecosystem Species and Community Profiles: Life histories and environmental requirements of 

key plants, fish and wildlife. Prepared by the San Francisco Bay Area Wetlands Ecosystem 

Goals Project (P. R. Olofson, Ed.). San Francisco Bay Regional Water Quality Control Board, 

Oakland, California. 

Riensche, D. L. 2007. California Least Tern habitat enhancement and nesting in the East Bay 

Regional Park District, California. Transactions of the Western Section of the Wildlife Society

43:62–71. 

Robinson, C., D. LeFer, J. Albertson, and C. Strong. 2007. Western Snowy Plover Numbers, 

Nesting Success, and Avian Predator Surveys in the San Francisco Bay, 2007. San Francisco 

Bay Bird Observatory report to Don Edwards San Francisco Bay National Wildlife Refuge. 

39 pp. 

Robinson, C., J. Demers, and C. Strong. 2008. Western Snowy Plover Numbers, Nesting 

Success, and Avian Predator Surveys in the San Francisco Bay, 2008. San Francisco Bay Bird 

Observatory report to Don Edwards San Francisco Bay National Wildlife Refuge. 39 pp. 

Robinson-Nilsen, C., J. Demers, and C. Strong. 2009. Western Snowy Plover Numbers, Nesting 

Success, Fledging Success, and Avian Predator Surveys in the San Francisco Bay, 2009. San 

Francisco Bay Bird Observatory report to Don Edwards San Francisco Bay National Wildlife 

Refuge. 34 pp. 

Robinson-Nilsen, C., J. Demers, and C. Strong. 2010. Western Snowy Plover Numbers, Nesting 

Success, Fledging Success, and Avian Predator Surveys in the San Francisco Bay, 2010. San 

Francisco Bay Bird Observatory report to Don Edwards San Francisco Bay National Wildlife 

Refuge. 36 pp. 

 

Sauer, J. R., J. E. Hines, and J. Fallon. 2008. The North American Breeding Bird Survey, Results 

and Analysis 1966 - 2007. Version 5.15.2008. USGS Patuxent Wildlife Research Center, Laurel, 

Maryland. Accessed 4 May 2009. 

Robinson-Nilsen C, C. Schacter, and J. Demers. 2009. Colonial Waterbird Nesting Summary for 

the South San Francisco Bay, 2009. Final report to Don Edwards San Francisco Bay National 

Wildlife Refuge and California Department of Fish and Game. Milpitas, California. 

15 pp. 
Avian Predator Management Plan

Don Edwards San Francisco Bay NWR, USFWS

J-24 

Shuford, W. D. 2008. A Synthesis of Information on California Gulls to Further Attainment of 

Salt Pond Restoration Goals in South San Francisco Bay. A report to the State Coastal 

Conservancy. 46 pp. 

Sibley, C.G. 1955. The responses of salt-marsh birds to extremely high tides. Condor 57(4): 

241-242. 

Smallwood, J. A. and D. M. Bird. 2002. American Kestrel (Falco sparverius), The Birds of North 

America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of 

North America Online: http://bna.birds.cornell.edu/bna/species/602doi:10.2173/bna.602 

Strong, C. M., L. B. Spear, T. P. Ryan, and R. E. Dakin. 2004a. Forster’s Tern, Caspian Tern, 

and California Gull colonies in San Francisco Bay: Habitat use, numbers and trends, 1982– 

2003. Waterbirds 27:411–423. 

Strong, C.M., N.R. Wilson, J.D. Albertson. 2004b. Western Snowy Plover Numbers, Nesting 

Success, and Avian Predator Surveys in the San Francisco Bay, 2004. San Francisco Bay Bird 

Observatory report to Don Edwards San Francisco Bay National Wildlife Refuge. 41 pp. 

Taylor, H.R. 1894. Among the California clapper rail. Nidiologist 1(10-11):153-155. 

Terres, J. 1980. The Audubon Society: Encyclopedia of North America Birds. The Audubon 

Society, NY.

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Portland, OR. 58 pp. 

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Final Environmental Assessment. Newark, California. 52 pages. 

USFWS. 1999. Alameda National Wildlife Refuge Draft Comprehensive Conservation Plan 

http://library.fws.gov/CCPs/alameda_draft.htm

USFWS. 2002. Salinas River National Wildlife Refuge Comprehensive Conservation Plan. 

http://www.fws.gov/cno/refuges/salinas/final_ccp.pdf 

USFWS. 2007. Recovery Plan for the Pacific Coast Population of the Western Snowy Plover 

(Charadrius alexandrinus nivosus). In 2 volumes. Sacramento, California. xiv + 751 pages. 

USFWS and CDFG. 2007. South Bay Salt Ponds Restoration Project Final Environmental 

Impact Statement/Report. Prepared by EDAW, Philip Williams and Associates, Ltd., H. T. 

Harvey & Associates, Brown and Caldwell, and Geomatrix. 

USFWS. 2009. Draft Recovery Plan for Tidal Marsh Ecosystems of Northern and Central 

California. Sacramento, California. xviii + 636 pp. 
Avian Predator Management Plan

Don Edwards San Francisco Bay NWR, USFWS

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9) ACKNOWLEDGEMENTS

Thanks to Dennis Orthmeyer, Brian Popper and Rob Doster for comments on a previous draft of 

this plan. 

Appendix K. Mosquito Management Plan 



Table of Contents

1 Introduction ........................................................................................................................................... 1

1.1 Guiding Principles ........................................................................................................................ 1

2 Coordination with Mosquito and Vector Control Districts ................................................................... 2

3 Regional/Local History of Mosquito Control and Associated Health Threats ..................................... 3

4 Mosquito Biology ................................................................................................................................. 5

4.1 Mosquito Abundance in Refuge Habitats ..................................................................................... 7

5 Health Threat Criteria ........................................................................................................................... 7

6 Monitoring Mosquito Populations ...................................................................................................... 14

6.1 Immature Stage Mosquito Monitoring at the Refuge ................................................................. 14

6.2 Adult Stage Mosquito Monitoring at the Refuge ........................................................................ 14

7 Disease Surveillance Activity ............................................................................................................. 15

8 Treatment Options .............................................................................................................................. 15

8.1 Habitat Enhancement/Restoration ............................................................................................... 16

8.2 Physical Controls ........................................................................................................................ 16

8.3 Biological Controls (B.s. and B.t.i.) ............................................................................................ 17

8.4 Chemical Controls ...................................................................................................................... 21

8.4.1 Larvicide ............................................................................................................................. 21

8.4.2 Pupacide .............................................................................................................................. 22

8.4.3 Adulticide ............................................................................................................................ 23

9 Mosquito Control Treatment Effects .................................................................................................. 23

9.1 Effects on non-target organisms ................................................................................................. 23

9.1.1 Vegetation ........................................................................................................................... 23

9.1.2 Other Invertebrates .............................................................................................................. 24

9.1.3 Fish ...................................................................................................................................... 25

9.1.4 Reptiles and Amphibians .................................................................................................... 25

9.1.5 Birds .................................................................................................................................... 25

9.1.6 Mammals ............................................................................................................................. 26

9.1.7 Threatened and Endangered Species ................................................................................... 27

10 Stipulations and Best Management Practices for Mosquito Monitoring, Surveillance, and Control

 29

APPENDICES

APPENDIX K1. USFWS Interim Guidance for Mosquito Management on National Wildlife 

Refuges

APPENDIX K2. Statement of Best Management Practices and Proposed Monitoring Plan for 

Coastal Region Mosquito and Vector Control Districts 

APPENDIX K3. Effects of Larvacides on Non-Target Organisms

APPENDIX K4. Environmental Effects of Mosquito Control 

APPENDIX K5. B.t.i. 

APPENDIX K6. Methoprene 

APPENDIX K7. Pyrethrins and Pyrethroids

APPENDIX K8. California Mosquito-Borne Virus Surveillance and Response Plan 

APPENDIX K9. Mosquito Management Maps

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1 Introduction

This Plan has been prepared to provide guidance for when and how mosquito-borne virus surveillance 

and response should be implemented on the Don Edwards San Francisco Bay National Wildlife Refuge 

(Refuge). Mosquito management is particularly important on this Refuge because of the proximity of the 

Refuge’s coastal wetlands to urban development. Mosquito management activities occur throughout the 

San Francisco Bay region where a large (over 7 million) human population occurs and a long history of 

mosquito management and documented mosquito-borne disease transmission to humans and wildlife 

exists. The Refuge lies within the jurisdiction of three mosquito abatement districts (MADs): Alameda 

County Mosquito Abatement District, Santa Clara County Vector Control District, and San Mateo 

Mosquito and Vector Control District.

This Plan for the Refuge is one of several step-down management plans to be developed concurrent with 

the Don Edwards San Francisco Bay NWR Comprehensive Conservation Plan (CCP). The CCP provides 

a general discussion of mosquito management on the Refuge, while the Plan provides specific details 

about the mosquito-borne disease management actions proposed for the Refuge. The potential effects on 

the environment of current and future mosquito management activities are addressed in the 

CCP/Environmental Assessment (EA).

The objectives of this plan are to:

• Provide guidelines on the surveillance of mosquitoes and of mosquito-borne viruses on the 

Refuge;

• Provide the Service and MADs with a decision support system for mosquito control activities that 

is consistent with Refuge purposes, the mission and goals of the Refuge System, DOI and Service 

policy, while minimizing public health risk (i.e., mosquito-borne diseases) from Refuge-produced 

or harbored mosquitoes; 

• Outline the roles and responsibilities of stakeholders involved with mosquito-borne virus 

surveillance and response.

1.1 Guiding Principles

Wildlife Conservation 

We allow populations of native mosquito species to exist unimpeded unless they pose a specific human or 

wildlife health threat. We recognize that mosquitoes are a natural component of most wetland 

ecosystems, and that they also may represent a threat to human and wildlife health. 

Compatibility with Refuge Purposes

We only allow mosquito management methods that are appropriate (603 FW 1) and compatible (603 FW 

2) with refuge purpose(s) and the mission of the Refuge System, and that comply with all applicable 

Federal laws, policies, and regulations.

Maintenance of Biological Integrity, Diversity and Environmental Health

We manage mosquitoes in such a way as to meet our statutory obligations to protect the biological 

integrity of refuges while meeting our policy obligations and our social obligation to protect the health 

and well-being of the human communities surrounding refuges. Mosquito management strategies and the 

altered ecological communities that may result can potentially impact the biological integrity, diversity, 

and environmental health of refuge lands that we must maintain under the Administration Act and 601 

FW 3.

Public Health Protection
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Although the fundamental goal of the Refuge System is wildlife conservation, we are committed to 

protecting the public from refuge-based mosquitoes that present a threat to human health. We manage 

such health threats using methods that we determine are appropriate refuge uses and compatible with the 

purpose(s) of the refuge and the mission of the Refuge System. We may make exceptions to this if, under 

the emergency provision of the Administration Act, it is necessary to temporarily suspend, allow, or 

initiate a mosquito management activity in a refuge to protect the health and safety of the public or a fish 

or wildlife population. Because mosquito-borne pathogens in equines and humans represent similar risks 

to public health, appropriate measures we take to protect human health from these diseases would also 

offer similar protection to equines. 

Integrated Pest Management

In partnership with the MADs, we will apply IPM principles to manage mosquito-borne disease threats on 

the Refuge. These principles will serve as the foundation for management strategy development and 

assessment. Ongoing mosquito population and mosquito-borne pathogen monitoring in addition to 

specific action thresholds generate the criteria that implement mosquito management measures. IPM 

employs a variety of mosquito control methods that include habitat management, biological control 

agents, and pesticide application. Best management practices (BMPs) for mosquito control have been 

developed for the Coastal Region Mosquito and Vector Control Districts (2001) and are a significant 

component of this plan (See Appendix K2). These BMPs can be used to lower the production of 

mosquitoes and reduce the need for chemical treatment, without significantly disrupting the ecological 

character, habitat function, or wildlife use of managed wetlands. 

2 Coordination with Mosquito and Vector Control Districts

An annual meeting will be held in November to discuss mosquito activities for the past year and any 

proposed wetland and mosquito management changes or issues for the upcoming season. Annual 

meetings will also allow for any changes that may need to be adopted as a result of changing 

environmental conditions or new treatment methods and pesticides. The following is a list of topics that 

should be covered: 

Service: 

• Staff introduction/changes 

• Acquisition changes

• Pest management policy changes 

• Summary of current wetland restoration and management program

• Proposed enhancement or restoration projects 

• Current wildlife populations & status as related to mosquito management locations 

• Listed species monitoring, including known locations of nests 

• Techniques to minimize disturbance to wildlife 

MADs: 

• Staff introduction/changes 

• Mosquito policy changes 

• Renewal of Special Use Permits

• Revisions to any Memorandums of Understanding or Agreements 

• Summary and map of mosquito production areas 

• Summary and map of mosquito monitoring and management activities, including method of 

access and mileage/feet of tidal marsh accessed 

• Updated Pesticide Use Proposals (PUPs) and label information 

• Submittal and/or review of Pesticide Use Reports (PURs) of the previous year

• Proposed changes to mosquito management program 
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• Current mosquito and disease information 

• Listed species monitoring, surveillance, and report of sightings 

• Techniques used to minimize disturbance to wildlife 

• Results of relevant mosquito research projects

• Proposed mosquito reduction projects 

The Refuge staff coordinates annually with local MADs to allow the monitoring and, if necessary, control 

of mosquitoes on the Refuge to minimize public health risks from mosquito-borne diseases . Wetland 

management BMPs for proactive mosquito control are regularly used by the Refuge. These include, but 

are not limited to, water management techniques, and maintenance and improvement of water control 

structures. Refuge staff coordinates closely with the MADs on timing of irrigations, flood-up schedules, 

and communication of any problems with unplanned flooding. 

In addition, PUPs developed cooperatively with the MADs, are reviewed by Service IPM specialists, and 

if approved, are issued along with a SUP that identifies conditions under which specific mosquito control 

activities can be conducted. Conditions specified in these documents include: products approved for use; 

application methods, rates, and timing; maximum number of applications allowed per season; measures to 

be taken to avoid sensitive areas; and annual reporting requirements for MADs. PUPs will be generated 

annually; SUPs will be generated biennially. PURs must be submitted by the MADs by the end of each 

calendar year to report type, amount, and location of pesticide used on the Refuge. 

3 Regional/Local History of Mosquito Control and Associated Health 

Threats

Due to its climate and topography, California has a history of serious arboviral disease problems. Historic 

documents concerning mosquitoes and mosquito-borne diseases in California focus on the presence of 

malaria and large nuisance populations of mosquitoes affecting the first immigrants and settlers. The 

most severe mosquito disease and pest outbreaks of the 1800s occurred in the Central Valley of California 

(Fontaine 1980). 

When California became one of the first states to launch mosquito control in early 1900s, the project was 

not for disease control, but to abate severe nuisance infestations of salt-marsh mosquitoes in the San 

Francisco Bay Area that were adversely affecting development (Fontaine 1980, Peters 1966). During this 

period, environments characterized by native estuarine and riverine systems were rapidly being altered or 

replaced by new irrigation systems, mining operations, and diked tidelands for agriculture (e.g., transition 

from tidal to seasonally flooded and shallow open water environments). These alterations expanded 

existing habitat for mosquitoes and likely altered mosquito population diversity and abundance in the 

region. The first campaigns to control mosquitoes were funded mainly by subscriptions from private 

individuals (Gray and Fontaine 1957, Fontaine 1980). Support for the creation of governmental control 

units and expenditure of public funds was not supported by public health agencies but came from real 

estate developers who were losing profits due to a perceived “excessive prevalence” of salt marsh 

mosquitoes (Gray and Fontaine 1957). In 1915, the real estate lobby introduced a bill to provide for the 

organization of mosquito abatement districts in the State Legislature. The law passed and was 

incorporated into the State Health and Safety Code that serves as the legal authority under which most 

mosquito control work is performed (Gray and Fontaine 1957). The first district organized was the Marin 

County District in December 1915. Other Bay area districts formed after 1920 (Gray and Fontaine 1957). 

Since establishment in 1915 and through the 1940s, the MADs of the San Francisco Bay region relied 

heavily upon physical controls to manage mosquitoes (Gray and Fontaine 1957, Woodworth 1915). 

Controls included ditching, levee building, and the installation of culverts. The Districts owned and 

rented heavy equipment and employed engineers, inspectors and laborers to accomplish their mission 
K-4 

(Alameda Co. MAD 1992). Chemical controls (distillate and crude oils) were also used during this 

period to prevent larvae and pupae from reaching adult stages (Woodworth 1915). 

During World War II, a fear of the return of large numbers of military personnel infected with mosquitoborne diseases stimulated the legislature in 1945 to provide special funds for mosquito control by the 

State Department of Public Health (Gray and Fontaine 1957). The program was oriented toward better 

control of pest mosquitoes, and of the vector of viral encephalitis, Culex tarsalis (Gray and Fontaine 

1957). The traditional pre-World War II methods were largely suspended and mosquito control 

programs became increasingly dependent on routine spraying of (dichlorodiphenyltrichloroethane) DDT 

(Fontaine 1980). By 1954, the major pest and vector mosquitoes developed a resistance to DDT and led 

to use of organophosphorous compounds (Fontaine 1980). During the late 1960s and 1970s, the Bay 

Area Districts began to implement Integrated Pest Management programs to counter-attack the 

development of insecticide resistance by some species of mosquitoes, and to address the environmental 

concerns of pesticides (Alameda Co. MAD 1992). District employees began to select control methods 

appropriate to each source of mosquitoes and the use of mosquito-eating fish became an integral part of 

mosquito control programs (Alameda Co. MAD 1992). 

By the mid-1980s most districts in the Bay area had replaced the majority of chemical controls materials 

with biorational methods that are relatively non-toxic and have fewer ecological side-effects. Principle 

biorational materials used today are Bacillus thuringiensis var. israelensis (B.t.i.), Bacillus sphaericus

(B.s.), and methoprene which is an insect growth regulator. 

Today, at least 18 known arboviruses have been recovered in California. Western equine (WEE) and St. 

Louis encephalitis (SLE) viruses are endemic and continue to represent significant public health threats 

throughout the state. Making the situation worse, a new cast of emerging pathogens has entered the 

California and national scene. Leading that list are important international arboviral diseases such as 

dengue, Venezuelan equine encephalitis, and West Nile virus (WNV). WEE tends to be most serious in 

very young children, whereas elderly people are most at risk to SLE and WNV (CA Dept. of Health 

Services 2003). WEE and WNV can cause serious diseases in horses and emus, and WNV kills a wide 

variety of endemic and imported birds. The top 4 species of birds affected by WNV are, American 

Crows, Western Scrub-Jays, Yellow-billed Magpies, and Steller’s Jays. 

From 1990 through 1999, 82 cases of arbovirus diseases were diagnosed in California and comprised 

<1% of patients hospitalized with acute encephalitis (Trevejo 2004). WEE and SLE viruses, both of 

which can be transmitted by mosquitoes, are important causes of encephalitis in California residents. 

Since the 1960s, incidence of WEE and SLE has decreased significantly in California although sporadic 

cases are still reported (Trevejo 2004). 

Since introduction to North America in 1999, WNV has now reached California, and is transmitted to 

humans by infected mosquitoes. Mosquitoes become infected with WNV when they feed on the blood of 

infected birds. The recent spread of the WNV to the Bay Area, and the increased number of vectors 

possible for WNV, has led to increases in mosquito monitoring and control activities by regional MADs 

to ensure public health and safety. California reporting for WNV dates back to 2005. There has been 16 

reported human case of WNV in Santa Clara County since 2005; four reported human cases for Alameda 

County since 2005; and one reported human case of WNV in San Mateo County since 2005 

(http://www.westnile.ca.gov, accessed June 27, 2012). Table 1 summarizes information on WNV cases 

in the three counties where the Refuge is located.
K-5 

Table 1. Cases of West Nile Virus by County, 2005-2011. 

County Human cases Dead birds Mosquito 

samples

Sentinel 

chickens

Squirrels

Alameda

2011 - - - - 1

2010 1 1 - - -

2009 - 10 1 - -

2008 1 12 1 - 1

2007 - 19 1 - 1

2006 1 41 9 - 2

2005 1 48 8 - n/a

San Mateo

2011 - - - - -

2010 - - - - 6

2009 - 1 - - -

2008 - 2 - - -

2007 - 2 - - 1

2006 - 7 - - 2

2005 1 10 - - n/a

Santa Clara

2011 1 36 16 - 1

2010 - 32 10 - 6

2009 - 14 14 - 2

2008 1 13 1 - -

2007 4 83 10 - 6

2006 5 224 9 1 2

2005 5 144 3 - n/a

Source: http://westnile.ca.gov/, accessed on 6/27/12 

4 Mosquito Biology

Mosquitoes are dipteran insects with aquatic immature stages and an aerial adult stage. They have four 

aquatic larval stages (instars) plus an aquatic pupal stage. The adult emerges from the pupal stage onto 

the surface of the water, expands its wings, hardens its exoskeleton, and flies off. Depending on seasonal 

and environmental conditions and the particular mosquito species involved, it generally takes from four 

days to up to a month for a mosquito to complete its life from developed egg to early adult stage (CDPH 

2008). In general, as ambient temperature increases, the number of days required from hatching to 

emergence as an adult decreases. Although some species of mosquitoes (e.g., Culex tarsalis, Aedes 

squamiger), are capable of long flights from the aquatic habitat, the mosquito problem created by a 

wetland will generally be inversely proportional to its distance from concentrations of human and 

domestic animal populations.

There are six species of mosquitoes frequently found breeding on the Refuge: Aedes dorsalis, Aedes 

squamiger, Aedes washinoi, Culex erythrothorax, Culex tarsalis, and Culiseta inornata. Due to the 

variety of breeding habits of these species, mosquito larvae can be found year round on the Refuge. 

Aedes mosquitoes are floodwater species. They lay their eggs singly on dry vegetation, and they hatch 

after a flooding episode. Culex and Culiseta mosquitoes require standing water on which to deposit their 

eggs. Figure 1 is a depiction of a typical salt marsh and the habitat types where immature marsh mosquito 

species are found. Many of the species’ habitats overlap. 
K-6 

Figure 1. Marsh Mosquito Habitat Types. 

Aedes squamiger (Winter salt marsh mosquito). Larvae develop in rainwater that collects in salt marsh 

depressions between November and March. Eggs are laid in these depressions during the spring. They 

hatch in winter when flooded by rainwater. Larvae develop over the winter to emerge in mid-March. 

Adults are relatively long-lived, sometimes lasting through May or June. Females disperse inland along 

streams and then spread out into surrounding residential neighborhoods to seek a blood meal. These 

mosquitoes can fly 20 miles or more from the larval source. Most of the control effort occurs during the 

winter. It is the only species found on the Refuge that produces a single generation per year. Control is 

by physical modifications to the marshes and by spraying with biologically-based larvicides. They are 

aggressive biters and known carriers of both WNV and California Group Encephalitis viruses.

Aedes dorsalis (Summer salt marsh mosquito). This species is found year round in tidal salt marsh 

areas but is most common after summer high tides. This species uses many of the same marsh habitats as 

A. squamiger, as well as intertidal marshes. Numerous generations can be produced from flooding tides 

between April and October. The eggs are laid in the marsh and hatch when the marsh is filled by high 

tides. Control is by application of biorationals and physical modifications. Adults are very aggressive, 

fly moderate distances, and are capable of producing very high numbers of service requests near marsh 

areas, especially in large grassy areas such as schools and parks. A. dorsalis females are aggressive biters 

capable of dispersing 15 miles or more from their larval source. They can harbor WNV, WEE, and SLE

as well as California Group Encephalitis viruses. 

Aedes washinoi (Woodland pond mosquito)

This mosquito is produced in depressions that fill with water. Eggs are laid on the mud and organic 

material along the edges of receding water in these areas. Adults are generally present in the early spring, 

are very aggressive, and may be found in large numbers. Most of the control effort on this species is by 

use of biorational materials. Although not considered a marsh mosquito, this species is found near 

marshy areas that flood with rainwater. This species is found mostly near the entrance to the visitor’s 

center at the Refuge.

Culex erythrothorax (Tule mosquito)

Larvae usually live in permanent or semi-permanent sources of water which contain large stands of 

cattails or tules. They are extremely sensitive to vibration and dive quickly so detecting them when they 

are immature is difficult. Adult females feed equally on mammals and birds; they will feed on humans in 
K-7 

the shade. Culex erythrothorax can become a major pest to human and other vertebrates that reside near 

their breeding habitats. This mosquito has been found naturally infected with SLE, WEE, and WNV. 

Although immature individuals have never been collected on the Refuge, adults have been collected in 

carbon dioxide-baited traps.

Culex tarsalis (Encephalitis mosquito). This species breeds in almost any type of flooded pool, 

including salt marsh, if the salt content does not exceed 1.0 percent. Multiple generations are produced 

between February and November in rainwater impounds in pickleweed marsh. This mosquito is an 

efficient vector of WNV, WEE and SLE (California Mosquito-Borne Virus Surveillance and Response 

Plan 2011, Appendix K8). These viruses are maintained in wild bird populations. Breeding of this 

species in areas occupied by large populations of migratory birds near dense human population centers is 

of particular concern to public health. 

Culiseta inornata (Winter marsh mosquito). This species rests during the summer and becomes active 

in the fall after the first rains. This species breeds in almost any ground depression, but seems to excel in 

habitats favored by A. squamiger. Females lay eggs on the surface of rain-filled ponds in the fall, and 

many generations can be produced in a single season (October through May). This mosquito bites at dusk 

in the fall and spring and is moderately aggressive, quite large, and may reach very high numbers. 

Culiseta inornata are very noticeable to the public because of their size and activity. Adults tend to stay 

within 1 – 2 miles of their larval source. This species is generally found close to temporary fresh water 

sources. Most of the control is by using biorational materials. They are capable of transmitting WNV

and feed preferentially on mammals. 

4.1 Mosquito Abundance in Refuge Habitats

Mosquito abundance on the Refuge is generally in and around brackish, standing water bodies with a 

range of plant diversity that are exposed to different levels of tidal waters. Characteristics of elevated 

mosquito production areas include shallow swales within the marsh plain (4-6 feet NGVD29) that hold 

water for extended periods following high tides and precipitation, and a lack of tidal channels that permit 

drainage. These characteristics, in combination with emergent vegetation, encourage mosquito 

production. Sedimentation has reduced the efficacy and longevity of historic ditching efforts (by MADs) 

to increase tidal flushing in some areas. In addition to the above characteristics, these sites generally 

exhibit poor habitat quality for estuarine wildlife and plants, including threatened and endangered species, 

relative to other tidal marsh areas of the Refuge. 

Mosquitoes are also in areas of the Refuge that are not exposed to tides (e.g., vernal pools), but where 

rainwater provides the habitat for larval development. Immature mosquitoes are not uniformly 

distributed, but are aggregated in clumps or pockets protected from predators. Mosquito production 

occurs in areas where standing water accumulates in depressions among the vegetation. During the 

winter months and into the early spring a combination of rainwater and tidal influence create an 

accumulation of water in upland areas. In the summer, high tides cause flooding in areas where drainage 

is inadequate. See the above graphic “Stylized Salt Marsh in Alameda County.”

District mosquito control technicians focus on sampling mosquitoes in these areas by dipping the 

shoreline vegetation and progressing outward to isolated tufts of emergent vegetation in standing water. 

Water that accumulates in cracks on the floor of old salt pans also provides a sheltered environment for 

larvae.

5 Threat Criteria

This section presents the process to be followed in making determinations regarding to what extent 

mosquito management should occur on the Refuge and how and when specific mosquito management 
K-8 

activities should be undertaken. Effective mosquito control results in the removal of a high percentage of 

one or more target species, although usually temporarily. Such control efforts can also result in direct and 

indirect adverse effects to one or more non-target species. The altered ecological communities that may 

result from mosquito control activities can impact biological integrity and diversity through disruptions in 

food webs and other ecological functions. Therefore, the decision to control mosquitoes and at what level 

requires careful evaluation. 

The potential threat posed by the presence of WNV and/or other pathogens in mosquitoes within the 

Refuge must be assessed. These health threat determinations will be based on the criteria depicted in 

Table 2 and a phased approach will be used to treat mosquitoes occurring on the Refuge. Threat level 

determinations will include the risk rating described in the California Mosquito-Borne Virus Surveillance 

and Response Plan (Response Plan) (Appendix K8). 

The Response Plan was developed to provide a semi-quantitative measure of virus transmission risk that 

could be used by local agencies to plan and modulate mosquito risk reduction measures. Various risk 

factors, including ecological dynamics, are rated on a scale of 1 to 5, based on their average status over at 

least five non-epidemic years in a specific region. A value of 5 represents conditions indicative of a high 

risk of human infection with a mosquito-borne virus. 

Table 1 in the Response Plan provides worksheets for assessing risk of WEE, SLE, and WNV 

transmission. Average risk values for a normal season range from 1.0 to 2.5, emergency planning from 

2.6 to 4.0, and epidemic conditions from 4.1 to 5.0. The Risk Assessment prepared by the MADs will be 

used in conjunction with the Health Threat criteria listed in Table 2 to assess treatment needs. Threat 

levels one through four correspond to a normal season with a value between 1.0 and 2.5. Threat Level 5 

corresponds to emergency planning and would have a risk rating between 2.6 and 4.0. 

As proposed, mosquito management on the Refuge will be consistent with an integrated pest management 

(IPM) approach to mosquito control. IPM is a sustainable approach to managing pests by combining 

biological, cultural, physical, and chemical tools in a way that minimizes economic, health, and 

environmental risks. When practical, the approach may include compatible actions that reduce mosquito 

production and do not involve pesticides. 

In some locations, mosquito production may be influenced by current site conditions. For example, 

historical human activities along the upper edges of a salt marsh complex may have altered the natural 

drainage patterns, creating areas where ponding now occurs during higher spring tides or after a 

significant rain event. In these situations, an integrated approach to mosquito management involving 

habitat manipulation and/or restoration and enhancement could provide benefits related to reducing the 

area available on the refuge for mosquito production. 

Restoration of wetlands to tidal influence may not result in complete control of mosquito populations, 

resulting in the need for mosquito monitoring, disease surveillance, and the potential application of 

pesticides. Application of pesticides would be approved based on the phased approach outlined below. 

The principle goal of a phased approach to mosquito management is to minimize adverse effects to 

Refuge resources while addressing legitimate human and wildlife health concerns, as well as complying 

with Service regulations and policies. The Plan proposes a phased-response to mosquito management and 

control that is consistent with Service and California guidelines. Because the occurrence of arboviruses 

and other human health issues resulting from mosquitoes vary by Refuge location, the phases of mosquito 

management to be implemented on the Refuge would vary through time. 

Except during high risk disease situations where there is a need to take action quickly, full consideration 

must be given to the integrity of non-target populations and communities when considering compatible 
K-9 

habitat management and pesticide uses for mosquito control. Mosquito control procedures must also be 

consistent with IPM strategies and existing pest management policies of the Department of the Interior 

and the Service (517 DM 1, 569 FW 1, and 30 AM 12). Even during high risk disease situations, proven 

mosquito-borne disease presence on or within flight range of the Refuge is required to warrant substantial 

intervention (e.g., the use of adulticides). Additionally, appropriate pesticide review (i.e., approval of the 

use of a pesticide through the PUPs process) must be completed, although this review will be expedited 

so that any necessary intervention measures will not be delayed. Such pesticide treatments for adult 

mosquito population control on Refuge lands will only be allowed when local, current data have been 

collected and indicate that refuge-based mosquito populations are contributing to a human or wildlife 

mosquito-borne disease health threat.

The proposed phased approach to mosquito management is dependent upon continued communication 

and cooperation among the Service, the local mosquito abatement districts, and the appropriate state and 

local public health agencies. As described in Chapter 2, communication is essential to the success of the 

Plan. Therefore: 

• The districts will coordinate all activities with the Refuge Manager.

• The districts will meet annually with Refuge staff to review the activities and results of the 

previous year and discuss the monitoring and possible control plans for the upcoming year. 

• A Refuge SUP will be prepared biennially for the districts that will include all appropriate BMPs 

presented in the Mosquito Management Plan, as well as special conditions related to location, 

timing, extent of mosquito monitoring, and stipulations for carrying out mosquito control, should 

it be warranted, under the guidance of the approved PUPs. 

• Prior to each year’s mosquito breeding season, the districts field staff will meet with Refuge staff 

to go over field protocols for avoidance and minimization of take to any trust resources including 

migratory birds and listed species and their habitats.

• At the beginning of the mosquito breeding season, the districts will provide a general schedule of 

seasonal activities and refuge locations to the Refuge Manager. If activities are proposed that 

significantly differ from the schedule, particularly accessing endangered species habitat, we 

request that the districts notify the Refuge Manager at least two business days prior to accessing 

the Refuge. 

• Access to sensitive wildlife areas (i.e., endangered species habitat) is preferred by foot; use of 

ATV or ARGOs will be coordinated with the Refuge staff prior to entry in these areas.

 

Although the districts would have the lead for monitoring, disease surveillance, and pesticide 

applications, evaluation of monitoring data and approval for each management action would be the 

responsibility of the Refuge. This approach, which requires the Refuge Manager to oversee the mosquito 

management program, process PUPs, prepare biennial SUPs, and comply with legal mandates (e.g., 

NEPA, Refuge Improvement Act) and Service policies (e.g., Compatibility, Appropriate Use), is 

necessary to ensure that the conditions for compatibility are met and the program is implemented so as to 

avoid or minimize effects on Refuge resources.

Because of the nature of mosquito-borne diseases, as well as the limited information available regarding 

the effects of these diseases on wildlife of the Refuge, this approach focuses on the implementation of a 

mosquito management program to protect human health. The table below describes the phased response 

thresholds that the San Francisco Bay NWR Complex has adopted for its refuges, based on guidance from 

the Service’s Interim Guidance for Mosquito Management on National Wildlife Refuges (2005). Further 

detail on each phase and individual district threshold requirements are described below and in Table 3. 
K-10 

Table 2. Health Threat Criteria for Mosquito Management on the Refuge. 

Threat 

Level

Condition Response

1 No documented existing health threat1.

Mosquito management issues have not been 

reported or identified by the appropriate public 

health authority4 or vector control district(s).

Monitoring and surveillance of areas surrounding 

the Refuge to inform management actions on the 

Refuge. Remove/manage artificial breeding sites 

such as tires, tanks, or similar debris/containers. 

Consult with MADs when planning wetland 

enhancement or restoration projects. 

2 Potential human or wildlife (incl. threatened and 

endangered species) health threat1 (presence of 

vector spp., historical health threat, etc.), as 

documented by appropriate public health 

authority(ies) or vector control district(s).

Response as in threat level 1, plus: allow 

compatible monitoring and disease surveillance. 

Consider compatible non-pesticide management 

options to reduce the potential for above-normal 

mosquito production (e.g., restore/enhance tidal 

marsh hydrology).

3 Mosquito larvae threshold exceeded for human 

and/or wildlife health2 on the Refuge as 

determined by standardized monitoring. 

Documented potential human or wildlife health 

threat (historic health threat, presence of vector 

species).

Response as in threat level 2, plus: allow 

compatible site-specific application of larvicide in 

areas with above average mosquito populations, as 

determined by monitoring. Conduct post larvicide 

monitoring to determine efficacy.

4 Mosquito larvae have begun to reach last instar 

stages or pupate reducing the efficacy of 

larvicides. Mosquito larval and pupal population 

thresholds2 exceeded on the Refuge. Mosquitoes 

produced by the Refuge pose a health threat1,4 as 

determined by the appropriate public health 

authority(s).

Response as in threat level 3, plus: if appropriate, 

increase the intensity and frequency of larvicides, 

allow compatible site-specific use of pupacides in 

areas with above average mosquito populations, 

determined through monitoring to be beyond 

control with larvicides. Increase monitoring and 

disease surveillance. Conduct post larvicide and 

pupacide monitoring to determine efficacy.

5 Mosquito-borne disease is documented on the 

Refuge or within flight range of vector mosquitoes

on the Refuge. Risk Assessment rating is at least 

2.63

. High risk for mosquito-borne disease 

(imminent risk of serious human disease or death, 

or an imminent risk of serious disease or death to 

populations of wildlife) within communities 

surrounding the Refuge has been documented by 

the appropriate public health authority4.

Response as in threat level 4, plus: Consider sitespecific adulticiding in areas with above average 

mosquito populations as determined by 

monitoring. Conduct post adulticide monitoring 

to determine efficacy.

1

An adverse impact to the health of human or wildlife populations from mosquito-borne disease identified and documented by 

Federal, State, and/or local public health authorities. Health threats are locally derived and are based on the presence of endemic 

or enzootic mosquito-borne diseases, including the historical incidence of disease, and the presence and abundance of vector 

mosquitoes. Health threat levels are based on current monitoring of vectors and mosquito-borne pathogens. 2

See Table 3. 3

Risk Assessment is calculated by considering several factors as determined by California Mosquito-Borne Virus Surveillance 

and Response Plan (Appendix K8). 4

Appropriate public health authority(s) is a Federal, State, or local public health or wildlife management authority with 

jurisdiction inclusive of Refuge boundaries and/or neighboring public health authorities. 

Threat Level 1

In Threat Level 1, an existing health threat has not been identified and mosquito management issues have 

not been reported or identified by the appropriate public health authority or MADs. To avoid any 

possible mosquito management issues, artificial mosquito breeding habitat throughout the Refuge, such as 

tires, open containers, and other equipment or objects that pool water where mosquitoes may breed, 

should be eliminated. 
K-11 

The Refuge would consult with the MADs when wetland enhancement or restoration projects are being 

planned on the Refuge. Consultation would allow Refuge staff and the MADs to identify potential issues 

or opportunities related to mosquito production and management in the future. Monitoring and 

surveillance of mosquito abundance and disease prevalence in areas similar and near the Refuge would be 

conducted by the MADs which would inform the potential for mosquito management needs on the 

Refuge.

Threat Level 2

In Threat Level 2, the Refuge Manager is contacted by the appropriate public health authority(ies) or 

MAD(s) regarding a potential human health threat posed by mosquitoes harbored or produced on the 

Refuge. The Service recognizes human health threats typically include the presence of a vector species 

and historical incidence of mosquito-borne disease in the local area. Some areas may already be 

operating under Threat Level 2 if they have had historical and recurring presence of mosquito-borne 

disease. In response, Refuge staff may allow compatible mosquito population monitoring and disease 

surveillance by the MADs on the Refuge. The initial step to developing a proactive prevention and 

management program for mosquitoes is to determine mosquito species presence and abundance on refuge 

lands, and to identify potential or documented vectors of mosquito-borne diseases that represent a 

potential human health threat. In addition to a species list of mosquitoes, the survey or inventory should 

determine locations on the Refuge being used for breeding and/or resting mosquitoes (harboring). 

Monitoring and surveillance activities should be well-documented and presented to Refuge staff by the 

MADs. 

In order to avoid or minimize the use of pesticides, habitat management practices or wetland 

enhancement/restoration projects that improve wildlife habitat and reduce seasonal abundance of larval 

and adult mosquitoes should be implemented where possible. 

Refuge staff and visitors would be informed of an increased health threat associated with mosquito-borne 

disease activity. Personal protection measures such as wearing mosquito repellant would be 

recommended to staff and visitors.

Threat Level 3

If non-pesticide attempts to reduce mosquito populations are unsuccessful or are not feasible and 

mosquito larvae thresholds have been exceeded, application of larvicides would be considered. Locations 

and types of larvicide treatments would be based on standardized methods as described in Chapter 8. The 

preferred larvicide treatments are biorationals (biological agents) B.t.i. and B.s. because of their limited 

non-target effects (Appendix K3, K4). Other larvicides treatments (e.g., methoprene) would be the 

second preferred method for larvicides control. Post larvicide monitoring would be conducted to 

determine efficacy.

Table 3. Larval and Pupal Mosquito Thresholds for Alameda, Santa Clara, and San Mateo 

Mosquito and Vector Control Districts

Species Common 

Name

Most Common Habitats Distance to 

Populated Area

Larval/Pupal 

Threshold

Notes

Aedes 

dorsalis

Salt marsh 

mosquito

Salt marshes 0 meters - 5 

miles

≥1 per 10 dips High Pest 

Significance

Aedes 

squamiger

Winter salt 

marsh 

mosquito

Salt Marshes, Reclaimed 

Marshes

0 meters - 10 

miles

≥1 per 10 dips High Pest 

Significance

Aedes 

washinoi

Woodland 

pool 

mosquito

Temporary Woodland 

Pools

0 meters - 5 mile ≥1 per 10 dips High Pest 

Significance
K-12 

Culex 

erythrothorax

Tule 

mosquito

Lakes and Ponds 

Associated with Tules

0 - 500 meters ≥1 per dip High Pest 

Significance, 

Vector of 

Encephalitis, 

WNV

Culex 

tarsalis

Encephalitis 

mosquito

Creeks, Marshes, 

Temporary Pools, 

Roadside Ditches, Fresh 

Water

0 meters - 5 

miles

≥1 per 10 dips Moderate Pest 

Significance, 

Vector of 

Encephalitis, 

WNV

Culiseta 

inornata

Winter salt 

marsh 

mosquito

Marshes, Temporary

Pools, Roadside Ditches

0 meters - 1 mile ≥1 per dip High Pest 

Significance

Threat Level 4

If appropriate, the intensity and frequency of larvicides would be increased. Larvicides (B.t.i. or B.s., and 

methoprene) are only effective on mosquitoes during early instar stages (up to the fourth) and do not 

control pupae. If developing mosquitoes have reached the last instar stages or have pupated, then we 

would consider site-specific pupacides in areas with above average mosquito populations (determined 

through monitoring). Because pupacides can negatively affect all invertebrates that require surface air 

(e.g., act as surfactants), the use of these pesticides should be carefully considered. For this reason, 

pupacides (Agnique) would only be used if large numbers of mosquitoes are considered an immediate 

threat to human health and thresholds developed by the appropriate public agency have been exceeded 

(there is active transmission of mosquito-borne disease from Refuge based mosquitoes or within flight 

range of vector mosquito species present on the Refuge). Post larvicide and pupacide monitoring would 

be conducted to determine efficacy and any adverse impacts. 

Threat Level 5

In this threat level, mosquito-borne disease activity has been documented on the Refuge or within flight 

range of vector mosquito species present on the Refuge. A risk of serious mosquito-borne human disease 

or death has been documented by the appropriate public health authority. Disease surveillance determines 

that there is a high risk for mosquito-borne disease within the vicinity of the Refuge. For example, 

pathogen presence in mosquito pool(s), wild birds, sentinel chicken flock(s), horses, or humans has been 

documented within the flight range of vector mosquito species present on the Refuge. These conditions 

would trigger consideration of a more aggressive treatment strategy, including the use of adulticides. If 

larvicide and/or pupacide treatments fail, pyrethrin-based adulticides would be considered for use on the 

Refuge to suppress populations of infected mosquitoes and interrupt epidemic virus transmission. 

Because the efficacy and effects of adulticides are variable, adulticides should not be applied broadly 

without site-specific data indicating a need for control.

Further, the use of adulticide would be considered in relation to the most current version of the Mosquitoborne Virus Risk Assessment in the California Mosquito-borne Virus Surveillance and Response Plan

(Appendix K8). The MADs would be required to include a risk assessment as part of their request to 

apply adulticides. The risk assessment evaluates a number of factors including environmental conditions, 

species presence, virus infection rate, sentinel chicken seroconversion, dead bird presence, and human 

cases to determine whether adulticide should be considered. We would only consider application in areas 

where a pathogen is present on the Refuge that can be effectively treated while minimizing non-target 

effects, especially to threatened and endangered species. However, specific areas treated and the extent of 

treatment would vary from year to year depending on mosquito populations and environmental 

conditions. 
K-13 

In order to limit human contact with adulticides, visitors would not be allowed in those parts of the 

Refuge that are being treated with adulticides. Information about treatment scheduling, location, and 

pesticide would be posted on the Refuge website, at the Refuge Headquarters, and at the treatment 

location. Post adulticide monitoring would be conducted to determine efficacy and any adverse impacts. 

In summary, application of adulticides on the Refuge would require the following steps:

• Prior approval from the National IPM Coordinator via an approved Pesticide Use Proposal

• The MAD must present the Refuge Manager with data supporting presence of a arboviral disease 

on the Refuge or within flight range of the vector mosquito species on the Refuge, including a 

Risk Assessment in the region

• The MAD must provide the Refuge Manager with types/quantities of adulticides proposed and 

locations 

• If beneficial, the MAD should conduct simultaneous application of larvicides with the adulticide 

application to prevent future adult outbreaks

Control strategies are selected to minimize their impact on the environment while maximizing the degree 

of control. The method used is based on the criteria above as well as:

• Habitat type

• Water conditions 

• Cost and feasibility

• Site accessibility

The efficacy of adulticiding is dependent upon a number of factors. First, the mosquito species to be 

treated must be susceptible to the insecticide applied. Some District mosquitoes are resistant or more 

tolerant to some adulticides, thus affecting the selection of the chemical. Adulticides are applied by handheld units when applied to limited areas, or by truck mounted sprayers when applications are made on a 

larger scale.

Each chemical application has its own set of conditions that determine success or failure. The application 

must be at a dosage rate that is lethal to the target insect and applied with the correct droplet size. The 

most common form of adulticiding is ultra-low volume (ULV). Typically with ground applications, 

vegetated habitats may require up to three times the dosage rates that open areas require. This is purely a 

function of wind movement and its ability to sufficiently carry droplets to penetrate foliage.

Environmental conditions may also affect the results of adulticiding. Wind determines how the ULV 

droplets will move from the spray equipment into the treatment area. Conditions of no wind will result in 

the material not moving from the application point. High wind, a condition that inhibits mosquito 

activity, will disperse the insecticide too widely to be effective. Light wind conditions (<10 mph) are the 

most desirable because they move the material through the treatment area and are less inhibiting to 

mosquito activity.

ULV application is avoided during hot daylight hours because thermal conditions will cause the small 

droplets to quickly rise and become completely ineffective on the adult mosquitoes. Generally, 

applications are made at night, when a thermal inversion is present, keeping the material near to the 

ground. 
K-14 

6 Monitoring Mosquito Populations

6.1 Immature Stage Mosquito Monitoring at the Refuge

Immature –principally larval stage– sampling will be conducted to monitor and gauge mosquito 

population levels. Routine surveillance occurs on a monthly, biweekly, or sometimes weekly schedule 

depending on season, habitat and other factors and conditions. Mosquito management activities are 

depicted generally through maps in Appendix K9. Monitoring consists of driving on levees to access 

points in the marsh, then walking into the marsh to sites where there is water present. Alternatively, some 

monitoring sites will require boat access through slough channels (i.e., Bair Island). 

Monitoring involves approximately four to five people cover a unit on foot, searching for larvae. They 

collect samples and return them to the laboratory for identification. The average number of immature 

mosquitoes per dip is recorded for each section of the parcel, along with the species found. Sampling is 

done with standard 1-pint dippers. The dipper has a cup of molded plastic attached to either a telescoping 

aluminum handle or a hardwood dowel. The length of dipper handles can vary from 3-4 feet for 

obtaining shoreline samples to 4-6 feet for sampling hard to reach areas. Immature mosquito population 

estimates are obtained by averaging the number of larvae or pupae collected in several dips. Boat access 

will be permitted in some areas of the Refuge (e.g., Bair Island) with seasonal restrictions on access or 

based on known locations of listed species. Samples are examined in the field or laboratory for the 

abundance, species, and life-stage of mosquitoes present. This information is compared to historical 

records and used as a basis for treatment decisions.

6.2 Adult Stage Mosquito Monitoring at the Refuge

Collecting adult mosquitoes on or near the Refuge signals the movement of adults off the Refuge to 

feeding sources (human populations). Adult mosquito population monitoring information is generally 

used to determine whether to apply treatment for adult mosquitoes off the Refuge. Adult mosquito 

populations may be monitored on the Refuge through carbon dioxide-baited traps, New Jersey light traps,

and landing rates. The mosquitoes are attracted to the trap by the sublimation of dry ice into carbon 

dioxide gas (CO2), which simulates the exhaled respiratory gasses of birds and mammals. The trap 

consists of a central 6-inch diameter plastic cylinder housing a battery-driven motor and 2-blade fan. The 

trap is suspended below an insulated container filled with dry ice. A mesh bag is attached to the bottom 

of the cylinder to collect the mosquitoes. Mosquitoes attracted to the CO2 are drawn in through the top of 

the trap and forced downward by the fan into the collection bag. Female mosquitoes thus collected are 

identified to species and counted. Samples are quantified as the number of females collected per trapnight. Traps require one day to set and access the next day to collect any specimens.

The New Jersey light trap is used in fixed locations where 110-volt electrical service is available. These 

traps consist of a 25 watt light bulb (the attractant) and a fan which are connected to a timer. During 

dusk, evening hours, and dawn, the trap is functioning and collecting night-flying insects into a jar that 

contains a pesticide strip. Jars are changed weekly. These traps are limited in that trap results are over a 

one week period, mosquitoes are killed when they enter the jar (rendering them useless for WNV testing), 

and different mosquito species show different levels of attraction to light sources, with mosquitoes in the 

genus Aedes showing the least attraction. Most significantly, these traps become less efficacious in areas 

of greater population density because of competing light sources. All traps will only be used in upland 

locations to protect sensitive habitat, when there is standing water on the Refuge, generally fall through 

spring. 

Landing rates are also used as a supplementary method for measuring adult mosquito activity. The 

technique involves counting the number of mosquitoes that land on a person within a given amount of 

time. Landing rates are particularly effective for monitoring salt marsh mosquitoes, which readily bite 

during daylight hours. This method is used as a direct observation of the number of host-seeking 
K-15 

mosquitoes present. This information is used to supplement carbon dioxide-baited traps in the decision to 

apply treatment for adult mosquitoes generally off Refuge. 

7 Disease Surveillance Activity

Disease surveillance is conducted year round. A variety of methods will be used on and off the Refuge to 

detect disease presence.

Dead wildlife. Testing of dead wild birds and squirrels is used to detect WNV in the area. This is the 

most sensitive method of detecting the presence of WNV and is usually the first indication of the presence 

of virus. Unlike WEE and SLE, this virus kills birds and affects tree squirrels. Moreover, it can be 

detected readily in their tissues. Birds in the corvid family (crows, ravens and jays) and raptors are 

especially susceptible. However, the virus has also been detected in shorebirds and waterfowl. 

Submission of dead birds and squirrels by the public is also solicited by the MADs. Residents are 

directed to call the California Department of Public Health’s West Nile Virus hotline if they find a dead 

bird or squirrel ((877) WNV-BIRD). This information is conveyed to the MADs, which collects the bird 

or squirrel and submits it for testing. 

Mosquito pools. MADs will collect live mosquitoes to test for the presence of a virus. Live trapping of 

mosquitoes will be permitted in upland areas of the Refuge (e.g., the Refuge’s Environmental Education 

Center in Alviso, Inner Bair Island, and the Refuge’s headquarters). Light traps are not used for adult 

mosquito disease surveillance because collected mosquitoes are killed upon entering the trap rendering 

them useless for virus detection. Host-seeking adult mosquitoes will be collected with carbon dioxidebaited traps. Carbon dioxide traps are portable battery-operated traps used to collect adults of nearly all 

species. The traps use dry ice –frozen CO2- as the attractant, and adults are captured in a mesh bag. 

These traps are left out for a single night and picked up the following day, so adult mosquitoes are still 

alive and useful for virus testing. Traps sites will be selected by MAD staff, and usually require hanging 

on trees, large bushes or other structures. Open, wind-swept areas are typically avoided when setting 

traps. The trapping will assess taxonomy, abundance, and disease presence. Mosquito traps in the 

surrounding community of the Refuge will also inform potential disease presence on the Refuge. 

Although not on Refuge lands, it is believed that some of the mosquitoes collected in theses traps are 

produced by sources on the Refuge. 

Sentinel Chickens. Sentinel chickens are an indirect way of monitoring for the presence of virus in the 

mosquito population. Chickens are maintained in outdoor cages where they are exposed to host-seeking 

mosquitoes. If bitten by an infected mosquito, these birds will develop an immune response. Blood 

samples are taken from the chickens bi-weekly to every two weeks to test for exposure to WNV, WEE, or 

SLE. Flocks of chickens are currently located in each of the counties where the Refuge is located. No 

sentinel flocks are maintained on the Refuge. Chickens have been used for many years to monitor 

mosquito populations in California for WEE and SLE. This method has not proven to be an effective 

early warning system for detecting WNV.

8 Treatment Options

MADs of the San Francisco Bay region employ an Integrated Pest Management approach to mosquito 

control that emphasizes permanent solutions such as wetland restoration, mechanical control of water 

levels or exchange, and/or includes the use of biorationals and larvicides (Appendix K2. Statement of 

Best Management Practices and Proposed Monitoring Plan for Coastal Region Mosquito and Vector 

Control Districts). 
K-16 

8.1 Habitat Enhancement/Restoration

Habitat enhancement and restoration can not only benefit wildlife, but benefit mosquito management as 

well. The Refuge is actively managing the South Bay Salt Pond Restoration Project (SBSPRP), the 

largest tidal wetland restoration project on the West Coast. When complete, the restoration will convert 

15,100 acres of former commercial salt ponds at the south end of San Francisco Bay to a mix of tidal 

marsh, mudflat, managed pond, open water, and other wetland habitats. The Refuge is also in the process 

of restoring former salt evaporator ponds on the Bair Island complex to tidal habitats. The objectives of 

the proposed project are: (1) to restore 1,400 acres of high quality tidal marsh habitat, mudflat/aquatic 

habitat, and uplands habitat; (2) maximize the function and values of tidal marsh habitats in a timely 

manner in order to provide habitat for endangered species and other native wildlife; and (3) enhance the 

public’s appreciation and awareness of the unique resources of Bair Island. Both projects will improve 

tidal circulation to marsh habitat which will reduce mosquito control efforts. 

New water control structure in 2011 in New Chicago Marsh will allow for increased tidal flows through 

the diked marsh and will increase the habitat value for the salt marsh harvest mouse and other tidal marsh 

species. The new water management capability will also lead to less standing, stagnant water and 

therefore reduce mosquito habitat. 

8.2 Physical Controls 

Physical controls that will also be coordinated between the Refuge and the MADs to reduce mosquito 

production include vegetation control and ditching. 

Ditching

In the 1990s the Alameda MAD created ditches using a speed scavel ditcher and tractor to facilitate 

drainage and/or allow access of larvivorous fish in marshlands. Now hand ditching is used to maintain 

existing ditches and create minor ditches. Most of this type of ditching is to trim vegetation and keep 

small ditches open to tidal flow and keep access open for fish to move within the marsh. Hand ditching is 

done using shovels, rakes, pitch forks, hoes, machetes and power weed cutters. This is a low impact type 

of ditching. Personnel, typically a group of no more than eight employees, walk to the site, spoils are 

spread by hand and removed vegetation is spread away from the ditch. Such work is only done on the 

parts of the existing ditch system that need maintenance. Ditching activities only take place between the 

months of September to January in order to avoid peak nesting seasons for the California clapper rail. All 

ditching work is subject to a permit issued by the U.S. Army Corp of Engineers (ACE), in cooperation 

with the San Francisco Bay Conservation and Development District and the San Francisco Bay Regional 

Water Quality Control Board. 

Currently the Alameda MAD conducts ditching activities in four locations on Refuge property: HetchHetchy Marsh, Mowry Slough, Mouse Pasture, and Albrae Marsh/Pintail Marsh. The current ACE 

permit allows the Alameda MAD to maintain up to 2,150 linear feet at Hetch-Hetchy, 8,000 linear feet at 

Mowry Slough, 3,775 linear feet at Mouse Pasture, and 16,000 linear feet at Albrae Marsh/Pintail Marsh. 

In 2010/2011 the Alameda MAD performed maintenance on a combined total of 5,524 linear feet of 

ditches in these four areas. Figure 2 shows the areas ditching activities occur on Refuge property.
K-17 

Figure 2. Ditching Activities on the Refuge in Alameda County

8.3 Biological Controls (B.s. and B.t.i.) 

When physical controls are not enough and larval mosquito populations exceed thresholds, the use of 

biological controls will be used. Because there is a historical presence of disease in the Refuge area, use 

of biological controls will be permitted. There are two types of biological controls currently permitted for 

use on the Refuge: B.s. and B.t.i. Control strategies among the MADs differ based on district size, 

budget, available equipment, product efficacy, and restrictions on difference control materials/methods. 

New control products will be considered based on their effects compared to those products identified in 

this plan. Current control products used by the MADs are listed in Table 4, 5, and 6.

Bacillus sphaericus (B.s.)

Description: Bacillus sphaericus is a commonly occurring spore-forming bacterium found throughout 

the world in soil and aquatic environments that is a common mosquito larvicide. The endotoxin destroys 

the insect’s gut by a process similar to that of B.t.i. However, it is active against a narrower spectrum of 

mosquito species. Species in the genera Aedes and Ochlerotatus have lower susceptibility to B.s. and 

MAD field tests have shown that commercially available formulations of B.s. are not effective against the 

saltmarsh species A. squamiger. There are three formulations currently permitted for use on the Refuge: 

VectoLex WDG, VectoLex CG, VectoLex WSP. Formulations are generally broadcast by hand. 

Product name: VectoLex CG, VectoLex G Granules, VectoLex WDG, VectoLex WSP

Advantages: B.s. is another bacterial pesticide with attributes similar to those of B.t.i. The efficacy of 

this bacterium is not affected by the degree of organic pollution in larval development sites and it may 
K-18 

actually cycle in habitats containing high densities of mosquitoes, reducing the need for repeated 

applications. 

Barriers to use: Like B.t.i., B.s. must be consumed by mosquito larvae and is therefore not effective 

against non-feeding stages such as late instar larvae or pupae. B.s. is also ineffective against mosquitoes 

in the genus Aedes. Toxicity of B.s. to mosquitoes is due to a single toxin rather than a complex of 

several molecules as is the case with B.t.i. Development of resistance has been reported in other 

countries, where the material has been applied for extended periods of time. Knowing the stage and 

species present can increase the effectiveness of this material, restricting it to sources containing 

susceptible species. Development of resistance can be overcome by rotating B.s. with other 

mosquitocidal agents described in this document. 

Impact on water quality: B.s. is a naturally occurring bacterium and is environmentally safe. It leaves 

no residues and is quickly biodegraded. At the application rates used in mosquito control programs, B.s. 

is unlikely to have any measureable effect on water quality. There are no established standards, 

tolerances, or EPA approved tests. Other naturally occurring strains of this bacterium are commonly 

found in aquatic habitats.

Bacillus thuringiensis var. israelensis (B.t.i.)

Description: Bacillus thuringiensis israelensis is an organism that produces a resting stage or spore 

whose walls contain five different microscopic protein pro-toxins packaged inside one larger protein 

crystal. The gut of mosquito larvae is unique in that it is an extremely alkaline environment (the stomach 

of vertebrate animals is acidic). When the crystal is ingested by mosquito larvae, the five proteins are 

released in the alkaline environment of the larva’s gut. The five proteins are then converted into five 

different toxins by specific enzymes present in the gut of larvae. Once converted, these toxins work to 

destroy the gut wall. This leads to paralysis and death of the larvae. 

Both liquid and granular formulations of B.t.i. are permitted for use on the Refuge. There are several 

formulations currently permitted for use on the Refuge: VectoBac G, VectoBac 12AS, Teknar HP-D, 

VectoBac WDG, Bactimos pellets, and Summit B.t.i. Briquettes. These formulations are appropriate for 

aquatic environments. Formulations are applied by ground (backpack spray, herd seeder, hand, lowvolume spray, boom spray) via foot, all-terrain vehicle (ATV), ARGO, or applied aerially by helicopter. 

Product names: Vectobac 12AS, Vectobac G, VectoBac WDG, Bactimos pellets, Teknar HP-D, Summit 

B.t.i Briquettes

Advantages: B.t.i. is highly target-specific and has been found to have significant effects only on 

mosquito larvae and closely related insects (e.g., black flies and midges). It is available in a variety of 

liquid, granular, and pelleted formulations, which provide some flexibility in application methods and 

equipment. B.t.i. has no measureable toxicity to vertebrates and is classified by the EPA as “Practically 

Non-Toxic” (i.e., Caution). B.t.i. formulations contain a combination of five different proteins with a 

larger crystal. These proteins have varying modes of action and synergistically act to reduce the 

likelihood of resistance developing in larval mosquito populations. 

Barriers to Use: To be effective, Bacillus insecticides must be ingested by the mosquito larvae during 

feeding. Therefore, applications must be carefully timed to coincide with periods in the life cycle when 

larvae are actively feeding. Pupae and late fourth stage larvae do not feed and therefore will not be 

controlled by B.t.i. Low water temperature inhibits larval feeding behavior, reducing the effectiveness of 

B.t.i. during very cold periods. High organic conditions also reduce the effectiveness of B.t.i. Therefore 

it is not feasible to use this material in sources with a high concentration of decaying organic material. 
K-19 

The cost per acre treated is generally higher for B.t.i. than for surface films. B.t.i. is used extensively by 

the MADs when appropriate, but other products may be used when later stages of mosquitoes are present.

Impact on water quality: B.t.i. contains naturally produced bacterial proteins generally regarded as 

environmentally safe. It leaves no residue and is quickly biodegraded. At the application rates used in 

mosquito control programs, B.t.i. is unlikely to have any measureable effect on water quality. There are 

no established standards, tolerances, or EPA approved tests. Other naturally occurring strains of this 

bacterium are commonly found in aquatic habitats. 

Information on B.t.i. and B.s. treatments done in the Alameda County portion of the Refuge can be found 

in the attached document “Five Year History of Materials Applied at DESFBNWR” (Alameda County 

MAD). Vernal pools and diked or poor quality tidal marshes are primarily treated with B.t.i. products. 

Highly vegetated areas are most effectively treated with granular formulations that can penetrate the 

dense canopy. Occasionally an ARGO, Polaris ATV, or 4 wheel drive truck equipped with an intellispray 

reel is used to treat a source. An ARGO has been used to treat South Marsh-Munster, Stevenson Field, 

and Newark Golf Course. There are no known California clapper rails in these areas. The majority of 

ARGO usage at Stevenson Field is in the area under the Pacific Gas & Electric towers which is not part of 

the Refuge. The Polaris ATV would be permitted for use in designated non-sensitive areas of the Bailey 

Ranch Vernal Pools/Warm Springs area. No vehicle contact is made with the actual pools; the Polaris is 

used to circumnavigate the pool to effect treatment. At the Newark Golf Course the intellispray rig is 

frequently used for treatments. Two people are need to operate the reel, one to spray and another to guide 

the hose.

Table 4. Pesticides permitted for use on the Refuge in 2012 for Alameda County. 

Trade Name Type Rate & Unit Method Equipment Applications per 

year

VectoLex CG Larvicide, B.s. 20 lbs./acre Hand Hand broadcast Not to exceed 10

VectoLex WDG Larvicide, B.s. 1.50 

lbs./acre

hand Hand broadcast Not to exceed 10

VectoLex WSP Larvicide, B.s. 50 ITUs/mg hand Hand broadcast Not to exceed 10

VectoBac 12AS Larvicide, B.t.i. 16 oz./acre Backpack Spray, LowVolume Spray, AerialATV, Helicopter Not to exceed 20

VectoBac G Larvicide, B.t.i. 10 lbs./acre Hand, Herd Seeder, Aerial ATV, Helicopter Not to exceed 20

Altosid Liquid 

Concentrate SR20

Larvicide, 

Methoprene

1 oz./acre Backpack, Boom Spray, 

Aerial

ATV, Helicopter Not to exceed 10

Altosid Pellets 

WSP

Larvicide, 

Methoprene

10 lbs./acre Hand ATV Not to exceed 10

Altosid XR 

Extended 

Residual 

Briquettes

Larvicide, 

Methoprene

35 lbs./acre Hand ATV Not to exceed 10

Altosid 

Briquettes

Larvicide, 

Methoprene

4.90 

lbs./acre

Hand ATV Not to exceed 10

Altosid XR-G Larvicide, 

Methoprene

20 lbs./acre Hand Hand-held Not to exceed 10

Mosquito 

Larvicide GB1111 (Clarke)

Larvicide, oil 640 oz./acre backpack spray, boom 

spray

ATV, truck Not to exceed 5

Agnique MMF Pupacide, 

Monomolecular 

film

128 oz./acre backpack spray, boom 

spray

ATV, Truck Not to exceed 2

Pyrenone 25-5 Adulticide, 0.87 oz./acre Backpack Spray, boom ATV Not to exceed 2
K-20 

Pyrethrin spray

Table 5. Pesticides permitted for use on the Refuge in 2012 for San Mateo County. 

Trade Name Type Rate & Unit Method Equipment Applications per 

year

VectoBac 12AS Larvicide, B.t.i. 32 oz./acre Backpack Spray, Boom 

Spray, Low-Volume Spray, 

Aerial

ATV, Helicopter Not to exceed 20

VectoBac G Larvicide, B.t.i. 10 lbs./acre Hand, Herd Seeder Truck Not to exceed 20

Teknar HP-D Larvicide, B.t.i. 0.16 oz./acre Backpack Spray, Boom 

Spray, Low-Volume Spray

Truck Not to exceed 20

VectoBac WDG Larvicide, B.t.i. 0.44 

lbs./acre

Backpack Spray, Boom 

Spray, Low-volume Spray

ATV Not to exceed 20

Altosid Liquid 

Concentrate SR20

Larvicide, 

Methoprene

1 oz./acre Backpack Spray, boom 

Spray, Low-Volume Spray, 

Aerial

ATV, helicopter Not to exceed 20

Altosid Liquid 

Larvicide 

Mosquito Growth 

Regulator

Larvicide, 

Methoprene

4 oz./acre Backpack Spray, boom 

Spray, Low-Volume Spray, 

Aerial

ATV, helicopter Not to exceed 20

Altosid Pellets 

WSP

Larvicide, 

Methoprene

5 lbs./acre hand ATV Not to exceed 20

Altosid XR-G Larvicide, 

Methoprene

20 lbs./acre hand Hand broadcast Not to exceed 20

Mosquito 

Larvicide GB1111 (Clarke)

Larvicide, oil 640 oz./acre backpack spray, boom 

spray

ATV, Truck Not to exceed 5

Agnique MMF Pupacide, 

Monomolecular 

film

128 oz./acre backpack spray, boom 

spray

ATV, Truck Not to exceed 2

Pyrenone 25-5 Adulticide, 

Pyrethrin

0.87 oz./acre Backpack Spray, boom 

spray

ATV Not to exceed 2

Table 6. Pesticides permitted for use on the Refuge in 2012 for Santa Clara County. 

Trade Name Type Rate & Unit Method Equipment Application per 

year

VectoLex CG Larvicide, B.s. 20 lbs./acre hand Hand broadcast Not to exceed 10

VectoLex WDG Larvicide, B.s. 1.50 

lbs./acre

hand Hand broadcast Not to exceed 10

VectoLex WSP Larvicide, B.s. 50 ITUs/mg hand Hand broadcast Not to exceed 10

VectoBac 12AS Larvicide, B.t.i. 32 oz./acre Backpack Spray, Boom 

Spray, Low-Volume Spray, 

hand, Aerial

Truck, Helicopter Not to exceed 10

VectoBac G Larvicide, B.t.i. 10 lbs./acre Hand Truck Not to exceed 10

Teknar HP-D Larvicide, B.t.i. 16 oz./acre Backpack Spray, Boom 

Spray, Low-Volume Spray, 

Hand

Truck Not to exceed 10

Bactimos pellets Larvicide, B.t.i. 8 lbs./acre Hand Truck Not to exceed 10

Summit B.t.i. 

Briquettes

Larvicide, B.t.i. 7000 

ITUs/mg

hand Hand broadcast Not to exceed 10

Altosid Pellets 

WSP

Larvicide, 

Methoprene

5 lbs./acre hand Hand broadcast Not to exceed 10

Altosid XR-G Larvicide, 20 lbs./acre hand Hand broadcast Not to exceed 10
K-21 

Methoprene

Altosid 

Briquettes

Larvicide, 

Methoprene

4.90 

lbs./acre

Hand ATV Not to exceed 10

Altosid XR 

Extended 

Residual 

Briquettes

Larvicide, 

Methoprene

35 lbs./acre Hand ATV Not to exceed 10

Altosid Liquid 

Larvicide 

Mosquito Growth 

Regulator

Larvicide, 

Methoprene

4 oz./acre Aerial, Backpack Spray, 

Low volume spray, boom 

spray, hand

Helicopter, truck Not to exceed 10

Altosid Liquid 

Concentrate SR20

Larvicide, 

Methoprene

1 oz./acre Aerial, Backpack Spray, 

Low volume spray, boom 

spray, hand

Helicopter, truck Not to exceed 10

8.4 Other Controls, Including Chemical Controls

When biological controls fail to manage larval and pupal mosquito populations below threshold levels, 

other controls may be considered. Larvicides, pupacides, adulticides that would be permitted for use 

include methoprene, Golden-Bear-1111, Agnique, and Pyrenone 25-5. Adulticides would be permitted 

only as a last resort, and with proof of mosquito-borne disease on the Refuge. Control strategies among 

the MADs differ based on district size, budget, available equipment, product efficacy, and restrictions on 

difference control materials/methods. New control products will be considered based on their effects 

compared to those products identified in this plan. Current control products used by the MADs are listed 

in Table 4, 5, and 6. 

8.4.1 Larvicide

Methoprene 

Description: Methoprene is a true analogue and synthetic mimic of a naturally occurring insect hormone 

called juvenile hormone (JH). JH is found during aquatic life stages of the mosquito; in other insects, it is 

most prevalent during the early instars. As mosquito larva mature, the level of JH steadily declines until 

the fourth-instar molt, when levels are very low. This is considered a sensitive period when all the 

physical features of the adult begin to develop. Methoprene in the aquatic habitat can be absorbed on 

contact and the insect’s hormone system becomes imbalanced. When this happens during the sensitive 

period, the imbalance interferes with fourth-instar larval development. One effect is to prevent adults 

from emerging. Since pupae do not eat, they eventually deplete body stores of essential nutrients and 

then starve to death. For these and perhaps other reasons, methoprene is considered an insect growth 

regulator (IGR).

Product names: Altosid briquettes, Altosid Liquid Larvicide, Altosid pellets, Altosid SBG, Altosid XR 

briquettes, Altosid XRG

Advantages: Methoprene can be applied as liquid or solid formulation or combined with B.t.i or B.s. to 

form a “duplex” application. Methoprene is a desirable IPM control strategy since affected larvae remain 

available as prey items for the rest of the food chain. This material breaks down quickly in sunlight, and 

when applied as a liquid formulation it is effective for only 3-5 days. In the briquette form, methoprene 

can persist in a source for either 30 or 150 days, depending upon the product. The availability of different 

formulations provides options for treatment under a wide range of environmental conditions. Studies on 

non-target organisms have found methoprene to be nontoxic to vertebrates and most invertebrates at 

concentrations used by mosquito control. It can be used for mosquito control in sources of water that are 

consumed by humans. 

Barriers to Use: Methoprene products must be applied (or present, if using a slow release formula) to 

the late fourth instar and/or pupal stages of mosquitoes. It is not effective against other life stages. 
K-22 

Monitoring for effectiveness is more challenging since mortality is delayed. Bringing samples of larvae 

in treated source water into the lab to observe normal or abnormal development is the best way to gauge if 

the treatment was effective. The use of methoprene may result in the delay of development of adult 

vernal pool crustacean, which may reduce the number of resting eggs (cysts) that are formed before 

vernal pools dry (Lawrenz 1984). Because of the effects of methoprene on vernal pool crustacean and a 

lack of information on how long the agents remain in the soil, methoprene will not be permitted for use in 

vernal pools at any time, in either wet or dry conditions. 

Several formulations of methoprene are permitted for use on the Refuge: Altosid Pellets WSP, Altosid 

Briquettes, Altosid XR Extended Residual Briquettes, Altosid XR-G, Altosid Liquid Concentrate SR-20, 

and Altosid Liquid Larvicide Mosquito Growth Regulator. These formulations are both liquid and pellet 

forms. Formulations are applied by ground (hand, ATV, backpack sprayer, boom sprayer, low-volume 

spray) or aerially by helicopter. Methoprene is typically applied in one of two ways. The liquid form can 

be mixed with liquid B.t.i. to form a duplex which is applied in moderate to lightly vegetated areas. Any 

species of mosquito can be targeted. The second form, a pellet, is used to pretreat heavily vegetated areas 

that will be flooded by high tides, prime locations for A. dorsalis production. 

8.4.2 Pupacide

When larvicide treatment fails, pupacide treatments may be considered. Golden Bear-1111 and Agnique 

Monomolecular Film will be permitted for use.

Surface Oils and Films 

Description: Surface oils and films are applied to mosquito breeding sites to kill mosquito larvae and 

pupae. This oil produces a visible sheen on the water surface. This pesticide acts as a film preventing 

larvae, pupae, and emerging adult mosquitoes for obtaining oxygen at the water surface. Golden Bear1111 is a “napthenic oil” (petroleum-based) applied only in closed water sources (e.g., ponds) and not in 

tidal waters. Depending on the product, the film may remain on the water’s surface from a few hours to a 

few days.

Product Names: Golden Bear Oil (GB1111) 

Advantages: These materials are efficacious in eliminating pupae. Treatments are simplified due to the 

spreading action of the surfactant across the water surface and into inaccessible areas. These surfactants 

are considered “practically nontoxic” by the EPA. 

Barriers to Use: The drawback of using oils in habitats where natural enemies are established is that all 

surface-breathing insects, particularly mosquito predators, are similarly affected. GB1111 forms a visible 

film on the water surface. As a general rule, surfactants are used only after alternative control strategies 

have been considered and ruled ineffective. Ideally, surfactants should not be used in a rich macroinvertebrate habitat such as vernal pools. Surface oils are sometimes the only feasible choice in cases 

where the material must have the ability to spread on water.

Monomolecular Film (Poly (oxy-1,2-ethanediyl), α-Isooctadecyl-ω-hydroxyl)

Description: Monomolecular Film (MMF) is a non-ionic surfactant that has an alcohol base. The film 

produced by MMF reduces the surface tension of the water making mosquito larvae and pupae unable to 

attach, thus causing them to drown. Emerging adult mosquitoes or midges are unable to fully emerge and 

will drown. The film produced by MMF is not visible on the water surface and should not be used in 

areas that are subject to unidirectional winds greater than 10 mph or where surface water overflow or 

runoff is an issue. MMF is applied only in closed water sources (e.g., ponds) and not it tidal waters. 

Depending on the product, the film may remain on the water’s surface from a few hours to a few days. 

Product Names: Agnique MMF
K-23 

Advantages: Agnique MMF is efficacious in eliminating pupae. Agnique forms an invisible 

monomolecular film that is visually undetectable. Treatments are simplified due to the spreading action 

of the surfactant across the water surface and into inaccessible areas. It is considered “practically 

nontoxic” by the EPA. Agnique is labeled “safe for use” in drinking water.

Barriers to Use: The drawback of using Agnique MMF in habitats where natural enemies are established 

is that surface-breathing insects, particularly mosquito predators, are similarly affected. As a general rule, 

Agnique MMF is used only after alternative control strategies have been considered and ruled ineffective. 

Ideally, it should not be used in a rich macro-invertebrate habitat such as vernal pools. Agnique MMF is

sometimes the only feasible choice in cases where the material must have the ability to spread on water. 

However, this material is not very effective.

8.4.3 Adulticide

Natural pyrethrins (pyrethrum) are extracted from chrysanthemum flower heads, mainly Chrysanthemum 

cinerarnaefolium, grown commercially in parts of Africa and Asia. The six pyrethrins are esters of three 

cyclopentenolone alcohols: Pyrethrolone, cinerolone, and jasmolone combined with either chrysanthemic 

acid or pyrethric acid.

Synthetic pyrethroids may be effectively applied at much lower rates of active ingredient per acre. The 

synthetic pyrethroids are mimics of natural pyrethrum, a botanical insecticide. However, pyrethroids are 

not permitted on the Refuge at this time due to their impacts on non-target species. 

Natural pyrethrum, sold under several trade names, is registered in California, but is used sparingly due to 

higher cost. Pyrethrins are the only adulticide permitted for use on the Refuge at this time. Only one 

formulation is allowed: Pyrenone 25-5, and only under extreme conditions such as presence of a 

mosquito-borne disease threat. 

Pyrenone 25-5 is a California-registered natural pyrethrin formulation. Pyrenone 25-5 contains 5% 

pyrethrin and 25% piperonyl butoxide. Pyrenone 25-5 is applied as a ultra-low volume (ULV) spray via 

backpack sprayer or boom spray on an ATV with a dosage per acre of typically 0.87 oz./acre (equivalent 

to 0.0027 lbs. of pyrethrins and 0.0135 pounds of piperonyl butoxide per acre).

Pyrenone 25-5 is labeled for use by government mosquito control programs controlling mosquitoes on 

residential, industrial, recreational and agricultural areas as well as swamps, marshes, overgrown waste 

areas and pastures where adult mosquitoes occur. 

9 Mosquito Control Treatment Effects

Under this plan, the MADs would conduct mosquito monitoring and surveillance, mosquito control 

through application of pesticides (i.e., larvicides, pupacides, and adulticides). Tables 4-6 summarize the 

pesticides that are currently permitted for use on the Refuge under this plan. Biological controls and 

chemicals allowed under this plan include B.s., B.t.i., methoprene, monomolecular films (Agnique, GB1111) and pyrethrins (in conditions with an imminent mosquito-borne virus disease threat only). 

9.1 Effects on non-target organisms

9.1.1 Vegetation

Impacts to vegetation could occur during access (on-foot, ARGOs) within tidal marsh to conduct 

mosquito management. The use of mechanized vehicles that traverse wetland areas (ARGOs and ATVs) 

have a much greater impact on vegetation than foot access, including the trampling and crushing of 

plants.
K-24 

B.t.i. has practically no acute or chronic toxicity to vascular plants (USEPA 1998) (Appendix K5). The 

application of other pesticides, including adulticides, are not likely to adversely affect vegetation directly 

because the pesticides used for mosquito control are not known to harm plants. Pyrethrins are not 

expected to affect plants because the sodium channel mechanism of action for pyrethrins does not indicate 

that pyrethrins would be toxic to plants (USEPA 2006). 

9.1.2 Other Invertebrates

Monitoring and surveillance activities are not expected to adversely affect non-target invertebrate 

populations. Biological and chemical treatment of mosquito populations on the Refuge has the potential 

to adversely affect non-target invertebrates and these are described below.

How reductions in certain invertebrate populations as a result of repeated pesticide applications would 

impact specific invertebrate-plant interactions (e.g., pollination) within tidal marsh and vernal pools of the 

Refuge are not known. However, because most pollinators do not have an aquatic lifecycle stage, it is 

likely that pollinators would not be affected by larvicide and pupacide application. Pollinators may be 

affected by adulticides which are broadcast in liquid form at ultra-low volume, but use of adulticides 

would only be used under extreme conditions and in limited areas. Moreover, application of adulticiding 

would occur during the evening which limits the target population primarily to mosquitoes and when 

generalist pollinators are not active.

The effect on local populations of invertebrate species over time with periodic and continued use of B.t.i.

is inconclusive, but potential for negative effects is a possibility (Appendix K3, K4, and K5). Host range 

and effect on non-target organisms indicates that B.t.i. is relatively specific to the Nematocera suborder of 

Diptera, in particular filter-feed mosquitoes (Culicidae) and blackflies (Simuliidae) (Glare and 

O’Callaghan 1998). B.t.i. is pathogenic to some species of midges (Chironomidae) and Tipulidae, 

although to a lesser extent than mosquitoes and biting flies and is not reported to affect a large number of 

other invertebrate species (Glare and O’Callaghan 1998). B.t.i. concentration may be important with 

regard to effects on nontarget organisms. Of particular concern is the potential for B.t.i. to kill midge 

larvae (family Chironomidae). Chironomid (non-biting midge) larvae are often the most abundant aquatic 

insect in wetland environments and form a significant portion of the food base for other wildlife (Batzer 

et al. 1993; Cooper and Anderson 1996; Cox et al. 1998). Reduced invertebrate populations as a result of 

food web effects (e.g., reduction of nematoceran, Diptera) have been shown in studies of B.t.i. (Hershey 

et al. 1998). However, current surveys indicate abundance of aquatic invertebrates in vernal pools 

receiving mosquito control with B.t.i. and B.s. (I. Loredo, pers. comm.). See 9.1.7 Threatened and 

Endangered Species, for more information on VPTS.

 

Because methoprene is a juvenile hormone (JH) mimic and all insects produce JH, there is concern about 

potential adverse effects on non-target aquatic insects when this pesticide is used for mosquito control 

(Appendix K6). As with B.t.i., there is concern regarding potential negative effects on chironomid larvae 

due to their importance in food webs. As with any pesticide, toxicity is a factor of dose plus exposure. 

At mosquito control application rates, methoprene is present in the water at very small concentrations (4-

10 parts per billion, initially). With regard to exposure, chironomid larvae occur primarily in the benthos, 

either within the sediments and/or within cases constructed of silk and detritus. Thus, there may be 

differences with regard to exposure to methoprene between chironomid and mosquito larvae, the latter 

occurring primarily in the water column. The published literature on the effects of methoprene to 

chironomids is not as extensive as that for B.t.i. However, there is evidence for potential toxicity to 

chironomid and other aquatic invertebrates from methoprene treatments. In summary, there is evidence 

for significant adverse non-target effects from methoprene even when applied at mosquito control rates. 

Monomolecular films (Agnique, GB-1111) are potentially lethal to any aquatic insect that lives on the 

water surface and requires periodic contact with the air-water interface to obtain oxygen (USFWS 2004). 
K-25 

The film interferes with larval orientation at the air-water interface and/or increases wetting tracheal 

structures, thus suffocating the organism. As the film spreads over the water surface, the treatment tends 

to concentrate the larvae, which may increase mortality from crowding stress (Dale and Hulsman 1990).

Under this plan, only pyrethrins (natural adulticides) could be applied when there is high risk of 

mosquito-borne disease (Chapter 5, Threat Level 5). Pyrethrins are known to cause acute toxicological 

effects to benthic invertebrates at rates used for mosquito abatement (USEPA 2006). Because pyrethrins 

are broad-spectrum insecticides, they are potentially lethal to most insects, including both terrestrial and 

benthic forms. All adulticides are very highly toxic to aquatic invertebrates in low concentrations (e.g., 1 

ppb) (Milam et al. 2000). Because most adulticides can be applied over or near water when used for 

mosquito control, there are risks to aquatic invertebrates from direct deposition and runoff of the 

pesticides.

9.1.3 Fish

Mosquito monitoring and surveillance activities are not expected to adversely affect fish because these 

activities do not occur within open sub-tidal waters of the Refuge (e.g., sloughs, channels, open bay) and 

are not expected to adversely affect water quality (e.g., turbidity, dissolved oxygen). Negative effects on 

fish populations are not expected from proposed larvicides and pupacides (USEPA 1998, Appendix K3

and K4). B.t. is practically non-toxic to fish (Appendix K5). However, the application of adulticides has 

the potential to adversely affect fish populations (Gunasekara 2005). Pyrethroids are considered highly 

toxic to fish and invertebrates (Appendix K4 and K7). 

The frequency of conditions that would require use of adulticides on the Refuge has been rare over the 

past few decades. This pattern suggests that future use of adulticides in discrete areas of the Refuge is 

unlikely, but if occurred, the frequency and scope of application is not likely to cause significant adverse 

effects to fish and invertebrate populations. To reduce impacts to fish, adulticides will only be permitted 

in upland areas and interior water bodies. They will be applied away from open water and navigable 

slough channels to reduce impacts to fish. Application would only occur during low tides to avoid 

potential impacts to fish that may move into the tidal marsh plain during higher high or extreme tides.

9.1.4 Reptiles and Amphibians

Reptiles are known to occur within both tidal and seasonal wetland areas of the Refuge. Amphibians are 

likely to occur in seasonal wetland and fresh water areas of the Refuge, including California tiger 

salamanders (CTS) in the vernal pool units (see 9.1.7, Threatened and Endangered Species). Pesticide 

effects on reptiles and amphibians may occur through reductions in insects that serve as food source 

(Hoffman et al. 2008), and through direct individual effects from pesticide application or from trampling 

of individuals or habitat (e.g., access via ARGOs and ATVs). Methoprene may affect, but is not likely to 

adversely affect CTS, through the reduction of direct food sources (Rexrode and Jones 2011). With 

regard to adulticides, direct chronic effects have been found for the San Francisco garter snake from 

application of labeled rates of permethrin (synthetic pyrethroid, Hoffman et al. 2008). While this species 

does not occur on the Refuge, these findings suggest other reptiles may incur direct chronic effects. 

Aquatic organisms (e.g., tadpoles, CTS) may be highly sensitive to pyrethrins and use of the compound 

near water bodies or waterways must be carefully evaluated prior to its application (Gunasekara 2005). 

Because mosquito control is applied directly to vernal pools, CTS may be directly affected. The Refuge 

has monitored these populations for more than ten years. The effects of pesticides on CTS are unknown 

at this time. However, refuge surveys over the last several years indicate that there is continued, longterm presence of CTS in these pools. Only trained personnel and limited vehicle use (with restrictions) 

will be permitted near vernal pools in order to limit impacts to dispersing California tiger salamanders.

9.1.5 Birds

Impacts to birds that use the Refuge may occur during access for mosquito monitoring, surveillance and 

control, as well as the application of pesticides. There are three federally listed bird species that inhabit 
K-26 

the Refuge: the California clapper rail (Rallus longirostris obsoletus), the western snowy plover 

(Charadrius alexandrinus nivosus), and the California least tern (Sterna antillarum browni). These 

species are covered in 9.1.7, Threatened and Endangered Species. There are many other bird species 

listed as Species of Special Concern by the California Department of Fish and Game that occur on the 

Refuge.

Birds may be temporarily flushed as a result of ground access via foot or mechanized vehicle, although 

birds will most likely return to roosting sites once operations have ceased in the area. It is anticipated that 

disturbance to most birds is likely to be low as a result of regular communication between the Refuge and 

the MADs on known nesting sites and other sensitive habitat locations, and limitations on marsh access in 

areas with nesting birds. However, repeated travel over the same areas creates paths through the marsh 

that increases access for predators.

B.t.i. has practically no acute or chronic toxicity to birds (USEPA 1998, Appendix K3 and K4). There is 

the potential for B.t.i. to kill midge larvae (family Chironomidae). Chironomid (non-biting midge) larvae 

can be abundant in wetlands and form a significant portion of the food base for other wildlife, including 

birds (Batzer et al. 1993; Cooper and Anderson 1996; Cox et al. 1998). As with B.t.i., there is concern 

regarding potential negative impacts to chironomid larvae from methoprene. Some studies have 

suggested methoprene impacts to other organisms that may form part of the food base for birds. 

McKenney and Celestial (1996) noted significant reductions in number of young produced in mysid 

shrimp at 2 ppb. Sub-lethal effects on the cladoceran, Daphnia magna, in the form of reduced fecundity, 

increased time to first brood, and reduced molt frequency have also been observed at lower concentrations 

of methoprene (Olmstead and LeBlanc 2001). Methoprene showed no toxicity to slight toxicity to birds

at high concentrations and repeated exposure (Appendix K3 and K6, USEPA 2001). Monomolecular film 

is not known to cause direct chronic or acute avian toxicological effects to birds (Appendix K4). But 

monomolecular films are potentially lethal to any aquatic insect that lives on the water surface or requires 

periodic contact with the air-water interface to obtain oxygen (Appendix K3 and K4).

Pyrethrins are not considered toxic to birds (Milam et al. 2000, USEPA 2006) when applied at labeled 

rates. However, non-target effects to birds from pesticide application may occur as a result of reduced 

food base (e.g., Chironomid invertebrates). There is uncertainty with regard to pyrethrins, which have 

been shown to have no impact on large-bodied arthropods, but have been shown to reduce invertebrate 

populations, especially among small-bodied arthropods (Boyce et al. 2007). 

 

Conversely, significant mosquito production and absence of mosquito control may negatively affect bird 

populations. Although mosquitoes themselves are a part of estuarine ecosystems, they are known vectors 

of disease, including diseases that cause harm to humans and wildlife (e.g., WNV). Mosquito-borne 

diseases such as WNV have shown to be lethal to wildlife. As of 2011, 326 bird species have been listed 

in the Center for Disease Control WNV avian mortality database 

(http://www.cdc.gov/ncidod/dvbid/westnile/birdspecies.htm, accessed May 2, 2011). The list includes 

wildlife that inhabit tidal marsh such as waterfowl, grebes, heron, egrets, cormorants, songbirds (wrens, 

yellowthroats, song sparrows), and rails (clapper rail, Virginia rail, common moorhen, American coot). 

9.1.6 Mammals

Impact to mammals that use the Refuge may occur during the monitoring, surveillance and control of 

mosquitoes, as well as the application of pesticides. The federally endangered salt marsh harvest mouse 

(Reithrodontomys raviventris haliocoetes) occurs throughout tidal marsh of the Refuge and is addressed 

below. Adverse impacts to salt marsh mammals may occur as a result of marsh access via foot or 

mechanized vehicles for mosquito management activities. Vehicle effects on habitat include compacted 

soil and destroyed vegetation (Bias and Morrison 1993). In addition, repeated vehicle travel over the 

same areas creates paths through the pickleweed that increases access for predators. Vehicle travel can 

also disrupt daily activity (e.g. movements) of small mammals and has the potential to cause mortality of 
K-27 

individuals. Past and current aerial imagery from a variety of sources show visible paths where 

mechanized vehicles have traversed the marsh. In addition, boat, ARGO and foot travel can flush harbor 

seals which are particularly sensitive during the pupping season. Important seal haul out location exist in 

Corkscrew Slough (Bair Island), Calaveras Point and Mowry Slough. 

The use of larvicides and pupacides for the purpose of mosquito management are not likely to directly 

affect native mammal populations of the Refuge (USEPA 1998). Adverse effects on mammals from 

B.t.i., methoprene, and monomolecular films are not expected (Appendix K3 and K4) when applied 

according to the label instructions. Extensive acute toxicity studies indicated that B.t.i. is virtually 

innocuous to mammals (Siegel and Shadduck 1992). These studies exposed a variety of mammalian 

species to B.t.i. at moderate to high doses and no pathological symptoms, disease, or mortality were 

observed. Methoprene is not considered toxic to mammals (Appendix K3, K4, and K6). Impacts to the 

mammalian community as a result of reduced invertebrate populations are not expected because many 

small mammal species that inhabit wetlands of the Refuge are herbivorous (invertebrates are not a 

primary component of their diet). Insectivorous species such as shrews (e.g., Sorex ornatus) do occur in 

wetlands of the Refuge, and reduced arthropod populations may impact food availability for these species. 

Impacts to fish-eating harbor seals could occur if population-level effects to fish occur through the use of 

adulticides directly in waters and slough channels (see 9.1.3, Fish, above).

Under this plan, the use of pyrethrin pesticides on the Refuge is only permitted under specific conditions. 

Oral exposure of pyrethrins could occur through consumption of plants or plant parts that have been 

sprayed (ground-based application). A terrestrial exposure model showed no acute or chronic risks to 

mammal or bird species (USEPA 2006). 

Conversely, significant mosquito production and absence of mosquito control may negatively affect 

mammal populations. Although mosquitoes themselves are a part of estuarine ecosystems, they are 

known vectors of disease, including diseases that cause harm to humans and wildlife (e.g., WNV). 

Mammals known to be infected by WNV include horses, bats, chipmunks, skunks, rabbits, and squirrels. 

9.1.7 Threatened and Endangered Species

Vernal pool tadpole shrimp 

The endangered vernal pool tadpole shrimp (VPTS) (Lepidurus packardi) occur in discrete habitats on the 

Refuge (e.g. Warm Springs) and spend their entire life cycle within the pools. Because mosquito control 

(B.t.i., B.s.) is applied directly to vernal pools, VPTS may be directly affected. Generally, these

pesticides are not expected to affect aquatic invertebrates such as VPTS (Appendix K3), but detailed

effects of pesticides on VPTS and CTS are unknown at this time. Other pesticides will not be permitted 

for use in the vernal pools. The Refuge has monitored these populations for more than ten years. These 

refuge surveys indicate continued, long-term presence of VPTS and CTS in these pools. Also, MAD staff 

would be required to receive training in order to access vernal pool areas.

Steelhead 

The federally threatened Central California Coast steelhead (Oncorhynchus mykiss) has the potential to 

occur on the Refuge. Impacts to the steelhead are the same as those listed in 9.1.3, Fish. 

It is not anticipated that larvicides and pupacides will impact steelhead. The frequency of conditions that 

would require use of adulticides on the Refuge has been rare (last application was in 2006 at Outer Bair 

Island), suggesting that future use of adulticides in discrete areas of the Refuge is unlikely, but if 

occurred, the frequency and scope of application is not likely to cause significant adverse effects to fish 

and invertebrate populations. To reduce impacts to steelhead, adulticides will only be permitted in upland 

areas and interior water bodies. They will be applied away from open water and navigable slough 

channels to reduce impacts to fish. Application would only occur during low tides to avoid potential 

impacts to fish that may move into the tidal marsh plain during higher high or extreme tides.
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North American green sturgeon 

The federally threatened Southern Distinct Population Segment of North American green sturgeon 

(Acipenser medirostris) has the potential to occur on the Refuge, but is an infrequent visitor. Impacts to 

the North American green sturgeon are the same as those listed in 9.1.3, Fish. 

It is not anticipated that larvicides and pupacides will impact the North American green sturgeon. The

frequency of conditions that would require use of adulticides on the Refuge has been rare (last application 

was in 2006 at Outer Bair Island), suggesting that future use of adulticides in discrete areas of the Refuge 

is unlikely, but if occurred, the frequency and scope of application is not likely to cause significant 

adverse effects to fish and invertebrate populations. To reduce impacts to the North American green 

sturgeon, adulticides will only be permitted in upland areas and interior water bodies. They will be 

applied away from open water and navigable slough channels to reduce impacts to fish. Application 

would only occur during low tides to avoid potential impacts to fish that may move into the tidal marsh 

plain during higher high or extreme tides.

California tiger salamander

The federally threatened Central California Distinct Population Segment of the California tiger 

salamander (Ambystoma californiense) occurs in the Warm Springs sub-unit of the Refuge. California 

tiger salamanders occur in vernal pool habitats. The larvae develop in the vernal pools and ponds in 

which they are born, but California tiger salamanders are otherwise terrestrial and typically spend the dry 

summer and fall months in the burrows of small mammals. California tiger salamanders could be 

adversely affected by mosquito monitoring, surveillance, or control due to crushing from access on foot 

or by mechanized vehicles. Motor vehicles would be restricted to established roads and berms in vernal 

pool areas. Use of larvicides and pupacides (methoprene, monomolecular films, and adulticides are not 

permitted in vernal pool areas) may have an indirect adverse effect on the California tiger salamander by 

reducing the availability of invertebrate prey. California tiger salamanders could also be adversely 

affected as described under the Reptiles and Amphibians section, 9.1.4. Also, MAD staff would receive 

training to access vernal pool areas.

California clapper rail 

The endangered California clapper rail forages, roosts and nests in tidal marsh channels where mosquito 

management could occur. Mosquito monitoring, surveillance, or control could adversely affect these 

species. Walking and especially ATV or ARGO driving in the marsh has the potential to disturb 

California clapper rails as well as crush nests, eggs, or chicks. Also, repeated travel over the same areas 

creates paths though the marsh that increases access for predators. Like other birds, as described in 9.1.5, 

Birds, mosquito control pesticides are not likely to have direct affects to California clapper rails. Instead, 

California clapper rails may be impacted indirectly by reduced invertebrate prey base as a result of 

adulticiding. However, this is a rarely used pesticide. It is not known what affect the frequent use of 

larvicides and pupacides in tidal marsh habitat would have on the invertebrate prey base of California 

clapper rails.

California least tern

The endangered California least tern forages in sloughs and large channels within the areas affected by 

this plan. However, they are more often found foraging in the Bay or in managed ponds, and are not 

likely to be adversely affected by mosquito monitoring, surveillance, or control if best management 

practices are followed (e.g., avoiding nesting areas). If population-level impacts to forage fish occur, then

California least terns could be negatively impacted (see 9.1.3, Fish).

Western snowy plover
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The Pacific Coast population of the western snowy plover is federally listed as threatened. Western 

snowy plovers may occasionally forage in areas affected by this mosquito management plan. However, 

they do not nest in areas affected by this plan, and are more likely to forage on mudflats or along tidal 

channels at low tide. Therefore they are not likely to be adversely affected by mosquito monitoring, 

surveillance, or control if the best management practices are followed. If population-level impacts to 

invertebrate prey occur, then western snowy plovers could be negatively impacted (See 9.1.2, Other 

Invertebrates and 9.1.5, Birds).

Salt marsh harvest mouse 

The federally endangered salt marsh harvest mouse (SMHM) occurs throughout tidal marsh of the 

Refuge. Adverse impacts to SMHM and other wetland mammals may occur as a result of marsh access 

via foot or mechanized vehicles for mosquito management activities. According to observations, vehicle 

effects on habitat include compacted soil, destroyed vegetation, and documented the destruction of at least 

one salt marsh harvest mouse nest (Bias and Morrison 1993). In addition, repeated vehicle travel over the 

same areas creates paths through the pickleweed that increases access for predators. Lastly, they reported 

that vehicle travel can disrupt daily activity (e.g. movements) and has the potential to cause mortality of 

individual SMHM.

Contra Costa goldfield

Impacts to the federally endangered Contra Costa goldfields (Lasthenia conjugens) are the same as those 

listed in 9.1.1, Vegetation. Contra Costa goldfields generally begin to appear in April, and can be easily 

trampled and crushed by mechanized vehicles. Trucks and ARGOs would be restricted to established 

roads and berms in vernal pools areas. Only small, all-terrain vehicles will be permitted near vernal 

pools. Refuge staff will advise MAD staff on areas appropriate for motor vehicles. Only trained staff 

will be allowed to access vernal pools on foot in order to limit impacts to goldfields. Foot access by 

trained personnel is not expected to have a significant impact on Contra Costa goldfields. Contra Costa 

goldfields may also be indirectly affected by MAD staff spreading non-native plant species by foot within 

the listed plant’s habitat. 

Most pollinators do not have an aquatic lifecycle stage, making it unlikely that pollinators would be 

affected by larvicide and pupacide application. Adulticide is not permitted in vernal pool areas, making it 

unlikely that Contra Costa goldfield pollinators would be affected by adulticide. 

10 Stipulations and Best Management Practices for Mosquito 

Monitoring, Surveillance, and Control

In order to minimize adverse effects to habitat and wildlife, the following best management practices will 

be required in all areas of the Refuge accessed for monitoring, surveillance, and control of mosquitoes. 

General Stipulations 

• The MADs will be required to minimize the use of pesticides (e.g., choosing less toxic materials, 

using smaller quantities of more toxic chemicals, conducting fewer applications) and continually 

investigate formulations and compounds that are least damaging to fish and wildlife (including 

invertebrate) populations. 

• Each MAD will be required to review the past year’s Pesticide Use Proposals and submit any 

changes in the pesticides or formulations of pesticides that they expect to use in the upcoming 

year. This information will be made available at or before the time of the annual meeting.

• New products will not be applied without prior Refuge approval. 

• Mosquito control will be authorized on a biennial basis by a SUP. The SUP conditions will 

stipulate that all mosquito control work will be carried out under the guidance of pre-approved 

PUPs.
K-30 

• Pesticides will be applied according to pesticide label instructions and per habitat type.

• Aerial mosquito control application is encouraged over ground-based application methods. 

• Aerial mosquito control applications will avoid low level flight over water to access or exit the 

Refuge as possible, thus minimizing bird disturbance. 

• Application of larvicides and pupacides will be discouraged during high tide events in order to 

avoid impacts to tidal marsh species.

• Unless permitted by the Refuge Manager, pesticide application should not occur within 100 feet 

of major natural sloughs and channels that can disperse into navigable waterways and open water. 

• Application of pesticides will be informed by monitoring of mosquito vector populations and 

surveillance indicating location of disease prevalence.

• MADs will adapt methods to reduce ecological risk to the environment (e.g., boom height, 

droplet size, application rate) as new information on ecological risk and avoidance measures are 

identified by appropriate regulatory agencies.

• To reduce the spread of non-native invasive plants all construction equipment, vehicles and 

personnel gear will be cleaned of seeds, soil or plant material before arriving on site. 

• Oil and other hazardous material spill contingency plans must be implemented.

• Marsh vegetation is to be hand mowed and removed down to the bare ground before dredging 

occurs to prevent harm to the salt marsh harvest mouse.

• Areas of marsh vegetation that are submerged in water do not need to be mowed before dredging 

occurs. 

• Before excavation occurs, crews must walk ahead of the equipment and haze mice out of 

vegetation.

• When clearing vegetation from an area, begin mowing from the center of the area to be cleared 

and work toward the edges to avoid trapping mice in remaining patches of vegetation. 

• Mowed vegetation should be cleared from the area and stockpiled for later re-use if possible. 

• A final report on activities will be provided by MADs by the end of the treatment year. MADs 

will provide dates of mosquito sampling and treatment, mapped locations and methods of 

sampling/treatment sites, species of mosquito and their population indices/frequencies. 

Motor Vehicle Operation: 

• Mechanized vehicles will only be allowed on levees and existing roads unless approved by the 

Refuge Manager.

• Techniques for approved ARGO operations are such that limit impact, including: slow speeds; 

slow, several point turns; and using existing levees or upland to travel through sites when 

possible. 

• Access along tidal channels and sloughs is restricted in order to reduce impacts to vegetation used 

as habitat by wildlife (e.g., nesting and escape habitat).

• MADs are required to attend Refuge-approved training on measures to avoid impacts to wetland 

wildlife and in identification of sensitive species.

• Aerial pesticide (larvicide or pupacide) application is encouraged over ground-based application 

methods in areas with endangered species.

• Boat access to Corkscrew Slough, Calaveras Point and Mowry Slough will be limited to the 

center channel during the harbor seal pupping season, March 15-June 15 to prevent flushing of 

pups from their mothers. 

Endangered Species Habitat: 

• Inspections and treatments will be primarily performed on foot, when possible. 

• Aerial pesticide (larvicide or pupacide) application is encouraged over ground-based application 

methods in areas with endangered species.
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• Access (via foot or mechanized vehicle) to tidal marsh and muted tidal marsh for the purpose of 

mosquito management would not be allowed access from February 1 to July 15 in areas that are 

inhabited by California clapper rails without authorization of the Refuge Manager. 

• Access (via foot or mechanized vehicle) to seasonal pond habitats for the purpose of mosquito 

management would not be allowed access from March 1 to September 15 in areas used by nesting 

snowy plovers without authorization of the Refuge Manager. 

• Trucks and ARGOs would be restricted to established roads and berms in vernal pools areas. 

Only small, all-terrain vehicles will be permitted near vernal pools. Refuge staff will advise 

MAD staff on areas appropriate for motor vehicles. Only trained staff will be allowed to access 

vernal pools on foot in order to limit impacts to dispersing California tiger salamanders. 

• MAD staff will avoid driving and stepping on Contra Costa goldfields. Refuge staff will provide 

a map of known Contra Costa goldfield sites and MAD staff will avoid driving in these areas 

during Contra Costa goldfield germination (coincides with vernal pool draw down) and blooming 

period. 

• Methoprene, monomolecular films, and adulticides will not be permitted for use in the vernal 

pool areas. 

Use of Pyrethrins: 

• Use of adulticides must meet the following criteria: (1) when mosquito-borne disease incidence 

has been documented on the Refuge or within flight range of vector mosquito species present on 

the Refuge and (2) when there are no practical and effective alternatives to reduce a mosquitoborne, disease-based health threat.

• Adulticides must be approved for use by the Service’s National IPM Coordinator. 

• The application of pyrethrins must be limited to reduce impacts to habitat and wildlife (i.e., 

during the time period when there is a mosquito-borne virus detected on or in mosquito flight 

range of the Refuge, or high risk to public health was documented), but sufficient to ensure 

effective mosquito control.

• The application of pyrethrins should occur at an ultra-low volume (according to pesticide label 

instructions and per habitat type).

• If beneficial, the MAD should conduct simultaneous application of larvicides with the adulticide 

application to prevent future adult outbreaks. 

• Application would only occur during low tides to avoid impacts to fish that may move into the 

tidal marsh plain during high tides.

• The application of pyrethrins should occur only where monitoring and surveillance data justify its 

use (e.g., incidence of mosquito-borne disease).

• Refuge staff and visitors must be notified prior to adulticide treatments. Information about 

treatment scheduling, location, and type of pesticide must be posted by the MADs in areas where 

treatments would occur when those areas could be accessible to Refuge staff or the public.

• The application of pyrethrins should occur only in specific, discrete areas where monitoring data 

justify its use.

• Pyrethrins will not be permitted for use in the vernal pool areas.
K-32 

GLOSSARY

Adulticide. Killing adult mosquitoes or a pesticide that kills adult mosquitoes. 

Arbovirus. Arthropod-borne virus. A viral disease carried and transmitted by mosquitoes or other 

arthropods. 

Biological Integrity. Biotic composition, structure, and functioning at genetic, organism, and community 

levels comparable with historic conditions, including the natural biological processes that shape genomes, 

organisms, and communities. (See 601 FW 3 for more information on biological integrity.) 

BMPs. Best management practices

CWA. Clean Water Act (33 U.S.C. 1251-1387) 

Environmental Health. Composition, structure, and functioning of soil, water, air, and other abiotic 

features comparable with historic conditions, including the natural abiotic processes that shape the 

environment. (See 601 FW 3.) 

Enzootic. A relatively consistent prevalence of disease in animals. The term is comparable to endemic, 

but refers to animals.

EPA. Environmental Protection Agency. 

ESA. Endangered Species Act (16 U.S.C. 1531-1544). 

Health Threat. For the purposes of allowing mosquito control on a particular refuge, the threshold of a 

“documented existing health threat” will be met when a positive virus (WNV, WEE, etc.) detection is 

made in humans, dead birds, mosquito pools, sentinel chickens, or horses in the vicinity of the Refuge, 

within the same county, and within the same annual mosquito season. 

Integrated Pest Management (IPM). A sustainable approach to managing pests by combining 

biological, cultural, physical, and chemical tools in a way that minimizes economic, health, and 

environmental risks. 

Larvicide. Killing mosquito larvae, or a pesticide that kills mosquito larvae. 

MAD. Mosquito Abatement District

Mosquito-borne disease. An illness produced by a pathogen that mosquitoes transmit to humans and 

other vertebrates. The major mosquito-borne pathogens presently known to occur in the United States 

that are capable of producing human illness are the viruses causing eastern equine encephalitis, WEE, St. 

Louis encephalitis, West Nile encephalitis/fever, LaCrosse encephalitis, and dengue, as well as the 

protozoans causing malaria. 

NEPA. National Environmental Policy Act (42 U.S.C. 4321-4347). 

NMFS. National Marine Fisheries Service.

Non-target Organisms. Species or communities other than those designated for population control. 
K-33 

NPDES. National Pollutant Discharge Elimination System established by section 402 of the 

NWRS. National Wildlife Refuge System.

Public Health Authority. A Federal, State, and/or local agency that has health experts with training and 

expertise in mosquitoes and mosquito-borne diseases and that has the official capacity to identify health 

threats and determine health emergencies. 

PUP. Pesticide Use Proposal.

Pupacide. A pesticide that kills the pupal stage of mosquitoes.

PUR. Pesticide Use Report.

Refuge-Based Mosquitoes. Mosquitoes that are produced within, or occur on, a refuge. 

Service. United States Fish and Wildlife Service. 

Service-Authorized Agent. A contractor, cooperating agency, cooperating association, refuge support 

group, volunteer, or other party working on a refuge on behalf of the Service to help achieve the refuge 

purpose(s) or NWRS mission. 

SLE. Saint Louis Encephalitis.

Surveillance (mosquito-borne disease). Activities associated with detecting pathogens causing 

mosquito-borne diseases, such as testing adult mosquitoes for pathogens or testing reservoir hosts for 

pathogens or antibodies. 

ULV. Ultra-low volume. 

Vector. An organism, such as an insect or tick, that is capable of acquiring and transmitting a diseasecausing agent, or pathogen, from one vertebrate host to another, or the act of transmitting a pathogen in 

such a manner. 

WEE. Western Equine Encephalitis. 

WNV. West Nile Virus.
K-34 

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APPENDIX K1. USFWS Interim Guidance for Mosquito 

Management on National Wildlife Refuges 

INTERIM MOSQUITO GUIDANCE 2005 4/2005 

1

In Reply Refer To: 

FWS/ANRS-NR-WR/020301 

Memorandum 

To: Regional Directors, Regions 1-7 

 Manager, California/Nevada Operations Office 

From: Director 

Subject: Interim Guidance for Mosquito Management on National Wildlife Refuges 

A draft policy on mosquito management for the National Wildlife Refuge System is expected to 

be released for public comment within the next few months. In the interim, and while the draft 

policy is undergoing public review, the attached document has been prepared to provide refuges 

with a Systemwide, consistent process for addressing mosquito management issues. 

Because refuges with existing mosquito management programs have already begun the process 

for the current season, there will be a 6-month transition period during which these refuges 

should review their existing programs to ensure consistency with this guidance. Refuges with no 

current mosquito management program should follow the attached guidance when health threats 

from refuge-based mosquitoes are identified. 

Mosquito management on national wildlife refuges can be a very controversial issue. The 

Service is committed to protecting the health of humans, wildlife, and domestic animals while 

maintaining our statutory and policy obligations for wildlife conservation. 

For additional information, please contact Michael Higgins at (410) 573-4520. 

Attachment 

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Cc: 3238-MIB-FWS/Directorate File 

 3238-MIB-FWS/CCU 

 3251-MIB-FWS/ANRS 

 670-ARLSQ-FWS/ANRS-DNRS 

 670-ARLSQ-FWS/ANRS-CPP 

 570-ARLSQ-FWS/ANRS-NR 

 570-ARLSQ-FWS/ANRS-NR-WR File 

 570-ARLSQ-FWS/ANRS-NR-WR Staff (Higgins) 

FWS/ANRS-NR-WR:MHiggins:kem:2/22/05:703-358-2043 

S:\Control Correspondence\2005\020301.doc 

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NATIONAL WILDLIFE REFUGE SYSTEM 

MOSQUITO MANAGEMENT GUIDELINES FOR 2005 

With the spread of West Nile virus across the country, national wildlife refuges (NWRs) may 

come under increasing pressure to manage refuge-based mosquitoes (mosquito populations that 

are bred or harbored within refuge boundaries). In addition to West Nile virus, there may be 

other human or wildlife health concerns from refuge-based mosquitoes. The following 

document provides refuges with guidance in addressing mosquito-associated health threats in a 

consistent manner. Generally, refuges will not conduct mosquito monitoring or control, but 

these activities may be allowed under special use permits. When necessary to protect the health 

of a human, wildlife, or domestic animal population, we will allow management of mosquito 

populations on National Wildlife Refuge System (Refuge System) lands using effective means 

that pose the lowest risk to wildlife and habitats. In summary, the guidance provides for the 

following: 

 Mosquito management can occur only when local and current monitoring data indicate 

that refuge-based mosquitoes are contributing to a human, wildlife, or domestic animal 

health threat. 

 Refuges may use compatible nonpesticide options to manage mosquito populations that 

represent persistent threats to health. 

 Refuges will collaborate with Federal, State, or local public health authorities and vector 

control agencies to identify refuge-specific health threat categories. These categories will 

represent increasing levels of health risks, and will be based on monitoring data. 

 Management decisions for mosquito control will be based on meeting or exceeding 

predetermined mosquito abundance or disease threshold levels that delimit threat 

categories. 

 In the case of officially determined mosquito-borne disease emergencies, we will follow 

the guidelines described in this document. Monitoring data are still required to ensure 

that intervention measures are necessary. 

 All pesticide treatments will follow Service and Department of the Interior pest 

management and pesticide policies. In an emergency, the pesticide approval process can 

be expedited. 

 Refuges must comply with Federal statutes and Service policies by completing the 

appropriate documentation prior to mosquito management activities taking place. 

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MOSQUITO MANAGEMENT GUIDANCE FOR 2005 

Although the National Wildlife Refuge System (Refuge System) does not engage in mosquito 

control activities directly, under certain circumstances we will allow State or local vector control 

agencies to conduct mosquito control on refuge lands when it is necessary to protect the health 

and safety of humans, wildlife, or domestic animals. 

In the management of the Refuge System, we will allow populations of native mosquito species 

to function unimpeded unless they cause a wildlife and/or human health threat. This interim 

guidance recognizes that mosquitoes are a natural component of most wetland ecosystems, but 

may also represent a threat to human, wildlife, or domestic animal health. When necessary to 

protect the health and safety of the public or a wildlife or domestic animal population, we will 

allow management of mosquito populations on Refuge System lands using effective means that 

pose the lowest risk to wildlife and habitats. Except in cases of officially determined health 

emergencies, any method we use to manage mosquito populations within the Refuge System 

must be compatible with the purpose(s) of an individual refuge and the Refuge System mission, 

and must comply with applicable Federal laws such as the Endangered Species Act. Compatible 

habitat management and pesticide uses for mosquito control must give full consideration to the 

integrity of nontarget populations and communities. They must also be consistent with 

integrated pest management strategies and with existing pest management policies of the 

Department of the Interior (Department) and the Service. We will allow pesticide treatments for 

mosquito population control on Refuge System lands only when local, current mosquito 

population monitoring data are collected and the data indicate that refuge-based mosquito 

populations are contributing to a human, wildlife, or domestic animal health threat. 

Mosquito-Associated Health Threats on National Wildlife Refuges 

A mosquito-associated health threat is defined as an adverse impact to the health of human, 

wildlife, or domestic animal populations from mosquitoes. A health threat determination will be 

made by the appropriate Federal, State, or local public health authority that has the expertise and 

the official capacity to identify human, wildlife, or domestic animal health threats. 

Documentation of a specific health threat on a refuge by a Federal, State, or local public health 

agency must be based on local and current mosquito population and/or mosquito-borne disease 

monitoring data. 

A health emergency indicates an imminent risk of serious human disease or death, or an 

imminent risk to populations of wildlife or domestic animals. A health emergency represents the 

highest level of mosquito-associated health threats. Health emergencies will be determined by 

Federal, State, or local public health authorities and documented with local and current mosquito 

population and disease monitoring data. 

Addressing Health Threats from Refuge-Based Mosquitoes 

Prior planning to address mosquito-associated health threats and emergencies is strongly 

encouraged. Refuges where health threats have been documented (see below) are encouraged to 

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work collaboratively with Federal, State, or local public health authorities and vector control 

agencies to develop integrated pest management (IPM) plans for monitoring and potentially 

managing refuge mosquito populations. Development of such plans (Exhibit 1) is particularly 

important for refuges currently lacking a mosquito monitoring/management program, but where 

a potential health threat has been identified by public health authorities. These refuge-specific 

IPM plans will outline the conditions under which monitoring and mosquito population 

management would occur (exhibit 1). Development of a mosquito management IPM plan during 

a health emergency is not appropriate; refer to the section below that addresses emergency 

procedures. 

Nonpesticide Options and Best Management Practices for Mosquito Control 

When necessary to protect human, wildlife, or domestic animal health, we will reduce mosquitoassociated health threats using an integrated pest management (IPM) approach, including, when 

practical, compatible, nonpesticide actions that reduce mosquito production. The procedures 

described in this section may be considered long-term options to reduce persistent mosquitoassociated health threats. Except in officially determined health emergencies, any procedure we 

use to reduce mosquito production must meet compatibility requirements as found in 603 FW 2 

and must give full consideration to the safety and integrity of nontarget organisms and 

communities, including federally listed threatened and endangered species. 

 For native or nonnative species of mosquitoes, we will remove or otherwise manage 

artificial breeding sites such as tires, tanks, or other similar debris/containers, where 

possible, to eliminate conditions that favor mosquito breeding regardless of health threat 

conditions. 

 When enhancing, restoring, or managing habitat for wildlife, we will consider using 

specific actions that do not interfere with refuge purposes or wildlife management 

objectives to reduce mosquito populations. Examples include water-level manipulation 

that disrupts mosquito life cycles, including timing and rate of flood-up and drawdown of 

managed wetlands, and/or vegetation management to discourage egg laying by 

mosquitoes. Except when determined appropriate during human or wildlife health 

emergencies, we prohibit habitat manipulations for mosquito management that conflict 

with wildlife management objectives, such as draining or maintaining high water levels 

inappropriate for other wildlife. 

 We will consider the introduction of predators for mosquito management only if we can 

contain such introductions. Such introductions must have demonstrated efficacy, have 

been evaluated by the refuge with respect to potential adverse impacts to nontarget 

organisms and communities, not interfere with the purpose(s) of the refuge or other 

refuge management objectives, and not adversely affect federally listed species. We must 

have appropriate procedures in place for all species introductions to ensure that we do not 

release other species with the desired introductions. Any introduction of a nonnative 

predator requires a compatibility determination, a written plan for containment of the 

introduced species to the desired location(s) and, if applicable, an Endangered Species 

Act (ESA), section 7(a)(2), consultation examining the evaluation of potential effects of 

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the introduced predator on federally listed threatened or endangered species. In 

compliance with Executive Order 13112, we will not authorize any activities likely to 

cause or promote the introduction or spread of invasive species (see 601 FW 3). 

Monitoring Mosquito Populations 

We recognize the importance of monitoring mosquito populations to document species 

composition and estimate their size and distribution because this information is used to make 

integrated pest management decisions. We will allow compatible monitoring of mosquito 

populations on Refuge System lands by State/local public health authorities or vector control 

agencies. 

The goal of mosquito monitoring is to detect relative changes in population sizes that can 

indicate an increased risk to human, wildlife, or domestic animal health (see section on action 

thresholds below). In addition, adult mosquitoes collected with certain traps can be tested for the 

presence of pathogens. Mosquito abundance data is recorded by the manner in which the 

mosquitoes are collected. The standard tool for monitoring larval and pupal mosquito 

populations is a long-handled 500 ml “dipper”. The tool is dipped at several locations within a 

mosquito breeding habitat and the number of larvae and pupae recovered is recorded. The 

density of mosquitoes within a specific habitat is recorded as the average number per dip. Adult 

mosquitoes are collected with a number of different portable or semi-permanent traps, and 

abundance is usually recorded, by species, as number of individuals per trapping period. 

Although some vector control agencies use the number of biting mosquitoes landing on a human 

subject per minute to assess mosquito abundance, this technique is not recommended on refuges 

due to the increased risk of the subject acquiring a mosquito-borne pathogen. 

We will allow compatible monitoring of larval and adult mosquito populations on refuges under 

special use permits (SUPs) issued by individual refuges. To avoid harm to wildlife or habitats, 

access to traps and sampling stations must meet the compatibility requirements found in 

603 FW 2 and may be subject to refuge-specific restrictions. Where federally listed species are 

present, monitoring methods must undergo an ESA, section 7(a)(2), consultation in order to 

determine whether or not such monitoring programs will adversely affect the listed species. 

Mosquito-Borne Disease Monitoring 

The purpose of mosquito-borne disease monitoring is to detect the presence of mosquito-borne 

pathogens and estimate the relative intensity of disease transmission over time. The data 

collected in such monitoring is used to estimate health risks to humans, wildlife, or domestic 

animals, and to make mosquito management decisions based on the level of risk. The ultimate 

goal in mosquito-borne disease monitoring is to detect disease activity prior to any human 

infection. Early detection of pathogenic activity, combined with up-to-date mosquito population 

monitoring, can allow for timely intervention measures to occur and thus potentially lessen the 

impact of disease on humans, wildlife, and domestic animals. 

Federal and/or State/local public health and wildlife management authorities can use 

documentation of previous or current mosquito-borne disease activity near the refuge to identify 

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a potential health threat. We will obtain mosquito-borne disease activity information from 

State/local public health authorities. 

Refuge personnel will note dead or sick wildlife during their routine outdoor activities. In most 

cases, this will only involve passive surveillance for affected wildlife. Refuges will identify a 

facility that will test dead or sick wildlife for mosquito-borne pathogens. This may be a State or 

local laboratory or the National Wildlife Health Center. Refuge personnel will receive 

instruction on proper procedures for safely collecting, handling, shipping, or disposing of 

potentially infected wildlife (refer to guidelines developed by the National Wildlife Health 

Center: http://www.nwhc.usgs.gov/research/west_nile/wnv_guidelines.html). If wildlife 

specimens from a refuge test positive for mosquito-borne disease, we will provide these results 

to the State/local public health authorities, State fish and wildlife agencies, and the refuge 

supervisor immediately. 

State/local public health authorities or vector control districts will generally be responsible for 

other disease surveillance methods, such as monitoring disease activity in reservoir hosts for 

pathogens or antibodies, and collecting adult mosquito samples using live traps and testing them 

in same-species pools for virus. These activities must meet the compatibility requirements of 

603 FW 2, and we must authorize the activities. We discourage using caged sentinel chickens on 

refuges for reservoir host surveillance due to the risk of spreading disease to wild birds. 

Individual refuges may allow compatible disease surveillance activities under SUPs or other 

agreements. To avoid harm to wildlife or habitats, access to traps and sampling stations must 

meet the compatibility requirements found in 603 FW 2 and may be subject to refuge-specific 

restrictions. Where federally listed species are present, monitoring methods must undergo an 

ESA, section 7(a)(2), consultation in order to determine whether or not such monitoring 

programs will adversely affect the listed species. 

Risk Assessment 

The first step in addressing mosquito management on a refuge is notification by the appropriate 

Federal, State, or local public health authority of a potential mosquito-associated health threat. 

Federal and/or State/local public health authorities with expertise in mosquitoes and mosquitoborne disease will identify and document a potential mosquito-associated human health threat 

and notify the refuge manager. Appropriate documentation may include species-specific larval 

or adult mosquito monitoring data from the refuge or areas adjacent to the refuge that indicate an 

abundance of species known to vector one or more endemic/enzootic diseases or otherwise 

adversely impact human health. For refuges with current mosquito monitoring programs, such 

documentation should already be in place. For refuges without an ongoing mosquito or disease 

monitoring program, documented mosquito-borne disease activity near the refuge would also 

identify a health threat (refer to section below on emergencies, if applicable). The identification 

and documentation of a potential mosquito-associated health threat does not necessarily imply a 

need to manage mosquito populations, but may indicate the need to initiate on-refuge monitoring 

(if not already underway) and contingency planning should mosquito management become 

necessary. 

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Health threat determinations will be made at the local level, based on the historical incidence of 

mosquito-borne health threats and current, local monitoring of mosquito populations and disease 

activity. When a potential health threat has been documented, we will work with local, State, or 

Federal public health authorities with expertise in mosquito-borne disease epidemiology to 

identify refuge-specific categories of mosquito-associated human health threats based on 

monitoring data. Where local or State public health expertise in mosquito-borne disease 

epidemiology is lacking, we will consult with the Department of Health and Human Service’s 

Centers for Disease Control and Prevention (CDC) to develop these categories. Health threats 

lie along a continuum in potential severity from secondary infection of mosquito bites to lethal 

infection by a mosquito-borne pathogen. Health threat categories will reflect increasing severity 

and risks to health (table 1). 

Federal and/or State/local public health authorities with jurisdiction inclusive of refuge 

boundaries will make actual mosquito-associated human health threat level determinations using 

current local monitoring data and take the appropriate response(s) developed for that threat 

category (table 1). We will also respond appropriately to determinations made by neighboring 

State/local public health authorities. Mosquito-associated wildlife health threat determinations 

will be made by wildlife health experts from Federal or State wildlife agencies. 

Action Thresholds 

We expect mosquito-associated health threat levels to vary over time and space. In general, the 

health threat levels can be expected to be relatively static, changing only when monitoring data 

indicate significant changes in mosquito populations and/or disease activity. When monitoring 

data indicate an increasing risk to human and/or wildlife health, health threat levels may be 

increased (table 1). Action thresholds are mosquito population levels and/or levels of disease 

activity that, once reached, indicate an increased health risk and trigger additional response. We 

will establish numerical action thresholds in collaboration with Federal and/or State/local public 

health authorities and vector control agencies. 

Mosquito abundance action thresholds represent mosquito population levels that may require 

intervention measures or more intense surveillance. It is important to consider the limitations of 

such numerical action thresholds, especially in the context of minimizing disease transmission. 

Thresholds are developed considering many factors which include, but are not limited to, those 

listed in table 2. Unfortunately, very few scientifically-determined estimates of mosquito 

abundance have been defined as threshold values for any mosquito species in the context of 

limiting disease transmission. Vector control agencies usually develop threshold values for their 

own immediate use based on years of experience. However useful such values are for limiting 

human annoyance from biting mosquitoes, these values often cannot be practically validated 

with respect to being accurate thresholds of disease transmission. Thus, in the absence of 

scientifically-determined threshold data, there will necessarily be some subjectivity in 

establishing numeric thresholds for mosquito abundance. 

The factors identified in table 2 can be used as a guide in establishing numeric thresholds 

collaboratively with public health authorities and vector control agencies. When establishing 

mosquito abundance thresholds in the context of mosquito-borne disease, it is appropriate to 

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consider the current and historical incidence of disease and the vector potential of the species. 

Also note that numerical thresholds can be raised or lowered depending upon current conditions 

(e.g., environmental conditions, abundance of mosquito predators, presence of pathogens; see 

table 2). 

Thresholds will be species specific (or species-group specific) for larval, pupal, and adult 

mosquito vectors and reflect the potential significance of a particular species or group of species 

in to a particular health threat. For example, mosquito vector species known to be important in 

the transmission cycle of a disease may have a lower action threshold than species with lesser 

transmission roles. We will implement intervention measures only when current mosquito 

population estimates, as determined by current mosquito monitoring data, meet or exceed action 

thresholds. 

Treatment Options 

Mosquito population management will be based on the level of health threat identified. The 

appropriate response to a health threat will be based on the level of severity and risk associated 

with that particular threat (table 1). 

We will choose treatment based on our pest management policy (30 AM 12). We will base the 

choice on, in order of preference: human safety and environmental integrity, effectiveness, and 

cost. We will use human, wildlife, and/or domestic animal mosquito-associated health threat 

determinations combined with refuge mosquito population estimates to determine the appropriate 

refuge mosquito management response (table 1). Where federally listed threatened or 

endangered species are present, we will use ESA, section 7(a)(2), consultation information to 

assist in the decision-making process. 

We will consider allowing pesticide treatments to control mosquitoes on Refuge System lands 

after we evaluate all other reasonable IPM actions (see above). We will determine the most 

appropriate pesticide treatment options based on monitoring data for the relevant mosquito life 

stage. We will use current monitoring data for larval, pupal, and adult mosquitoes to determine 

the need for larvicides, pupacides, and adulticides, respectively. We will allow the use of 

adulticides only when there are no practical and efficacious alternatives to reduce a health threat. 

We will not allow pesticide treatments for mosquito control on Refuge System lands without 

current mosquito population data indicating that such actions are warranted. We require an 

approved pesticide use proposal (PUP) prior to application of a pesticide to Refuge System 

lands. 

Emergency Procedures 

Federal, State, or local public health authorities may officially identify a mosquito-borne disease 

human health emergency based on documented disease activity in humans, wildlife, or domestic 

animals. A human health emergency indicates an imminent risk of serious human disease or 

death. Public health authorities may request pesticide treatments to Refuge System lands to 

decrease mosquito vector populations and lower the health risk to humans. Refuges with 

ongoing mosquito monitoring programs should have addressed potential emergency situations 

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and appropriate responses within those documents. Refuges without an ongoing monitoring 

program should immediately contact their refuge supervisor and Regional IPM coordinator in the 

event of an emergency and review the steps listed below. Even in emergency situations, we will 

only allow pesticide treatments for mosquito population control on Refuge System lands when 

local and current mosquito population monitoring data are available and the data indicate that 

refuge-based mosquito populations are contributing to a human and/or wildlife health threat. In 

the context of a mosquito-borne disease emergency, appropriate documentation would include 

identification of infected mosquitoes or abundant populations of vector species within refuge 

boundaries. In mosquito-borne disease emergency situations, we will undertake the following: 

 If no mosquito population data are available for the refuge, we will request (or undertake, 

if applicable) short-term (24 hours or less) monitoring of adult and/or larval mosquito 

populations on the refuge to ensure that intervention is necessary. 

 We will complete and submit a pesticide use permit (PUP) to the Regional IPM 

coordinator and Washington Office IPM coordinator, if applicable, for emergency 

review. Actual use of any pesticide will be contingent on current mosquito population 

monitoring data indicating intervention with pesticides is warranted. However, in an 

emergency we will not wait for monitoring results to initiate the PUP process, and we 

will expedite the review of PUPs. 

 If there is no site-specific National Environmental Policy Act (NEPA) documentation for 

the proposed emergency intervention measure(s), contact the Regional NEPA coordinator 

for guidance (see below). 

 If federally listed species are present and an ESA, section 7(a)(2) consultation has not 

been completed for the potential intervention measures, we will contact the local 

Ecological Services (ES) office for recommendations (see below). 

 We will notify refuge employees and visitors of the increased human health risk and 

provide information for personal protection against mosquito-borne disease. Where 

appropriate, we will consider restricting or closing all or part of the refuge to visitors and 

restricting outdoor activities of employees. 

 If monitoring data indicate that intervention with pesticides is warranted, we will prepare 

an SUP for pesticide application(s), in which we may identify pertinent conditions and 

restrictions on pesticide application activities to ensure compatibility. 

 Following pesticide applications, we will require (or undertake, if applicable) additional 

mosquito population monitoring to assess the efficacy of the pesticide treatment(s). 

Communication and Conflict Resolution 

It is important to develop a communication plan with public health and vector control agencies, 

particularly in regard to addressing emergencies. Timely communication at the outset of an 

emergency will speed any necessary response. Contact information should be shared among 

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agencies, and refuges should have the necessary contact information of appropriate Service 

personnel to expedite any needed compliance documentation (see below). 

Mosquito management on NWRs can be a very controversial issue, especially with regard to 

applying pesticides to control mosquito populations. Developing health threat categories and 

establishing action thresholds in collaboration with public health and vector control agencies can 

be a difficult process. This may be especially true in establishing mutually-agreed upon action 

thresholds, where the science is often lacking and the numbers become somewhat subjective. In 

cases where agreements cannot be reached, we will work with the public health and vector 

control agencies to identify third-party agencies or individuals with appropriate expertise in 

mosquito biology and vector-borne disease ecology for further guidance. 

Compliance Documentation 

The following statutes and policies may be relevant to mosquito management activities on 

refuges. In most cases, proper documentation must be in place prior to any mosquito 

management occurring. 

A. National Environmental Policy Act (NEPA) (42 U.S.C. 4321-4347). 

(1) Categorical Exclusions. Under most circumstances, we can categorically exclude 

monitoring and surveillance activities under existing Department NEPA procedures for data 

collection and inventory (516 DM 2, appendix 1.6; and 516 DM 8.5B(1), see 

516 DM 2, appendix 2, for exceptions to categorical exclusions). In addition, some habitat 

management actions as described above may be categorically excluded. If a proposed refuge 

mosquito management activity qualifies as a categorical exclusion, refuges should document that 

determination by preparing an environmental action statement (EAS). We generally cannot 

categorically exclude intervention measures such as pesticide applications for mosquito-borne 

health threats. 

(2) Environmental Assessments. Refuges that have completed the NEPA process for mosquito 

management should ensure that they addressed the environmental consequences of potential 

intervention measures for mosquito-associated health threats. Refuges that have not completed 

the NEPA process for mosquito management should prepare an environmental assessment (EA) 

if they can reasonably expect to need intervention measures (e.g., pesticide applications). You 

may reasonably expect intervention measures if the State/local public health agency has 

documented a potential health threat from refuge-based mosquitoes. In a nonemergency 

situation, when a State/local public health agency documents a potential threat, you must 

complete an EA with the appropriate finding (such as a finding of no significant impact 

(FONSI)) prior to any substantial intervention activities. You must consider local conditions in 

an EA. When assessing the potential environmental effects of pesticide applications, consider 

such factors as the spatial and temporal extent of the treatment, the toxicity and specificity of the 

proposed pesticide(s) to fish and wildlife populations, the persistence of the proposed 

pesticide(s), and the alternatives to the proposed action (e.g., different pesticides, using larvicides 

versus adulticides, compatible habitat management). To minimize potential impacts, identify 

and document restricted areas and activities in an EA. 

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(3) Emergencies. In a health emergency, you may need to take immediate intervention 

measures without completing a NEPA review. If such measures cannot be categorically 

excluded, contact the Regional NEPA coordinator who will consult with the Council on 

Environmental Quality (CEQ) for guidance. The CEQ may require follow-up documentation 

once the emergency has passed. Once an emergency has passed, you must complete proper 

NEPA documentation that addresses future mosquito management activities on the refuge. 

B. Endangered Species Act (16 U.S.C. 1531-1544). Comply with ESA, section 7(a)(2), for 

listed species. You should complete this prior to an emergency. In order to complete 

consultation in a timely manner, please submit consultation documents at least 135 days prior to 

proposed mosquito management activities. Note that the Department pesticide use policy (517 

DM 1) and the Department/Service pest management policy (30 AM 12) do not allow for 

adverse impacts to listed species from pesticides. Should a health emergency occur prior to the 

completion of an ESA, section 7(a)(2), consultation, contact the local ES office for 

recommendations. An “after-the-fact” consultation may be required once the emergency has 

passed. 

C. Federal Insecticide, Fungicide, and Rodenticide Act (7 U.S.C. 136 et seq.). On Service 

lands, we may only use pesticides that are registered with the Environmental Protection Agency. 

We must apply them according to the pesticide label directions. 

D. Compatibility Determination (50 CFR 26.41 and 603 FW 2). We must complete a 

compatibility determination before allowing surveillance and intervention activities to be 

undertaken by an outside agency. However, we may waive this requirement in a health 

emergency involving humans, wildlife, and/or domestic animals. In health emergencies 

involving wildlife, we will consult with the State fish and wildlife agency. In health emergencies 

involving domestic animals, we will consult with the State Agricultural Department. 

E. Pest Management and Pesticide Use Policies (516 DM 1 and 30 AM 12). Follow all 

Department and Service pest management and pesticide use policies. Before applying any 

pesticide to Refuge System lands, you must have a PUP reviewed and approved by the 

appropriate Regional or National IPM coordinator. The National IPM coordinator must approve 

the use of all adulticides. We can expedite PUP approvals in a health emergency. If an outside 

agency conducts pesticide applications, as will usually be the case, we require an SUP, 

memorandum of understanding, or other agreement. The agreement will detail the justification 

for pesticide applications, identify the specific areas to be treated, and list any restrictions or 

conditions that must be followed before, during, or after treatment. 

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Table 1. Example of Mosquito-Borne Disease Health Threat and Response Matrix

Current Conditions

Health Threat 

Category1

Refuge 

Mosquito 

Populations2

Threat 

Level

Refuge Response

No documented existing 

or historical health 

threat/emergency 

No action threshold 1 Remove/manage artificial 

mosquito breeding sites such as 

tires, tanks, or similar 

debris/containers. Allow 

compatible monitoring. 

Below action 

threshold 

2 Response as in threat level 1, 

plus: evaluate compatible 

nonpesticide management 

options to reduce mosquito 

production. 

Documented historical 

health threat/emergency 

Above action 

threshold 

3 Response as in threat level 2, 

plus: allow compatible sitespecific larviciding of infested 

areas as determined by 

monitoring. 

Below action 

threshold 

4 Response as in threat level 2, 

plus: increase monitoring and 

disease surveillance. 

Documented existing 

health threat (specify 

multiple levels, if 

necessary; e.g., disease 

found in wildlife, 

disease found in 

mosquitoes, etc.) 

Above action 

threshold 

5 Response as in threat levels 3 

and 4, plus: allow compatible 

site-specific larviciding, 

pupaciding, or adulticiding of 

infested areas as determined by 

monitoring data. 

Below action 

threshold 

6 Maximize monitoring and 

disease surveillance. 

Officially determined 

existing health 

emergency 

Above action 

threshold 

7 Response as in threat level 6, 

plus: allow site-specific 

larviciding, pupaciding, and 

adulticiding of infested areas as 

determined by monitoring. 

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1 Health threat/emergency as determined by Federal and/or State/local public health or wildlife 

management authorities with jurisdiction inclusive of refuge boundaries and/or neighboring 

public health authorities. 

2

 Action thresholds represent mosquito population levels that may require intervention measures. 

Thresholds will be developed in collaboration with Federal and/or State/local public health or 

wildlife management authorities and vector control districts. They must be species and life stage 

specific (see text). 

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Table 2. Factors to be considered in establishing thresholds for use of 

larvicides/pupacides/adulticides to control mosquitoes to address human health threats. 

Factor Description Consideration

 Mosquito species Mosquito species vary in the 

following: their ability to carry and 

transmit disease; flight distances; 

feeding preference (birds, mammals, 

humans); seasonality; and type of 

breeding habitat 

These factors should be considered 

when establishing adult and larval 

thresholds. Often the species and 

biology of the mosquito will be more 

important in developing thresholds 

than the relative abundance. 

Proximity to human populations The distance from potential 

mosquito habitat on NWRs to 

population centers (numbers and 

density). 

The potential to produce large 

numbers of mosquitoes in close 

proximity to population centers may 

result in less tolerance or lower 

thresholds for implementation of 

mosquito control on NWRs. 

Weather patterns Prevailing wind patterns, 

precipitation, and temperatures. 

Prevailing wind patterns that carry 

mosquitoes from refuge habitats to 

population centers may require lower 

thresholds. Inclement weather 

conditions may prevent mosquitoes 

from moving off-refuge resulting in 

higher thresholds. 

Cultural mosquito tolerance The tolerance of different 

populations may vary by region of 

the Country and associated culture 

and tradition. 

In many parts of the Country, 

mosquitoes are accepted as a way of 

life, resulting in higher mosquito 

management thresholds. NWRs in 

highly populated areas may require 

lower thresholds because of the 

intolerance of urban dwellers to 

mosquitoes. 

Adults harbored, but not produced, 

on-refuge 

Refuge provides resting areas for 

adult mosquitoes produced in the 

surrounding landscape. 

Threshold for mosquito management 

on the refuge should be high with an 

emphasis for treatment of mosquito 

breeding habitat off refuge. 

Spatial extent of mosquito breeding 

habitat 

The relative availability of mosquito 

habitat within the landscape that 

includes the refuge. 

If the refuge is a primary breeding 

area for mosquitoes that likely affect 

human health, threshold may be 

lower. If refuge mosquito habitats 

are insignificant in the context of the 

landscape, thresholds may be higher. 

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INTERIM MOSQUITO GUIDANCE 2005 4/2005 

16

Factor Description Consideration

Natural predator populations Balanced predator-prey populations 

may limit mosquito production. 

If refuge vertebrate and invertebrate 

prey populations are adequate to 

control mosquitoes, threshold for 

treatment should be high. 

Type of mosquito habitat Preferred breeding habitat for 

mosquitoes is species- specific. 

Because breeding habitat is speciesspecific, thresholds for each species 

to initiate control should be 

correlated with appropriate habitat 

types. 

Water quality Water quality influences mosquito 

productivity. 

High organic content in water may 

increase mosquito productivity, 

lower natural predator abundance, 

and may require lower thresholds. 

Opportunities for water and 

vegetation management 

Management of water levels and 

vegetation may reduce mosquito 

productivity. 

Thresholds for treatment should be 

higher where mosquitoes can be 

controlled through habitat 

management. 

Presence/absence of vector control 

agency 

Many areas do not have adequate 

human populations to support 

vector control. In addition, 

resources available for mosquito 

management vary among districts. 

Thresholds for management may be 

much higher or non-existent in areas 

without vector control. 

Accessibility for monitoring/control Refuges may not have adequate 

access to monitor or implement 

mosquito management. 

Thresholds will probably be higher 

for refuges with limited access that 

will require cost- prohibitive 

monitoring and treatment strategies. 

History of mosquito borne diseases in 

area 

Past monitoring of wildlife, 

mosquito pools, horses, sentinel 

chickens, and humans have 

documented mosquito-borne 

diseases. 

Thresholds in areas with a history of 

mosquito-borne disease(s) will 

likely be lower. 

K1-16
INTERIM MOSQUITO GUIDANCE 2005 4/2005 

17

EXHIBIT 1 

Outline: Integrated Pest Management Plan for Mosquito Associated Threats on Refuges

I. Health Threat Determination. 

A. Describe the communication process and identify points of contact and their contact 

information for Federal and/or State/local public health authorities, vector control districts, and 

recognized experts in vector ecology, epidemiology, public health, and wildlife health. Identify 

agency with public human health authority and personnel with medical training regarding the 

epidemiology of mosquito-borne diseases that has the official capacity to make a human health 

determination. 

B. Elaborate on regional/local history of mosquito associated health threat(s). Identify endemic 

and enzootic mosquito-borne diseases. 

C. Determine health threat using criteria in table 1 based on documentation from Federal or 

State fish and wildlife agency health experts, Federal and/or State/local public health authorities, 

and/or public health veterinarians employed by the appropriate public health authorities that 

refuge-based mosquitoes threaten human, wildlife, or domestic animal health. 

1. Off-refuge (or on-refuge, if available) mosquito surveillance summary data (species 

and abundance). 

2. List of mosquito species present, enzootic/endemic diseases they may vector, and any 

other potential adverse impacts to health they may have. 

II. Monitoring Mosquito Populations (developed in cooperation with Federal/State/local 

public health authorities, vector control agencies, and State fish and wildlife agencies). 

A. Identify the purpose and goals of monitoring on the refuge. 

B. Identify who will be conducting the monitoring on the refuge and their contact information. 

C. Identify when monitoring will be conducted. 

1. Routine, seasonal; or 

2. Monitoring only when threat level is elevated (identify triggers for monitoring). 

D. Description of monitoring protocols. 

1. Larval and pupal mosquito monitoring and breeding habitat inventory and mapping. 

(a) Objective(s) 

(b) Method(s). 

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INTERIM MOSQUITO GUIDANCE 2005 4/2005 

18

(c) Sampling locations and numbers of samples/location. 

(d) Frequency of sampling. 

(e) Processing/identification of samples (species, larval stage). 

2. Adult mosquito monitoring. 

(a) Method(s) of sampling (e.g., traps, landing counts). 

(b) Sampling locations and frequency of sampling. 

(c) Processing/identification of samples. 

3. Post-treatment monitoring: Monitoring should continue after any treatment to 

determine efficacy. 

E. Reporting. 

1. Refuge receives copies of all monitoring data concerning refuge. 

2. Refuge shares annual habitat management plans, if applicable, with public health or 

vector control agency. 

F. Restrictions/Stipulations: Identify any restrictions/stipulations on monitoring activities (e.g., 

access, vehicle use, sensitive species or habitats, time of day, etc.) to ensure compatibility. 

III. Surveillance of Mosquito-Borne Disease (developed in cooperation with 

Federal/State/local public health authorities, vector control agencies, and State fish and 

wildlife agencies). 

A. Identify the purpose and goals of surveillance. 

B. Identify who will be conducting surveillance on or near the refuge and their contact 

information. 

C. Identify when surveillance will be conducted. 

1. Routine, seasonal surveillance; or 

2. Surveillance only when threat level is elevated (identify triggers for surveillance). 

D. Description of surveillance protocols. 

1. Disease monitoring. 

(a) Objective(s). 

(b) Method(s). 

(c) Monitoring locations. 

(d) Wildlife testing facility (for dead or sick wildlife found on the refuge). 

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INTERIM MOSQUITO GUIDANCE 2005 4/2005 

19

2. Disease activity notification procedures between public health agency, State fish and 

wildlife agency, and refuge (these procedures are developed cooperatively). 

3. Post-treatment monitoring: Surveillance should continue after any treatment to 

determine efficacy. 

E. Restrictions/Stipulations: Identify any restrictions/stipulations on surveillance activities (e.g., 

access, vehicle use, sensitive species or habitats, time of day, etc.). 

IV. Treatment Options (developed in cooperation with Federal/State/local public health 

authorities, and vector control agencies, and State fish and wildlife agencies using stepwise 

approach, table 1). 

A. Identify and categorize refuge-based mosquito species or species groups based on role in 

transmission cycle(s) of enzootic/endemic diseases and other impacts to human, wildlife, or 

domestic animal health. 

B. Identify species-specific larval, pupal, and adult mosquito vector action threshold levels that 

reflect the importance of vector species in identified health threats (see table 2). 

C. Identify health threat levels and describe potential intervention measures for each level (table 

1). Include non-pesticide and pesticide intervention options. 

D. Complete NEPA process, as necessary, to examine potential environmental effects of 

potential intervention measures. In an emergency, contact the Regional NEPA coordinator for 

guidance. 

E. Complete ESA, section 7, consultation for potential impacts to endangered species from 

intervention measures. 

F. Identify specific pesticides or other management actions to use at specific threat levels based 

on NEPA and ESA, section 7, analyses. 

G. Unless it is an emergency, complete a compatibility determination for intervention measures. 

H. Follow Service pesticide use and permitting procedures, and attach approved pesticide use 

proposal (PUP) and special use permits (SUP). 

1. Complete PUP. 

2. Submit PUP to Regional IPM coordinator. In an emergency, contact Regional pest 

management coordinator (and national IPM coordinator, if applicable) to expedite PUP 

approval. 

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20

3. Prepare SUP or other agreement for agency conducting intervention measures, 

outlining specific actions to be taken (when, where, how) and describing any restrictions, 

stipulations, or other conditions on such actions.

K1-20
APPENDIX K2. Statement of Best Management Practices 

and Proposed Monitoring Plan for Coastal 

Region Mosquito and Vector Control 

Districts 

March 13, 2002 K2-1

Statement of Best Management Practices 

and 

Proposed Monitoring Plan 

for 

Coastal Region Mosquito and Vector Control 

Districts 

Alameda County Mosquito Abatement District 

Contra Costa Mosquito and Vector Control District 

Marin-Sonoma Mosquito and Vector Control District 

Napa County Mosquito Abatement District 

Santa Clara County Vector Control District 

San Mateo Mosquito Abatement District 

Solano County Mosquito Abatement District 

FOR WATER QUALITY ORDER NO 2001-12-DWQ STATEWIDE GENERAL NATIONAL 

POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) PERMIT FOR 

DISCHARGERS OF AQUATIC PESTICIDES TO WATERS OF THE UNITED STATES 

(GENERAL PERMIT) NO. CAG990003 

BACKGROUND 

Mosquito and vector control districts (MVCD) within the jurisdiction of the San Francisco Bay 

Region (2) Water Quality Control Board, are seeking coverage under the General Permit as "public 

entities" that apply aquatic pesticides for vector and weed control in waters of the United States. As 

provisioned by the State Water Resources Control Board (SWRCB) Policy for Implementation of 

Toxics Standards for Inland Surface Waters, Enclosed Bays, and Estuaries of California, MVCD 

are allowed categorical exemptions from meeting priority pollutant/objectives for public health pest 

management. Although the administrations of the MVCD vary between special, independent, and 

dependent districts, the underlying health and safety statutory mandates and requirements are one 

and the same (California Health and Safety Code, Division 3). 

While various mosquito larvicides used by the MVCD (Table 1) are directly applied to water 

bodies with the purpose and intent of killing mosquito larvae, extensive research has indicated that 

little or no lasting environmental impacts are imparted. Currently used aquatic pesticides (Bacillus

thuringiensis israelensis, B. sphaericus and methoprene) degrade rapidly in the environment, thus 

the areal extent and duration of residues may be considered negligible. When integrated with other 

strategies including vegetation management, surface acting agents, and predatory mosquitofish, 

these aquatic pesticides constitute safe and effective best management practices (BMP). 
March 13, 2002 K2-2

Similarly, a limited use by MVCD of herbicides, glyphosate and sulfometuron methyl (Table 1) is 

largely restricted to Napa County. These compounds are probably not reaching Waters of the U.S. 

since they are used on the berms of wastewater channels and ponds and are not applied directly to 

water. 

This document presents and discusses the BMPs of the MVCD and proposes a monitoring plan as a 

requisite to the General Permit. The MVCD are confident that currently-established practices are 

very much environmentally safe due to the use of non-toxic or less toxic alternatives and proven 

BMP systems. Additionally, the aquatic pesticides are applied at rates sufficiently low to leave the 

physical parameters of the environment (i.e., temperature, salinity, turbidity and pH) unchanged. 

Therefore, the MVCD are proposing broad exemptions to General Permit requirements that are 

presented and justified below. 

Statement of Best Management Practices 

INTRODUCTION 

The MVCD in the S.F. Bay Region (see map below) are some of the oldest organized programs of 

mosquito control in North America, most have been in existence since the early 1900's. These 

districts were formed (pursuant to California Health and Safety Code Sections 2200-2280) by local 

citizens and governments to reduce the risk of vector-borne disease or discomfort to the residents of 

San Francisco Bay area. This includes vector-borne diseases such as mosquito-borne encephalides 

and malaria. Vector control districts are indirectly regulated by the Department of Pesticide 

Regulation (DPR). Supervisors and applicators are licensed by the California Department of 

Health Services (CDHS). Pesticide use by vector control agencies is reported to the County 

Agricultural Commission (CAC) in accordance with a 1995 Memorandum of Understanding 

among DPR, CDHS, and the CACs for the Protection of Human Health from the Adverse Effects 

of Pesticides and with cooperative agreements entered into between DHS and vector control 

agencies, pursuant to Health and Safety Code section 116180. 
March 13, 2002 K2-3

Map of San Francisco Bay Water Quality Control Region with counties. 

Mosquito and vector control districts in the coastal region have all implemented Best Management 

Practices (BMP)s based on the philosophy of integrated pest management (IPM). The basic 

components of the programs are: (1) surveillance of pest populations, (2) determination of 

treatment thresholds, (3) selection from a variety of control options including physical, cultural, 

biological and chemical techniques (4) training and certification of applicators and (5) public 

education. 

1. MOSQUITO SURVEILLANCE 

Surveillance of pest populations is essential for assessing the necessity, location, timing and choice 

of appropriate control measures. It reduces the areal extent and duration of pesticide use, by 

restricting treatments to areas where mosquito populations exceed established thresholds. The 54 

mosquito species known in California differ in their biology, nuisance and disease potential and 

susceptibility to larvicides. Information on the species, density, and stages present is used to select 

an appropriate control strategy from integrated pest management alternatives. 

A. Larval Mosquito Surveillance 

Surveillance of immature mosquitoes is conducted by MVCD staff assigned to zones within 

“districts”. These technicians maintain a list of known mosquito developmental sites and visit them 

on a regular basis. When a site is surveyed, water is sampled with a 1 pint dipper to check for the 

presence of mosquitoes. Samples are examined in the field or laboratory to determine the 
March 13, 2002 K2-4

abundance, species, and life-stage of mosquitoes present. This information is compared to 

historical records and used as a basis for treatment decisions 

B. Adult Mosquito Surveillance 

Although larval mosquito control is preferred, it is not possible to identify all larval sources. 

Therefore, adult mosquito surveillance is needed to pinpoint problem areas and locate previously 

unrecognized or new larval developmental sites. Adult mosquitoes are sampled using standardized 

trapping techniques (i.e., New Jersey light traps, carbon dioxide-baited traps and oviposition traps). 

Mosquitoes collected by these techniques are counted and identified to species. The spatial and 

seasonal abundance of adult mosquitoes is monitored on a regular basis and compared to historical 

data. 

C. Service Requests 

Information on adult mosquito abundance from traps is augmented by tracking mosquito 

complaints from residents. Analysis of service requests allows district staff to gauge the success of 

control efforts and locate undetected sources of mosquito development. All MVCD conduct public 

outreach programs and encourage local residents to contact them to request services. When such 

requests are received, technicians visit the area, interview residents and search for sources that may 

have been missed. Residents are asked to provide a sample of the insect causing the problem. 

Identification of these samples provides information on the species present and can be helpful in 

locating the source of the complaint. 

2. PRE-TREATMENT DECISION-MAKING 

A. Thresholds 

Treatment thresholds are established for mosquito developmental sites where potential disease 

vector and/or nuisance risks are evident. Therefore, only those sources that represent imminent 

threats to public health or quality of life are treated. Treatment thresholds are based on the 

following criteria: 

- Mosquito species present 

- Mosquito stage of development 

- Nuisance or disease potential 

- Mosquito abundance 

- Flight range 

- Proximity to populated areas 

- Size of source 

- Presence/absence of natural enemies or predators 

- Presence of sensitive/endangered species 

B. Selection of Control Strategy 
March 13, 2002 K2-5

When thresholds are exceeded an appropriate control strategy is implemented. Control strategies 

are selected to minimize potential environmental impacts while maximizing efficacy. The method 

of control is based on the above threshold criteria but also: 

- Habitat type 

- Water conditions and quality 

- Weather conditions 

- Cost 

- Site accessibility 

- Size of site and number of other developmental sites 

3. CONTROL STRATEGIES 

A. Source Reduction 

Source reduction includes elements such as, physical control, habitat manipulation and water 

management, and forms an important component of the Coastal Region MVCD IPM program. 

B. Physical Control 

The goal of physical control is to eliminate or reduce mosquito production at a particular site 

through alteration of habitat. Physical control is usually the most effective mosquito control 

technique because it provides a long-term solution by reducing or eliminating mosquito 

developmental sites and ultimately reduces the need for chemical applications. 

Historically (circa 1903), the first physical control efforts were projects undertaken to reduce the 

populations of salt marsh mosquitoes in marshes near San Rafael. Two years later, similar work 

was undertaken in the marshes near San Mateo. Networks of ditches were created by hand to 

enhance drainage and promote tidal circulation. Since then, various types of machinery have been 

used since then to create ditches necessary to promote water circulation. In recent years, a number 

of environmental modification projects have been undertaken in collaboration with the U.S. Fish 

and Wildlife Service (USFWS) to reduce potential mosquito developmental sites and enhance 

wildlife habitat. Re-circulation ditches allow tidewater to enter the marsh at high tide and drain off 

at low tide. Water remaining in the ditch bottoms at low tide provides habitat for mosquito-eating 

fish. These projects have reduced the need to apply chemicals on thousands of acres of salt marsh 

in the San Francisco Bay. 

Physical control programs conducted by the MVCD may be categorized into three areas: 

"maintenance", "new construction", and "cultural practices" such as vegetation management and 

water management. 

Maintenance activities are conducted within tidal, managed tidal and non-tidal marshes, seasonal 

wetlands, diked, historic baylands and in some creeks adjacent to these wetlands. The following 

activities are classified as maintenance: 

* Removal of sediments from existing water circulation ditches 
March 13, 2002 K2-6

* Repair of existing water control structures 

* Removal of debris, weeds and emergent vegetation in natural channels 

* Clearance of brush for access to streams tributary to wetland areas 

* Filling of existing, non-functional water circulation ditches to achieve required water circulation 

dynamics and restore ditched wetlands. 

 

The preceding activities are included within the permits required by U.S. Army Corps of Engineers 

(USACE) and San Francisco Regional Water Quality Control Board (SFRQWB) (Waste 

Discharge) and coordinated by the California DHS. Additional agencies involved include the 

Coastal Conservancy and San Francisco Bay Conservation and Development Commission. 

New projects, such as wetland restoration, excavation of new ditches, construction of new water 

control structures, all require application by individual districts directly to the USACE. Currently, 

few districts in the coastal region have the resources available to initiate new physical control 

projects. Instead, most districts try to work with landowners to manage their lands in a manner that 

does not promote mosquito development. Coastal region MVCD staff review proposals for 

wetlands construction to assess their impact on mosquito production. The districts then submit 

recommendations on hydrological design and maintenance that will reduce the production of 

mosquitoes and other vectors. This proactive approach involves a collaborative effort between 

landowners and MVCD. Implementation of these standards may include cultural practices such as 

water management and aquatic vegetation control. 

C. Biological control 

Biological control agents of mosquito larvae include predatory fish, predatory aquatic invertebrates 

and mosquito pathogens. Of these, only mosquitofish are available in sufficient quantity for use in 

mosquito control programs. Natural predators may sometimes be present in numbers sufficient to 

reduce larval mosquito populations. Biological control is sometimes used in conjunction with 

selective bacterial or chemical insecticides. 

Mosquitofish (Gambusia affinis) 

The mosquitofish, Gambusia affinis, is a natural predator of mosquito larvae used throughout the 

world as a biological control agent for mosquitoes. Although not native to California, mosquitofish 

are now ubiquitous throughout most of the State's waterways and tributaries, where they have 

become an integral part of aquatic food chains. They can be stocked in mosquito larval sources by 

trained district technicians or distributed to the public for stocking in backyard ornamental ponds 

and other artificial containers. 

Advantages: The use of mosquitofish as a component of an IPM program may be environmentally 

and economically preferable to habitat modification or the exclusive use of pesticides, particularly 

in altered or artificial aquatic habitats. Mosquitofish are self-propagating, have a high reproductive 

potential and thrive in shallow, vegetated waters preferred by many mosquito species. They prefer 

to feed at the surface where mosquito larvae concentrate. These fish can be readily mass-reared for 

stocking or collected seasonally from sources with established populations for redistribution. 
March 13, 2002 K2-7

Barriers to Use: Water quality conditions, including temperature, dissolved oxygen; pH and 

pollutants may reduce or prevent survival and/or reproduction of mosquitofish in certain habitats. 

Mosquitofish may be preyed upon by other predators. They are opportunistic feeders and may 

prefer alternative prey when available. Introduction of mosquitofish may modify food chains in 

small-contained pools and have potential impacts on endemic fish and shrimp in such situations. 

Some wildlife agencies suspect mosquitofish may impact survival of amphibian larvae through 

predation. Recent research has shown no significant impact on survival of the threatened 

California red-legged frog (Lawler et al. 1998), but mosquitofish have been shown to negatively 

impact the survival of the California tiger salamander (Leyse and Lawler 2000). 

Impact on water quality: Mosquitofish populations are unlikely to impact on water quality. 

Solutions to Barriers: Strict stocking guidelines adopted by MVCD restrict the use of mosquitofish 

to habitats such as artificial containers, ornamental ponds, abandoned swimming pools, cattle 

troughs, stock ponds, etc. . . . where water quality is suitable for survival and sensitive or 

endangered aquatic organisms are not present. Fish are generally stocked at population densities 

lower than those required for effective mosquito control and allowed to reproduce naturally 

commensurate with the availability of mosquito larvae and other prey. Guidelines prevent seasonal 

stocking in natural habitats during times of year when amphibian larvae or other sensitive 

species/life stages may be present. 

Natural predators: aquatic invertebrates 

Many aquatic invertebrates, including diving beetles, dragonfly and damselfly naiads, 

backswimmers, water bugs and hydra are natural predators of mosquito larvae. 

Advantages: In situations where natural predators are sufficiently abundant, additional mosquito 

control measures including application of pesticides may be deemed unnecessary. 

Barriers to Use: Predatory aquatic invertebrates are frequently not sufficiently abundant to achieve 

effective larval control, particularly in disturbed habitats. Most are generalist feeders and may 

prefer alternative prey to mosquito larvae if available and more accessible. Seasonal abundance 

and developmental rates often lag behind mosquito populations. Introduction or augmentation of 

natural predators has been suggested as a means of biological control, however there are currently 

no commercial sources since suitable mass-rearing techniques are not available. 

Solutions to Barriers: The presence and abundance of natural predators is noted and taken into 

account during the larval surveillance process. Conservation of natural predators, whenever 

possible, is achieved through use of highly target-specific pesticides including bacterial 

insecticides, with minimal impacts on non-target taxa. 

Impact on water quality: As predatory invertebrates represent a natural part of aquatic ecosystems, 

they are unlikely to impact water quality. There are no established standards, tolerance, or EPA 

approved tests for aquatic invertebrate populations. 

Fungal pathogens (Lagenidium giganteum) 
March 13, 2002 K2-8

Product name: Laginex 

Lagenidium giganteum is a fungal parasite of mosquito larvae. It is highly host-specific; other 

aquatic organisms are not susceptible and there is no mammalian toxicity. Unfortunately, the 

effectiveness of this pathogen has proven to be extremely variable due to stringent environmental 

requirements for growth and development of the fungus. Although commercial formulations 

(aqueous suspension) of this pathogen have been produced, severe limitations on its availability, 

shelf life and handling, as well as inconsistent results have prevented its integration into mosquito 

control programs in California. 

Advantages: Use of fungal pathogens as part of an integrated pest management program may 

reduce the need for use of conventional insecticides. Lagenidium may recycle naturally in certain 

habitats, providing long-term larval reducing the need for repeated applications. 

Barriers to Use: Commercial availability is uncertain. Because it contains living fungal mycelium 

the material has a very limited shelf life and is difficult to handle and apply. It is also very 

sensitive to environmental conditions (i.e., pH, salinity, and temperature), which makes its 

effectiveness highly variable. 

Solutions to Barriers: Lagenidium is not currently in routine use in Coastal Region mosquito 

control programs due to problems with availability and reliability of control. 

Impact on water quality: Lagenidium is a naturally occurring biological control agent At a typical 

application rate of 10 oz of active ingredient (mycelium) per acre it is unlikely to have any 

detectable effect on water quality. There are no established standards, tolerances or EPA approved 

tests for Lagenidium.

 D. Bacterial insecticides 

Bacterial insecticides contain naturally produced bacterial proteins that are toxic to mosquito larvae 

when ingested in sufficient quantity. Although they are biological agents, such products are labeled 

and registered by the Environmental Protection Agency as pesticides and are considered by some to 

be a form of Chemical Control. 

Bacillus thuringiensis var. israelensis (BTI) 

Product names: Acrobe, Bactimos pellets, Teknar HP-D, Vectobac 12AS, Vectobac G, Vectobac 

TP. 

Advantages: BTI is highly target-specific and has been found to have significant effects only on 

mosquito larvae, and closely related insects (e.g., blackflies and some midges). It is available in a 

variety of liquid, granular and pelleted formulations that provide some flexibility in application 

methods and equipment. BTI has no measurable toxicity to vertebrates and is classified by EPA as 

"Practically Non-Toxic" (Caution). BTI formulations contain a combination of five different 
March 13, 2002 K2-9

proteins within a larger crystal. These proteins have varying modes of action and synergistically 

act to reduce the likelihood of resistance developing in larval mosquito populations. 

Barriers to Use: Bacterial insecticides must be fed upon by larvae in sufficient quantity to be 

effective. Therefore applications must be carefully timed to coincide with periods in the life cycle 

when larvae are actively feeding. Pupae and late 4th stage larvae do not feed and therefore will not 

be controlled by BTI. Low water temperature inhibits larval feeding behavior, reducing the 

effectiveness of BTI during the cooler months. High organic conditions also reduce the 

effectiveness of BTI. Cost per acre treated is generally higher than surfactants or organophosphate 

insecticides. 

Solutions to Barriers: An increased frequency of surveillance of larvae ensures that bacterial 

insecticides can be applied during the appropriate stages of larval development to prevent adult 

mosquito emergence. 

Impact on water quality: BTI contains naturally produced bacterial proteins generally regarded as 

environmentally safe. It leaves no residues and is quickly biodegraded. At the application rates 

used in mosquito control programs, BTI is unlikely to have any measurable effect on water quality. 

There are no established standards, tolerances or EPA approved tests. Other naturally occurring 

strains of this bacterium are commonly found in aquatic habitats. 

Bacillus sphaericus (BS) 

Product names: Vectolex CG, Vectolex WDG 

Advantages: BS is another bacterial pesticide with attributes similar to those of BTI. The efficacy 

of this bacterium is not affected by the degree of organic pollution in larval development sites and 

it may actually cycle in habitats containing high densities of mosquitoes, reducing the need for 

repeated applications. 

Barriers to Use: Like BTI, BS must be consumed by mosquito larvae and is not is therefore not 

effective against nonfeeding stages such as late 4th instar larvae or pupae. BS is also ineffective 

against certain mosquito species such as those developing in saltmarshes, seasonal forest pools or 

treeholes. Toxicity of BS to mosquitoes is due to a single toxin rather than a complex of several 

molecules as is the case with BTI. Development of resistance has been reported in Brazil. Thailand 

and France in sites where BS was the sole material applied to control mosquitoes for extended 

periods of time. 

Solutions to Barriers: Information obtained from larval surveillance on the stage and species of 

mosquitoes present can increase the effectiveness of this material, restricting it use to sources 

containing susceptible mosquitoes. Development of resistance can be delayed by rotating BS with 

other mosquitocidal agents. 

 

Impact on water quality: BS is a naturally occurring bacterium and is environmentally safe. It 

leaves no residues and is quickly biodegraded. At the application rates used in mosquito control 

programs, BS is unlikely to have any measurable effect on water quality. There are no established 
March 13, 2002 K2-10

standards, tolerances or EPA approved tests. Other naturally occurring strains of this bacterium are 

commonly found in aquatic habitats. 

E. Chemical Control 

Methoprene 

Product Names: Altosid briquets, Altosid liquid larvicide, Altosid pellets, Altosid SBG, Altosid 

XR briquets, Altosid XRG

Advantages: 

Methoprene is a larvicide that mimics the natural growth regulator used by insects. Methoprene 

can be applied as liquid or solid formulation or combined with BTI or BS to form a "duplex" 

application. Methoprene is a desirable IPM control strategy since affected larvae remain available 

as prey items for predators and the rest of the food chain. This material breaks down quickly in 

sunlight and when applied as a liquid formulation it is effective for only 3 to 5 days. Methoprene 

has been impregnated into charcoal-based carriers such as pellets and briquettes for longer residual 

activity ranging up to 150 days. The availability of different formulations provides options for 

treatment under a wide range of environmental conditions. Studies on nontarget organisms have 

found methoprene to be nontoxic to vertebrates and most invertebrates when exposed at 

concentrations used by mosquito control. 

Barriers to Use: Methoprene products must be applied to larval stage mosquitoes since it is not 

effective against the other life stages. Monitoring for effectiveness is difficult since mortality is 

delayed. Methoprene is more expensive than most other mosquitocidal agents. Methoprene use is 

avoided in vernal pools. There may be toxicity to certain nontarget crustacean and insect species. 

Solutions to Barriers: Surveillance and monitoring can provide information on mosquito larval 

stage present, timing for applications and efficacy of the treatments. 

Impact on Water Quality: Methoprene does not have a significant impact on water quality. It is 

rapidly degraded in the environment and is not known to have persistent or toxic breakdown 

products. It is applied and has been shown to be effective against mosquitoes at levels far below 

those that can be detected by any currently available test. Methoprene has been approved by the 

World Health Organization for use in drinking water containers. 

Surfactants 

Product Names: Golden Bear 1111, Agnique MMF 

Surfactants are "surface-acting agents" that are either petroleum or isostearyl alcohol-based 

materials that form a thin layer on the water surface. These materials typically kill surfacebreathing insects by mechanically blocking the respiratory mechanism. 
March 13, 2002 K2-11

Advantages: These materials are the only materials efficacious for reducing mosquito pupae since 

other larviciding strategies (i.e., methoprene, BTI and BS) are ineffective to that life stage. 

Agnique forms an invisible monomolecular film that is visually undetectable. Treatments are 

simplified due to the spreading action of the surfactant across the water surface and into 

inaccessible areas. These surfactants are considered "practically nontoxic" by the EPA. Agnique is 

labeled "safe for use" in drinking water. 

Barriers to Using: The drawback of using oils in habitats where natural enemies are established is 

that surface-breathing insects, particularly mosquito predators, are similarly affected. GB1111 

forms a visible film on the water surface. 

Solutions to Barriers: As a general rule, surfactant use is considered after alternate control 

strategies have been ruled out or in habitats that are not supporting a rich macro-invertebrate 

community (i.e., manmade sites). 

F. Cultural Practices 

Wetland design criteria were developed and endorsed by DHS and the San Francisco Bay 

Conservation and Development Commission in 1978 as part of the Suisun Marsh Protection Plan 

under California State Assembly Bill 1717. These criteria have been sent to various governmental 

agencies and private parties involved in the planning process for projects having the potential of 

creating mosquito breeding problems. Guidelines for the following source types are included in the 

above marsh protection plan and may be considered cultural control techniques: 

* Drainageway construction and maintenance practices 

* Dredge material disposal sites 

* Irrigated pastures 

* Permanent ponds used as waterfowl habitat 

* Permanent Water impoundments 

* Salt marsh restoration of exterior levee lands 

* Sedimentation ponds and retention basins 

* Tidal marshes 

* Utility construction practices 

The MVCD also provide literature and education programs for homeowners and contractors on 

elimination of mosquito developmental sites from residential property. These sources include rain 

gutters, artificial containers, ornamental ponds, abandoned swimming pools, tree holes, septic 

tanks, and other impounded waters. 

Water Management consists of techniques to control the timing, quantity and flow rate of water 

circulation in managed wetlands to minimize mosquito development. MVCD have established 

guidelines for water management based on information from University of California Agricultural 

Extension Service (UCAES). Districts provide these guidelines to property owners to promote 

proper irrigation techniques for pastures, duck clubs and other wetlands to reduce mosquito 

development. Some MVCD operate structures such as tide gates that control water levels in 

marshes to minimize mosquito production. 
March 13, 2002 K2-12

G. Vegetation Management 

Vegetation Management consists of the removal of vegetation within mosquito developmental sites 

to promote water circulation, increase access of natural predators such as fish or provide MVCD 

staff access for surveillance and treatment operations. Vegetation management is achieved either 

through recommendations to the landowner or by the use of hand tools and the application of 

selective herbicides. 

Vegetation management, one aspect of physical mosquito control, is an effective long-term control 

strategy that is occasionally employed by MVCD. This methodology utilizes water management, 

burning, physical removal, and chemical means to manage vegetation within mosquito 

developmental sites. The presence of vegetation provides harborage for immature and adult 

mosquitoes by protecting them from potential predators as well as the effects of wind and wave 

action, which readily cause mortality. Vegetation reduction not only enhances the effects of 

predators and abiotic factors, but also reduces the need for chemical control. Several factors can 

limit the utilization of vegetation management. These include: sensitivity of the habitat, presence 

of special status species, size of the site, density and type of vegetation, species of mosquito and 

weather. 

A. Burning 

This technique is used to achieve effective mosquito control where the density of unwanted 

vegetation precludes the use of other methodologies. Burning requires a permit, and coordination 

with local fire agencies and the Bay Area Air Quality Management District. This strategy is limited 

to manmade impoundments and fallow farm lands. Factors limiting the use of this technique 

include weather, the limited number of approved burn days, and proximity of human habitation. As 

a general rule, burning is a last resort and not a primary method. 

B. Physical Removal/Mowing/Trimming 

Physical removal of vegetation is used to clear obstructed channels and ditches to promote water 

circulation, effectiveness of predators and improve access for mosquito control personnel to enter 

mosquito developmental sites. Ditches and channels can be cleared with a variety of tools ranging 

from shovels and small pruners to weed whackers and large mechanized equipment. Most removal 

activities performed by MVCD utilize small hand tools. This is the most frequently employed 

management technique once all necessary permits have been obtained and it is performed in all 

types of habitats. Unfortunately, its effectiveness is temporary and labor intensive, and therefore 

requires routine maintenance on an annual or at least biennial basis. Other limiting actors include 

cost, the presence of sensitive species or habitats and the limited time period that MVCD are 

allowed to perform the activity for many types of mosquito developmental sites. 

C. Chemical 

Chemical control of vegetation occurs only in man-made habitats such as impoundments, channels 

and ditches. Both pre- and post-emergent herbicides are used, with strict attention given to label 
March 13, 2002 K2-13

requirements, weather conditions, potential for runoff and drift, and proximity of sensitive 

receptors such as special-status species, sensitive habitats, livestock, crops, and people. Routine 

intensive surveys are conducted to address many of these factors. Most MVCD use little or no 

herbicides. For those that do, two types of herbicides are currently in use. These are: glyphosate 

based (Roundup and Rodeo) and sulfonylurea based (Oust). 

Chemical name: Glyphosate 

Product names: Roundup, Rodeo, Gallup, Landmaster, Pondmaster, Ranger, Touchdown, and 

Aquamaster 

Advantages: Glyphosate based herbicides are not applied directly to water, but along the levee tops 

and margins of wastewater ponds, channels, ditches and access roads as post-emergence herbicides. 

These are non-selective, low-residual herbicides used to control weeds and low-growing brush. 

These materials come in a variety of formulations, allowing for flexibility of use and application. 

MVCD in recent years have only used the Roundup, Rodeo and Aquamaster formulations 

(Aquamaster being the registered replacement for Rodeo). Glyphosate acts in plants by inhibiting 

amino acid synthesis. Roundup (41% of the isopropylamine salt of glyphosate with surfactants) 

and Aquamaster (53% of the isopropylamine salt of glyphosate without surfactants) are applied 

from March through October for spot control of weed growth. Both of these materials are also 

occasionally used to control growth of poison oak, blackberry vines and non-native aquatic weeds 

such as Spartina and peppergrass that would prevent access, impede water flows or out-compete 

native vegetation in sensitive habitats. 

Barriers to using: Landowners are notified before glyphosate is applied to any site and applications 

are timed with their operations. Furthermore, to prevent large, tall stands of dead vegetative 

material, applications must be timed so that weed growth is minimal. Weather conditions, 

specifically wind and rainfall, also affect timing and application of glyphosate based products. The 

proximity of food crops and sensitive habitats must also be considered. 

Solutions to barriers: Intensive surveillance in and around target sites ensures that nontargets are 

not affected. Coordination with landowners and appropriate regulatory authorities verifies that 

reasonable and acceptable applications occur. 

Impact on water quality: In water, glyphosate is strongly adsorbed to suspended organic and 

mineral matter and is broken down primarily by microorganisms. Its half life in pond water ranges 

from 12 days to 10 weeks (Extoxnet). 

Chemical name: Sulfometuron methyl, chemical class sulfonylurea 

Product names: Oust Weed Killer and DPX 5648 

Advantages: Sulfometuron-methyl is a broad spectrum, general use category III pesticide that is 

classed by the US EPA as slightly toxic (acute oral LD50 in rats and mallards greater than 5,000 

mg/kg, acute dermal LD50 in rabbits greater than 2000 mg/kg and acute inhalation LC50 in rats 

greater than 5.3 mg/L). This herbicide can be applied either pre- or post-emergence for the control 
March 13, 2002 K2-14

of a wide variety of grasses and broadleaf weeds and acts by stopping cell division in the growing 

tips of roots and stems. Sulfometuron-methyl is readily broken down in animals (half-life in rats 

shown to be 28-40 hours) with no environmental bioaccumulation having been detected or 

reported. Furthermore, this pesticide is rapidly degraded in water and is broken down in soil by 

microorganisms, chemical action of water (hydrolysis) and sunlight. No teratogenic, mutagenic or 

carcinogenic effects have been detected or reported. 

Barriers to using: Because sulfometuron-methyl is non-selective, this compound may affect nontarget aquatic and terrestrial plant species. This herbicide also does not bind strongly to soil and is 

slightly soluble in water. 

Solutions to barriers: Intensive surveillance in and around target sites ensures that sensitive 

receptors are not affected. Furthermore, coordination with landowners and appropriate regulatory 

authorities verifies that reasonable and acceptable applications occur. No applications occur where 

there is a potential for unwanted runoff. 

Impact on water quality: The reported half-life for sulfometuron-methyl in water varies from 24 

hours to more than two months depending on factors such as light, pH, dissolved oxygen and 

amount of vegetation present. In well aerated acidic water, this herbicide is broken down very 

quickly (Extoxnet). Due to the nature and condition of the application sites (principally wastewater 

ponds) it is not likely that use of this herbicide poses any threat to sensitive habitats or drinking 

water. 

 

H. ORGANOPHOSPHATES (OP) 

While all districts in the San Francisco bay area have used organophosphates in the past, nearly all 

have stopped using these products. Some districts have not used OP's for over 14 years. Mosquito 

and vector control agencies that operate under the California Health and Safety Codes may utilize 

those materials registered as mosquito larvicides under the Federal Fungicide, Insecticide, and 

Rodenticide Act. Such materials used in accordance with label instructions are allowed by law. 

However, as a result of heightened concern over environmental impacts and worker health and 

safety, most of the districts have voluntarily eliminated their use. Organophosphate use will 

probably be reserved for emergency use against disease outbreaks and epidemics. 

4. TRAINING AND CERTIFICATION 

All MVCD applicators must be certified to apply public health pesticides. The CDHS VectorBorne Disease Section administers certification training and testing. All mosquito control 

personnel applying pesticides or overseeing the application of pesticides must obtain a Vector 

Control Technician certificate number. The Mosquito and Vector Control Association of 

California provides training materials and exams are conducted by the CDHS. All certificate 

holders must maintain continuing education credit in at least two and as many as four 

subcategories. Category A (Laws and Regulations) and category B (Mosquito Biology) is 

mandatory for all certificate holders and requires 12 and 8 continuing education units (CEU) 

respectively, in a two year period. Category C (Terrestrial Invertebrate Control) and Category D 

(Vertebrate Control) are optional both with 8 hours of CEU per two-year cycle. 
March 13, 2002 K2-15

Individual districts conduct a number of in-house educational and safety programs to increase the 

expertise of the operational staff. Ultimate decisions regarding the need for and application of 

pesticides rest on the field staff based on information acquired from surveillance data. Decisions to 

apply a particular product are made in accordance to each California Environmental Quality Act 

(CEQA) documentation including threshold levels and other information regarding habitat type, 

distance from populated areas, and water quality data. Training opportunities to accumulate CEU 

credits are made available by the MVCAC regional committees that develop training programs 

fine-tuned to the local ecology and unique problems of the region. Training programs are 

submitted to the MVCAC state training coordinator for approval and then to the California 

Department of Health Services for final approval. Thirty-six hours of CEU credits are offered each 

two-year cycle. 

5. OVERSIGHT 

Members of the MVCAC operate under the California Health and Safety Code and the California 

Government Code (reference Division 1, Administration of Public Health, Chapter 2, Powers and 

Duties; also Part 2, Local Administration, Chapter 8, State Aid for Local Health Administration; 

Division 3, Pest Abatement, Chapter 5, Mosquito Abatement Districts or Vector Control Districts, 

Sections 2200 - 2910). In addition, members of the MVCAC that are signatories to the California 

Department of Health Services Cooperative Agreement (Pursuant to Section 116180, Health and 

Safety Code) are required to comply with the following: 

1. Calibrate all application equipment using acceptable techniques before using; maintain 

calibration records for review by the County Agricultural Commissioner (CAC). 

2. Maintain for at least two years, pesticide use data for review by the CAC including a record of 

each pesticide application showing the target vector, the specific location treated, the size of the 

source, the formulations and amount of pesticides used, the method and equipment used, the type of 

habitat treated, the date of the application, and the name of the applicator. 

3. Submit to the CAC each month a Pesticide Use Report on Department of Pesticide Regulation 

form PR-ENF-060. The report shall include the manufacturer and product name, the EPA 

registration number from the label, the amount of pesticide used, the number of applications of 

each pesticide, and the total number of applications, per county, per month. 

4. Report to the CAC and the CDHS, in a manner specified any conspicuous or suspected adverse 

effects upon humans, domestic animals and other non-target organisms, or property from pesticide 

applications. 

5. Require appropriate certification of its employees by CDHS in order to verify their competence 

in using pesticides to control pest and vector organisms, and to maintain continuing education unit 

information for those employees participating in continuing education. 

6. Be inspected by the CAC on a regular basis to ensure that local activities are in compliance with 

state laws and regulations relating to pesticide use. 
March 13, 2002 K2-16

Other agencies such as local fire departments, California Department of Fish and Game, U.S. Fish 

and Wildlife Service, U.S. Army Corps of Engineers, and others have jurisdiction and oversight 

over our activities. We work closely with these agencies to comply with their requirements. 

Public Education 

An integral part of the MVCD BMP is to provide information to the public to assist them in 

resolving their pest problems. Specialized staff at the MVCD provide public outreach in the form 

of presentations to schools, utility districts, homeowner associations, county fairs, home and garden 

shows, as well through the media such as newspaper, television, and radio. Information is provided 

on biological, physical and cultural control methods (i.e., BMPs) that property owner and managers 

can use to preclude or reduce mosquitoes and other disease and nuisance pests within their 

jurisdictions. 

Proposed Monitoring Plan for S.F. Bay Region Mosquito and Vector Control 

Districts 

INTRODUCTION 

Mosquito and vector control districts (MVCD) within the San Francisco Bay Region (2) are 

seeking regional coverage under the General Permit for discharges of aquatic pesticides to surface 

waters. The monitoring plan is presented in this document to the Regional Water Quality Control 

Board and shall be implemented as approved. Implementation of nontoxic or least toxic control 

alternatives within a BMP program eliminates the need for water quality and chemical residue 

monitoring. Microbial larvicides, thin-film larvicides and methoprene are justifiably exempted 

from such requirements. 

Characterization of Pesticide Application Projects by Region MVCD 

Types of sources treated 

Activities of the MVCD are directed toward control of mosquitoes in their aquatic, larval stage. 

This approach allows control activities to be concentrated in localized areas using least toxic 

materials. Adult mosquitoes may occasionally be targeted for control, such as in the case of disease 

outbreaks. However, this approach requires the use of more potent pesticides applied over a greater 

area and is therefore avoided whenever possible. 

There are 19 species of mosquitoes in the coastal region (Table 2) that vary in their seasonality and 

the type of sources in which their larvae develop (Table 3). Mosquitoes are generally weak 

swimmers and cannot survive in waters with substantial flow or surface disturbance due to wind 

action. Therefore, larval development is largely restricted to small bodies of still water. The 

timing and location of pesticide applications follows seasonal changes in distribution of water 

sources. Many times heavy populations of immature mosquitoes are found in still shallow water 
March 13, 2002 K2-17

containing dense emergent vegetation. Species vary in their tolerance to salinity, degree of organic 

pollution and temperature extremes. 

Climate and Seasonality 

The San Francisco Bay Area has a mild, Mediterranean climate, with the preponderance of rain 

deposited during winter months (November through May). The climate and seasonal patterns of 

rainfall in this area influence the distribution of mosquitoes and hence the timing and location of 

pesticide applications. The mild climate of this area allows mosquitoes to develop throughout the 

year. However, the mosquito species and type of source targeted varies seasonally. For example, 

creeks and waterways that have substantial flow during winter months are only treated in summer 

after the water has receded into scattered, isolated pools. Similarly, mosquitoes are generally 

flushed out of storm drains during winter months. These sources are typically treated only during 

the summer. In contrast, seasonal wetland such as saltmarshes, require treatment from fall through 

spring. In summer months the rainwater deposited in low areas disappears and mosquitoes are no 

longer able to survive. Tables 2 and 3 include information on the seasonality of mosquito species 

and their development sites. 

PESTICIDES USED AND ASSESSMENT OF IMPACTS ON BENEFICIAL USE 

Pesticides used by MVCD fall into the 4 categories: bacterial larvicides, methoprene, surfactants 

(surface-acting agents) and herbicides. Table 1 summarizes the amount of these products applied 

annually by each district in the region. The accompanying document “Technical Review” provides 

a detailed review of available literature on nontarget effects. 

A. Bacterial Larvicides 

Bacterial insecticides consist of the spores of certain species of bacteria containing naturally 

produced proteins, which are toxic to mosquito larvae when ingested in sufficient quantities. 

Although they are biologically-derived agents, products containing them are labeled and registered 

by the Environmental Protection Agency (EPA) as pesticides and are considered by some to be a 

form of chemical control. 

 1. Bacillus thuringiensis var. israelensis (BTI) 

Advantages: BTI is highly target-specific and has been found to have significant effects only on 

mosquito larvae, and closely related insects (e.g. blackflies and midges). It is available in a variety 

of liquid, granular and pellet formulations, providing some flexibility in application methods and 

equipment. BTI has no measurable toxicity to vertebrates and is classified by EPA as “Practically 

Non-Toxic” (Caution). BTI formulations contain a combination of five different proteins within a 

larger crystal. These proteins have varying modes of action and synergistically act to reduce the 

likelihood of resistance developing in larval mosquito populations. 

Barriers: Bacterial insecticides must be fed upon by larvae in sufficient quantity to be effective. 

Therefore applications must be carefully timed to coincide with periods in the life cycle when 
March 13, 2002 K2-18

larvae are actively feeding. Pupae and late 4th stage larvae do not feed and therefore will not be 

controlled by BTI. Low water temperature inhibits larval feeding behavior, reducing the 

effectiveness of BTI during the cooler months. The presence of high concentrations of organic 

material in treated water also reduces the effectiveness of BTI. Cost per acre treated is generally 

higher than surfactants or organophosphate insecticides. 

Solutions to Barriers: Increasing the frequency of surveillance for larvae can ensure that bacterial 

insecticides are applied during the appropriate stages of development to prevent adult mosquito 

emergence. 

Impact on water quality: BTI contains naturally produced bacterial proteins that are generally 

regarded as environmentally safe. Naturally occurring strains of this bacterium are ubiquitous in 

aquatic habitats. BTI leaves no residues and is quickly biodegraded. At the application rates used 

in mosquito control programs, this product is unlikely to have any measurable effect on water 

quality. There are no established standards, tolerances or EPA approved tests for this material. 

Product names: Acrobe, Bactimos pellets, Teknar HP-D, Vectobac 12AS, Vectobac G, Vectobac 

TP. 

Formulations and dosages There are five basic BTI formulations available for use: liquids, 

powders, granules, pellets, and briquets. Liquids, produced directly from a concentrated 

fermentation slurry, tend to have uniformly small (2-10 micron) particle sizes, which are suitable 

for ingestion by mosquito larvae. Powders, in contrast to liquids, may not always have a uniformly 

small particle size. Clumping, resulting in larger sizes and heavier weights, can cause particles to 

settle out of the feeding zone of some target mosquito larvae, preventing their ingestion as a food 

item. Powders must be mixed with an inert carrier before application to the larval habitat, and it 

may be necessary to mix them thoroughly to achieve a uniformly small consistency. BTI. granules, 

pellets, and briquets are formulated from BTI primary powders and an inert carrier. BTI. labels 

contain the signal word “CAUTION”. 

BTI is applied by MVCD as a liquid or sometimes bonded to an inert substrate (i.e.: corn cob 

granules) to assist penetration of vegetation. Application can be by hand, ATV, or aircraft. 

Persistence is low in the environment, usually lasting three to five days. Kills are usually observed 

within 48 hours of toxin ingestion. As a practical matter, apparent failures are usually followed 

with oil treatments. 

BTI LIQUIDS. Currently, three commercial brands of BTI liquids are available: Aquabac XT, 

Teknar HP-D, and Vectobac 12AS. Labels for all three products recommend using 4 to 16 liquid 

oz/acre in unpolluted, low organic water with low populations of early instar larvae (collectively 

referred to below as clean water situations). The Aquabac XT and Vectobac 12 AS (but not Teknar 

HP-D) labels also recommend increasing the range from 16 to 32 liquid oz/acre when late 3rd or 

early 4th instar larvae predominate, larval populations are high, water is heavily polluted, and/or 

algae are abundant. The recommendation to increase dosages in these instances (collectively 

referred to below as dirty water situations) also is seen in various combinations on the labels for all 

other BTI. formulations discussed below. 
March 13, 2002 K2-19

BTI liquid may also be combined with the Altosid Liquid Larvicide discussed earlier. This mixture 

is known as Duplex. Because BTI is a stomach toxin and lethal dosages are somewhat proportional 

to a mosquito larvae’s body size, earlier instars need to eat fewer toxic crystals to be adversely 

affected. Combining BTI with methoprene (which is most effective when larvae are the oldest and 

largest or when you have various, asynchronous stages of one or more species) allows a district to 

use less of each product than they normally would if they would use one or the other. Financially, 

most savings are realized for treatments of mosquitoes with long larval development periods, 

asynchronous broods or areas with multiple species of mosquitoes. 

BTI CORNCOB GRANULES. There are currently two popular corncob granule sizes used in 

commercial formulations. Aquabac 200G, Bactimos G, and Vectobac G are made with 5/8 grit 

crushed cob, while Aquabac 200 CG (Custom Granules) and Vectobac CG are made with 10/14 

grit cob. Aquabac 200 CG is available by special request. The 5/8 grit is much larger and contains 

fewer granules per pound. The current labels of all B.t.i. granules recommend using 2.5 to 10 

lb./acre in clean water and 10 to 20 lb./acre in dirty water situations. 

 2. Bacillus sphaericus (BS) 

Advantages: BS is another bacterial pesticide with attributes similar to those of BTI. The efficacy 

of this bacterium is not affected by the degree of organic pollution in larval development sites and 

it may actually cycle in habitats containing high mosquito densities reducing the need for repeated 

applications. 

Barriers: Like BTI, BS must be consumed by mosquito immatures and is therefore not effective 

against nonfeeding stages such as late 4th instar larvae or pupae. BS is also ineffective against 

certain species of mosquitoes such as those developing in saltmarshes, seasonal forest pools or 

treeholes. Toxicity of BS to mosquitoes is due to a single toxin rather than a complex of several 

molecules as is the case with BTI. Development of resistance has been reported in Brazil, Thailand 

and France where BTI was used as the sole control method for extended periods of time. 

Solutions to Barriers: Information obtained from larval surveillance on the stage and species of 

mosquitoes present can increase the effectiveness of this material, restricting its use to sources 

containing susceptible mosquitoes. The development of resistance can be delayed by rotating BS 

with other mosquitocidal agents. 

Impact on water quality: At the application rates used in mosquito control programs, BS is 

unlikely to have any measurable effect on water quality. It is a naturally occurring bacterium and 

like BTI, occurs naturally in most aquatic environments. There are no established standards, 

tolerances or EPA approved tests for BS. 

Product names: Vectolex CG, Vectolex WDG 

Formulations and dosages VECTOLEX CG. VectoLex-CG is the trade name for the granular 

formulation of B. sphaericus (strain 2362). The product has a potency of 50 BSITU/mg (Bacillus 

sphaericus International Units/mg) and is formulated on a 10/14 mesh ground corn cob carrier. 

The VectoLex-CG label carries the “CAUTION” hazard classification. VectoLex-CG is intended 
March 13, 2002 K2-20

for use in mosquito breading sites that are polluted or highly organic in nature, such as dairy waste 

lagoons, sewage lagoons, septic ditches, tires, and storm sewer catch basins. VectoLex-CG is 

designed to be applied by ground (by hand or truck-mounted blower) or aerially at rates of 5-10 

lb./acre. Best results are obtained when applications are made to larvae in the 1st to 3rd instars. Use 

of the highest rate is recommended for dense larval populations 

 B. Methoprene 

Advantages: Methoprene is a larvicide that mimics the natural growth regulator used by insects. 

Methoprene can be applied as liquid or solid formulation or combined with BTI or BS to form a 

“duplex” application. Methoprene is a desirable IPM control strategy since affected larvae remain 

available as prey items for predators and the rest of the food chain. This material is breaks down 

quickly in sunlight and when applied as a liquid formulation is effective for only 24 hours. 

Methoprene can be impregnated into charcoal-based carriers such as pellets and briquettes for 

longer residual activity ranging from 30 to 150 days. The availability of different formulations 

provides options for treatment under a wide range of environmental conditions. Studies on 

nontarget organisms have found methoprene to be nontoxic to all vertebrates and most 

invertebrates when exposed at concentrations applied for control of mosquitoes. 

Barriers: Methoprene products must be applied to mosquitoes at the larval stage, since it is not 

effective against the other life stages. Monitoring for effectiveness is difficult since mortality is 

delayed. Methoprene is more expensive than most other mosquitocidal agents. Use is restricted in 

vernal pools and certain other aquatic habitats where red-legged frogs are unlikely to occur. 

Solutions to Barriers: Surveillance and monitoring can provide information on the stage of 

mosquito immatures present, so that timing of applications can maximize efficacy of the 

treatments. 

Impact on Water Quality: Methoprene does not have a significant impact on water quality. It is 

applied and has been shown to be effective against mosquitoes at levels far below those that can be 

detected by any currently available test approved by the EPA. Studies on nontarget organisms have 

shown methoprene to be nontoxic to all vertebrates and most invertebrates when exposed at 

concentrations applied for control of mosquitoes.

Product Names: Altosid Liquid Larvicide, Altosid Single Brood Granule, Altosid Pellets, and 

Altosid Briquets, Altosid Extended Release Briquets XR . . 

Formulations and dosages. s-Methoprene is a very short-lived material in nature, with a half-life 

of about two days in water, two days in plants, and ten days in soil (Wright 1976 in Glare & 

O’Callaghan 1999, La Clair et al 1998). The manufacturer has developed a number of formulations 

to maintain an effective level of the active material in the mosquito habitat (0.5-3.0 parts per billion

= ppb1

; (Scientific Peer Review Panel 1996)) for a practical duration, thus minimizing the cost and 

potential impacts associated with high-frequency repeat applications. Currently, five s-methoprene 

 

1Note that this concentration is measured in parts per billion, and is equivalent to 0.0005 to 0.003 ppm (parts per 

million) when comparing application rates and toxicity studies. 
March 13, 2002 K2-21

formulations are sold under the trade name of Altosid. These include Altosid Liquid Larvicide 

(A.L.L.) and Altosid Liquid Larvicide Concentrate, Altosid Briquets, Altosid XR Briquets, and 

Altosid Pellets. Altosid labels contain the signal word “CAUTION”. 

ALTOSID LIQUID LARVICIDE (A.L.L.) & A.L.L. CONCENTRATE. These two 

microencapsulated liquid formulations have identical components and only differ in their 

concentrations of active ingredients (AI). A.L.L. contains 5% (wt./wt.) s-Methoprene while A.L.L. 

Concentrate contains 20% (wt./wt.) s-Methoprene. The balance consists of inert ingredients that 

encapsulate the s-Methoprene, causing its slow release and retarding its ultraviolet light 

degradation. Maximum labeled use rates are 4 ounces of A.L.L. and 1 ounce of A.L.L. Concentrate 

(both equivalent to 0.0125 lb. AI) per acre, mixed in water as a carrier and dispensed by spraying 

with conventional ground and aerial equipment. In sites which average a foot deep, these 

application rates are equivalent to a maximum active ingredient concentrations of 4.8 ppb, although 

the actual concentration is substantially lower because the encapsulation does not allow 

instantaneous dissolution of all of the active ingredient into the water. 

Because the specific gravity of Altosid Liquid is about that of water, it tends to stay near the target 

surface. Therefore, no adjustment to the application rate is necessary in varying water depths when 

treating species that breathe air at the surface. Cold, cloudy weather and cool water slow the 

release and degradation of the active ingredient as well as the development of the mosquito larvae. 

ALTOSID BRIQUETS. Altosid Briquets consist of 4.125% s-methoprene (.000458 lb. 

AI/briquet), 4.125% (wt./wt.) r-methoprene (an inactive isomer), and plaster (calcium sulfate) and 

charcoal to retard ultra violet light degradation. Altosid Briquets release methoprene for about 30 

days under normal weather conditions and, as noted earlier, this means that the concentration of AI 

in the environment at any time is much lower than the value calculated from the weight of material 

applied. The recommended application rate is 1 Briquet per 100 sq. ft. in non-flowing or lowflowing water up to 2 feet deep. Small sites with any mosquito genera may be treated with this 

formulation. Typical treatment sites include storm drains, catch basins, roadside ditches, 

ornamental ponds and fountains, cesspools and septic tanks, waste treatment and settlement ponds, 

transformer vaults, abandoned swimming pools, and construction and other man-made depressions. 

ALTOSID XR BRIQUETS. This formulation consists of 2.1% (wt./wt.) s-methoprene (.00145 lb. 

AI/briquet) embedded in hard dental plaster (calcium sulfate) and charcoal. Despite containing 

only 3 times the AI as the “30-day briquet”, the comparatively harder plaster and larger size of the 

XR Briquet change the erosion rate allowing sustained s-methoprene release for up to 150 days in 

normal weather. The recommended application rate is 1 to 2 briquets per 200 sq. ft. in no-flow or 

low-flow water conditions, depending on the target species. Many applications are similar to those 

with the smaller briquets, although the longer duration of material release can also make this 

formulation economical in small cattail swamps and marshes, water hyacinth beds, meadows, 

freshwater swamps and marshes, woodland pools, flood plains and dredge spoil sites. 

ALTOSID PELLETS. Altosid Pellets contain 4.25% (wt./wt.) s-methoprene (0.04 lb. AI/lb.), 

dental plaster (calcium sulfate), and charcoal in a small, hard pellet. Like the Briquets discussed 

above, Altosid Pellets are designed to slowly release s-methoprene as they erode. Under normal 

weather conditions, control can be achieved for up to 30 days of constant submersion or much 
March 13, 2002 K2-22

longer in episodically flooded sites (Kramer 1993). Label application rates range from 2.5 lbs. to 

10.0 lbs. per acre (0.1 to 0.4 lb. AI/acre), depending on the target species and/or habitat. At 

maximum label application rates, as with the Briquets, the slow release of material means that the 

actual concentration of active ingredient in the water never exceeds a few parts per billion. 

The target species are the same as those listed for the briquet and liquid formulations. Listed target 

sites include pastures, meadows, rice fields, freshwater swamps and marshes, salt and tidal 

marshes, woodland pools, flood plains, tires and other artificial water holding containers, dredge 

spoil sites, waste treatment ponds, ditches, and other man-made depressions, ornamental pond and 

fountains, flooded crypts, transformer vaults, abandoned swimming pools, construction and other 

man-made depressions, tree holes, storm drains, catch basins, and waste water treatment settling 

ponds. 

ALTOSID XR-G. Altosid XR-G contains 1.5% (wt./wt.) s-methoprene. Granules are designed to 

slowly release s-methoprene as they erode. Under normal weather conditions, control can be 

achieved for up to 21 days. Label application rates range from 5 lbs. to 20.0 lbs. per acre, 

depending on the target species and/or habitat. The species are the same as listed for the briquet 

formulations. Listed target sites include meadows, rice fields, freshwater swamps and marshes, salt 

and tidal marshes, woodland pools, tires and other artificial water holding containers, dredge spoil 

sites, waste treatment ponds, ditches, and other natural and man-made depressions. 

G. Surfactants 

Surfactants are “surface-acting agents” that are either petroleum-based or isostearyl alcohol agent 

that form a thin layer on the water surface. These materials typically kill surface-breathing insects 

by blocking the respiratory mechanism. 

Advantages: These materials are the only materials efficacious for reducing mosquito pupae since 

other larviciding strategies (i.e., methoprene, BTI and BS) are ineffective to that life stage. 

Agnique forms a monomolecular film that is visually undetectable. Treatments are simplified due 

to the spreading action of the surfactant across the water surface and into inaccessible areas. These 

surfactants are considered “practically nontoxic” by the EPA. Agnique is labeled “safe for use” in 

drinking water. 

Barriers to Use: The drawback of using oils in habitats where natural enemies are established is 

that surface-breathing insects, particularly mosquito predators, are similarly affected. GB1111 

forms a visible film on the water surface. 

Solutions to Barriers: As a general rule, surfactant use is considered after alternate control 

strategies or in habitats that are not supporting a rich macro-invertebrate community. 

Product Names: Golden Bear 1111, Agnique MMF 

Formulations and dosages
March 13, 2002 K2-23

MOSQUITO LARVICIDE GB-1111 (GOLDEN BEAR 1111). This product, generally referred to 

as Golden Bear 1111 or simply GB-1111, is a highly-refined petroleum based “napthenic oil” with 

very low phytotoxicity and no detectible residual products within days after application. Volatility 

is very low (“non-volatile” according to the MSDS), and environmental breakdown presumably 

results primarily from natural microbial degradation into simple organic compounds. The label for 

GB-1111 contains the signal word “CAUTION”. GB-1111 contains 99% (wt./wt.) oil and 1% 

(wt./wt.) inert ingredients including an emulsifier. The nominal dosage rate is 3 gallons per acre or 

less. Under special circumstances, such as when treating areas with high organic content, up to 5 

gallons per acre may be used. 

GB-1111 provides effective control on a wide range of mosquito species. Low dosages (1 gallon 

per acre) of oil work slowly, especially in cold water, and can take 4 to 7 days to give a complete 

kill. Higher dosage rates are sometimes used (up to 5 gallons per acre) to lower the kill time. It is 

typically applied by hand, ATV, or truck. Aerial application is possible for large areas, but is not 

routine. 

AGNIQUE: Agnique is the trade name for a recently reissued surface film larvicide, comprised of 

ethoxylated alcohol. According to the label, Agnique has very low vertebrate toxicity; an average 

persistence in the environment of 5-14 days at label application rates; and no toxic breakdown 

products, skin irritation, carcinogenicity, mutagenicity, or teratogenicity has been reported. 

Because of its similar mode of action and effectiveness against pupae, Agnique can be used as an 

alternative to Golden Bear 1111, especially in sites where the moderate temporary sheen associated 

with GB-1111 might be objectionable. Because the application rate of Agnique is much lower than 

that of Golden Bear, this potential shift would not include an increase in volume of materials 

applied. 
March 13, 2002 K2-24

Overall assessment of existing or potential impacts of mosquito control pesticides on 

beneficial use 

All of the materials currently in routine use by MVCD can be considered “less toxic” or “least 

toxic” according to US EPA toxicity data (Fig. 1). 

0.1

1

10

100

nicotinecaffeine

aspirin

table salt

Karmex (Diuron)+

Abate (Temephos)#

Rodeo (Glyphosate)+

Oust (Sulfometuron)+

Roundup (Glyphosate)+

alcohol

GB-1111 (mineral oil)*

Agnique MMF*

Altosid (Methoprene)*

BTI*

BS*

relative toxicity

+herbicide

*larvicide

#not in use

Fig. 1. Relative toxicities of pesticides used by mosquito and vector control programs, based on rat 

LD50 data from product labels, in comparison with some common household chemicals. 

Relevance of water quality analyses for the demonstration of full restoration following project 

completion: 

Mosquito control “projects” are ongoing and do not have a specific duration or date of completion, 

since the goal is to prevent mosquito populations from exceeding specific injury levels rather than 

to eradicate them. As in the above “Statement of BMP”, surveillance of larval sources is 

conducted on a continuous basis and treatments are applied as necessary to prevent significant 

nuisance or disease risks to the public. The materials used routinely in mosquito control programs 

are applied at extremely low dosages relative to the volume of the habitat, are inherently less-toxic 

or least-toxic materials (Fig. 1) and are not known to have measurable impacts on water quality. 

However, existing water quality conditions may have significant impacts on the selection and 

efficacy of control methods applied (see BMP). Alternative control methods such as physical 

control (manipulation of drainage, tidal flow etc.) may have significant effects on water quality 

(salinity, hardness etc) as they can change the hydrodynamics of the entire habitat. The goal of 

these activities is to enhance water circulation, which directly reduces mosquito production while 

improving habitat values for natural predators of mosquito larvae. Large-scale physical control 

projects require individual permits from the U.S. Army Corps of Engineers and the San Francisco 

Bay Conservation and Development Commission (BCDC), which review potential impacts prior to 

approval. Documentation of our existing BMP may be considered a “demonstration of full 

restoration” since it prevents impacts to water quality and makes restoration unnecessary. 
March 13, 2002 K2-25

b. Relevance of parameters suggested by the water board 

The less-toxic control methods and materials used by our programs are designed not to produce 

measurable impacts on the water quality parameters generally monitored under NPDES permits. 

Therefore, monitoring of these parameters would represent an added cost while not providing 

significant benefits to the public or the environment. Parameters normally monitored under 

NPDES include the following: 

i. Dissolved oxygen: Materials used in mosquito control are applied at volumes of several ounces 

(methoprene) to less than 10 gallons (surfactants) per acre of active ingredient. At these dosage 

rates it is extremely unlikely there would be any measurable effects on dissolved oxygen. 

ii. Temperature: Materials used in mosquito control are generally applied at or near ambient 

environmental temperature. At the dosage rates used in mosquito control it is extremely unlikely 

there would be any measurable effects on water temperature. 

iii. pH: Materials used in mosquito larval control are not strongly acidic or basic as this could 

damage application equipment. At the application rates used in mosquito control they are 

extremely unlikely to have a measurable effect on pH. 

iv: Turbidity: Turbidity, particularly due to suspended organic material, may influence the 

selection or efficacy of materials used in mosquito control. At the application rates used in our 

programs, these materials are extremely unlikely to have a measurable effect on turbidity. 

v: Hardness: Materials used in mosquito control do not have a high mineral. At the dosage rates 

used in mosquito control it is extremely unlikely there would be any measurable effects on water 

hardness. 

vi: Electrical conductivity: Materials used in mosquito control do not have high concentrations of 

chlorides or other ions. At the dosage rates used in mosquito control it is extremely unlikely there 

would be any measurable effects on conductivity. 

vii: Pesticide residues: In general, materials used by MVCD are non-persistent, do not 

bioaccumulate, and are designed to biodegrade or break down after achieving the desired control 

of larval populations. Exceptions are slow-release formulations of methoprene, which are 

specifically designed for extended release of small amounts of active ingredient, and biological 

agents such as Bacillus sphaericus, Lagenidium giganteum, and mosquitofish, which may 

reproduce and recycle naturally under favorable conditions. In this case the “residue” actually has a 

beneficial effect by prolonging the period of larval control and reducing the need for repeated 

applications or use of more toxic materials. There are currently no EPA approved laboratories or 

protocols for detecting residues of larvicides used routinely by MVCD. Monitoring of mosquito 

larval populations, as already practiced routinely under our BMP, is the most sensitive method 

available for determining whether residual larvicide activity is present. 
March 13, 2002 K2-26

EVALUATION OF LESS-TOXIC CONTROL METHODS 

Pesticide use by MVCD is only one aspect of an Integrated Pest Management (IPM) strategy. This 

strategy includes the use of physical and biological control techniques whenever possible and is 

based on a program of continuous monitoring of both adult and immature mosquito populations A 

complete description of the MVCD IPM strategy is given in the accompanying document 

“Statement of Best Management Practices”. Nonchemical control methods, barriers to their use, 

and solutions to those barriers are listed below: 

Physical control (see discussion in BMP document). 

Cost: high, requires specialized equipment and expertise, may be labor intensive. 

Barriers: high cost; lack of equipment in some districts; problems with disturbing habitats of 

endangered species; wetlands are sensitive habitats and highly regulated; requires extensive permit 

process . 

Solutions to barriers: encourage landowners to do this work; some districts have personnel with 

expertise in wetlands restoration; work with restoration agencies. 

Relative usefulness of this technique: used whenever possible; first choice because it is a 

permanent solution. If physical control is not feasible, or while working toward a physical control 

solution we will use biological or chemical control techniques. 

Water management

Cost: cost of equipment and engineering can be very high initially; may be labor intensive; 

requiring someone on hand at all times to monitor water levels and operate gates. 

Barriers: most land we treat is not under our control and it is difficult to force landowners to 

cooperate; most districts don’t have adequate staff or budget to install and operate floodgates; 

conflict with other uses of wetlands such as waterfowl conservation, recreation (hunting). 

Solutions to barriers: work with land owners as much as possible to encourage good water 

management; treat only when necessary. 

Relative usefulness of this technique: used whenever possible; first choice because it is a 

permanent solution. When water management fails we use biological or chemical control 

Biological control 

Mosquito fish 

Cost: low 

Barriers: release of non native fish into natural sources is controversial; may compete with native 

fish; requires facilities and personnel to rear and maintain fish. 

Solutions to barriers: use only in manmade sources; get fish from other districts and only keep a 

small supply on hand. 

Relative usefulness of Mosquito fish: fish are considered when physical control is out of the 

question. Can be very useful but only under a very restricted set of conditions. If a source is 

suitable for fish and fish will not impact native species we will use this strategy; some districts treat 

only manmade sources or those lacking native fish 

Bacterial pesticides: The primary pesticides used by MVCD may be considered a form of 

biological control 
March 13, 2002 K2-27

Bacillus sphaericus and B. thuringiensis var. israelensis

Cost: these materials are more expensive than organophosphate pesticides but cheaper than 

physical control. 

Barriers: requires more careful monitoring of mosquito populations and more thorough knowledge 

of their ecology. Not effective against some species or some stages or in some types of sources. 

Very short duration of control; requires frequent retreating. Reliance on a single product may 

result in development of resistance. 

Solutions to barriers: monitoring program for mosquitoes; training for district staff; rotate 

products. 

Relative usefulness of this technique: these agents are considered when physical control is out of 

the question and fish cannot be stocked or maintained. Sometimes used in conjunction with 

stocking fish since these materials have been shown not to adversely affect fish. In this case, fish 

may be a long term solution but chemical are needed to initially bring down mosquito populations. 

Also need to consider possibility of development of resistance, therefore the need to rotate products 

used. 

Chemical Control using methoprene and surface oils instead of organophosphates 

Cost: these materials are more expensive than OPs but cheaper in the short term than physical 

control 

Barriers: requires more careful monitoring of population and more thorough knowledge of 

ecology, resistance 

Solutions to barriers: monitoring program for mosquitoes, training for techs, biologists on staff, 

rotate materials, investigate new materials 

Relative usefulness of this technique: Like biological pesticides these materials are considered 

when physical control is out of the question and fish cannot be stocked or maintained. Sometimes 

used in conjunction with stocking fish since these materials have been shown not to adversely 

affect fish.. Decisions on whether to use these materials or bacterial pesticides are based on: stage 

and species of mosquitoes present, quality of water, access Also need to consider possibility of 

development of resistance, therefore the need to rotate products used. 

EVALUATION OF THE EFFECTIVENESS OF BMP’S TO REDUCE DISCHARGES AND 

MINIMIZE AREA AND DURATION OF IMPACTS 

Our Best Management Practices insure that all available less-toxic or least-toxic control methods 

are considered and that new methods are evaluated on an ongoing basis and, if effective, 

incorporated into our larval control programs. Implementation of BMP resulted in the complete 

elimination of the routine use of conventional chemical insecticides (organophosphates and 

carbamates) between 1982 and 1993 and a concomitant increase in use of less toxic methods 

including bacterial insecticides and insect growth regulators (Fig. 2, a and b). 
March 13, 2002 K2-28

A.

Chemical insecticide use

0

1000

2000

3000

4000

1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993

Pounds of A.I.

Dursban (Chlorpyrifos) Baytex (Fenthion) Malathion

Baygon (Propoxur) Abate (Temephos) Pyrethroids

B. 

"Biorational" insecticide use

0

5000

10000

15000

20000

25000

30000

35000

1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993

Pounds of A.I.

BTI Altosid (Methoprene)

Fig. 2 a. Reduction in use of chemical larvicides by Coastal Region Districts, 1982-1993. b. 

Increase in use of bacterial insecticides and insect growth regulators. 

PROPOSED MONITORING PLAN 

We propose a monitoring plan consisting primarily of record-keeping and reporting elements. 

Records shall be kept by each district of all pesticide applications made to waters of the U.S. by its 

staff and/or contractors. These records shall include the site, material, concentration, quantity 

applied, habitat type, approximate water surface area, and the date and time for each application. In 

addition, each district shall report annually to the SFRWQCB on its aquatic pesticide applications, 

summarizing the recorded data to indicate the quantity of each pesticide active ingredient applied to 

each habitat type within the zone of each district that drains to each major final receiving body. If 

organo-phosphate or other non-standard larvicides, or herbicides with active ingredients other than 

glyphosate, are required, the SFRWQCB will be promptly notified so that an appropriate 

supplemental monitoring plan can be developed. 

We will also conduct an annual review of our BMP to reflect any new practices and ensure that 

less-toxic methods and materials continue to be evaluated and incorporated as they become 

available. Any changes or revisions to our BMP will also be reported annually. 
APPENDIX K3. Effects of Larvacides on Non-Target 

Organisms 

Effects of Larvicides on Non-Target Organisms 

USFWS 2003 

Prepared By

Wennona Brown

USFWS, Maryland Coop Unit

1120 Trigg Hall 

University of Maryland Eastern Shore 

Princess Anne, MD 21853 

(410) 651-7505 FAX (410) 651-7662 

e-mail: wbrown@umes-bird.umd.edu

Introduction

The information contained within this document is a guide to mosquito larvicide effects on nontarget organisms. Included is information on the four most commonly used larvicides: 

monomolecular surface films (Arosurf7

), Bacillus thuringiensis israelensis (BTI), methoprene 

(Altosid7

) and temephos (Abate7). Articles presented are representative entries whose 

information would lend itself to tabulation. This does not represent a comprehensive treatment 

of the subject. 

The following information is provided for each larvicide: a short description of how the larvicide 

works, a generalized synopsis of non-target effects, label application rates of various 

formulations of the product, references cited within the effects table, and a tabulation of nontarget effects on various organisms. The table is arranged by taxonomic categories (e.g., birds, 

insects), and alphabetical within category. Taxonomy may not be the most current. Label 

application rates are excerpted from the manufacturer=s information sheets as follows: 

Arosurf7

 now manufactured as Agnique7 by the Henkel Corporation; 

BTI (Vectobac7 products) manufactured by Abbott Laboratories; 

Methoprene (Altosid7 products) manufactured by Sandoz Agro, Inc., and Zoecon; 

Temephos (Abate7

 products) manufactured by Clarke Mosquito Control Products, Inc. 

At the end of each section is an extensive bibliography of mosquito larvicide articles. 

Additional information is available on the Internet. Two web sites that are useful include: 

http://ace.ace.orst.edu/info/extoxnet/pips/ghindex.html These Pesticide Information 

Profiles provide general information on many registered pesticides, such as mode of 

action, toxicity, ecological effects, and references.

http://www.famu.edu/jamsrl/peis/mosquito/mosqsearch.html The Non-target 

Search Form provides a searchable database for mosquito literature. A search can 

be conducted by author, organism, pesticide, or a key word search. The database 

provides abstracts for many of the articles.

K3-1 
Table of Contents

Arosurf (ISA-20E) ......................................................................................................................... 5

Synopsis of Non-target Effects ......................................................................................... 5

Label Application Rates for Agnique .............................................................................. 5

References Cited ................................................................................................................ 5

Table 1. Non-target Effects of Arosurf .............................................................................. 6

Fish ......................................................................................................................... 6

Mollusks ................................................................................................................. 6

Crustaceans ........................................................................................................... 6

Insects ..................................................................................................................... 7

Annelids ................................................................................................................. 7

Bacillus thuringiensis israelensis (BTI) ....................................................................................... 8

Synopsis of Non-target Effects ......................................................................................... 8

Label Application Rates ................................................................................................... 8

References Cited ................................................................................................................ 9

Table 2. Non-target Effects of BTI .................................................................................. 11

Fish ....................................................................................................................... 11

Crustaceans ......................................................................................................... 11

Insects ................................................................................................................... 12

Methoprene .................................................................................................................................. 24

Synopsis of Non-target Effects ....................................................................................... 24

Label Application Rates ................................................................................................. 24

References Cited .............................................................................................................. 26

Table 3. Non-target Effects of Methoprene ..................................................................... 28

Fish ....................................................................................................................... 28

Amphibians .......................................................................................................... 29

Arachnids ............................................................................................................. 29

Mollusks ............................................................................................................... 29

Crustaceans ......................................................................................................... 29

Insects ................................................................................................................... 34

Annelids ............................................................................................................... 43

Aschelminths ....................................................................................................... 44

Flatworms ............................................................................................................ 44

Protozoa ............................................................................................................... 44

Phytoplankton ..................................................................................................... 44

Temephos ..................................................................................................................................... 45

Synopsis of Non-target Effects ....................................................................................... 45

Label Application Rate ................................................................................................... 45

References Cited .............................................................................................................. 46

Table 4. Non-target Effects of Temephos ........................................................................ 49

Birds ..................................................................................................................... 49

Reptiles ................................................................................................................. 50

Amphibians .......................................................................................................... 50

Fish ....................................................................................................................... 50

Arachnids ............................................................................................................. 52

K3-2 
Mollusks ............................................................................................................... 52

Crustaceans ......................................................................................................... 53

Insects ................................................................................................................... 57

Annelids ............................................................................................................... 61

Aschelminths ....................................................................................................... 61

Flatworms ............................................................................................................ 62

Plankton ............................................................................................................... 62

Mosquito Bibliography ............................................................................................................... 63

K3-3 
K3-4 
Arosurf7 (ISA-20E)

now produced as Agnique7

Arosurf is a monomolecular surface film, which reduces the water surface tension. This 

interferes with larval orientation at the air-water interface and/or increases wetting tracheal 

structures, thus suffocating the organism. As the film spreads over the water surface, it tends to 

concentrate the larvae, which may increase mortality from crowding stress (Dale and Hulsman 

1990). 

According to the Henkel Corporation, Agnique=s improvements over Arosurf center around 

removal of the byproducts that left the white residues in the drums and application equipment. 

Removing these byproducts lowered the freezing point of the product. The spreading ability was 

also improved, so that application of the product was made easier.

Synopsis of Non-target Effects

 

Arosurf had no adverse effect on any of the organisms tested. However, none of the studies 

listed investigated species such as water boatman or backswimmers.

Label Application Rates for Agnique

Example habitat: Salt-marsh, ponds, storm water retention basins, roadside ditches, grassy 

swales, potholes, fields, reservoirs, irrigated croplands, etc. Larvae: 0.2-0.5 gal/surface 

acre Pupae: 0.2-0.3 gal/surface acre

Example habitat: Pumping station bunkers, settings, polishing and evapo-percolation ponds of 

sewage treatment systems, drainage areas containing effluent from slaughter houses, etc.

Larvae: 0.4-0.5 gal/surface acre Pupae 0.2-0.3 gal/surface acre

References Cited:

Dale, P.E.R. and K. Hulsman. 1990. A critical review of salt marsh management methods for 

mosquito control. Review in Aquatic Sciences 3:281-311. 

Hester, P.G., M.A. Olson, and J.C. Dukes. 1991. Effects of ArosurfR

 MSF on a variety of 

aquatic nontarget organisms in the laboratory. J. Amer. Mosq. Control Assn. 7:48-51. 

Mulla, M.S., H.A. Darwazeh, and L.L. Luna. 1983. Monolayer films as mosquito control agents 

and their effects on non-target organisms. Mosq. News. 43:489-495. 

K3-5 
 Table 1. Non-target Effects of Arosurf7

 (now produced as Agnique7) 

Classification Organism Reference Formulation Application 

Rate (study)

Adverse 

Effects

No 

Effects

Comments

 Fish

Atheriniformes

Longnose 

killifish 

(Fundulus 

simulus)

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

 Mollusks

Basommatophora 

Snail (Physa sp.) Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

 Crustaceans

Amphipoda 

Amphipod 

(Grammarus

spp.& unknown) 

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

Anostraca Fairy shrimp 

(Streptocephalus 

seali)

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

Copepoda Copepods Mulla et al 

1983 

MSF 0.5-0.75 

gal/acre

 X information from abstract 

Decapoda Fiddler crab 

(Uca spp.)

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test 

(3.3% mortality, not attributed to 

test)

Decapoda Freshwater 

shrimp 

(Palaemonetes 

paludosus)

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

K3-6 
Decapoda Grass shrimp 

(Palaemonetes 

pugio)

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

Decapoda Crayfish 

(Procambarius 

spp.)

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

Isopoda Isopod (Asellus 

spp.)

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

Ostracoda Seed shrimp Mulla et al 

1983 

MSF 0.5-0.75 

gal/acre

 X information from abstract 

 Insects

Coleoptera 

Diving Beetle 

adults (Berosus 

metalliceps)

Mulla et al 

1983 

MSF 0.5-0.75 

gal/acre

 X information from abstract 

Ephemeroptera Mayfly naiads 

(Callibaetis 

pacificus) 

Mulla et al 

1983 

MSF 0.5-0.75 

gal/acre

 X information from abstract 

 Annelids

Polychaeta

Polychaete 

(Laeonereis 

culveri)

Hester et 

al.1991 

MSF 47 ml/m2

(50 

gal/acre)

 X 96-hour acute static toxicity lab test

K3-7 
Bacillus thuringiensis israelensis (BTI)

BTI is a bacterial pathogen which produces a parasporal body know as a Acrystal.@ This toxin kills larvae 

rapidly by attacking the plasma membrane of the gut epithelia (Dale and Hulsman, 1990). BTI forms 

asexual reproductive spores that enable it to survive adverse conditions; during spore formation, BTI 

produces unique crystalline bodies as a companion product. These spores and crystals must be ingested 

before they act as poisons to target insects (referred to as a Astomach@ poison). The crystals dissolve in 

response to intestinal conditions of susceptible insect larvae. The toxins released paralyze the gut, thus 

interfering with normal digestion which triggers the insect to stop feeding. Then the BTI spores can 

invade other tissues and multiply in the bloodstream until the insect dies. BTI is ineffective against adult

insects. BTI is effective against mosquitoes, black flies, and certain midges. Other strains of Bacillus 

thuringiensis are effective against other insects, such as the wax moth, gypsy moth and cabbage looper, 

and a new strain has been found is effective against the boll weevil (Pesticide Information Profile, 

EXTOXNET).

Synopsis of Non-target Effects

The attached Table 2 presents detailed information regarding the effects of BTI on non-target organisms. 

A few generalizations can be drawn from this information. Target organisms for BTI applications are 

various species of mosquitoes (both freshwater and salt marsh) and black flies. Effectiveness of BTI on 

mosquito species is not included. Chironomids, also a Dipteran (like mosquitoes and black flies), were 

primarily the non-target group adversely affected by BTI, but this also varied by species. A 3-year study 

found the other Dipterans (crane flies and stone flies) were affected in the third year of the study, as were 

the Ephemeropterans (mayflies). 

Label Application Rates

Vectobac G (200 International Toxic Units/mg = 0.091 billion ITU/lb) 

Habitat: irrigation/roadside ditches, floodwater, standing ponds, woodland pools, catch basins, 

storm water retention ponds, tidal water, and salt marshes 

Application Rate: 2.5 - 10 lbs/acre 

Late 3rd instar or early 4th instar, high populations, or heavily polluted water (sewage lagoons, 

etc.) or abundant algae 

Application Rate: 10 - 20 lbs/acre.

Allow 7 to 14 days between applications. 

Vectobac 12AS (1200 ITU/mg = 4.84 billion ITU/gal or 1.279 billion ITU/liter) 

Mosquito habitat: irrigation/roadside ditches, floodwater, standing ponds, woodland pools, catch 

basins, storm water retention ponds, tidal water, salt marshes, rice fields 

Application rate: 0.25 - 1 pt/acre

Use higher rate in polluted water and when late 3rd and early 4th instar larvae predominate, when 

mosquito population is high, water is heavily polluted, or abundant algae 

Application rate: 1- 2 pts/acre

K3-8 
Blackfly habitat B streams

stream water (=ppm) for 1 minute exposure time: 0.5 - 25mg/liter

stream water (=ppm) for 10 minute exposure time: 0.05 - 2.5 mg/liter

(use higher rate range when stream contains high concentration of organic 

materials, algae or dense aquatic vegetation)

Vectobac CG (200 ITU/mg = 0.091 billion ITU/lb) 

Habitat: irrigation/roadside ditches, floodwater, standing ponds, woodland pools, catch basins, 

storm water retention ponds, tidal water, salt marshes, rice fields

Application rate: 2.5 - 10 lb/acre 

Allow 7 to 14 days between applications. 

Web Site:

Pesticide Information Profiles, EXTOXNET

http://ace.ace.orst.edu/info/extoxnet/pips/ghindex.html 

References Cited:

Charbonneau, C.S., R.D. Drobney, and C.F. Rabeni. 1994. Effects of Bacillus thuringiensis var. 

Israelensis on nontarget benthic organisms in a lentic habitat and factors affecting the efficacy of 

the larvicide. Environ. Tox. Chem. 13:267-279. 

Cilek, J.E. and F.W. Knapp. 1992. Distribution and control of Chironomus riparius (Diptera: 

Chironomidae) in a polluted creek. J. Amer. Mosq. Control Assn. 8:181-183. 

Colbo, M.H. and A.H. Undeen. 1980. Effect of Bacillus thuringiensis var. israelensis on non-target 

insects in stream trials for control of Simuliidae. Mosq. News 40:368-371. 

Dale, P.E.R. and K. Hulsman. 1990. A critical review of salt marsh management methods for mosquito 

control. Review in Aquatic Sciences 3:281-311. 

Hershey, A.E., A.R. Lima, G.J. Niemi, and R.R. Regal. 1998. Effects of Bacillus thuringiensis 

israelensis (BTI) and methoprene on nontarget macroinvertebrates in Minnesota wetlands. Ecol. 

 Appl. 8:41-60. 

Knepper, R.G. and E.D. Walker. 1989. Effect of Bacillus thuringiensis israelensis (H-14) on the isopod 

Asellus forbesi and the spring Aedes mosquitoes in Michigan. J. Am Mosq. Control Assoc. 

5:596-598. 

Lee, B.M. and G.I. Scott. 1989. Acute toxicity of temephos, fenoxycarb, diflubenzuron, and 

methoprene and Bacillus thuringiensis var. israelensis to the Mummichog (Fundulus 

heteroclitus). Bull. Environ. Contamin. And Toxicol. 43:827-832. 

Miura, T., R.M. Takahashi, and F.S. Mulligan, III. 1980. Effects of the bacterial mosquito larvicide, 

Bacillus thuringiensis serotype 14 on selected aquatic organisms. Mosq. News 40:619-622. 

K3-9 
Molloy, D.P. 1992. Impact of the black fly (Diptera: Simuliidae) control agent Bacillus thuringienses

var. Israelensis on chironomids (Diptera: Chironomidae) and other nontarget insects: results of 

ten field trials. J. Amer. Mosq. Control Assn. 8:24-31. 

Molloy, D. And H. Jamnback. 1981. Factors influencing efficacy of Bacillus thuringiensis var. 

israelensis as a blackfly biocontrol agent and its effect on nontarget stream insects. J. Econ. 

Entomol. 74:314-318. 

Mulligan, F.S., III and C.H. Schaefer. 1981. Integration of a selective mosquito control agent Bacillus 

thuringiensis Serotype H-14, with natural predator populations in pesticide-sensitive 

habitats. Proceedings California Mosquito Vector Control Association 49:19-22. 

Rodcharoen, J., M.S. Mulla and J.D. Chaney. 1991. Microbial larvicides for the control of nuisance 

aquatic midges (Diptera: Chironomidae) inhabiting mesocosms and man-made lakes in 

California. J. Amer. Mosq. Control Assn. 7:56-62. 

K3-10 
 Table 2. Non-target Effects of BTI

Classification Organism Reference Formulation Application Rate 

(study) 

Adverse 

Effects

 No 

Effects

Comments

 Fish

Atheriniformes

Mummichog 

(Fundulus 

heteroclitus)

Lee & Scott 

1989 

Vectobac EC 96-hour LC50 = 980 mg/L 

(1,176,000 ITU/L); no effect 

conc. =22.36 mg/L 

Cypriniformes Golden Shiner 

(Notemigonus 

crysoleucas)

Mulligan & 

Schaefer 

1981 

B.t. H-14 

(69269 

ITU/mg)

1.0 kg/ha & 

2.0 kg/ha 

 X hand applied to bait fish ponds 

 Crustaceans

Cladocera

Water fleas Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Cladocera Water fleas Mulligan & 

Schaefer 

1981 

B.t. H-14 

(55222 

ITU/mg)

0.8 kg/ha X aerially applied to wetlands

Conchostraca Clam Shrimp Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Copepoda Copepods Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

 X experimental plots

K3-11 
spores/ml)

Copepoda Eucopepoda Mulligan & 

Schaefer 

1981 

B.t. H-14 

(55222 

ITU/mg)

0.8 kg/ha X aerially applied to wetlands

Isopoda Asellus forbesi Knepper & 

Walker 1989 

Bti X hardwood bottomland pools; 

isopods not negatively affected 

(information from abstract)

Ostracoda Podocopa Mulligan & 

Schaefer 

1981 

B.t. H-14 

(55222 

ITU/mg)

0.8 kg/ha X aerially applied to wetlands

Ostracoda Seed shrimp Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Insects

Coleoptera 

Beetles Colbo & 

Undeen 1980 

B.t. H-14 1x105spores/ml X flowing stream

Coleoptera Beetles Mulligan & 

Schaefer 

1981 

B.t. H-14 

(57620 

ITU/mg)

1.1 kg/ha X aerially applied to duck club pond 

Coleoptera Beetles Mulligan & 

Schaefer 

1981 

B.t. H-14 

(55222 

ITU/mg)

0.8 kg/ha X aerially applied to wetlands

Coleoptera Beetles Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

K3-12 
effects study); significantly 

reduced in 1993 season only; not 

significantly reduced over the 3-

yr period

Coleoptera Dytiscid beetles Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Coleoptera Elmids Molloy & 

Jamnback 

1981 

Primary powder 

(R153-78) 

0.5ppm conc. 

(1.4x108

spores/mg) 

 X stream study, flow rate 1770 

l/min; water temp. range 8o- 17oC 

Coleoptera Hydrophilid 

beetles

Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Diptera Biting midges 

Ceratopogonids 

Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study); not affected until 

3rd year, reduced by 67% in 1993; 

reduced by 29% over the 3-yr 

period 

Diptera Black flies Molloy & 

Jamnback 

1981 

Primary powder 

(R153-78) 

0.5ppm conc. 

(1.4x108

spores/mg)

 X stream study, flow rate 1770 

l/min; water temp. range 8o- 17oC 

K3-13 
Diptera Black flies Molloy 1992 Bactimos WP

Teknar WDC

Vectobac WP

ranged from 

3.7ppm/15 min 

to 50ppm/1min 

 X flowing streams; water temp. 

ranged from 3oC to 17oC; 

discharge rates ranged from 168 

l/min to 20,740 l/min

Diptera Black flies 

(Simuliidae)

Colbo & 

Undeen 1980 

B.t. H-14 1x105spores/ml X flowing stream

Diptera Chironomid: 

Procladius 

bellus & 

Tanypus 

neopunctipenni

s

Rodcharoen 

et al. 1991 

Vectobac 6253 

(200 ITU/mg) 

corn grit 

granules

56 kg/ha X lake study; no effect

Diptera Chironomid: 

Chironomus 

decorus

Rodcharoen 

et al. 1991 

Vectobac 6253 

(200 ITU/mg) 

corn grit 

granules

56 kg/ha X lake study; 42-67% control for 3 

weeks

Diptera Chironomid: 

Procladius 

bellus & 

Tanypus 

neopunctipenni

s

Rodcharoen 

et al. 1991 

Vectobac ABG 

6164 (technical 

powder) 

1.4 kg/ha 

2.8 kg/ha 

 X lake study; no effect noted 

Diptera Chironomid: 

Chironomus 

decorus

Rodcharoen 

et al. 1991 

Vectobac 

technical powder 

(5,000 ITU/mg) 

2.2 kg/ha 

4.5 kg/ha 

6.7 kg/ha 

 X lake study; lower rate yielded 

maximum control of 66% at 2 

weeks; middle rate yielded higher 

level of control; higher rate 

yielded 95% control at 1 week, 

then 100% at 2-3 weeks; higher 2 

K3-14 
rates yielded over 70% control for

4 weeks

Diptera Chironomid: 

Chironomus 

decorus

Rodcharoen 

et al. 1991 

Vectobac 6264 

(400 ITU/mg) 

corn grit 

granules

11.2 kg/ha 

19.1 kg/ha 

lake study: Amediocre@ control 

(32 & 47% respectively) for 

about 2 weeks 

Diptera Chironomid: 

Procladius 

bellus & 

Tanypus 

grodhausi

Rodcharoen 

et al. 1991 

Vectobac 6253 

(200 ITU/mg) 

corn grit 

granules

13.5 kg/ha 

28 kg/ha 

56kg/ha 

 X lake study; unaffected even at 

highest rate

Diptera Chironomid: 

Dicrotendipes

sp. 

Rodcharoen 

et al. 1991 

Vectobac 6264 

(400 ITU/mg) 

corn grit 

granules

11.2 and 22.4 

kg/ha 

 X mesocosm studies; highly 

susceptible 

Diptera Chironomid: 

Chironomus 

decorus

Rodcharoen 

et al. 1991 

Vectobac ABG 

6164 (technical 

powder) 

1.4 kg/ha 

2.8 kg/ha 

 X lake study; lower rate yielded 

maximum reduction of 73% 2 

weeks post treatment and lasted 

about 4 weeks; high rate yielded 

max. control of 87% at 3 weeks 

post treatment

Diptera Chironomid: 

Chironomus sp. 

Rodcharoen 

et al. 1991 

Vectobac 6253 

(200 ITU/mg) 

corn grit 

granules

22.4 and 44.8 

kg/ha 

 X mesocosm studies; highly 

susceptible to higher rate 

Diptera Chironomid: 

Chironomus sp. 

Rodcharoen 

et al. 1991 

Vectobac 6 AS 

(aqueous 

11.2 and 22.4 

kg/ha 

 X mesocosm studies; 11.2 kg/ha 

yielded 37% control at 1 week 

K3-15 
suspension) post treatment; 22.4 kg/ha yielded 

57% control at 2 weeks post 

treatment; conclusion that control 

not evident until 2 weeks post 

treatment

Diptera Chironomid: 

Procladius sp. 

Rodcharoen 

et al. 1991 

Vectobac 6264 

(400 ITU/mg) 

corn grit 

granules

11.2 and 22.4 

kg/ha 

 X mesocosm studies; lower rate 

yielded 24% control after 1 week; 

higher rate no effect; conclusion 

little to no control

Diptera Chironomid: 

Chironomus sp. 

Rodcharoen 

et al. 1991 

Vectobac ABG6164 (technical 

powder) 

5.6 and 11.2 

kg/ha 

 X mesocosm studies; yielded 98% 

and 100% control (respectively) 

at 2 weeks post treatment

Diptera Chironomid: 

Paratanytarsus

sp. 

Rodcharoen 

et al. 1991 

Vectobac 6264 

(400 ITU/mg) 

corn grit 

granules

11.2 and 22.4 

kg/ha 

 X mesocosm studies; conclusion 

little to no control

Diptera Chironomid: 

Paratanytarsus

sp. 

Rodcharoen 

et al. 1991 

Vectobac 6253 

(200 ITU/mg) 

corn grit 

granules

22.4 and 44.8 

kg/ha 

 X mesocosm studies; conclusion 

little to no control

Diptera Chironomid: 

Chironomus 

decorus

Rodcharoen 

et al. 1991 

Vectobac 6253 

(200 ITU/mg) 

corn grit 

granules

13.5 kg/ha 

28 kg/ha 

56kg/ha 

 X lake study; lowest rate showed 

only 22% control at 2 weeks; 

higher rates showed 83% and 

96% control (respectively); 

control of over 70% at 2 higher 

rates lasted over 4 weeks

K3-16 
Diptera Chironomid: 

Dicrotendipes

sp. 

Rodcharoen 

et al. 1991 

Vectobac 6253 

(200 ITU/mg) 

corn grit 

granules

22.4 and 44.8 

kg/ha 

 X mesocosm studies; highly 

susceptible 

Diptera Chironomid: 

Chironomus sp. 

Rodcharoen 

et al. 1991 

Vectobac 6264 

(400 ITU/mg) 

corn grit 

granules

11.2 and 22.4 

kg/ha 

 X mesocosm studies; highly 

susceptible 

Diptera Chironomid: 

Procladius sp. 

Rodcharoen 

et al. 1991 

Vectobac 6253 

(200 ITU/mg) 

corn grit 

granules

22.4 and 44.8 

kg/ha 

 X mesocosm studies; lower rate no 

effect; higher rate yielded 17% 

control after 1 week conclusion 

little to no control

Diptera Chironomidae Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study); reduced by 66% in 

1992 & 84% in 1993 

Diptera Chironomids Cilek & 

Knapp 1992 

Vectobac-6AS 50 ppm X field test in flowing creek, 

velocity 0.8 m/s & 0.5 m/s, water 

temp. 25oC, pH 7.5 

Diptera Chironomids Cilek & 

Knapp 1992 

Vectobac-G 22.4 kg/ha X field test in flowing creek, 

velocity 0.1 m/s, water temp. 

25o

C, pH 7.5 

K3-17 
Diptera Chironomids Mulligan & 

Schaefer 

1981 

B.t. H-14 

(55222 

ITU/mg)

0.8 kg/ha aerially applied to wetlands; peak 

numbers 1 day after treatment, 

with gradual decline thereafter

Diptera Chironomids Molloy & 

Jamnback 

1981 

Primary powder 

(R153-78) 

0.5ppm conc. 

(1.4x108

spores/mg) 

 X stream study, flow rate 1770 

l/min; water temp. range 8o- 17oC 

Diptera Chironomids Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots; all larvae 

collected were killed w/i 2 days 

of treatment, but daily collections 

rapidly increased indicating shortterm effects

Diptera Chironomids 

(filter-feeders; 

Rheotanytarsus 

spp.) 

Molloy 1992 Bactimos WP

Teknar WDC

Vectobac WP

ranged from 

3.7ppm/15 min 

to 50ppm/1min 

 X flowing streams; water temp. 

ranged from 3oC to 17oC; 

discharge rates ranged from 168 

l/min to 20,740 l/min

Diptera Chironomids B

Other

Molloy 1992 Bactimos WP

Teknar WDC

Vectobac WP

ranged from 

3.7ppm/15 min 

to 50ppm/1min 

 X flowing streams; water temp. 

ranged from 3o

C to 17oC; 

discharge rates ranged from 168 

l/min to 20,740 l/min

Diptera Chironomids Colbo & 

Undeen 1980 

B.t. H-14 1x105spores/ml X flowing stream

Diptera Chironomids Charbonneau 

et at 1994 

Vectobac-G 28.1 kg/ha X adversely affected in lab, but 

environmental factors 

(temperature, larval instar, water 

depth & water surface area 

coverage) reduced efficacy in the 

field

K3-18 
Diptera Chironomids Charbonneau 

et al 1994 

Vectobac-G 5.6 kg/ha X adversely affected in lab, but 

environmental factors 

(temperature, larval instar, water 

depth & water surface area 

coverage) reduced efficacy in the 

field

Diptera Chironomids B

predatory 

Hershey et

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study); reduced 62% in 

1992 & 83% in 1993 

Diptera Crane flies 

(Tipulidae) 

Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study); reduced by 73% 

over the 3-yr treatment period

Diptera Diptera Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study); over 3-yr study 

total reduction = 63% 

Diptera Nematocera Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study); over 3-yr treatment 

total reduction = 67% 

Diptera Soldier flies 

(Stratiomyidae)

Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

K3-19 
for 3 years (1991-1993 long-term 

effects study); reduced in 1993 

season only, reduction =74%; 

yielding 56% reduction over the 

3-yr period

Ephemeroptera May flies 

(Brachycera)

Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study); showed no effect 

until 1993 when reduced by 66% 

Ephemeroptera Mayflies Mulligan & 

Schaefer 

1981 

B.t. H-14 

(55222 

ITU/mg)

0.8 kg/ha X aerially applied to wetlands

Ephemeroptera Mayflies Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Ephemeroptera Mayflies Molloy 1992 Bactimos WP

Teknar WDC

Vectobac WP

ranged from 

3.7ppm/15 min 

to

50ppm/1min 

 X flowing streams; water temp. 

ranged from 3oC to 17oC; 

discharge rates ranged from 168 

l/min to 20,740 l/min

Ephemeroptera Mayflies Molloy & 

Jamnback 

1981 

Primary powder 

(R153-78) 

0.5ppm conc. 

(1.4x108

spores/mg) 

 X stream study, flow rate 1770 

l/min; water temp. range 8o

- 17oC 

Ephemeroptera Mayflies Colbo & 

Undeen 1980 

B.t. H-14 1x105spores/ml X flowing stream

K3-20 
Hemiptera Corixids Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Hemiptera Notonectids Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Hemiptera True bugs Mulligan & 

Schaefer 

1981 

B.t. H-14 

(55222 

ITU/mg)

0.8 kg/ha X aerially applied to wetlands

Hemiptera True bugs Mulligan & 

Schaefer 

1981 

B.t. H-14 

(57620 

ITU/mg)

1.1 kg/ha X aerially applied to duck club pond 

Odonata Damselflies Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Odonata Damselflies 

(Zygoptera)

Mulligan & 

Schaefer 

1981 

B.t. H-14 

(55222 

ITU/mg) 

0.8 kg/ha X aerially applied to wetlands

Odonata Dragonflies & 

Damselflies

Colbo & 

Undeen 1980 

B.t. H-14 1x105spores/ml X flowing stream

Dragonflies Mulligan & B.t. H-14 

K3-21 
Odonata (Anisoptera) Schaefer 

1981 

(55222 

ITU/mg)

0.8 kg/ha X aerially applied to wetlands

Odonata Dragonflies 

(Anisoptera) 

Mulligan & 

Schaefer 

1981 

B.t. H-14 

(57620 

ITU/mg)

1.1 kg/ha X aerially applied to duck club pond 

Odonata Dragonflies Miura et al 

1980 

SAN 402 I 

WDC

0.25 kg/ha 

(~1.3x103

spores/ml) & 1 

kg/ha (~5.4x103

spores/ml)

 X experimental plots

Plecoptera Stoneflies Colbo & 

Undeen 1980 

B.t. H-14 1x105spores/ml X flowing stream

Plecoptera Stoneflies Molloy & 

Jamnback 

1981 

Primary powder 

(R153-78) 

0.5ppm conc. 

(1.4x108

spores/mg) 

 X stream study, flow rate 1770 

l/min; water temp. range 8o- 17oC 

Trichoptera Caddisflies Colbo & 

Undeen 1980 

B.t. H-14 1x105spores/ml X flowing stream

Trichoptera Caddisflies Molloy & 

Jamnback 

1981 

Primary powder 

(R153-78) 

0.5ppm conc. 

(1.4x108

spores/mg) 

 X stream study, flow rate 1770 

l/min; water temp. range 8o

- 17oC 

Trichoptera Caddisflies Molloy 1992 Bactimos WP

Teknar WDC

Vectobac WP

ranged from 

3.7ppm/15 min 

to

50ppm/1min

 X flowing streams; water temp. 

ranged from 3o

C to 17oC; 

discharge rates ranged from 168 

l/min to 20,740 l/min. 

Miscellaneous Non-dipteran 

predators 

Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

K3-22 
for 3 years (1991-1993 long-term 

effects study); no significant 

seasonal effect in 1991 & 1992, 

but significant reduction in 1993 

Miscellaneous Total predatory 

insects

Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study); no significant 

seasonal effect in 1991 & 1992, 

but 60% reduction in 1993 

Miscellaneous Non-insect 

macroinvertebrates

Hershey et 

al. 1998 

Vectobac G 11.720.64 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (1991-1993 long-term 

effects study) 

K3-23 
Methoprene

Methoprene is an insect growth regulator (IGR), which mimics juvenile hormones (Dale and 

Hulsman 1990). It interferes with the insect=s maturation stages and makes it impossible for the 

insect to reach the adult stage, thus preventing it from reproducing. Methoprene is considered a 

biochemical pesticide because it interferes with the life cycle rather than direct toxicity. To be 

effective, it must be administered at the proper life stage of the mosquito (or target species). It is 

not toxic to pupal or adult stages. Treated larvae will pupate, but will not emerge as adults 

(Pesticide Information Profiles, EXTOXNET).

Synopsis of Non-target Effects

As seen in Table 3, methoprene had no effect on the vertebrate species tested. Mixed effects 

were seen for snails, and crustaceans such as grass shrimp and mud crabs. Insects most affected 

were dipterans, with some mixed effects reported for mayflies and some coleopterans.

Label Application Rates

Altosid7

 Liquid Larvicide (A.L.L.) effective on 2nd, 3rd, or 4th instar larvae of floodwater 

mosquitoes; has no effect on pupae or adult mosquitoes 

Crop Areas: irrigated croplands after flooding, e.g. vineyards, rice fields, irrigated 

pastures, berry fields, orchards, bogs. Application Rate: 3 to 4 fluid ounces/acre (219 to 

293 ml/hectare) in water.

Intermittently Flooded Areas: freshwater swamps and marshes, salt marshes, woodland 

pools and meadows, dredging spoil sites, drainage areas, waste treatment and settling 

ponds, ditches and other natural or man-made depressions. Application Rate: 3 to 4 fluid 

ounces/acre (219 to 293 ml/hectare) in water. 

Dense Vegetation or Canopy Areas: Apply A.L.L. on sand granules at standard 

application rate (as stated above).

Altosid7 Pellets is toxic to aquatic dipteran (mosquitoes) and Chironomid (midge) larvae. It has 

no effect on pupal or adult stage mosquitoes; pellets release effective levels for up to 30 

days.

Floodwater Sites: pastures, meadows, rice fields, freshwater swamps and marshes, salt 

and tidal marshes, cattail marshes, woodland pools, floodplains, tires, and other artificial 

water-holding containers. Application Rate: 2.5 - 5.0 lb/acre. 

Floodwater Sites: dredging spoil sites, waste treatment and settling ponds, ditches and 

other man-made depressions. Application Rate: 5.0 - 10.0 lb/acre. 

Permanent Water Sites: ornamental ponds and fountains, fish ponds, cattail marshes, 

water hyacinth beds, flooded crypts, transformer vaults, swimming pools and other manmade depressions, etc. Application Rate: 2.5 - 5.0 lb/acre 

K3-24 
Permanent Water Sites: storms drains, catch basins, roadside ditches, cesspools, septic 

tanks, waste settling ponds, vegetation-choked phosphate pits. Application Rate: 5.0 - 

10.0 lb/acre. 

Altosid7 XR-G (extended residual granules) is toxic to aquatic dipteran; it has no effect on pupal 

or adult life stages; length of control up to 21 days, but actual length depends on duration 

and frequency of flooding. 

Non-Crop Areas: snow pools, salt and tidal marshes, freshwater swamps and marshes, 

woodland pools and meadows, dredging spoil sites, drainage areas, ditches, water-holding 

receptacles and other natural or man-made depressions. 

Aedes, Anopheles, and Psorophora spp. Application Rate: 5 - 10 lb/acre (5.6 - 11.2 

kg/ha). Culex, Culiseta, Coquillettidia, and Mansonia spp. Application Rate: 10 - 20 

lb/acre (11.2 - 22.4 kg/ha). Within these rates, use lower rate when water is shallow (2 

ft. [60 cm]) and vegetation and/or pollution are minimal. Use higher rates when water is 

deep (2 feet) and vegetation and/or pollution are heavy. 

Altosid7 Briquets: toxic to aquatic dipterans; no effect on pupal or adult stage mosquitoes; under 

normal conditions, repeat treatment every 30 days; designed to control mosquitoes in 

small bodies of water.

Sites: storm drains, catch basins, roadside ditches, fish ponds, ornamental ponds and 

fountains, septic tanks, waste treatment and settling ponds, abandoned swimming pools, 

other man-made depressions, cattail marshes, water hyacinth beds, pastures, meadows, 

rice fields, freshwater swamps and marshes, salt and tidal marshes, woodland pools, 

floodplains, dredging spoil sites. 

Application Rates: non-(or low) flow, shallow depressions (up to 2 ft. deep), treat on 

basis of surface area placing one briquet per 100 sq. ft. Flowing water or deeper than 2 

ft, treat on basis of volume, one briquet per 10 cu ft. (75 gal of water). 

Altosid7

 XR (extended residual briquets): toxic to aquatic dipterans; no effect of pupal or adult 

stage mosquitoes; one application should last entire breeding season, or 150 days. 

Sites: storm drains, catch basins, roadside ditches, fish ponds, waste treatment and 

settling ponds, cattail marshes, meadows, rice fields, freshwater swamps and marshes, 

salt and tidal marshes, woodland pools, floodplains and dredging spoil sites. 

Application Rates: Aedes and Psorophora spp. in non-(or low) flow shallow depressions 

(2 ft. deep) treat on basis of surface area - 1 briquet per 200 ft2

. Culex, Culiseta, and 

Anopheles spp. - 1 briquet per 100 ft2. Coquillettidia and Mansonia spp. for application 

to cattail marshes and water hyacinth beds, place 1 briquet per 100 ft.2

. 

Web Site:

K3-25 
Pesticide Information Profiles, EXTOXNET

http://ace.ace.orst.edu/info/extoxnet/pips/ghindex.html 

References Cited:

Ali, A. 1991. Activity of new formulations of methoprene against midges (Diptera: 

Chironomidae) in experimental ponds. J. Amer. Mosq. Control Assn. 7:616-620. 

Breaud, T.P., J.E. Farlow, C.D. Steelman and P.E. Schilling. 1977. Effects of the insect growth 

regulator methoprene on natural populations of aquatic organisms in Louisiana 

intermediate marsh habitats. Mosq. News 37:704-712. 

Celestial, D.M. and C.L. McKenney, Jr. 1994. The influence of an insect growth regulator on 

the larval development of the mud crab Rhithropanopeus harrisii. Environ. Poll. 85:169-

173. 

Dale, P.E.R. and K. Hulsman. 1990. A critical review of salt marsh management methods for 

mosquito control. Review in Aquatic Sciences 3:281-311. 

Ellgaard, E.G., J.T. Barber, S.C. Tiwari and A.L. Friend. 1979. An analysis of the swimming 

behavior of fish exposed to the insect growth regulators, methoprene and diflubenzuron. 

Mosq. News 39:311-314. 

Hershey, A.E., A.R. Lima, G.J. Niemi, and R.R. Regal. 1998. Effects of Bacillus thuringiensis 

israelensis (BTI) and methoprene on nontarget macroinvertebrates in Minnesota 

wetlands. Ecol. Appl. 8:41-60. 

Lee, B.M. and G.I. Scott. 1989. Acute toxicity of temephos, fenoxycarb, diflubenzuron, and 

methoprene and Bacillus thuringiensis var. israelensis to the Mummichog (Fundulus 

heteroclitus). Bull. Environ. Contamin. And Toxicol. 43:827-832. 

McAlonan, W.G., F.J. Murphey and R.W. Lake. 1976. Effects of two insect growth regulators 

on some selected saltmarsh non-target organisms. Proc. Ann. Meet. N.J. Mosq. Control 

Assoc. 63:198. 

McKenney, C.L., Jr. and D.M. Celestial. 1996. Modified survival, growth, and reproduction in 

an estuarine mysid (Myosidposis bahia) exposed to a juvenile hormone analogue through 

a complete life cycle. Aquatic Toxicol. 35:11-20. 

McKenney, C.L., Jr. and E. Matthews. 1990. Influence of an insect growth regulator on the 

larval development of an estuarine shrimp. Environ. Poll. 64:169-178. 

Miura, T. And R.M. Takahashi. 1973. Insect development inhibitors. 3. Effects on nontarget 

aquatic organisms. J. Econ. Entomol. 66:917-922. 

Norland, R.L. and M.S. Mulla. 1975. Impact of Altosid on selected members of an aquatic 

ecosystem. Environ. Entomol. 4:145-152. 

K3-26 
Quistad, G.B., D.A. Schooley, L.E. Staiger, B.J. Bergot, B.H. Sleight, and K.J. Macek. 1976. 

Environmental degradation of the insect growth regulator methoprene. IX. Metabolism 

by bluegill fish. Pest. Biochem. Physiol. 6:523-529. 

K3-27 
 Table 3. Non-target Effects of Methoprene 

Classification Organism Reference Formulation Application 

Rate (study)

Adverse 

Effects

No 

Effects

Comments

 Fish

Atheriniformes

Killifish McAlonan et 

at. 1976 

Altosid 10-

F 

0.012 to 0.120 

lbs AI/A

 X caused no mortality 

Atheriniformes Mosquitofish 

(Gambusia affinis)

Ellgaard et 

al 1979 

methoprene 0.2 ppm X exposed for 12 days; methoprene 

was added at rate every 2 days 

such that total conc was increased 

by 0.1 ppm; no effect on motility 

Atheriniformes Mosquitofish 

(Gambusia affinis)

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Atheriniformes Mosquitofish 

(Gambusia affinis)

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 1 ppm; 60% at 100 

ppm; test duration 312 hours 

Atheriniformes Mummichog 

(Fundulus 

heteroclitus)

Lee & Scott 

1989 

methoprene 

EC

96-hour LC50 = 124.95 mg/L; no 

effect concentration = 24.68 mg/L 

Cypriniformes Goldfish Ellgaard et 

al 1979 

methoprene 0.2 ppm X exposed for 13 days; methoprene 

was added at rate every 2 days 

such that total conc was increased 

by 0.1 ppm; no effect on motility 

Cypriniformes Heterandria 

formosa

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Perciformes Bluegill Quistad et 

al. 1976 

methoprene 0.31 & 0.005 

ppm 

radioactive tag to study uptake; 

higher dose, fish exhibited stress 

(LC50 = 2.1 ppm); within 2 weeks 

after treatment, 93-95% residue 

K3-28 
had been eliminated

 Amphibians

Anura 

Western toad 

tadpoles, Bufo 

borcas helophilus

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 1 ppm; test duration 

24 hours 

 Arachnids

Acarina

Oribateid mites Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

 Mollusks

Basommatophora 

Physa sp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Basommatophora Pond snail, Physa 

spp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

 X laboratory toxicity tests: 0% 

mortality at 100 ppm; test 

duration 72 hours 

Basommatophora Snail, Lymnaea sp. Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

 X laboratory toxicity tests: 0% 

mortality at 1 ppm; test duration 

72 hours 

 Crustaceans

Amphipoda 

Hyallela azteca 

(Scud) 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; greater reduction in open 

water habitats

Amphipoda Sideswimmers, 

Hyallela azteca

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 1.25 ppm; test duration 

24-120 hours 

Cladocera Water fleas, 

Daphnia magna

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 0.90 ppm; test duration 24 

hours 

Cladocera Water fleas, 

Daphnia magna

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

K3-29 
Cladocera Water fleas, 

Daphnia magna

Miura & 

Takahashi 

1973 

technical 

ZR-515 

0.7 lb corncob 

granular/acre

 X outdoor cage study

Cladocera Water fleas, 

Daphnia magna

Miura & 

Takahashi 

1973 

technical 

ZR-515, 

10% 

flowable 

liquid (slow 

release)

0.1 ppm X outdoor test in artificial container; 

no detectable effects

Conchostraca Clam shrimp, 

Eulimnadia sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

0.1 lb EC/acre X outdoor caged study 

Conchostraca Clam shrimp, 

Eulimnadia sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 1.00 ppm; test duration 24 

hours 

Conchostraca Clam shrimp, 

Eulimnadia sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

0.7 lb corncob 

granular/acre

 X outdoor caged study 

Conchostraca Clam shrimp, 

Eulimnadia sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Copepoda Copepods, 

Cyclops sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Copepoda Copepods, 

Cyclops sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

0.1 lb EC/acre X pond study 

Copepoda Copepods, Miura & 

Takahashi 

technical 5 laboratory acute toxicity tests: 

LC50 = 4.60 ppm; test duration 24 

K3-30 
Cyclops sp. 1973 ZR-515 concentrations hours

Copepoda Copepods, 

Cyclops sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515, 

10% 

flowable 

liquid (slow 

release)

0.1 ppm X outdoor test in artificial container; 

no detectable effects

Decapoda Crayfish 

(Procambarius 

clarki and 

Cambarellus sp.) 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; population increases 

attributed to reduced predator 

populations 

Decapoda Fiddler Crab McAlonan et 

at. 1976 

Altosid SR10 0.024 to 0.384 

lbs AI/A; 3 

treatments at 

2-week 

intervals

 X no significant mortality nor 

frequency of ecdysis affected

Decapoda Fiddler Crab McAlonan et 

at. 1976 

Altosid 10-

F 

0.012 to 0.120 

lbs AI/A

 X caused no mortality 

Decapoda Grass Shrimp 

(Palaemonetes 

pugio) 

McKenney 

& Matthews 

1990 

methoprene, 

technical 

grade

1000 g/l X lab study; all larvae died

Decapoda Clam Shrimp 

(Palaemonetes 

paludosus)

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Decapoda Grass Shrimp 

(Palaemonetes 

pugio) 

McKenney 

& Matthews 

1990 

methoprene, 

technical 

grade

0.1 g/l

10 g/l

100 g/l

lab study; 100 g/l rate had 

significant effect; other rates had 

no effect

Decapoda Grass Shrimp McKenney A.L.L. 1000 g/l X lab study; all larvae died

K3-31 
(Palaemonetes 

pugio) 

& Matthews 

1990 

Decapoda Grass Shrimp McAlonan et 

at. 1976 

Altosid SR10 0.024 to 0.384 

lbs AI/A; one 

series of 4 

treatments & 

second series 

of 3 treatments 

at 2-week 

intervals

 X no significant mortality nor 

frequency of ecdysis affected

Decapoda Grass Shrimp 

(Palaemonetes 

pugio) 

McKenney 

& Celestial 

1993 

A.L.L. 8, 16, 32, 62, 

125, 250 g/l

 X lab study; significant mortality 

was seen after 2 days exposure for 

250, after 4 days for 62 & greater, 

and after 8 days for all conc. ; 

both dry weights & daily growth 

rates for 1- and 9-day old larvae 

significantly reduced by 8 g/l 

and greater conc. exposures

Decapoda Grass Shrimp 

(Palaemonetes 

pugio) 

McKenney 

& Matthews 

1990 

A.L.L. 0.1 g/l

10 g/l

100 g/l

 X lab study; no effect 

Decapoda Grass Shrimp McAlonan et 

at. 1976 

Altosid 10-

F 

0.048 to 0.120 

lbs AI/A

 X produced greater than 60% 

mortality

Decapoda Mud Crab 

(Rhithropanopeus 

harrisii) 

Celestial & 

McKenney 

1994 

A.L.L. varying conc.: 

 0.1, 1.0, 10.0 

g/l

 X lab study; no statistically 

significant reductions in survival 

rates; although zoeal stages I & II 

showed reduced survival rates; no 

significant differences in 

cumulative development duration 

at these conc.

K3-32 
Decapoda Mud Crab 

(Rhithropanopeus 

harrisii) 

Celestial & 

McKenney 

1994 

A.L.L. 100 g/l X lab study; significant reductions in 

survival for all development 

stages except zoeal stage II; 

significant development duration, 

increased total development 

duration by 4 days 

Decapoda Mud Crab 

(Rhithropanopeus 

harrisii) 

Celestial & 

McKenney 

1994 

A.L.L. 1000 g/l X lab study; no larvae survived 

beyond zoeal stage I

Decapoda Mysidiopsis bahia McKenney 

& Celestial 

1996 

A.L.L. varying: 

2,4,8,16,32, 62 

g/l

 X lab study; no significant effects on 

mortality through life cycle

Decapoda Mysidiopsis bahia McKenney 

& Celestial 

1996 

A.L.L. varying: 

2,4,8,16,32, 62 

g/l

 X lab study; reproduction affected 

by sublethal concentrations 

greater than 2 g/l; average time 

to first brood release significantly 

delayed for all conc. except 2 & 

16 g/l; brood size reduced in all 

conc. greater than 8 g/l.

Decapoda Mysidiopsis bahia McKenney 

& Celestial 

1996 

A.L.L. 125 g/l X lab study; 100% mortality by 4 

days of exposure 

Decapoda Mysidiopsis bahia McKenney 

& Celestial 

1996 

A.L.L. varying: 

2,4,8,16,32, 62 

g/l

lab study; 62 g/l significantly 

affected dry weights after 15 days 

of exposure; other concentrations 

had no effect

Mysidacea Taphromysis 

louisiana

(opossum shrimp) 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; greater numbers collected 

in open water habitats, but slightly 

higher mortality occurred in 

K3-33 
emergent plant habitat

Notostraca Tadpole shrimp, 

Triops 

longicaudatus

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 5.00 ppm; test duration 

24-96 hours 

Notostraca Tadpole shrimp, 

Triops 

longicaudatus

Miura & 

Takahashi 

1973 

technical 

ZR-515 

0.1 lb EC/acre X outdoor caged study 

Notostraca Tadpole shrimp, 

Triops 

longicaudatus

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Ostracoda Ostracod 

(Cyprinotus sp.) 

Norland & 

Mulla 1975 

Altosid EC 0.1 ppm X repeated treatments of 

experimental ponds; (information 

from abstract)

Ostracoda Seed shrimp, 

Cypricercus sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Ostracoda Seed shrimp, 

Cypricercus sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 1.50 ppm; test duration 24 

hours 

Ostracoda Seed shrimp, 

Cypricercus sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

0.7 lb corncob 

granular/acre

 X outdoor caged study 

 Insects

Coleoptera 

Berosus sp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Berosus exiguus Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Berosus infuscatus Breaud et al. methoprene 28 gm AI/ha X 6 aerial applications over 18 

K3-34 
1977 months;

Coleoptera Coleoptera Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); 46% reduction in 1992; 

59% reduction in 1993; 48% 

reduction over 4-yr period

Coleoptera Copelatus sp. Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Coleoptera Dytiscid beetle 

(Laccophilus sp.) 

Norland & 

Mulla 1975 

Altosid EC 0.1 ppm X repeated treatments of 

experimental ponds; eliminated 

from treated ponds (information 

from abstract)

Coleoptera Enochrus 

blatchleyi

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Hydrocanthus spp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Hydrovatus 

cuspidatus

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Laccophilus 

proximus

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Liodessus affinis Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; population increases 

attributed to reduced predator 

populations 

Coleoptera Lissorhoptrus spp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

K3-35 
Coleoptera Lixellus sp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Noteridae Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Predaceous water 

beetle, 

Laccophilus sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Coleoptera Predaceous water 

beetle, 

Laccophilus sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 2.00 ppm; test duration 

48-72 hours 

Coleoptera Scavenger beetle 

(Tropisternus 

lateralis)

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Suphisellus spp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Coleoptera Water scavenger 

beetle, 

Tropisternus 

lateralis

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 1 ppm; test duration 

120 hours 

Coleoptera Water scavenger 

beetle, Helophorus

sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 57% 

mortality at 0.8 ppm; 48% at 2.5 

ppm; test duration 72-96 hours 

Coleoptera Water scavenger 

beetle, Helophorus

sp. 

Miura & 

Takahashi 

1973 

Miura & 

Takahashi 

1973 

 X irrigated pasture study 

Coleoptera Water scavenger 

beetle, 

Miura & 

Takahashi 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 24 ppm; 100% at 100 

K3-36 
Hydrophilus 

triangularis

1973 ppm ; test duration 144-240 hours 

Coleoptera Water scavenger 

beetle, 

Tropisternus 

lateralis

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Coleoptera Water scavenger 

beetle, 

Hydrophilus 

triangularis

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Coleoptera Whirligig beetle, 

Gyrinus punctellus

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 100% 

mortality at 6 ppm; test duration 

48 hours 

Diptera Anopheles sp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Diptera Biting Midges - 

Ceratopogonids 

Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); reduced in 1992 & 1993; 

3-yr period showed reduction of 

55% 

Diptera Chironomid Norland & 

Mulla 1975 

Altosid EC 0.1 ppm X repeated treatments of 

experimental ponds; twofold 

reduction by treatment 

(information from abstract)

Diptera Chironomidae Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); seasonal significant 

K3-37 
reduction in 1992 & 1993, and for 

overall 3-yr treatment period

Diptera Chironomids Ali 1991 XR 

Briquets 

0.82 kg AI/ha X experimental pond; 38-96% 

control for 7 weeks 

Diptera Chironomids Ali 1991 Pellets 0.22 kg AI/ha X experimental pond; 64-98% 

control for 7 weeks 

Diptera Chironomids Ali 1991 Granular 

(SAN 810 I 

1.3 GR) 

0.17 kg AI/ha X experimental pond; lost 

effectiveness in 3rd week posttreatment

Diptera Chironomids Ali 1991 A.L.L. 0.28 kg AI/ha X experimental pond; returned to 

pre-treatment levels in 3rd week 

after treatment

Diptera Chironomids Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Diptera Chironomids Ali 1991 A.L.L. 0.015 kg AI/ha X experimental pond 

Diptera Crane flies --

Tipulidae 

Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); reduced in 1992 & 1993; 

3-yr period showed reduction of 

73% 

Diptera Culex salinarius Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Diptera Diptera Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); exhibited 3-yr reduction of 

66% 

K3-38 
Diptera Flower fly, Nylota 

sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 6 ppm; test duration 

72 hours 

Diptera Flower fly, Nylota 

sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Diptera Green heads - 

Dolichopodidae 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Diptera Lispe sp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Diptera Midge, 

Chironomus 

stigmaterus

Miura & 

Takahashi 

1973 

technical 

ZR-515 

irrigated pasture study; some dead 

pupae 

Diptera Midge, 

Chironomus 

stigmaterus

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 50% 

mortality at 0.01 ppm; test 

duration 288 hours 

Diptera Mothfly, Pericoma

sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 50% 

mortality at 0.1 ppm; test duration 

480 hours 

Diptera Nematocera Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); exhibited 3-yr reduction of 

68% 

Diptera Notophila ap. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Diptera Predatory Hershey et Altosid 3- 5.820.44 X natural wetlands; aerial 

K3-39 
chironomids al. 1998 wk release 

granules

kg/ha application, 6 treatments per year 

for 3 years (long-term effects 

study); seasonal significant 

reduction in 1992 & 1993, and for 

overall 3-yr treatment period

Diptera Sandflies 

(Psychoda sp.) 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; population increases 

attributed to reduced predator 

populations 

Diptera Shorefly, 

Brachydeutera 

argentata

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 irrigated pasture study; some dead 

pupae 

Diptera Shorefly, 

Brachydeutera 

argentata

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 70% 

mortality at 0.01 ppm; test 

duration 504 hours 

Diptera Soldier flies 

(Eulalia sp.) 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Diptera Soldier flies --

Stratiomyidae

Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); no effect seen until 1993, 

then showed 71%, with overall 3-

yr reduction of 44% 

Ephemeroptera Mayflies --

Brachycera

Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); no effect seen until 1993, 

then showed 69%, with overall 3-

yr reduction of 36% 

K3-40 
Ephemeroptera Mayflies 

(Callibaetis sp.) 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Ephemeroptera Mayfly nymphs, 

Callibaetis sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% at 10 

ppm; test duration 48 hours 

Ephemeroptera Mayfly (Caenis

sp.) 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Ephemeroptera Mayfly nymphs, 

Callibaetis sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Ephemeroptera Mayfly 

(Callibaetis 

pacificus) 

Norland & 

Mulla 1975 

Altosid EC 0.1 ppm X repeated treatments of 

experimental ponds; mortality in 

early and late instars during 

winter; effect lessened with rising 

water temperatures (information 

from abstract)

Hemiptera Backswimmer, 

Notonecta 

unifasciata

Miura & 

Takahashi 

1973 

technical 

ZR-515, 

10% 

flowable 

liquid (slow 

release)

technical ZR515, 10% 

flowable liquid 

(slow release)

 X outdoor test in artificial container; 

 no visible effects on populations 

Hemiptera Backswimmer, 

Notonecta 

unifasciata

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 1.20 ppm; test duration 24 

hours 

Hemiptera Backswimmer, 

Notonecta 

unifasciata

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Breaud et al. 6 aerial applications over 18 

K3-41 
Hemiptera Buenoa spp. 1977 methoprene 28 gm AI/ha X months;

Hemiptera Corixids 

(Trichocorixa 

louisianae)

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; population increases 

attributed to reduced predator 

populations 

Hemiptera Giant water bug 

(Belostoma 

testaceum) 

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Hemiptera Water treader 

(Mesovelia 

mulsanti)

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Hemiptera Waterboatman, 

Corisella decolor

Miura & 

Takahashi 

1973 

technical 

ZR-515, 

10% 

flowable 

liquid (slow 

release)

0.1 ppm X outdoor test in artificial 

containers; no visible effects on 

populations 

Hemiptera Waterboatman, 

Corisella decolor

Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Hemiptera Waterboatman, 

Corisella decolor

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 1.65 ppm; test duration 

24-96 hours 

Odonata Coenagrionidae Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Odonata Damselfly 

nymphs, Argia sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 1 ppm; test duration 

48 hours 

K3-42 
Odonata Dragonflies 

(Belonia & Anax)

Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Odonata Dragonfly 

nymphs, Orthemis

sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 24 ppm; 30 % at 100 

ppm; test duration 72 hours 

Odonata Odonata naiads Norland & 

Mulla 1975 

Altosid EC 0.1 ppm X repeated treatments of 

experimental ponds; (information 

from abstract)

Odonata Pachydiplax sp. Breaud et al. 

1977 

methoprene 28 gm AI/ha X 6 aerial applications over 18 

months; 

Miscellaneous Non-dipteran 

predators 

Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); significant reduction in 

1992 (46%) and 1993 (64%), 

Miscellaneous Total predatory 

insects

Hershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha 

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); significant reduction in 

1992 (65%) and 1993 (77%), and 

over 3-yr period (62%) 

Miscellaneous Non-insect macroinvertebratesHershey et 

al. 1998 

Altosid 3-

wk release 

granules

5.820.44 

kg/ha

 X natural wetlands; aerial 

application, 6 treatments per year 

for 3 years (long-term effects 

study); 

 Annelids

Oligochaeta

Aquatic 

earthworms, 

Aulophorus sp. (3 

species)

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations

laboratory toxicity tests: 0% 

mortality at 100 ppm; test 

duration 168 hours 

K3-43 
Oligochaeta Mud worm, 

Tubifex tubifex

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 10 ppm; test duration 

168 hours 

Rhynochobdellida Leeches,

Helobdella 

stagnalis

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 0% 

mortality at 1 ppm; test duration 

72 hours 

Aschelminths

Nematoda

Nematodes Miura & 

Takahashi 

1973 

technical 

ZR-515 

 X irrigated pasture study 

Rotifera Rotifer, Philodina

sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 5% 

mortality at 100 ppm; test 

duration 48-72 hours

 Flatworms

Tricladida

Brown planarian, 

Dugesia tigrina

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory toxicity tests: 33% 

mortality at 10 ppm; test duration 

168 hours 

 Protozoa

Hymenostomatida

Paramecia, 

Paramecium sp. 

Miura & 

Takahashi 

1973 

technical 

ZR-515 

5 

concentrations 

laboratory acute toxicity tests: 

LC50 = 1.25 ppm; test duration 48 

hours 

Phytoplankton Diatom, Diatoma 

vulgare

Miura & 

Takahashi 

1973 

technical 

ZR-515 

0.1 ppm 

solution 

 X lab study; no visible effects after 1 

week

Phytoplankton Green algae (3 

species), 

Pithaphora 

ocdogonia, 

Spirogyra sp., 

Hydrodictyon 

reticulatum

Miura & 

Takahashi 

1973 

technical 

ZR-515 

0.1 ppm 

solution 

 X lab study; no visible effects after 1 

week

K3-44 
Temephos

Temephos is an organophosphate pesticide, which functions by competing with acetylcholine for 

cholinesterase, the enzyme that transmits nerve impulses across synapses to other nerves and 

muscles (known as a Acholinesterase inhibitor@). While acetylcholine is present, the neurons 

continue to be stimulated; paralysis results from the failure of cholinesterase to destroy the 

acetylcholine (Dale and Hulsman 1990). Temephos is a general use pesticide; temephoscontaining products are moderately toxic and are labeled with WARNING, due to the high 

toxicity of xylene, one of the carrier compounds found in many trade products. Toxicological 

effects include both acute and chronic toxicity (Pesticide Information Profiles, EXTOXNET).

Synopsis of Non-target Effects

Effects of temephos on some non-target organisms are presented in Table 4. Moderate toxicity 

to birds and fish; was shown to accumulate in tissues of fish and snails, but effect was reversible. 

Wide range of crustaceans, insects and mollusks were affected by temephos. Some crustacean 

and mollusks exhibited sub-lethal effects (slowed responses resulting in increased susceptibility 

to predation). 

Label Application Rate

5% Skeeter Abate7 (Abate7

 5-BG) is used for the control of mosquito and midge larvae. It is 

toxic to birds and fish; fish and other aquatic organisms in water treated with this product 

may be killed. Consult state fish and game agency before applying this product to waters 

or wetlands. Do not use on crops used for food, forage or pasture. 

Habitat: standing water, shallow ponds, lakes and woodland pools. 

Application Rate: 2 lbs/acre

Habitat: tidal waters, marshes, swamps and waters high in organic content. 

Application Rate: 4 lbs/acre

Habitat: highly-polluted water. Application Rate: 10 lbs/acre. 

1% Skeeter Abate7 (Abate7

 1-BG) is used for the control of mosquito and midge larvae. It is 

toxic to birds and fish; fish and other aquatic organisms in water treated with this product 

may be killed. Consult state fish and game agency before applying this product to waters 

or wetlands. Do not use on crops used for food, forage or pasture.

Habitat: standing water, shallow ponds, lakes, woodland pools, catch basins. 

Application Rate: 5 - 10 lbs/acre 

Habitat: tidal waters, marshes, swamps and waters high in organic content. 

Application Rate: 10 - 20 lbs/acre 

Web Site:

K3-45 
Pesticide Information Profiles, EXTOXNET

http://ace.ace.orst.edu/info/extoxnet/pips/ghindex.html 

References Cited

Ali, A. and M.S. Mulla. 1978. Effects of chironomid larvicides and diflubenzuron on nontarget 

invertebrates in residential-recreational lakes. Environ. Entomol. 71:21-27. 

Ali, A. and M.S. Mulla. 1977. Chemical control of nuisance midges in the Santa Ana River 

Basin, Southern California. J. Econ. Entomol. 70:191-195. 

Balcomb, R., R. Stevens and C. Bowen. 1984. Toxicity of 16 granular insecticides to wildcaught songbirds. Bull. Environ. Contam. Toxicol. 33:302-307. 

Campbell, B.C. and R.F. Denno. 1976. The effect of Temephos and Chlorpyrifos on the aquatic 

insect community of a New Jersey salt marsh. Environ. Entomol. 5:477-483 

Chambers, H. And D.L. Fabacher. 1972. Midge larvae control in commercial catfish ponds: 

toxicity of Abate7 to channel catfish (Ictularus punctatus). Proc. Annu. Conf. Southeast. 

Assoc. Game Fish Comm. 26:399-401. (Abstract) 

Dale, P.E.R. and K. Hulsman. 1990. A critical review of salt marsh management methods for 

mosquito control. Review in Aquatic Sciences 3:281-311. 

Dale, W.E., J.W. Miles and G.O. Guerrant. 1974. Monitoring of residues of Abate in streams 

treated for Similium control. IN Environmental Quality and Safety Supplement, Vol. III, 

Pesticides. Pp 780-783. 

Denno, R.F. 1974. Initial studies of Abate in a salt-marsh ecosystem: sampling the non-target 

component. Proc. N.J. Mosq. Exterm. Assn. 61:138-144. 

Fales, J.H., P.J. Spangler, O.F. Bodenstein, G.D. Mills, Jr. and C.G. Durbin, Jr. 1968. 

Laboratory and field evaluation of Abate against a backswimmer Notonecta undulata Say 

(Hemiptera: Notonectidae). Mosq. News 28:77-81. 

Fleming, W.J., G.H. Heinz, J.C. Franson, and B.A. Rattner. 1985. Toxicity of Abate 4E 

(temephos) in mallard ducklings and the influence of cold. Environ. Toxicol. Chem. 

4:193-199. 

Frank, A.M. and R.D. Sjogren. 1978. Effect of temephos and chlorpyrifos on Crustacea. Mosq. 

News 38:138-139. 

Franson, J.C., J.W. Spann, G.H. Heinz, C. Bunck and T. Lamont. 1983. Effects of dietary 

AbateR

 on reproductive success, duckling survival, behavior, and clinical pathology in 

game-farm mallards. Arch. Environ. Contam. Toxicol. 12:529-534. 

K3-46 
Fitzpatrick, G. and D.J. Sutherland. 1976. Uptake of the mosquito larvicide temefos by the salt 

marsh snail, New Jersey--1973-74. Pesticide Monitoring J. 10:4-6. 

Hanazato, T., T. Iwakuma, M. Yasuno, and Mitsuru Sakamoto. 1989. Effects of temephos on 

zooplankton communities in enclosures in a shallow eutrophic lake. Environ. Pollut. 

59:305-314. 

Hill, E.F. 1971. Toxicity of selected mosquito larvicides to some common avian species. J. 

Wildl. Manage. 35:757-762. 

Kpekata, A.E. 1983. Acute toxicity of O,O=-(thio-di-4,1-phenylene) bis (O,O-dimethyl 

phosphorothioate) (temephos) to Lebistes reticulatus and Sarotherodon galilea. Bull. 

Environ. Contam. Toxicol. 31:120-124. 

Lee, B.M. and G.I. Scott. 1989. Acute toxicity of temephos, fenoxycarb, diflubenzuron, and 

methoprene and Bacillus thuringiensis var. israelensis to the Mummichog (Fundulus 

heteroclitus). Bull. Environ. Contamin. And Toxicol. 43:827-832. 

Levy, R. And T.W. Miller, Jr. 1977. Susceptibility of the mosquito nematode, Romanomermis 

culicivorax (Mermithidae) to pesticides and growth regulators. Environ. Entomol. 6:447-

448. 

Mathavan, S. And E. Jayakumar. 1987. Long-term effects of pesticides (fenthion and temephos) 

on growth and fecundity of an aquatic bug Laccotrephes griseus (Guerin). Ind. J. Exp. 

Biol. 25:48-51. 

Mohsen, A.H. and M.S. Mulla. 1981. Toxicity of blackfly larvicidal formulations to some 

aquatic insects in the laboratory. Bull. Environ. Contam. Toxicol. 26:696-703. 

Muirhead-Thomson, R.C. 1979. Experimental studies on macroinvertebrate predator-prey 

impact of pesticides. The reactions of Rhyacophilia and Hydropsyche (Trichoptera) 

larvae to Simulium larvicides. Can. J. Zoo. 57:2264-2270. 

Nelson, F.R.S., J. Gray and F. Aikhionbare. 1994. Tolerance of the planarian Dugesia tigrina

(Tricladida: Turbellaria) to pesticides and insect growth regulators in a small-scale field 

study. J. Am. Mosq. Control Assoc. 10:104-105. 

Pierce, R.H., R.C. Brown, K.R. Hardman, M.S. Henry, C.L.P. Palmer, T.W. Miller, and G. 

Wichterman. 1989. Fate and toxicity of temephos applied to an intertidal mangrove 

swamp. J. Amer. Mosq. Control Assn. 5:569-578. 

Sanders, H.O., D.F. Walsh, and R.S. Campbell. 1981. Abate: Effects of the organophosphate 

insecticide on bluegills and invertebrates in ponds. U.S. Fish & Wildl. Serv. Tech. Pap. 

104, 6pp. 

Tietze, N.S., P.G. Hester, C.F. Hallmon, M.A. Olson, and K.R. Shaffer. 1991. Acute toxicity of 

mosquitocidal compounds to mosquitofish, Gambusia affinis. J. Amer. Mosq. Control 

Assn. 7:290-293. 

K3-47 
Von Windeguth, D.L. and R.S. Patterson. 1966. The effects of two organic phosphate 

insecticides on segments of the aquatic biota. Mosq. News 26:377-380. 

Wall, W.J., Jr. and V.M. Marganian. 1973. Control of salt marsh Culicoides and Tabanus larvae

in small plots with granular organophosphorus pesticides, and the direct effect on other 

fauna. Mosq. News 33:88-93. 

Wall, W.J. Jr. and V.M. Marganian. 1971. Control of Culicoides mellus (Coq.) (Diptera: 

Ceratopogonidae) with granular organophosphorus and the direct effect on other fauna. 

Mosq. News 31:209-214. 

Wallace, R.R., A.S. West, A.E.R. Doune and H.B.N. Hynes. 1973. The effects of experimental 

blackfly (Diptera: Simuliidae) larviciding with Abate, Dursban, and methoxychlor on 

stream invertebrates. Can. Entomol. 105:817-831. 

Ward, D.V. and D.A. Busch. 1976. Effects of temefos, an organophosphorous 

insecticide, on survival and escape behaviors of the marsh fiddler crab Uca 

pugnax. Oikos 27:331-335. 

Ward, D.V. and B.H. Howes. 1974. The effects of Abate, an organophosphorous 

insecticide, on marsh fiddler crab populations. Bull. Environ. Contam. Toxicol. 

12:694-697. 

Ward, D.V., B.L. Howes, and D.F. Ludwig. 1976. Interactive effects of predation 

pressure and insecticide (temefos) toxicity on populations of the marsh fiddler 

crab Uca pugnax. Marine Biol. 35:119-126. 

Yasuno, M., Y. Sugaya and T. Iwakuma. 1985. Effects of insecticides on benthic 

community in a model stream. Environ. Pollut. 38:31-43. 

K3-48 
 Table 4. Non-target Effects of Temephos

Classification Organism Reference Formulation Application 

Rate (study)

Adverse 

Effects

No 

Effects

Comments

 Birds

Aves

Blue Jays Hill 1971 technical 

grade

5 conc. 

tested

 X 30 ppm killed all birds in test; birds fed 

for 5 days on toxic diet 

Aves Bobwhites Hill 1971 technical 

grade

5 conc. 

tested

LC50 = 1,540 ppm; birds fed for 5 days 

on toxic diet 

Aves Cardinals Hill 1971 technical 

grade

5 conc. 

tested

LC50 = 76 ppm; birds fed for 5 days on 

toxic diet

Aves House Sparrows Hill 1971 technical 

grade

5 conc. 

tested

LC50 = 47 ppm; birds fed for 5 days on 

toxic diet

Aves House Sparrows Balcomb et 

al 1984 

granules 

4%AI

0.078 mg 

mean 

granule 

weight

 X no mortality in doses up to 40 granules 

Aves Mallard 

ducklings 

Fleming, et 

al. 1985 

Abate 4E 0.1ppm; 1 

ppm; 10 

ppm; 

100ppm 

treatments of 10 ppm or less did not 

enhance cold effects on ducklings nor 

depressed brain cholinesterase (ChE); 

100pm did significantly affect cold 

tolerance and depressed brain ChE and 

degree of inhibition was less than 

previously used to document death from 

anticholinesterase insecticides

Aves Mallard adults Franson et 

al. 1983 

Abate 4E 1 ppm & 10 

ppm 

females took longer to complete egglaying with 10 ppm concentration diet 

Aves Mallard 

ducklings 

Franson et 

al. 1983 

Abate 4E 1 ppm & 10 

ppm 

ducklings in both treatment diets had 

20% body weight (not statistically 

significant but noteworthy); survivability 

reduced 40% in both treatments 

K3-49 
Aves Red-winged 

Blackbirds 

Balcomb et 

al 1984 

granules 

4%AI

0.078 mg 

mean 

granule 

weight

 X no mortality in doses up to 40 granules

 Reptiles

Squamata

Natrix sipedon Fales et al. 

1968 

Abate 4E 

(EC

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; no dead found 

Testudines Chrysemys picta Fales et al. 

1968 

Abate 4E 

(EC

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; no dead found 

 Amphibians

Anura 

Rana clamitans Fales et al. 

1968 

Abate 4E 

(EC

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; no dead found 

Caudata Triturus 

viridescens

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; no dead found 

 Fish

Atheriniformes

Guppies 

(Sarotherodon 

galilaea) 

Kpekata 

1983 

temephos acute effect lab study; 96-hour LC50 = 

0.47 mg/l (information from abstract) 

Atheriniformes Guppies 

(Lebistes 

reticulatus) 

Kpekata 

1983 

temephos acute effect lab study; 96-hour LC50 = 

1.9 mg/l (information from abstract)

Atheriniformes Guppy (Lebistes 

reticulatus) 

Von 

Windeguth 

and 

Patterson 

1966 

Abate, 

technical 

material

0.20-0.25 

lb/acre 

(conc. of 

0.1 ppm in 

1 ft water 

depth or 

0.01 ppm in 

10 ft. depth) 

 X safe at 0.1 ppm; 24-hour LD50 = 200 ppm 

+ 

Atheriniformes Juvenile snook 

(Centropomis 

undecimalis) 

Pierce et 

al. 1989 

temephos, 

aerially 

applied

 X no mortality observed (information from 

abstract)

Atheriniformes Killifish Wall and Abate 1% 0.3 lb/acre fish in 2 traps were dead, but those in 3rd

K3-50 
(Fundulus spp.) Marganian 

1973 

on sand 

granules

trap survived with no apparent effect for 

7 days; unable to attribute mortality to 

pesticide

Atheriniformes Killifish 

(Fundulus spp.)

Wall and 

Marganian 

1971 

Abate 1% 

on sand 

granules

0.4 lb/ac X 

Atheriniformes Mosquito fish 

(Gambusia 

affinis) 

Von 

Windeguth 

and 

Patterson 

1966 

Abate, 

technical 

material

0.20-0.25 

lb/acre 

(conc. of 

0.1 ppm in 

1 ft water 

depth or 

0.01 ppm in 

10 ft. depth) 

 X safe at 0.1 ppm; 24-hour LD50 = 200 ppm 

+ 

Atheriniformes Mosquitofish Tietze et al 

1991 

Abate 4-E various X no affect at recommended application 

rate; 24-hour LC50 = 5.60 ppm 

Atheriniformes Mummichog 

(Fundulus 

heteroclitus)

Lee & 

Scott 1989 

technical 

grade

96-hour LC50 = 0.04 mg/L; no effect 

concentration = 0.02 mg/L 

Atheriniformes Sheepshead 

minnow 

(Cyprinodon 

variegatus) 

Pierce et 

al. 1989 

temephos, 

aerially 

applied

 X no mortality observed (information from 

abstract)

Cypriniformes Catfish Chambers 

& 

Fabacher 

1972 

Abate R LC50 determined to be 5-7ppm in 

laboratory 

Perciformes Blue gill 

(Lepomis 

macrochirus) 

Von 

Windeguth 

and 

Patterson 

1966 

Abate, 

technical 

material

0.20-0.25 

lb/acre 

(conc. of 

0.1 ppm in 

1 ft water 

 X safe at 0.1 ppm; 24-hour LD50 = 200 ppm 

+ 

K3-51 
depth or 

0.01 ppm in 

10 ft. depth) 

Perciformes Bluegills Sanders et 

al 1981 

Abate EC 18 g/ha X 3 treatments in experimental ponds; 

initially more rapid growth and higher 

reproduction presumably from increased 

food (dead Dipterans), but declined after 

3rd treatment attributed to decline in 

Dipterans

Perciformes Bluegills Sanders et 

al 1981 

Abate EC 180 g/ha 3 treatments in experimental ponds; brain

acetylcholinesterase activity depressed 

40% when water temperature exceeded 

20oC; lower growth and production rates 

attributed to greater losses of Dipterans 

from first treatment

Perciformes Largemouth bass 

(Micropterus 

salmoides)

Von 

Windeguth 

and 

Patterson 

1966 

Abate, 

technical 

material 

0.20-0.25 

lb/acre 

(conc. of 

0.1 ppm in 

1 ft water 

depth or 

0.01 ppm in 

10 ft. depth) 

 X safe at 0.1 ppm; 24-hour LD50 = 200 ppm 

+ 

 Arachnids

Acarina

Water Mites --

Hydrachnidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 1 species, no dead 

found 

 Mollusks

Anisomyaria

Ribbed mussel 

(Modiolus 

demissus) 

Wall and 

Marganian 

1973 

Abate 1% 

on sand 

granules

0.3 lb/acre X 

Basommatophora Snails --

Planorbidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 1 species, no live 

individuals in samples 

K3-52 
Basommatophora Snails --

Physidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 1 species, no live 

individuals in samples 

Gastropoda Snail (Melampus 

bidentatus)

Fitzpatrick 

and 

Sutherland 

1976 

Abate 2% 

granular

0.10 lb/acre; 

10 

applications 

at 2 week 

intervals

 X uptake detectable 1 day after 1st 

treatment; residues persisted for more 

than 5 weeks after last treatment; 

Gastropoda Snail (Melampus 

bidentatus)

Fitzpatrick 

and 

Sutherland 

1976 

Abate 

emulsion

0.032 

lb/acre; 4 

applications 

at 2 week 

intervals

 X uptake detectable 6 days after 2nd

treatment; residues rose gradually as 

number of treatments increased, then 

decreased below detection limit 3-weeks 

after last treatment; data indicate 

significant but reversible decline in 

population density 

Mesogastropoda Mud snail 

(Nassarius 

obsoletus) 

Wall and 

Marganian 

1973 

Abate 1% 

on sand 

granules

0.3 lb/acre X 

Mesogastropoda Mud snail 

(Nassarius 

obsoletus) 

Wall and 

Marganian 

1971 

Abate 1% 

on sand 

granules

0.4 lb/ac those confined in traps were alive but 

some appeared to have slowed responses 

Mesogastropoda Periwinkle 

(snail) (Littorina 

littorea) 

Wall and 

Marganian 

1973 

Abate 1% 

on sand 

granules

0.3 lb/acre X 

 Crustaceans

Amphipoda 

Sideswimmer 

(Hyallela 

azteca) 

Ali and 

Mulla 

1978 

temephos 0.28 kg 

AI/ha 

(0.0092 

ppm) & 

0.17 kg 

AI/ha 

(0.0042 

ppm) 

 X tolerant to temephos; higher 

concentration used in lake fingers, lower 

concentration in main lake area; 

(information from abstract)

K3-53 
Amphipoda Sideswimmer 

(Hyallela 

azteca)

Von 

Windeguth 

and 

Patterson 

1966 

Abate, 

technical 

material

0.20-0.25 

lb/acre 

(conc. of 

0.1 ppm in 

1 ft water 

depth or 

0.01 ppm in 

10 ft. depth) 

safe at 0.1 ppm; 24-hour LD50 = 0.65 

ppm; LD90 = 2-2.5 ppm 

Calanoida Calanoid Hanazato 

et al. 1989 

Abate 500g AI/l X shallow lake; eliminated; nauplii showed 

slight recovery by end of experiment 

Calanoida Diaptomus spp. Ali and 

Mulla 

1978 

temephos 0.28 kg 

AI/ha 

(0.0092 

ppm) & 

0.17 kg 

AI/ha 

(0.0042 

ppm) 

higher concentration used in lake fingers, 

lower concentration in main lake area; 

(information from abstract)

Cladocera Bosmina 

longirostris

Ali and 

Mulla 

1978 

temephos 0.28 kg 

AI/ha 

(0.0092 

ppm) & 

0.17 kg 

AI/ha 

(0.0042 

ppm) 

 X higher concentration used in lake fingers, 

lower concentration in main lake area; 

(information from abstract)

Cladocera Cyclops sp. Ali and 

Mulla 

1978 

temephos 0.28 kg 

AI/ha 

(0.0092 

ppm) & 

0.17 kg 

AI/ha 

(0.0042 

ppm) 

 X higher concentration used in lake fingers, 

lower concentration in main lake area; 

(information from abstract)

K3-54 
Cladocera Water fleas --

Cladocerans

Hanazato 

et al. 1989 

Abate 500g AI/l X shallow lake; all eliminated; had not 

recovered by end of experiment 

Cladocera Water flea 

(Daphnia pulex) 

Ali and 

Mulla 

1978 

temephos 0.28 kg 

AI/ha 

(0.0092 

ppm) & 

0.17 kg 

AI/ha 

(0.0042 

ppm) 

 X higher concentration used in lake fingers, 

lower concentration in main lake area; 

population reduced in fingers but 

recovered within 1-3 weeks (information 

from abstract)

Cladocera Water flea 

(Daphnia 

galeata) 

Ali and 

Mulla 

1978 

temephos 0.28 kg 

AI/ha 

(0.0092 

ppm) & 

0.17 kg 

AI/ha 

(0.0042 

ppm) 

 X higher concentration used in lake fingers, 

lower concentration in main lake area; 

population reduced in fingers but 

recovered within 1-3 weeks (information 

from abstract)

Crustacea Crustacea Frank and 

Sjogren 

1978 

temephos 0.025 lb 

AI/acre

 X copepods, ostracods, amphipods, & 

cladocerans; no effect on occurrence 

(numbers not studied) 

Cyclopoida Cyclopoids Hanazato 

et al. 1989 

Abate 500g AI/l X shallow lake; eliminated; nauplii showed 

slight recovery by end of experiment 

Cyclopoida Paracyclops 

fimbriatus

Yasuno et 

al 1985 

temephos 5 mg/l; 30 

min 

exposure 

 X model stream study

Decapoda Brown shrimp 

(Panaeus 

aztecus) 

Pierce et 

al. 1989 

temephos, 

aerially 

applied

 X no mortality observed (information from 

abstract)

Decapoda Fiddler Crab Ward and 

Busch 

Abate 99% 

pure 

12 

concentratio

 X 24-hour lab experiments; number of 

crabs either dead or not responding to 

K3-55 
1976 crystalline 

powder 

ns from 0.5 

ppm to 15 

ppm 

stimulus (EC) increased with increasing 

temephos concentration; LC20 = 2.06 

ppm; LC50 = 9.12 ppm; LC80 = 39.8 

ppm; EC20 = 1.10 ppm; EC50 = 4.31 

ppm; EC80 = 16.6 ppm 

Decapoda Fiddler Crab 

(Uca sp.)

Wall and 

Marganian 

1973 

Abate 1% 

on sand 

granules

0.3 lb/acre few dead crabs found in treated area

Decapoda Fiddler Crab 

(Uca pugilator)

Wall and 

Marganian 

1971 

Abate 1% 

on sand 

granules

0.4 lb/ac X numerous dead crabs found in treated 

areas; however, those confined in traps 

were not visibly affected at 7 days when 

released 

Decapoda Fiddler Crab Ward et al. 

 1976 

Abate 2% 

granular

0.1 lb 

AI/acre

 X field experiment; population reduced 

14% after 2nd application and 30% after 

4th application; conclusion that temephos 

has primarily sublethal effect on crabs 

that renders them more susceptible to 

predation 

Decapoda Fiddler Crab Ward and 

Howes 

1974 

Abate 2% 

granular

0.1 lb 

AI/acre; 3 

treatments 2 

weeks 

apart; 

expected 

conc. 0.5 

ppm 

 X field test; populations declined over time 

in treated areas

Decapoda Freshwater 

shrimp 

(Palomonetes 

paludosus) 

Von 

Windeguth 

and 

Patterson 

1966 

Abate, 

technical 

material 

0.20-0.25 

lb/acre 

(conc. of 

0.1 ppm in 

1 ft water 

depth or 

0.01 ppm in 

 X safe at 0.1 ppm; 24-hour LD50 = 1.0 ppm; 

LD90 = 2.0 ppm 

K3-56 
10 ft. depth) 

Decapoda Grass shrimp 

(Palaemonetes 

pugio) 

Pierce et 

al. 1989 

temephos, 

aerially 

applied

 X no mortality observed (information from 

abstract)

Mysidacea Mysids 

(Mysidopsis 

bahia) 

Pierce et 

al. 1989 

temephos, 

aerially 

applied

 X significant mortality at 1 site during 1 of 

3 applications monitored (information 

from abstract)

Ostracoda Seed shrimp 

(Cyprinotus sp.) 

Ali and 

Mulla 

1978 

temephos 0.28 kg 

AI/ha 

(0.0092 

ppm) & 

0.17 kg 

AI/ha 

(0.0042 

ppm) 

 X tolerant to temephos; higher 

concentration used in lake fingers, lower 

concentration in main lake area; 

(information from abstract)

 Insects

Coleoptera 

Burrowing 

Water Beetles --

Noteridae

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application;1 species, some 

mortality

Coleoptera Crawling Water 

Beetles --

Halipidae

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application; 5 species found, all of 

which had some mortality

Coleoptera Predaceous 

Diving Beetles --

Dytiscidae

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application; 13 species found, of 

which 6 had some mortality 

Coleoptera Water Scavenger 

Beetles --

Hydrophilidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application; 11 species found, all of 

which had some mortality

Coleoptera Whirligig 

Beetles --

Gyrinidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application; 3 species found, of 

which 2 had some mortality 

K3-57 
Collembola Springtails --

Poduridae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 1 species, no live 

individuals found at 24-hour sample 

Diptera Black flies Dale et al. 

1974 

Abate 20% 

EC

50 ppb for 

10 min. 

 X complete kill 45-50 km downstream 

Diptera Blackfly 

(Simulium 

argus) 

Mohsen 

and Mulla 

1981 

Abate 50% 

EC

various 

dilutions 

 X 24- hour LC50 = 0.020 ppm; LC90 = 

0.038 ppm 

Diptera Blackfly 

(Simulium 

virgatum) 

Mohsen 

and Mulla 

1981 

Abate 50% 

EC

various 

dilutions 

 X 24-hour LC50 = 0.0082 ppm; LC90 = 

0.020 ppm 

Diptera Blackfly 

(Simulium spp.) 

MuirheadThompson 

1979 

Abate 20% 

EC

various 

conc. 

ranging 

from 0.05 to 

2.0 ppm 

 X exposures ranged from 15 minutes to 1 

hour; 24-h mortality ranged from 24% at 

0.2 ppm to 98% at 1.0 ppm 

Diptera Chironomidae Wallace et 

al 1973 

Abate initial conc. 

0.1 ppm 

 X stream study;

Diptera Chironomids Ali and 

Mulla 

1977 

temephos 

granules 1% 

0.28 kg 

AI/surface 

ha 

 X 88-95% control of total midge larvae 

after 3 weeks of treatment; control lasted 

5-6 weeks

Diptera Chironomids (3 

species)

Yasuno et 

al 1985 

temephos 5 mg/l; 30 

min 

exposure 

 X model stream study

Diptera Dipterans Sanders et 

al 1981 

Abate EC 18 g/ha X 3 treatments in experimental ponds; 

biomass similar to control ponds, 

however biomass declined rapidly after 

3rd treatment

Diptera Dipterans Sanders et 

al 1981 

Abate EC 180 g/ha X 3 treatments in experimental ponds; 

biomass declined rapidly after 1st

K3-58 
application and remained low

Diptera Midge 

(Procladius sp.) 

Yasuno et 

al 1985 

temephos 5 mg/l; 30 

min 

exposure 

 X model stream study

Diptera Phantom Midges 

-- Chaoboridae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 1 species, estimated 

millions dead

Diptera True flies Denno 

1974 

Abate 2% 

on celatom 

granules

 X densities reduced in Spartina patens

community

Ephemeroptera Mayflies Wallace et 

al 1973 

Abate initial conc. 

0.1 ppm 

 X stream study;

Ephemeroptera Mayfly (Baetis 

parvus)

Mohsen 

and Mulla 

1981 

Abate 50% 

EC

various 

dilutions 

 X 24-hour LC50 = 0.0097ppm; LC90 = 

0.018 ppm 

Hemiptera Laccotrephes 

griseus

Mathavan 

and 

Jayakumar 

1987 

temephos 0.1 ppm X growth affected; fecundity severely 

reduced (information from abstract) 

Heteroptera Backswimmers -

-Notonectidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 3 species, heavy 

mortality; in lab experiments 0.02 ppm 

produced 100% mortality of 

backswimmers in 4 days 

Heteroptera Creeping Water 

Bugs --

Naucoridae

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application; 1 species, some 

mortality

Heteroptera Giant Water 

Bugs B 

Belostomatidae

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application; 1 species, some 

mortality

K3-59 
Heteroptera Marsh Treaders -

-Hydrometridae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 1 species

Heteroptera Water Boatmen 

B Corixidae 

(Trichocorixa 

verticalis)

Campbell 

and Denno 

1976 

4E 

emulsifiable 

conc.

34.75 g 

AI/ha; 4 

biweekly 

treatments

 X applications by helicopter 

Heteroptera Water Boatmen 

B Corixidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 4 species, only 1 of 

which had some live individuals 

Heteroptera Water Scorpions 

-- Nepidae

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 

Heteroptera Water Treaders 

B Mesovliidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 1 species, no live 

individuals found post-treatment

Heteroptera Water Striders B

Gerridae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application; 3 species, 2 of which 

had some mortality

Homoptera Cicadas/leaf 

hoppers 

Denno 

1974 

Abate 2% 

on celatom 

granules

 X densities reduced in Spartina patens

community

Hymenoptera Ants/bees/wasp Denno 

1974 

Abate 2% 

on celatom 

granules

 X densities reduced in both Spartina 

alterniflora and Spartina patens

communities

Odonata Damselfly --

Coenagrionidae 

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre X lake application, sampled 24- & 48-hr. 

post-application; 2 species, only dead 

found in samples 

Odonata Dragonfly --

Aeschnidae

Fales et al. 

1968 

Abate 4E 

(EC)

0.39 lb/acre lake application, sampled 24- & 48-hr. 

post-application; 1 species, some 

mortality

Dragonfly -- Fales et al. Abate 4E lake application, sampled 24- & 48-hr. 

K3-60 
Odonata Libellulidae 1968 (EC) 0.39 lb/acre post-application; 3 species, 1 only dead 

found, 1 no dead found, 1 some dead 

found 

Plecoptera Stone flies Wallace et 

al 1973 

Abate initial conc. 

0.1 ppm 

 X stream study;

Trichoptera Caddis flies Wallace et 

al 1973 

Abate initial conc. 

0.1 ppm 

 X stream study;

Trichoptera Caddisfly 

(Hydropsyche 

pellucidula) 

MuirheadThompson 

1979 

Abate 20% 

EC

various 

conc. 

ranging 

from 0.05 to 

1.0 ppm 

 X exposed for 1 hour to Abate solution; 24-

h mortality 29% at 0.2 ppm; 76% at 0.5 

ppm; 74% at 1.0 ppm 

Trichoptera Caddisfly 

(Rhyacophila 

dorsalis) 

MuirheadThompson 

1979 

Abate 20% 

EC

various 

conc. 

ranging 

from 0.2 

ppm to 2.0 

ppm 

 exposures ranged from 15 minutes to 30 

minutes; 24-h mortalities reported were 

12% at 0.5 ppm (15 min); 18% at 1.0 

ppm (15 min); 8% at 2.0 ppm (15 min); 

48% at 1.0 ppm (30 min); 33% at 2.0 

ppm (30 min) 

Trichoptera Caddisfly 

(Hydropsyche 

californica) 

Mohsen 

and Mulla 

1981 

Abate 50% 

EC

various 

dilutions 

24-hour LC50 = 1.3 ppm; LC90 = 4.0 ppm 

 Annelids

Oligochaeta

Oligochaetes Ali and 

Mulla 

1978 

temephos 0.28 kg 

AI/ha 

(0.0092 

ppm) & 

0.17 kg 

AI/ha 

(0.0042 

ppm) 

 X higher concentration used in lake fingers, 

lower concentration in main lake area; 

(information from abstract)

 Aschelminths

Nematoda

Nematode 

(Romanomermis 

culicivorax) 

Levy and 

Miller 

1977 

Abate 0.001 ppm X information from abstract 

K3-61 
Rotifera Rotifers Hanazato 

et al. 1989 

Abate 500g AI/l X shallow lake; original species eliminated 

and replaced by other rotifer species

 Flatworms

Tricladida

Brown planaria 

(Dugesia 

tigrina)

Nelson et 

al. 1994 

temephos 4E X only minimal effect under field 

conditions (information from abstract) 

Plankton Microscopic 

plankton 

(Rotifers, 

Euglena, Coleps,

Ileonema, etc.)

Von 

Windeguth 

and 

Patterson 

1966 

Abate, 

technical 

material

0.20-0.25 

lb/acre 

(conc. of 

0.1 ppm in 

1 ft water 

depth or 

0.01 ppm in 

10 ft. depth) 

safe at 0.1 ppm; 48-hour LD100 =50 ppm 

K3-62 
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last revised: 5/20/98 K3-94 
APPENDIX K4. Environmental Effects of Mosquito 

Control 

K4-1

ENVIRONMENTAL EFFECTS OF MOSQUITO CONTROL 

(USFWS, 2004) 

This paper provides a summary of the potential impacts of mosquito control practices. This is 

not intended to discount the important role that mosquitoes play in the transmission of disease, 

nor is it intended to diminish the role that mosquito control can play in reducing the incidence of 

such vector-borne disease in humans. The first part discusses the ecological role of mosquitoes 

in the environment, aside from that as vectors of disease. The second part addresses the potential 

impacts of mosquito control pesticides to nontarget organisms and communities. 

1. The Ecological Role of Mosquitoes 

Mosquitoes are most often associated with their roles as vertebrate ectoparasites and vectors of 

disease-causing microorganisms. However, do mosquitoes provide any Abeneficial@ role in the 

environment, or are they, as Spielman and D=Antonio (2001) claim Aself-serving@ and of Ano 

purpose other than to perpetuate her species@? 

Mosquitoes As Prey

Larvae. Mosquitoes have evolved to use a wide variety of both permanent and temporary 

aquatic habitats for larval development. There are nearly as many habitats for mosquito larvae as 

there are types of lentic water bodies. For purposes of this discussion, mosquitoes will be 

divided into those that develop in ephemeral water bodies and those that develop in permanent to 

semi-permanent water. 

The evolution of a drought- and sometimes freeze-resistant egg has allowed certain species of 

mosquitoesCthe most common in the genera Aedes, Ochlerotatus, and PsorophoraCto colonize 

a wide variety of ephemeral habitats large and small, from the tropics to sub-arctic zones. These 

mosquitoes lay eggs in dry or moist areas that will flood later. This strategy has at least two 

advantages: 1) the recently flooded detritus provides a nutrient-rich and abundant source of food 

for developing larvae; and 2) in many habitats there is a lag time before invertebrate predators 

colonize these temporary water bodies, allowing the larvae to develop in relatively predator-free 

environments. In most ephemeral habitats, mosquito eggs will hatch within hours of being 

flooded, often in very large numbers. In many of these habitats, such as summer flood pools and 

salt marshes, colonization by invertebrate predators occurs from highly mobile insects like 

dragonflies, beetles, and backswimmers that fly from more permanent bodies of water. Although 

some predators will arrive relatively quickly, it can take several days to weeks for an invertebrate 

predator community to become established. During the summer, a floodwater mosquito brood 

can develop from egg to adult in a week, and thereby mostly escape predation by these 

colonizing invertebrates. 

In unpredictably flooded ephemeral habitats such as summer flood pools and storm-flooded salt 

marshes, there are few predators that have been identified to rely principally on mosquito larvae 

as a source of food. The unreliable nature of mosquito larvae as prey in these habitats prevents 

the development of any close predator-prey relationship unless the predator shares diapausing 

strategies similar to those of floodwater mosquitoes. The only predators in these habitats that 

rely on mosquito larvae for prey are other mosquitoes. A few species of Psorophora mosquitoes 
K4-2

have larvae that are predatory in late instar stages. These species are generally found in summer 

flood pools. Although there are few predators that specialize on mosquito larvae in these 

habitats, generalist predators such as beetles (larvae and adults), backswimmers, and some 

odonates (damselflies and dragonflies) will take advantage of the temporary abundance of 

mosquitoes if the timing of arrival into the habitats coincides with the presence of mosquito 

larvae. 

Some ephemeral aquatic habitats, however, have flooding regimes that are more predictable. In 

at least two of these habitats, vernal pools and treeholes, we see the development of very close 

predator-prey relationships with mosquito larvae. In treeholes, species of another mosquito, 

Toxorhynchites, have evolved as predators of other treehole-dwelling mosquito larvae. Vernal 

pools in northern temperate regions predictably flood to their maximum extent in the early spring 

from rain and snowmelt, and this triggers a hatch of one or more species of Ochlerotatus

mosquitoes. These are usually univoltine (single generation) species that laid eggs in the dry 

pool basin the previous summer. Hatching of mosquito larvae in vernal pools often occurs when 

water temperatures are still well below 10 C, with few predators active in such cold 

environments. The predators present at this time of the year are generally those that share similar 

overwintering strategies with mosquitoes, such as cyclopoid copepods (e.g., Macrocyclops) and a 

few species of beetles. Some species of predaceous diving beetles (family Dytiscidae) in the 

genus Agabus have evolved a diapausing strategy that closely resembles that of the Ochlerotatus

mosquitoes. Unlike most dytiscid beetles, these species have drought- and freeze-resistant eggs 

that are laid in the dry basin the previous summer and hatch in the early spring concurrently with 

mosquitoes. The beetle larvae are active in the cold water and appear to feed primarily on 

mosquito larvae and pupae (Nilsson and Soederstroem 1988; Higgins and Merritt 1999). The 

predictable abundance of mosquitoes and general paucity of other potential prey species during 

the early spring in these pools has probably contributed to this specialization. Other predators in 

vernal pools will feed opportunistically on mosquito larvae. Some species of dragonflies and 

damselflies (Odonata, primarily Sympetrum and Lestes) have also evolved drought- and freezeresistant eggs, but hatch later in the spring. Colonizing species of backswimmers (Notonectidae), 

water striders (Gerridae), and water beetles (Hydrophilidae and Dytiscidae) will feed on lateinstar mosquito larvae and pupae, but are considered generalist predators (Higgins and Merritt 

1999). 

Mosquitoes that require water for oviposition include the common genera Culex and Anopheles. 

These mosquitoes colonize permanent to semi-permanent bodies of water, laying eggs on the 

surface. In many natural bodies of water, the larvae of these species must develop in the 

presence of an oftentimes-diverse invertebrate predator community. The co-occurrence of 

mosquito larvae and predatory invertebrates is more predictable in these habitats, but the 

diversity of other potential prey species may preclude the development of specialized predatorprey relationships. Potential invertebrate predators in these habitats include: backswimmers, 

water striders, giant water bugs (Belostomatidae), water measurers (Hydrometridae), adult and 

larval beetles (Dytiscidae, Hydrophilidae, Gyrinidae), many species of damselflies and 

dragonflies (Odonata), phantom midge larvae (Chaoboridae), and even copepods and flatworms. 

Although all of these predators can be considered generalists with regard to prey consumption, 

experimental evidence suggests that mosquito larvae, when available, are a preferred prey of 

some species (Helgen 1989; Urabe et al. 1990; Robert and Venkatesan 1997; Safurabi and 

Madani 1999). 
K4-3

Adults. Like other aquatic insects with terrestrial adult stages, mosquitoes provide a link 

between aquatic and terrestrial ecosystems as they convert detritus and aquatic microbial biomass 

into flying insect biomass. Most adult mosquitoes are relatively short lived. The probability of 

daily survival for adult mosquitoes, an important factor in disease transmission, varies among 

species and habitats. Daily survival probabilities usually range from 0.6-0.9, with much of the 

mortality coming from predation (Service 1993). Mosquitoes are fed upon by a variety of 

invertebrate predators, including spiders (Strickman et al. 1997; Fox 1998) and odonates 

(Sukhacheva 1996), although there are no known specialist predators that prey exclusively on 

mosquitoes. Vertebrate predators include insectivorous birds and bats (Zinn and Humphrey 

1981), although mosquitoes often account for only a small percentage of the total biomass 

consumed. Consumption of mosquitoes by the Indiana bat, Myotis sodalis, for example, 

accounted for up to 6.6 percent of the total diet (Kurta and Whitaker 1998). The apparent 

absence of any specialized predator-prey relationships among adult mosquitoes and predators, 

however, does not necessarily discount the contribution of mosquitoes to the diet of a wide 

variety of generalized predators. 

Other Ecological Roles of Mosquitoes 

Mosquito larvae may feed by one or more of several different mechanisms. They may filter-feed, 

graze microbial biofilms, or even shred detritus (Merritt et al. 1992). In this sense, mosquitoes 

are a component of a functioning wetland ecosystem, processing detritus and aquatic microbes, 

and eventually providing a link between aquatic and terrestrial systems when they emerge. 

Most adult mosquitoes require sugar meals during their lifetimes as a source of energy. The 

primary sources of sugars consumed by mosquitoes are nectar from flowers and honeydew 

excreted by aphids (Foster 1995). Both male and female mosquitoes frequently take nectar meals 

from flowers, but are they important as pollinators? Due to their small size and the limited 

probing abilities of the proboscis, mosquitoes are limited to feeding on nectar sources within 

flowers that have shallow or flat corollas. Unlike relatively large pollinators like bees and 

butterflies, mosquitoes can nectar feed efficiently without coming into contact with pollen-coated 

stamens. Thus, although they may transfer some pollen during the course of acquiring a meal of 

nectar, mosquitoes are probably not important pollinators in general (Foster 1995). A 

documented exception to this occurs in the subarctic where mosquitoes are significant pollinators 

of many plants (Kevan 1972). 

The impact of reducing the density of mosquitoes in aquatic or terrestrial systems has not been 

studied. Generalist predators probably switch to alternate prey, which in turn may be impacted 

by the increased predation. The few specialist predators of mosquito larvae may be impacted the 

greatest due to the lack of alternate prey and/or the inability of such predators to uncouple from a 

closely evolved predator-prey relationship. 

2. Nontarget Effects of Mosquito Control Pesticides 

Mosquito control pesticides can be categorized into three groups: larvicides, adulticides, and 

water surface films (for controlling mosquito larvae and pupae). Compared with other forms of 
K4-4

pest control, there are relatively few pesticides available within each of these categories, and all 

differ with regard to efficacy and effects on nontarget organisms. 

Larvicides 

Bacillus thuringiensis var. israelensis (Bti). Like other varieties of the natural soil bacterium, 

Bacillus thuringiensis (Bt), Bti is a stomach poison that must be ingested by the larval form of 

the insect in order to be effective. Bt contains crystalline structures containing protein 

endotoxins that are activated in the alkaline conditions of an insect=s gut. These toxins attach to 

specific receptor sites on the gut wall and, when activated, destroy the lining of the gut and 

eventually kill the insect. The toxicity of Bt to an insect is directly related to the specificity of 

the toxin and the receptor sites. Without the proper receptor sites, the Bt will simply pass 

harmlessly through the insect=s gut. Several varieties of Bt have been discovered and identified 

by the specificity of the endotoxins to certain insect orders. Bacillus thuringiensis var. kurstaki, 

for example, contains toxins that are specific to lepidopterans (butterflies and moths), while Bti 

is specific only to certain primitive dipterans (flies), particularly mosquitoes, black flies, and 

some chironomid midges. Bti is not known to be directly toxic to nondipteran insects. 

Because Bti must be ingested to kill mosquitoes, it is much more effective on first-, second-, and 

early third-instar larvae than on late third and fourth instars since the earlier instars feed at a 

faster rate (fourth instar larvae feed very little). The pesticide is completely ineffective on pupae 

because they do not feed at all. Formulated products may be granular or liquid, and potency is 

expressed in International Toxicity Units (ITU), usually ranging from 200-1200 ITU. The 

concentrations of Bti in water necessary to kill mosquito larvae vary with environmental 

conditions, but are generally 0.05-0.10 ppm. Higher concentrations (0.1->0.5 ppm) of Bti are 

necessary when there is a high amount of organic material in the water, late-third and early fourth 

instar larvae predominate, larval mosquito density is high, or water temperature is low (Nayar et 

al. 1999). Operationally, Bti is applied within a range of volume or weight of formulated product 

per acre as recommended on the pesticide label, with the goal to achieve an effective 

concentration. The label recommended range of application rates under most conditions varies 

by a factor of 4 for most formulations (e.g., for granular formulations, 2.72-11.12 kg/ha (2.5-10 

lb/acre)). For later instar larvae and water with a high organic content, higher application rates 

are recommended that may reach 8 times the lowest rate (e.g., for granular formulations, the 

higher rate is 11.1-22.5 kg/ha (10-20 lb/acre)). Mosquito control agencies use the recommended 

label rates, along with previous experience, to administer an effective dose. Typical application 

rates are often in the mid- to upper values of the normal ranges recommended on the labels 

(Abbott Laboratories 1999). Because water depths even within a single wetland can vary greatly, 

field concentrations of Bti can vary widely, especially when the pesticide is applied aerially. 

Efficacy is monitored by post-application reductions in mosquito larval density, but the actual 

concentration of Bti following an application is not measured. Thus, an insufficient 

concentration of Bti can be detected by low mortality of mosquito larvae, but an overdose (i.e., a 

concentration greater than necessary to kill mosquito larvae) of the pesticide is rarely monitored 

for.

The issue of Bti concentration is important with regard to impacts on nontarget organisms. Of 

particular concern is the potential for Bti to kill midge larvae (family Chironomidae). 

Chironomid (non-biting midge) larvae are often the most abundant aquatic insect in wetland 
K4-5

environments and form a significant portion of the food base for other wildlife (Batzer et al. 

1993; Cooper and Anderson 1996; Cox et al. 1998). Negative impacts on chironomid 

density/biomass could have deleterious effects on wetland/wildlife food webs and could also 

lower biodiversity. 

The potential for Bti to impact chironomid populations depends on the fate and availability of the 

pesticide, the ingestion of the pesticide, and the presence and number of specific receptor sites in 

the insect gut for the toxins (as discussed above). Fate and availability encompass both the initial 

dose/concentration and the fate of the pesticide in the aquatic environment. Chironomid larvae 

live primarily in the benthos of wetlands. Mosquito larvae ingest Bti primarily within the water 

column, but Bti readily adheres to suspended particulate matter and settles to the benthos 

(Yousten et al. 1992). 

Ingestion of Bti by chironomid larvae depends primarily on the feeding mechanism. The family 

Chironomidae is a relatively large group, with nearly 1,000 species identified for North America 

(Merritt and Cummins 1996). This family encompasses a variety of feeding strategies: filterfeeders, collector-gatherers, scrapers, shredders, and even predators. Filter-feeding larvae are 

more likely to ingest Bti than larvae with other feeding strategies (Pont et al. 1999). 

Chironomid larvae appear to possess mid-gut receptor sites for Bti endotoxins similar to those in 

mosquito larvae, and exhibit similar histopathological changes in the gut lining that lead to death 

of the insects when exposed to lethal concentrations of the pesticide (Yiallouros et al. 1999). 

There are, however, differences in the susceptibility of midge larvae to Bti at the subfamily level 

and among larval instars. In general, larvae in the subfamily Chironominae (Tribes Chironomini 

and Tanytarsini) are more susceptible to Bti than larvae of other subfamilies (Yiallouros et al. 

1999) (Pont et al. 1999) (Ali 1981). Also, early-instar larvae are much more susceptible to Bti 

than later instars (Ali et al. 1981; Charbonneau et al. 1994). 

There have been a number of laboratory and field studies examining the toxicity of Bti to 

chironomid larvae (Boisvert and Boisvert 2000). There have been many different formulations 

and potencies of Bti products used in these studies, and in many cases actual concentrations of 

Bti within the water were not measured. Also, differences in the species and instar of the 

chironomid larvae used (sometimes not specified), and in the environmental conditions of the 

field experiments make direct comparisons among the studies difficult. Most field studies 

examined the nontarget effects from a single application of Bti and did not address the potential 

long-term impacts from repeated applications over a season or over several seasons. 

It is clear that in laboratory studies Bti is lethally toxic to some species of chironomid larvae at 

concentrations expected for mosquito control. Charbonneau et al. (1994) determined an EC50 (the 

concentration required to cause an effect in 50 percent of the test population) of 0.20 ppm for 

Chironomus riparius (fourth instar?), and the toxicity of Bti to earlier instars was over two orders 

of magnitude greater. Similarly, Ali et al. (1981) found the LC50 (the concentration required to 

kill 50 percent of the test population) for first-instar Glyptotendipes paripes (0.034 ppm) to be 

over two orders of magnitude lower than the LC50 for third instar larvae (8.31 ppm). 

Charbonneau et al. (1994) studied the effects of Bti on chironomid larvae in the laboratory and 

the field. Laboratory toxicity tests on Chironominae larvae (the most susceptible subfamily) 
K4-6

demonstrated up to 100 percent mortality at label-recommended rates, but the toxicity of Bti to 

chironomids was influenced by several environmental factors. Factors that lowered toxicity to 

chironomids included higher water temperature, greater water depth, organic matter, and 

coverage by macrophytes. Field enclosure tests with Bti applied at 5.6 kg/ha (5 lb/acre) failed to 

demonstrate any pesticide effects on midge larvae within the enclosures, leading the authors to 

conclude that environmental factors reduce the toxicity of Bti to chironomids in the field. 

However, mortality of nontarget organisms within the enclosures was measured after 48 hours. 

Apparent effects of Bti on chironomids may not be detectable for 5-7 days post application (Ali 

1981; Lacey and Mulla 1990; Pont et al. 1999). Also, because early instar larvae are much more 

susceptible to Bti, first and second instars would likely exhibit the greatest mortality. The 575 

m mesh used to sample benthic invertebrates in the field tests of the Charbonneau et al. (1994) 

study, however, was too large to effectively sample first- and some second-instars. Thus, the 

conclusions regarding the field component of this study must be viewed with caution. 

There is some evidence from field studies in which negative impacts to chironomid larvae were 

observed that such impacts are relatively short-lived (e.g., Miura et al. 1980). In most of these 

studies, however, it is not clear if the rebounding densities of midge larvae represent the same 

species or even the same subfamily that was initially reduced by the pesticide. Furthermore, 

population-level impacts to species from repeated applications over a season were usually not 

addressed. Although many species of chironomids are capable of producing several generations 

per year and could re-colonize a treated wetland relatively quickly, other species have only one 

generation per year and therefore would not be able to re-colonize until the following year. The 

ability of Bti-susceptible species to re-colonize a wetland following pesticide treatment would 

also depend on 1) the frequency of Bti applications, 2) the extent of Bti treatments within the 

wetland, and 3) the extent of Bti applications in the surrounding landscape. Widespread 

larviciding with Bti would provide few refugia for re-colonizing source populations of 

susceptible species. 

In a study that examined population-level impacts to chironomids from a single application of Bti 

at a mosquito control rate, investigators showed that, while there was no statistical difference in 

the number of emerging adult chironomids between control and treatment enclosures, the species 

composition was different (Pont et al. 1999). Species sensitive to Bti (Tanytarsus horni, T. 

fimbriatus, and Microchironomus deribae) were 24-54 percent less abundant in enclosures 

treated at mosquito control rates than in control enclosures, while a less sensitive species 

(Polypedilium nubifer) was over 200 percent more abundant in the treated enclosure versus 

control. Higher application rates resulted in greater reductions of the Bti-sensitive species. This 

suggests that as Bti-sensitive chironomid larvae are killed by the pesticide, less sensitive species 

may thrive as they are released from competition (Pont et al. 1999). Thus, although chironomid 

larval numbers often appear to rebound after a treatment with Bti, this may be indicative of a 

shift in the species composition of the community, with species less sensitive to Bti replacing the 

sensitive species. It is unknown how or if such a shift would affect food web dynamics, but 

biodiversity would be lowered. 

There is only one published study that examined the long-term, nontarget effects of Bti (Hershey 

et al. 1998; Niemi et al. 1999). In this study conducted in Minnesota, 27 wetlands were sampled 

for macroinvertebrates over a 6-year period. All wetlands were sampled for 3 pre-treatment 

years and randomly assigned to 3 treatment groups: Bti, methoprene (see discussion below), and 
K4-7

an untreated control group. The wetlands were sampled for 3 treatment years. Bti was applied to 

wetlands in a granular formulation at the rate of approximately 11.1 kg/ha (10 lb/ac), which 

represents the high end of the normal label-recommended application range. Bti was applied to 

each treatment wetland 6 times per year at intervals of 3 weeks or after rainfall of >1.25 cm, 

whichever came first (Niemi et al. 1999). Although this frequency of application is high, it is 

within the range that could occur from operational mosquito control. 

After the first year of treatment, no differences in macroinvertebrate density, biomass, or 

community composition (richness of genera) among the treatments were observed (Hershey et al. 

1998). However, in the second and third years of treatment, highly significant differences were 

observed in the two treatment groups compared to control. Chironomid larvae were significantly 

impacted by Bti treatments, with reductions in density of 66 percent and 84 percent for the 

second and third years of the study, respectively, compared to densities in control wetlands 

(Hershey et al. 1998). Significant declines in other nematoceran (primitive) dipteran larvae were 

also observed during the last two years of the study. There were also declines in 

macroinvertebrate predator densities in the Bti treated wetlands that the authors interpret as 

indirect effects from the reduction in a prey base dominated by chironomid larvae (Hershey et al. 

1998; Niemi et al. 1999). 

In summary, there is clear evidence from both laboratory and field studies that Bti can kill some 

chironomid larvae. Species in the subfamily Chironominae are apparently the most susceptible 

to direct toxicity; other subfamilies exhibit little mortality at mosquito control rates. Even within 

the subfamily Chironominae there are apparent differences among in susceptibility to Bti, 

relating perhaps to feeding mode (Pont et al. 1999). Within susceptible species, toxicity is 

greatest to early instars. Lethal concentrations of Bti are orders of magnitude lower for early 

versus late instars, and well within the concentrations expected from operational mosquito 

control. There is evidence that environmental conditions such as temperature, organic content of 

the water, vegetation, and density of larvae can ameliorate some of the potential negative impacts 

to chironomid larvae (Charbonneau et al. 1994), although field experiments designed to test this 

may be suspect. 

The only long-term study on the nontarget effects of Bti for mosquito control demonstrated 

significant adverse effects on the chironomid community of treated wetlands, and this translated 

into numerous significant negative effects within the food web (Hershey et al. 1998; Niemi et al. 

1999). The intensity of Bti applications used in this study, both the application rate and the 

frequency of applications, would represent the high end of those that would normally occur for 

operational mosquito control. In addition, entire wetlands were treated, which may or may not 

occur with aerial applications of Bti. Thus, the Minnesota study may represent a Aworst-case 

scenario@ of potential mosquito control operations, but it has generated the only data available on 

the long-term nontarget effects from Bti. Studies that examine nontarget effects of Bti from a 

single application or even within a single season may not be adequate to detect potential longterm impacts from pesticide use (Hershey et al. 1995). 

There is also evidence that application rate can have a profound effect on impacts to chironomids 

from Bti (Rodcharoen et al. 1991). Because application rates of Bti for mosquito control can 

vary by a factor of 8, field concentrations of the pesticide can reach levels that are toxic to 

chironomid larvae, yet are still within the pesticide label directions. In addition, there are no 
K4-8

label restrictions on the number of applications of Bti to any one area. Economic considerations 

may preclude regular applications at the highest label rate, yet even at lower rates, adverse 

impacts to chironomid midge larvae have been demonstrated (Miura et al. 1980; Ali 1981; Ali et 

al. 1981).

Bacillus sphaericus 

Bacillus sphaericus (Bsph) is a naturally-occurring soil bacterium similar to Bti, and has been 

developed as a commercially-available mosquito larvicide since the early 1990s. Like Bti, it 

releases a protein endotoxin in the alkaline gut of larval mosquitoes that attaches to specific 

receptor sites of susceptible species. This endotoxin dissolves the lining of the gut wall and 

eventually kills the larva. Unlike Bti, Bsph has only one endotoxin (Bti has two or more). Also, 

unlike Bti, Bsph is very effective in water with a high organic content, and is therefore often used 

in such habitats for control of Culex mosquitoes. Bsph is also capable of Acycling@ in the aquatic 

environment, meaning it can retain its larvicidal properties after passing through the gut of a 

mosquito andCunlike BtiCprovide effective mosquito control for weeks after a single 

application. Bsph, however, is not effective on all species of mosquitoes. 

Because Bsph is a more recently developed larvicide than Bti, there are fewer studies that have 

examined the nontarget effects of this pesticide. The data available, however, indicate a high 

degree of specificity of Bshp for mosquitoes, with no demonstrated toxicity to chironomid larvae 

at any mosquito control application rate (Mulla et al. 1984; Ali and Nayar 1986; Lacey and Mulla 

1990; Rodcharoen et al. 1991). This high specificity to some mosquito species and low toxicity 

to chironomid larvae is probably the consequence of the one endotoxin contained with the Bsph 

spore. Unfortunately, this also makes the development of resistance to this pesticide more likely 

if this pesticide becomes widely and frequently used. 

Methoprene 

Methoprene is a synthetic mimic of a naturally produced insect hormone, juvenile hormone (JH). 

All insects produce JH in the larval stages, with the highest levels occurring in the insect=s early 

developmental stages. As an insect reaches its final stage of larval development, the level of JH 

is very low. This low level of JH triggers the development of adult characteristics. When an 

insect is exposed to methoprene, a hormonal imbalance in the development of the insect results, 

and it fails to properly mature into an adult. The insect eventually dies in the pupal stage. The 

most susceptible stages of development to methoprene are the later instars (for mosquitoes, third 

and fourth instars). In mosquito control applications, methoprene is applied directly to the larval 

breeding habitat. Larvae will continue to feed and may reach the pupal stage, but they will not 

emerge as adults. Methoprene is completely ineffective on mosquito pupae and adults. It is 

available in several formulations: liquid, granular, pellet, and briquet. There are several microencapsulated and extended-release formulations that remain effective for up to 150 days. 

The amount of methoprene necessary for mosquito control is < 1.0 part per billion (ppb). The 

initial concentrations of methoprene when applied to aquatic habitats may reach 4-10 ppb, but 

residual concentrations are approximately 0.2 ppb (Ross et al. 1994). Once released into the 

aquatic environment, it is non-persistent, with a half-life of about 30-40 hours. Microencapsulated and extended-release formulations will, of course, be present in the water longer as 
K4-9

the pesticide is slowly released over time, 7-150 days, depending on the formulation. In field 

applications, efficacy is determined only by an observed inhibition of emergence of adults, since 

larvae are not directly killed by the pesticide. 

Because methoprene is a JH mimic and all insects produce JH, there is concern about potential 

adverse impacts to nontarget aquatic insects when this pesticide is used for mosquito control. As 

with Bti, there is particular concern regarding potential negative impacts to chironomid larvae 

due to their importance in food webs. As with any pesticide, toxicity is a factor of dose plus 

exposure. At mosquito control application rates, methoprene is present in the water at very small 

concentrations (4-10 ppb, initially). With regard to exposure, chironomid larvae occur primarily 

in the benthos, either within the sediments and/or within cases constructed of silk and detritus. 

Thus, there may be differences with regard to exposure to methoprene between chironomid and 

mosquito larvae, the latter occurring primarily in the water column. 

The published literature on the impacts of methoprene to chironomids is not as extensive as that 

for Bti. However, there is evidence for potential toxicity to chironomid and other aquatic 

invertebrates from methoprene treatments. Some early experiments indicated approximately 50 

percent mortality of Chironomus stigmaterus (Chironomidae) and 70 percent of Brachydeutera 

argentata (Diptera: Ephidridae) larvae when exposed to 0.01 ppm of technical grade methoprene 

(Miura and Takahashi 1973). Mulla et al. (Mulla et al. 1974) noted up to 100 percent inhibition 

of emergence for some midge species, although the lowest concentration tested was 0.1 ppm. 

Breaud et al. (1977) observed reductions in several aquatic invertebrate taxa, including 

chironomids, after six applications of methoprene over an 18-month period in a Louisiana marsh. 

The application rate in this latter study was 0.028 kg/ha of active ingredient, although the 

formulation was not specified (Breaud et al. 1977). 

In testing different formulations of methoprene against chironomids in experimental ponds, Ali 

(1991a) found that sustained-released formulations inhibited emergence of midges by 38-98 

percent, in some cases for up to 7 weeks. A liquid, microencapsulated formulation applied at 

mosquito control rates resulted in a 60 percent inhibition of emergence in the tribe Chironomini 

for 14 days post-treatment. A pelletized, sustained-release (30 days) formulation applied at 

mosquito control rates inhibited all chironomid emergence by 64-98 percent for 7 weeks. A 

briquet formulation (30 days sustained-release) produced 38-98 percent inhibition of all 

chironomids for 7 weeks. The granular formulation applied at the high end of mosquito control 

rates reduced chironomid emergence by 61-87 percent (Ali 1991a). 

In the multi-year Minnesota study cited above, a 3-week sustained-release, granular formulation 

of methoprene was applied to treatment wetlands at a label-recommended rate of 5-10 kg/ha 

(Hershey et al. 1998; Niemi et al. 1999). The pesticide was applied six times per season at 3-

week intervals. The impacts from methoprene in this study were very similar to those observed 

for Bti. Negative impacts were not observed until the second and third years of treatment. In 

those years, significant declines in aquatic insect density and biomass were detected in 

methoprene-treated wetlands compared to controls. Total insect biomass was 70 percent and 81 

percent lower in the second and third years of treatment, respectively, than in control wetlands 

(Hershey et al. 1998). Reductions were observed across many insect taxa, including predators 

and non-predators, suggesting direct (pesticide) and indirect (food web) effects from methoprene 

treatments (Hershey et al. 1998). 
K4-10

Although the application rate of methoprene used in the Minnesota study was well within 

operational rates used in mosquito control, the frequency of application exceeded what would 

probably occur under most field situations. Using a 3-week sustained release formulation and 

applying that every 3 weeks ensured a nearly constant exposure of methoprene to aquatic 

invertebrates in the treated wetlands throughout the season. Under such a scenario, it is unlikely 

that most impacted invertebrate populations would be able to re-colonize the wetlands during the 

treatments. However, this does not discount the conclusion that nontarget aquatic invertebrates 

were indeed impacted by methoprene at rates and concentrations used for mosquito control. 

Whether or not the observed food web effects would have been lessened under a more realistic 

pesticide application regime is debatable. 

Studies of adverse impacts from methoprene on insect taxa other than chironomids are less 

conclusive. Because methoprene affects insect development and does not directly kill larvae, 

traditional toxicity testing over a few days is often inadequate when looking for potential 

impacts. Methoprene toxicity can only be observed at the point in which the immature insects 

reach (or fail to reach) adulthood. Thus, many published laboratory and field studies looking at 

nontarget impacts from methoprene were of insufficient duration to detect actual negative 

impacts (e.g., Miura and Takahashi 1973). 

Breaud et al. (1977) observed adverse effects from methoprene on 14 aquatic invertebrate taxa, 

including Callibaetis sp. mayflies, odonates (dragonflies and damselflies), predaceous diving 

beetles, and chironomids. Negative impacts to Callibaetis mayflies from methoprene treatments 

have been observed by others (Steelman et al. 1975; Norland and Mulla 1975). Miura and 

Takahashi (1973) did not observe any mortality on Callibaetis from methoprene in laboratory or 

field studies, but neither was of sufficient duration (48 hours and 1 week, respectively) to 

adequately detect developmental effects (Miura and Takahashi 1973). Pinkney et al. (2000) 

observed consistently lower numbers of mayflies emerging from methoprene-treated wetlands 

compared to controls, but these differences were not statistically significant (Pinkney et al. 2000). 

There is evidence of methoprene impacts to non-insects as well. McKenney and Celestial (1996) 

noted significant reductions in number of young produced in mysid shrimp at 2 ppb (McKenney 

and Celestial 1996). Sub-lethal effects on the cladoceran, Daphnia magna, in the form of 

reduced fecundity, increased time to first brood, and reduced molt frequency have also been 

observed at concentrations < 0.1 ppb (Olmstead and LeBlanc 2001). 

There has been speculation and some preliminary data to suggest that methoprene causes limb 

malformations in amphibians (La Clair et al. 1998). However, experiments with methoprene and 

its degradation products have failed to demonstrate developmental toxicity even at concentrations 

exceeding 100 times that expected for mosquito control (Ankley et al. 1998; Degitz et al. 2003). 

Therefore, current data do not support a role of methoprene in amphibian malformations. 

In summary, there is evidence for significant adverse nontarget effects from methoprene even 

when applied at mosquito control rates. With regard to negative impacts to chironomid midges, 

there may be differences in susceptibility among species and differences depending on the 

formulation used. One study in particular suggested that methoprene formulations with shortterm residual activity may have smaller impacts to chironomids (Ali 1991a). However, even the 
K4-11

"ineffective" liquid formulation used in this study reduced emergence of Chironomini midges by 

60 percent for two weeks. Certainly, not all midges will be affected by a single application of 

methoprene for mosquito control. However, the apparent differences in pesticide formulations, 

the varied susceptibility of species, and perhaps even the influence of some as-yet-undetermined 

environmental factors, make predicting the degree of any impacts nearly impossible. 

Because methoprene does not immediately kill susceptible chironomid larvae, they are still 

available for predators. However, repeated applications of methoprene over a mosquito breeding 

season would eventually hinder recruitment as adults repeatedly fail to emerge (Hershey et al. 

1998). Longer-term studies conducted over the course of a season or over multiple seasons are 

especially necessary for examining nontarget impacts from methoprene in order to detect 

potential impacts on longer-lived larvae (e.g., odonates, mayflies, and aquatic beetles) and to 

detect potential impacts to long-term recruitment. As was the case with Bti, the ability for a 

population to re-colonize a wetland following a methoprene treatment would depend on the 

intensity and frequency of applications at different spatial scales. 

Temephos 

Temephos is the only remaining organophosphate pesticide used for larval mosquito control. 

Like all organophosphate pesticides, it functions on the nervous system by inhibiting the 

production of acetylcholinesterase. Without this enzyme, nerves continue to fire, eventually 

resulting in death of the insect. Temephos is available in liquid or granular formulations that are 

applied directly to aquatic breeding habitats of mosquitoes. Expected environmental 

concentrations of temephos in water are 20-35 ppb, but actual field concentrations can vary 

widely (Pierce et al. 1996). Temephos is not persistent, but can remain effective for 7-10 days 

(Fortin et al. 1987). 

There have been many studies examining the adverse nontarget impacts of temephos. Many of 

these studies have documented significant negative impacts to a wide range of aquatic taxa, 

especially in freshwater wetlands. Temephos is very highly toxic to cladocerans (water fleas, 

e.g., Daphnia) at fractions of expected mosquito control concentrations (Fortin et al. 1987; 

Helgen et al. 1988). The U.S. Environmental Protection Agency (EPA) has determined an LC50

value of 0.01 ppb for Daphnia magna (EPA 1999), orders of magnitude lower than the expected 

environmental concentration of 20-35 ppb. The pesticide is highly toxic to chironomid larvae at 

or below mosquito control concentrations (Mulla and Khasawinah 1969; Iannacone and Alvarino 

1998; Pinkney et al. 2000), although some researchers have documented only minimal effects on 

some species (Ali et al. 1978) (Ali 1991b). Temephos is especially toxic to larvae of the nonbiting phantom midge, Chaoborus (Fales et al. 1968; Helgen et al. 1988; Pinkney et al. 2000). 

Temephos has also been found to be very toxic to potential mosquito predators such as odonates 

and backswimmers (Fales et al. 1968). Pinkney et al. (2000) reported significant reductions in 

insect diversity, richness, and density within temephos-treated experimental ponds, with 

significant declines in Ephemeroptera (mayflies), Odonata, Diptera, and Chironomidae compared 

to control ponds. 

The effects of temephos on nontarget estuarine species are less studied. There are some data that 

suggest negative impacts from temephos are not as pronounced on estuarine species (Lawler et 

al. 1999b). However, there is evidence for toxicity to estuarine crustaceans from temephos at 
K4-12

concentrations below those expected from field applications for mosquito control (Mortimer and 

Chapman 1995; Brown et al. 1996). Studies have also shown sublethal and indirect impacts of 

temephos on fiddler crabs (Ward and Busch 1976; Pinkney et al. 1999). In addition, at least 

some chironomid species in salt marsh habitats are susceptible to temephos (Ali et al. 1992). 

Temephos has also been shown to be lethal to tadpoles of green frogs at concentrations < 10 ppb 

(Sparling et al. 1997).

It is clear that temephos is a much less specific larvicide compared to Bti and methoprene. 

Severe, negative impacts from temephos at mosquito control concentrations have been 

documented for a broad range of aquatic taxa in both freshwater and estuarine habitats, although 

some estuarine species are apparently more tolerant of the pesticide. 

Surface Oils and Films 

Surface oils and films are applied to mosquito breeding sites to kill mosquito larvae and pupae. 

The products create a barrier to the air-water interface and suffocate the insects, which require at 

least periodic contact with the water surface in order to obtain oxygen. The oils are mineral oil 

based and are effective for 3-5 days. Surface films are alcohol based and produce a 

monomolecular film over the water surface. 

Both the oils and the films are potentially lethal to any aquatic insect that lives on the water 

surface or requires periodic contact with the air-water interface to obtain oxygen. Studies have 

demonstrated very significant negative impacts to water surface-dwelling insects from 

applications of oils (Mulla and Darwazeh 1981; Lawler et al. 1998). 

Surface oils may also adversely impact wildlife by wetting the feathers of young waterfowl. This 

may be of particular concern at low temperatures when the oil could affect thermoregulation 

(Lawler et al. 1998). 

Adulticides 

All pesticides used to kill adult mosquitoes are broad-spectrum insecticides. The only selective 

aspect of these pesticides is in the manner in which they are applied. Most adulticides used 

currently are applied as ultra-low volume (ULV) sprays, meaning relatively small amounts are 

used (compared to some agricultural pesticides) and they are sprayed as very fine droplets (10-30 

m in diameter). This small droplet size allows the spray to drift for a relatively longer period of 

time compared to larger droplets, and the small size delivers an appropriate dose of the pesticide 

to kill an adult mosquito. Drift is a necessary component of adulticiding because these sprays are 

most effective on flying insects. For this reason, adulticide applications generally occur in the 

evening or early morning hours when the majority of mosquito species are most active. 

Adulticides may be applied by truck-mounted sprayers or applied aerially by helicopter or fixedwing aircraft. 

There are only two general classes of adulticides: organophosphates and pyrethroids. Both 

classes of pesticides work on the nervous system, although have different modes of action. 

Organophosphates are cholinesterase inhibitors while pyrethroids are sodium channel blockers. 
K4-13

There are currently three organophosphate adulticides: malathion, naled, and fenthion, although 

fenthion is used only in a few counties in Florida and will be removed from the market in 2004. 

The most common pyrethroids are the synthetic pyrethroids, permethrin, resmethrin, and 

sumithrin. The pyrethroids are usually combined with the synergist piperonyl butoxide, which 

interferes with an insect's detoxifying mechanisms. None of these pesticides is persistent, with 

half-lives ranging from hours (naled) to several days (malathion and some pyrethroids). 

Nontarget toxicity from adulticides may occur in either terrestrial or aquatic habitats as a result of 

deposition, runoff, inhalation, or ingestion. In general, pyrethroids have lower toxicity to 

terrestrial vertebrates than the organophosphates. With the exception of fenthion, which is highly 

toxic to birds, the application rates of the organophosphate adulticides are not likely to cause any 

direct mortality of vertebrates. Pyrethroids, although less toxic to birds and mammals, are very 

toxic to fish and aquatic invertebrates (Anderson 1989; Siegfried 1993; Milam et al. 2000). The 

actual toxicity of pyrethroids in aquatic habitats, however, is less than may be anticipated 

because of the propensity of these pesticides to adsorb to organic particles in the water (Hill et al. 

1994). There are also data that indicate synthetic pyrethroid degradates have endocrine 

disrupting properties (Tyler et al. 2000). 

In general, there are very few studies that have examined the nontarget effects of mosquito 

control adulticides. As all of these chemicals are broad-spectrum insecticides, they are 

potentially lethal to most insects. Yet there is a paucity of data available on the nontarget 

impacts to either terrestrial or aquatic invertebrates. There are data indicating the high toxicity of 

adulticides to honey bees (Taylor et al. 1987; Hagler et al. 1989; Pankiw and Jay 1992a; Pankiw 

and Jay 1992b), although the timing of adulticide applications in the evening can be expected to 

minimize these impacts. 

Salvato (2001) examined the toxicity of naled, malathion, and non-synergized permethrin to 5 

species of butterflies, including larval and adult stages. Naled and permethrin were found to be 

the most toxic to all life stages. The LD50 data presented for some larvae and adults coincide 

with that delivered by a single ULV droplet of 5-23 m, within the desired range for mosquito 

control (Salvato 2001). Mosquito control adulticiding has been identified as a likely contributing 

factor in the decline of several rare lepidopteran species in the Florida Keys (Calhoun et al. 2000; 

Salvato 2001). 

All adulticides are very highly toxic to aquatic invertebrates in concentrations < 1 ppb (Milam et 

al. 2000). Because most adulticides can be applied over or near water when used for mosquito 

control, there are risks to aquatic invertebrates from direct deposition and runoff of the 

pesticides. However, very few field studies have been conducted that have examined the impacts 

to aquatic organisms from mosquito control adulticides. Jensen et al. (1999) failed to detect 

reductions in aquatic invertebrate abundance or biomass from truck-mounted applications of 

pyrethrin, permethrin, and malathion. However, the potentially most sensitive group of 

invertebrates, cladocerans (water fleas), were not sampled (Jensen et al. 1999). This could be 

important given that malathion residues of 6 ppb were recovered from water in the treatment 

areas during this study. This is several times the LC50 values of 0.69 ppb and 1.8 ppb of 

malathion for Simocephalis serrulatus and Daphnia magna, respectively (USEPA 2000), 

indicating that cladocerans would be at risk from applications of malathion for mosquito control. 
K4-14

Declines in flying insect abundance were also observed during this study following pesticide 

applications, but the numbers quickly rebounded (Jensen et al. 1999). 

As was the case with studies of nontarget impacts from larvicides, the limited numbers of studies 

on adulticide impacts all involve examining short-term effects, usually from a single application 

of a pesticide. It is difficult to extrapolate the results of short-term experiments into predictions 

of long-term impacts, whether the short-term studies detected impacts or not. In addition, 

mosquito control is most often conducted at a landscape level. Studies of impacts at such larger 

temporal and spatial scales are non-existent, and would be a challenge both scientifically and 

economically. 

Biological Control 

The mosquitofish, Gambusia affinis, has been used for decades as a biological control of 

mosquito larvae. These fish are effective in removing mosquito larvae from relatively small, 

closed, and artificial aquatic systems, such as backyard ponds. In more complicated natural 

systems however, Gambusia are not selective predators, and can adversely impact native 

vertebrate and invertebrate communities (Rupp 1996). They can out-compete many native 

species of fish by feeding on eggs and fry, and they can actually reduce the density of natural 

invertebrate predators. There is also evidence that mosquitofish may cause direct and indirect 

impacts on tadpoles (Lawler et al. 1999a). 

Summary/Conclusions

Mosquitoes are a natural component of many aquatic and terrestrial ecosystems. Like other 

aquatic insects with terrestrial adult stages, mosquitoes provide a link between aquatic and 

terrestrial habitats. Predation is probably the largest source of mortality for both larval and adult 

mosquitoes and, although there are relatively few predators that specialize on mosquitoes, these 

insects are fed upon by a wide variety of invertebrate and vertebrate predators. The impact of 

greatly reducing mosquito populations in aquatic and terrestrial ecosystems has not been studied. 

Virtually every pesticide currently used to manage mosquito populations has the potential to 

adversely impact nontarget species. Widely used larvicides such as Bti and methoprene have 

been demonstrated to kill susceptible chironomid midge larvae, with experimental evidence 

suggesting that such population-level impacts may result in community-level food web effects. 

All adulticides are broad-spectrum insecticides that can potentially impact a wide variety of 

invertebrates and some vertebrates. The degree to which nontarget organisms or communities 

may be impacted by mosquito control pesticides is often difficult to predict because of 

differences in susceptibility among species, differences in toxicity of various formulated 

products, and basic knowledge gaps in toxicity data to certain species. An additional factor is the 

paucity of studies examining nontarget impacts of mosquito control at large spatial and temporal 

scales. 

Organized mosquito control most often occurs at a landscape level such as a county or parish. 

When pesticides are applied to manage mosquito populations, it is often at multiple locations 

over relatively large spatial scales. Furthermore, pesticides may be applied to any given area 

multiple times in a season, year after year. The majority of nontarget mosquito control pesticide 
K4-15

studies have examined impacts at much smaller temporal and spatial scales, such as one 

application in a single wetland. While these studies provide useful data, it is difficult to 

extrapolate the results of these small-scale experiments into predictions of impacts from much 

larger scale treatments. 
K4-16

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Metabolism and degradation of pyrethroid insecticides produce compounds with 

endocrine activities. Environmental Toxicity and Chemistry 19: 801-809.

Urabe, K., T. Ikemoto, and S. Takei. 1990. Studies on Sympetrum frequens (Odonata: 

Libellulidae) nymphs as natural enemies of the mosquito larvae, Anopheles sinensis , in 

rice fields. 4. Prey-predator relationship in the rice field areas. Japanese Journal of 

Sanitary Zoology 41: 265-272.

USEPA. 1999. Revised Environmental Fate and Effects Division Reregistration Eligibility 

Document for Temephos. U.S. Environmental Protection Agency, Washington, D.C. 

USEPA. 2000. Malathion Reregistration Eligibility Document, Environmental Fate and Effect 

Chapter (Revised). U.S. Environmental Protection Agency, Washington, D.C. 

Ward, D. V. and D. A. Busch. 1976. Effects of temephos, an organophosphate insecticide, on 

survival and escape behavior of the marsh fiddler crab Uca pugnax. Oikos 27: 331-335.

Yiallouros, M., V. Storch, and N. Becker. 1999. Impact of Bacillus thuringiensis var. israelensis

on Larvae of Chironomus thummi thummi and Psectrocladius psilopterus (Diptera: 

Chironomidae). Journal of Invertebrate Pathology 74: 39-47.

Yousten, A. A., F. J. Genthner, and E. F. Benfield. 1992. Fate of Bacillus sphaericus and 

Bacillus thuringiensis serovar israelensis in the aquatic environment. Journal of the 

American Mosquito Control Association 8: 143-148.

Zinn, T. L. and S. R. Humphrey. 1981. Seasonal food resources and prey selection of the 

southeastern brown bat (Myotis austroriparius ) in Florida. Florida Scientist 44: 81-90.
APPENDIX K5. B.t.i. 

EXTOXNET PIP - BACILLUS THURINGIENSIS Page 1 of5

The information in this profile may be out-of-date. It was last revised in

1996. EXTOXNET no longer updates this information, but it may be useful

as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated

pesticide fact sheets. If you don't find a fact sheet related to your question, feel

free to call1-800-858-7378. NPIC is open seven days a week from 6:30am to

4:30pm Pacific Time.

EXTOXNET

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State

University, the University of Idaho, and the University of California at Davis and the Institute for

Environmental Toxicology, Michigan State University. Major support and funding was provided by the

USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Bacillus thuringiensis

Trade and Other Names: Trade names include Aerobe, Bactospeine, Berliner (variety kurstaki),

Certan (variety aizawai), Dipel, Javelin, Leptox, Novabac, Teknar (variety israelensis), Thuricide, and

Victory. Bacillus thuringiensis is also known at B.t.

Regulatory Status: This microbial insecticide was originally registered in 1961 as a General Use

Pesticide (GUP). It is classified as toxicity class III - slightly toxic. Products containing B.t. bear the

Signal Word CAUTION because of its potential to irritate eyes and skin.

http://extoxnet.orst.edu/pips/bacillus.htm 12/15/2011

K5-1
Introduction: Bacillus thuringiensis (B.t.) is a naturally-occurring soil bacterium that produces

poisons which cause disease in insects. B.t. is considered ideal for pest management because of its

specificity to pests and because of its lack of toxicity to humans or the natural enemies of many crop

pests. There are different strains ofB.t., each with specific toxicity to particular types of insects: B.t.

aizawai (B.t.a.) is used against wax moth larvae in honeycombs; B.t. israelensis (B.t.i.) is effective

against mosquitoes, blackflies and some midges; B.t. kurstaki (B.t.k.) controls various types of

lepidopterous insects, including the gypsy moth and cabbage looper. A newer strain, B.t. san diego, is

effective against certain beetle species and the boll weevil. To be effective, B.t. must be eaten by insects

during their feeding stage of development, when they are larvae. B.t. is ineffective against adult insects.

More than 150 insects, mostly lepidopterous larvae, are known to be susceptible in some way to B.t.

EXTOXNET PIP - BACILLUS THURINGIENSIS

Chemical Class: bacterium

Page 2 of5

B.t. forms asexual reproductive cells, called spores, which enable it to survive in adverse conditions.

During the process of spore formation, B.t. also produces unique crystalline bodies. When eaten, the

spores and crystals ofB.t. act as poisons in the target insects. B.t. is therefore referred to as a stomach

poison. B.t. crystals dissolve in the intestine of susceptible insect larvae. They paralyze the cells in the

gut, interfering with normal digestion and triggering the insect to stop feeding on host plants. B.t. spores

can then invade other insect tissue, multiplying in the insect's blood, until the insect dies. Death can

occur within a few hours to a few weeks ofB.t. application, depending on the insect species and the

amount ofB.t. ingested. Typical agricultural formulations include wettable powders, spray concentrates,

liquid concentrates, dusts, baits, and time release rings.

Formulation: Typical agricultural formulations include wettable powders, spray concentrates, liquid

concentrates, dusts, baits, and time release rings.

Toxicological Effects:

• Acute toxicity: B.t. is practically non-toxic to humans and animals. Humans exposed orally to

1000 mg/day ofB.t. showed no effects [146]. A wide range of studies have been conducted on test

animals, using several routes of exposure. The highest dose tested was 6.7 x 10/\11 spores per

animal. The results of these tests suggest that the use ofB.t. products causes few, if any, negative

effects. B.t. was not acutely toxic in tests conducted on birds, dogs, guinea pigs, mice, rats, and

humans. No oral toxicity was found in rats, or mice fed protein crystals from B.t. var. israelensis

[147]. The LD50 is greater than 5000 mg/kg for the B.t. product Javelin in rats and greater than

13,000 mg/kg in rats exposed to the product Thuricide [147,148]. Single oral dosages of up to

10,000 mg/kg did not produce toxicity in mice, rats, or dogs [148]. The dermal LD50 for a

formulated B.t. product in rabbits is 6280 mg/kg. A single dermal application of 7200 mg/kg of

B.t. was not toxic to rabbits [148]. B.t. is an eye irritant; 100 grams of formulated product applied

in each eye of test rabbits caused continuous congestion of the iris as well as redness and swelling

[149]. Very slight irritation from inhalation was observed in test animals. This may have been

caused by the physical rather than the biological properties ofthe B.t. formulation tested [8]. Mice

survived 1 or more I-hour periods of breathing mist that contained as many as 6.0 x 10/\10 spores

B.t. per liter [143].

• Chronic toxicity: No complaints were made by 8 men after they were exposed for 7 months to

fermentation broth, moist bacterial cakes, waste materials, and final powder created during the

commercial production ofB.t. [143]. Dietary administration ofB.t. for 13 weeks to rats at dosages

of 8400 mg/kg/day did not produce toxic effects [143]. Some reversible abnormal redness of the

skin was observed when 1 mg/kg/day of formulated B.t. product was put on scratched skin for 21

days. No general, systemic poisoning was observed [8].

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EXTOXNET PIP - BACILLUS THURINGIENSIS Page 3 of5

• Reproductive effects: There is no indication that B.t. causes reproductive effects [143].

• Teratogenic effects: There is no evidence indicating that formulated B.t. can cause birth defects

in mammals [143,148].

• Mutagenic effects: B. thuringiensis appears to have mutagenic potential in plant tissue. Thus,

extensive use ofB.t. on food plants might be hazardous to these crops [143]. There is no evidence

of mutagenicity in mammalian species.

• Carcinogenic effects: Tumor-producing effects were not seen in 2-year chronic studies during

which rats were given dietary doses of 8400 mglkglday ofB.t. formulation [148]. It is unlikely

that B.t. is carcinogenic.

• Organ toxicity: There is no evidence of chronic B.t. toxicity in dogs, guinea pigs, rats, humans,

or other test animals.

• Fate in humans and animals: B.t. does not persist in the digestive systems of mammals that

ingest it [149].

Ecological Effects:

• Effects on birds: B.t. is not toxic to birds [8,150]. The LD50 in bobwhite quail is greater than

10,000 mglkg. When autopsies were performed on these birds, no pathology was attributed to B.t.

Field observations of 74 bird species did not reveal any population changes after aerial spraying of

B.t. formulation [148].

• Effects on aquatic organisms: B.t. is practically nontoxic to fish [150]. Rainbow trout and

bluegills exposed for 96 hours to B.t. at concentrations of 560 and 1000 mgIL did not show

adverse effects. A small marine fish (Anguilla anguilla) was not negatively affected by exposure

to 1000 to 2000 times the level ofB.t. expected during spray programs. Field observations of

populations of brook trout, common white suckers, and smallmouth bass did not reveal adverse

effects 1 month after aerial application ofB.t. formulation [148]. However, shrimp and mussels

may be affected adversely [8].

• Effects on other organisms: Applications of formulated B.t. are not toxic to most beneficial or

predator insects [148]. Treatment of honeycombs with B.t. var. aizawai does not have a

detrimental effect upon bees, nor on the honey produced [151]. Very high concentrations (108

spores/ ml sucrose syrup) ofB.t. var. tenebrionis, which is used against beetles such as the

Colorado potato beetle, reduced longevity of honey bee adults but did not cause disease [151]. B.t.

applied at rates used for mosquito control may cause the death of some non-target species [8].

Users ofB.t. are encouraged to consult local officials or the nearest EPA regional office

responsible for protecting endangered species before using B.t. products in counties where

susceptible endangered species of Lepidoptera are known to be present [146]. It did not have

negative effects on frogs and salamanders [150].

Environmental Fate:

• Breakdown in soil and groundwater: B.t. is a naturally-occurring pathogen that readily breaks

down in the environment. Due to its short biological half-life and its specificity, B.t. is less likely

than chemical pesticides to cause field resistance in target insects. B.t. is moderately persistent in

soil. Its half-life in suitable conditions is about 4 months [152]. B.t. spores are released into the

soil from decomposing dead insects after they have been killed by it. B.t. is rapidly inactivated in

soils that have a pH below 5.1 [148]. Microbial pesticides such as B.t. are classified as immobile

because they do not move, or leach, with groundwater. Because of their rapid biological

breakdown and low toxicity, they pose no threat to groundwater.

• Breakdown in water: The EPA has not issued restrictions for the use ofB.t. around bodies of

http://extoxnet.orst.edu/pips/bacillus.htm 12/15/2011

K5-3
EXTOXNET PIP - BACILLUS THURINGIENSIS Page 4 of5

water. It can be effective for up to 48 hours in water. Afterwards, it gradually settles out or

adheres to suspended organic matter [150].

• Breakdown in vegetation: B.t. is relatively short-lived on foliage because the ultraviolet (UV)

light of the sun destroys it very rapidly. Its half-life under normal sunlight conditions is 3.8 hours

[153]. It is not poisonous to plants and has not shown any adverse effect upon seed generation or

plant vigor [150].

Physical Properties:

• Appearance: The insecticidal action ofB.t. is attributed to protein crystals produced by the

bacterium. The vegetative cells ofB.t. are approximately 1 micron wide and 5 microns long, and

are motile [146]. The commercial product contains about 2.5 x lOA11viable spores per gram. B.t.

products lose some of their effectiveness when stored for more than 6 months [8]. B.t. is

incompatible with alkaline materials. Formulated products are not compatible with captafol,

dinocap, or, under some conditions, leaf (or foliar) nutrients [8].

• Chemical Name: Bacillus thuringiensis [1]

• CAS Number: (B.t. variety kurstaki) 68038-71-1

• Molecular Weight:

• Water Solubility: Not Applicable

• Solubility in Other Solvents: Not Applicable

• Melting Point: Not Applicable

• Vapor Pressure: Not Applicable

• Partition Coefficient: Not Applicable

• Adsorption Coefficient: Not Applicable

Exposure Guidelines:

• ADI: Not Available

• MCL: Not Available

• RID: Not Available

• PEL: Not Available

• HA: Not Available

• TLV: Not Available

Basic Manufacturer:

Sandoz Agro, Inc., and Abbott Laboratories

1300 E. Touhy Ave.

Des Plaines IL 60018

and

Chern. and Agric. Prod. Div.

1401 Sheridan Rd.

North Chicago, IL 60064

• Phone: 708-699-1616 ; 708-937-2739

• Emergency: 708-699-1616; Not Available

http://extoxnet.orst.edu/pips/bacillus.htm 12/15/2011

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EXTOXNET PIP - BACILLUS THURINGIENSIS

References:

References for the information in this PIP can be found in Reference List Number 10

Page 5 of5

DISCLAIMER: The information in this profile does not in any way replace or supersede the

information on the pesticide product labeling or other regulatory requirements. Please refer to the

pesticide product labeling.

http://extoxnet.orst.edu/pips/bacillus.htm 12/15/2011

K5-5

APPENDIX K6. Methoprene 

EXTOXNET PIP - METHOPRENE Page 1 of4

The information in this profile may be out-of-date. It was last revised in

1996. EXTOXNET no longer updates this information, but it may be useful

as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated

pesticide fact sheets. If you don't find a fact sheet related to your question, feel

free to call1-800-858-7378. NPIC is open seven days a week from 6:30am to

4:30pm Pacific Time.

EXTOXNET

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State

University, the University of Idaho, and the University of California at Davis and the Institute for

Environmental Toxicology, Michigan State University. Major support and funding was provided by the

USDAlExtension ServicelNational Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Methoprene

Trade and Other Names: Trade names include Altosid, Apex, Diacan, Dianex, Kabat, Minex,

Pharorid, Precor, and ZR-515.

Regulatory Status: Methoprene is a slightly to practically nontoxic compound in EPA toxicity

class IV. It is a General Use Pesticide (GUP). Labels for containers of products containing methoprene

must bear the Signal Word CAUTION.

http://extoxnet.orst.edu/pips/methopre.htm 12/15/2011

K6-1
EXTOXNET PIP - METHOPRENE

Chemical Class: Not Available

Page 2 of 4

Introduction: Methoprene is a compound which mimics the action of an insect growth regulation

hormone. It is used as an insecticide because it interferes with the normal maturation process. In a

normal life cycle, an insect goes from egg to larva, to pupa, and eventually to adult. Methoprene

artifically stunts the insects' development, making it impossible for insects to mature to the adult stages,

and thus preventing them from reproducing.

To be effective, it is essential that this growth inhibitor be administered at the proper stage of the target

pest's life cycle. Methoprene is not toxic to the pupal or adult stages. Treated larvae will pupate but

adults do not hatch from the pupal stage. Methoprene is also considered a larvicide since it is effective in

controlling the larval stage of insects. Methoprene is used in the production of a number of foods

including meat, milk, eggs, mushrooms, peanuts, rice, and cereals. It is also used in aquatic areas to

control mosquitoes and several types of ants, flies, lice, moths, beetles, and fleas. It is available in

suspension, emulsifiable and soluble concentrate formulations, as well as in briquette, aerosol, and bait

form.

Formulation: It is available in suspension, emulsifiable and soluble concentrate formulations, as

well as in briquette, aerosol and bait form.

Toxicological Effects:

• Acute toxicity: Methoprene is practically nontoxic when ingested or inhaled and slightly toxic by

dermal absorption. The oral LD50 for methoprene in rats is greater than 34,600 mg/kg, and in

dogs is greater than 5000 mg/kg [1]. It is slightly toxic by skin exposure, with reported dermal

LD50 values of greater than 2000 to 3000 mg/kg in rabbits [1]. Methoprene is not an eye or skin

irritant, and it is not a skin sensitizer [1]. The inhalation LC50 for methoprene in rats is greater

than 210 mg/L [155]. No overt signs of poisoning have been reported in incidents involving

accidental human exposure to methoprene [155].

• Chronic toxicity: No methoprene-related effects were observed in 2-year feeding trials with rats

given doses of250 mg/kg/day, nor in mice given 30 mg/kg/day [1]. Liver changes were observed

in mice fed 50 to 250 mg/kg/day ofmethoprene during an 18-month study [155]. Increased liver

weights occurred in rats fed 250 mg/kg/day for 90 days, but not during a 24-month feeding study

in which rats were fed 125 mg/kg/day [155].

• Reproductive effects: Experimental data indicate that no reproductive hazards are associated

with methoprene [155]. No methoprene-related effects were observed in three-generation

reproduction studies in rats receiving dietary doses of 125 mg/kg/day [1].

• Teratogenic effects: There have been no teratogenic effects in animals dosed with methoprene;

teratogenic effects were not seen in rats at doses of about 25 mg/kg/day, or in rabbits at doses of

about 15 mg/kg/day [156,157]. Methoprene does not appear to be teratogenic.

• Mutagenic effects: Methoprene does not appear to be mutagenic. No methoprene-related

mutagenic effects were observed in rats following a single dose of 2000 mg/kg [158].

• Carcinogenic effects: No tumors were seen in an l8-month feeding study with mice, or in a 24-

month oncogenicity study with rats [156]. These data suggest that methoprene is not carcinogenic.

• Organ toxicity: The target organ primarily affected by methoprene after long-term exposure is

the liver.

• Fate in humans and animals: In mammals, methoprene is rapidly and completely broken down

and excreted, mostly in the urine and feces [157]. Some evidence suggests that methoprene

metabolites are incorporated into natural body components [155]. Methoprene is excreted

unchanged in cattle feces in amounts that are sufficient to kill some larvae that breed in dung

http://extoxnet.orst.edu/pips/methopre.htm 12/15/2011

K6-2
EXTOXNET PIP - METHOPRENE

[131].

Ecological Effects:

Page 3 of4

• Effects on birds: Methoprene is slightly toxic to birds [1,158]. The reported 5- to 8-day LC50

values for Altosid, a methoprene formulation, are greater than 10,000 ppm in mallard ducks and

bobwhite quail, and the acute oral LD50 for Altosid is greater than 4640 ppm in chickens [1,158].

In mallards an acute oral LD50 of greater than 2000 mg/kg was determined [158]. Nonlethal

effects that may affect survival of the birds did appear at acute oral doses of 500 mg/kg. These

effects appeared as soon as 2 hours after treatment and persisted for up to 2 days and included

slowness, reluctance to move, sitting, withdrawal, and incoordination [63]. These effects may

decrease bird survival by making them temporarily more susceptible to predation. No effects were

observed in the reproduction of bobwhite quail and mallard ducks at 30 ppm constant feeding of

Altosid [158].

• Effects on aquatic organisms: Methoprene is slightly to moderately toxic to fish [157]. The

reported 96-hour LC50 values for the methoprene formulation Altosid were 4.6 mg/L in bluegill

sunfish, 4.4 mg/L in trout, and greater than 100 mg/L in channel catfish and largemouth bass

[1,8]. Methoprene residues may have a slight potential for bioconcentration in bluegill sunfish and

crayfish [155]. Methoprene is very highly toxic to some species of freshwater, estuarine, and

marine invertebrates, while the acute LC50 values are greater than 100 mg/L in freshwater shrimp,

and it is greater than 0.1 mg/L in estuarine mud crabs [159]. Altosid had very little effect, if any,

on exposed non-target aquatic organisms including waterfleas, damselflies, snails, tadpoles, and

mosquito fish [159].

• Effects on other organisms: Tests with earthworms showed little if any toxic effects on contact

[159]. It is nontoxic to bees [1].

Environmental Fate:

• Breakdown in soil and groundwater: 'Methoprene is of low persistence in the soil environment;

reported field half-lives are up to 10 days [155]. In sandy loam, its half-life was calculated to be

about 10 days [155]. When Altosid was applied at an extremely high application rate of 1 pound

per acre, its half-life was less than 10 days [155]. In soil, microbial degradation is rapid and

appears to be the major route of its disappearance from soil [155,157]. Methoprene also readily

undergoes degradation by sunlight [157]. Methoprene is rapidly and tightly sorbed to most soils

[155]. It is slightly soluble in water [1]. These properties, along with its low environmental

persistence make it unlikely to be significantly mobile. In field leaching studies, it was observed

only in the top few inches of the soil, even after repeated washings with water [155,159].

• Breakdown in water: Methoprene degrades rapidly in water [8]. Studies have demonstrated halflives in pond water of about 30 and 40 hours at initial concentrations of 0.001 mg/L and 0.01

mg/L, respectively [49]. At normal temperatures and levels of sunlight, technical Altosid is

rapidly degraded, mainly by aquatic microorganisms and sunlight [159,49].

• Breakdown in vegetation: Altosid is biodegradable and nonpersistent, even in plants treated at

very high rates. It has a half-life ofless than 2 days in alfalfa when applied at a rate of 1 pound per

acre [159]. In rice, the half-life is less than 1 day [49]. In wheat, its half-life was estimated to be 3

to 7 weeks, depending on the level of moisture in the plant [155]. Plants grown in treated soil are

not expected to contain methoprene residues.

Physical Properties:

• Appearance: Technical methoprene is a amber or pale yellow liquid with a faint fruity odor [1]

http://extoxnet.orst.edu/pips/methopre.htm

K6-3

12/15/2011
EXTOXNET PIP - METHOPRENE Page 4 of4

• Chemical Name: ispropyl(E,E)-(R,S)-ll-methoxy- 3,7, ll-trimethyldodeca-2,4-dienoate [1]

• CAS Number: 40596-69-8

• Molecular Weight: 310.48

• Water Solubility: 1.4 mg/L @ 25 C [1]

• Solubility in Other Solvents: Miscible in organic solvents [1]

• Melting Point: Not Available

• Vapor Pressure: 3.15 mPa @ 25 C [1]

• Partition Coefficient: Not Available

• Adsorption Coefficient: Not Available

Exposure Guidelines:

• ADI: 0.1 mg/kg/day [12]

• MCL: Not Available

• RID: Not Available

• PEL: Not Available

• HA: Not Available

• TLV: Not Available

Basic Manufacturer:

Zoecon Corp.

12005 Ford Rd., Suite 800

Dallas, TX 75234

• Phone: Not Available

• Emergency: 708-699-1616

References:

References for the information in this PIP can be found in Reference List Number 10

DISCLAIMER: The information in this profile does not in any way replace or supersede the

information on the pesticide product labeling or other regulatory requirements. Please refer to the

pesticide product labeling.

http://extoxnet.orst.edu/pips/methopre.htm

K6-4

12/15/2011
APPENDIX K7. Pyrethrins and Pyrethroids 

K7-1 

PYRETHRINS AND PYRETHROIDS 

(http://extoxnet.orst.edu/pips/pyrethri.htm) 

Produced By the Extension Toxicology Network 

Pesticide Information Profiles 

A Pesticide Information Project of Cooperative Extension Offices of Cornell 

University, Oregon State University, the University of Idaho, and the University 

of California at Davis and the Institute for Environmental Toxicology, Michigan 

State University. Major support and funding was provided by the USDA/Extension 

Service/National Agricultural Pesticide Impact Assessment Program. 

EXTOXNET primary files maintained and archived at Oregon State University 

Revised 3/94 

PYRETHRINS AND PYRETHROIDS 

TRADE OR OTHER NAMES: Several trade names associated with these compounds are 

Buhach, Chrysanthemum Cinerariaefolium, Ofirmotox, Insect Powder, Dalmation Insect Flowers, 

Firmotox, Parexan and NA 9184. 

INTRODUCTION: Pyrethrins are natural insecticides produced by certain species of 

the chrysanthemum plant. The flowers of the plant are harvested shortly after blooming and are 

either dried and powdered or the oils within the flowers are extracted with solvents. The resulting 

pyrethrin containing dusts and extracts usually have an active ingredient content of about 30%. 

These active insecticidal components are collectively known as pyrethrins. Two pyrethrins are 

most prominent, pyrethrin-I and pyrethrin-II. The pyrethrins have another four different active 

ingredients, Cinerin I and II and Jasmolin I and II. The typical composition of pyrethrin is pyrethrin 

I (38.0%), cinerin I (7.3%), jasmolin I (4.0%), pyrethrin II (35.0%), cinerin II (11.7%) and jasmolin 

II (4.0%); the composition of piperonyl butoxide is 80% 5-[2-(2-butyloxyethoxy)ethoxymethyl]-6- 

propyl-1,3-benzodioxole and 20% related compounds. Pyrethrin compounds have been used 

primarily to control human lice, mosquitoes, cockroaches, beetles and flies. Some "pyrethrin 

dusts," used to control insects in horticultural crops, are only 0.3% to 0.5% pyrethrins, and are used 

at rates of up to 50 lb/A. Other pyrethrin compounds may be used in grain storage and in poultry 

pens and on dogs and cats to control lice and fleas. The natural pyrethrins are contact poisons 

which quickly penetrate the nerve system of the insect. A few minutes after application, the insect 

cannot move or 
K7-2 

fly away. But, a "knockdown dose" does not mean a killing dose. The natural pyrethrins are swiftly 

detoxified by enzymes in the insect. Thus, some pests will recover. To delay the enzyme action so a 

lethal dose is assured, organophosphates, carbamates, or synergists may be added to the pyrethrins. 

Semisynthetic derivatives of the chrysanthemumic acids have been developed as insecticides. 

These are called pyrethroids and tend to be more effective than natural pyrethrins while they are 

less toxic to mammals. One common synthetic pyrethroid is allethrin. In this report, the term 

"pyrethrins" refers to the natural insecticides derived from chrysanthemum flowers; "pyrethroids" 

are the synthetic chemicals, and "pyrethrum" is a general name covering both compounds. The 

EPA classifies pyrethrin-I as a Restricted Use Pesticide (RUP). Restricted Use Pesticides may be 

purchased and used only by certified applicators. 

TOXICOLOGICAL EFFECTS 

Acute Toxicity: Synthetic pyrethroid compounds vary in their toxicity as do the natural pyrethrins. 

Pyrethrum carries the signal word CAUTION. Inhaling high levels of pyrethrum may bring about 

asthmatic breathing, sneezing, nasal stuffiness, headache, nausea, incoordination, tremors, 

convulsions, facial flushing and swelling, and burning and itching sensations (102). The most 

severe poisonings have been reported in infants, who are not able to efficiently break down 

pyrethrum. The lowest lethal oral dose of pyrethrum is 750 mg/kg for children and 1,000 mg/kg for 

adults (102). Oral LD50 values of pyrethrins in rats range from 200 mg/kg to greater than 2,600 

mg/kg (96). Some of this variability is due to the variety of constituents in the formulation. 

Mice have a pyrethrum oral LD50 of 370 mg/kg (102). Animals exposed to toxic amounts may 

experience tongue and lip numbness, nausea, and diarrhea. Symptoms may also include 

incoordination, tremors, convulsions, paralysis, respiratory failure, and death. Pyrethroids can 

cause two quite different responses at near lethal doses in rats; aggressive sparring and a sensitivity 

to external stimuli progressing to tremors is the one response and pawing and burrowing behavior, 

and salivation leading to chronic seizures is the other (105). Human response to these two different 

types of pyrethroids has not yet been evaluated. Recovery from serious poisoning in mammals is 

fairly rapid. Rats and rabbits are not affected by large dermal applications (96, 102). On broken 

 skin, pyrethrum produces irritation and sensitization, which is further aggravated by sun exposure. 

Chronic Toxicity: Absorption of pyrethrum through the stomach and intestines and through the 

skin is slow. However, humans can absorb pyrethrum more quickly through the lungs during 

respiration. Response appears to depend on the pyrethrum compound used. Overall, pyrethrins and 

pyrethroids are of low chronic toxicity to humans and the most common problems in humans have 

resulted from the allergenic properties of pyrethrum (104). Patch tests for allergic reaction are an 

important tool in determining an individuals sensitivity to these compounds. Many of the natural 

and synthetic compounds can produce skin irritation, itching, pricking sensations and local burning 

 sensations. These symptoms may last for about two days (105). 

Reproductive Effects: Rabbits that received pyrethrins orally at high doses during the sensitive 

period of pregnancy had normal litters. A group of rats fed very high levels of pyrethrins daily for 

three weeks before first mating had litters with weanling weights much lower than normal (96). 

Overall, pyrethrins appear to have low reproductive toxicity. 

 

Teratogenic Effects: The one rabbit reproduction study performed showed no effect of pyrethrins 

on development of the offspring (101). More information is needed. 
K7-3 

Mutagenic Effects: No information was found. 

 

 Carcinogenic Effects: No carcinogenic status has been established for pyrethrins or pyrethroids. 

 

Organ Toxicity: In mammals, tissue storage has not been recorded. At high doses, pyrethrum can 

be damaging to the central nervous system and the immune system. When the immune system is 

attacked by pyrethrum, allergies can be worsened. Animals fed large doses of pyrethrins may 

experience liver damage. 

 

Rats fed pyrethrin at high levels for two years showed no significant effect on survival, but slight, 

definite damage to the livers was observed (96). Inhalation of high doses of pyrethrum for 30 

minutes each day for 31 days caused slight lung irritation in rats and dogs (102). Fate in Humans 

and Animals: Pyrethrins, pyrethroids, and their metabolites are not known to be stored in the body 

nor excreted in the milk (100). The urine and feces of people given oral doses of pyrethrum contain 

chrysanthemumic acid and other metabolites (100, 96). These metabolites are less toxic to 

mammals than are the parent compounds (101). Pyrethrins I and II are excreted unchanged in the 

feces (100). Other pyrethrum components undergo rapid destruction and detoxification in the liver 

and gastrointestinal tract (96). 

ECOLOGICAL EFFECTS 

Pyrethrin is extremely toxic to aquatic life, such as bluegill and lake trout while it is slightly toxic 

to bird species, such as mallards. Toxicity increases with higher water temperatures and acidity. 

Natural pyrethrins are highly fat soluble, but are easily degraded and thus do not accumulate in the 

body. These compounds are toxic to bees also.Because pyrethrin-I, pyrethrin-II, and allethrin have 

multiple sites in their structures that can be readily attacked in biological systems, it is unlikely that 

they will concentrate in the food chain (100). 

ENVIRONMENTAL FATE 

Two pyrethroid synthetic insecticides, permethrin and cypermethrin, break down in plants to 

produce a variety of products (103). Pyrethrins have little residual effect. In stored grain, 50% or 

more of the applied pyrethrins disappear during the first three or four months of storage. At least 

80% of what remains is removed by handling, processing, and cooking (101). Pyrethrins alone 

provide limited crop protection because they are not stable. As a result, they are often combined 

with small amounts of antioxidants to prolong their effectiveness. Pyrethrum compounds are 

broken down in water to nontoxic products. Pyrethrins are inactivated and decomposed by 

exposure to light and air. Pyrethrins are also rapidly decomposed by mild acids and alkalis. Stored 

pyrethrin powders lose about 20% of their potency in one year. As the pyrethrins are purified, their 

stability decreases; thus, pure pyrethrin-I and pyrethrin-II are the least stable of the pyrethrins (96). 

Purified pyrethrins are very expensive and are only available for laboratory uses. 

PHYSICAL PROPERTIES AND GUIDELINES 

Physical Properties: 

 Appearance: The pyrethrins are viscous brown resins, liquids, or solids which inactivate readily in 

air. 

 Chemical Name: n/a 
K7-4 

 CAS Number: 8003347 

 Molecular Weight: Due to differences in the types and amounts of esters in the pyrethrum 

mixture, its molecular weight ranges from 316 to 374. 

 Water Solubility: considered to be insoluble in water. 

 Solubility in Other Solvents: soluble in organic solvents like: alcohol, kerosene, nitromethane, 

petroleum ether, carbon tetrachloride, and ethylene dichloride. 

 Melting Point: n/a 

 Vapor Pressure: about 0 mm/Hg 

 Partition Coefficient: n/a 

 Adsorption Coefficient: n/a 

Exposure Guidelines: 

 ADI: 0.04 mg/kg body weight (humans) (101) 

 MCL: Not Available 

 RfD: Not Available 

 PEL: 5 mg/m3 

 HA: Not Available 

 TLV: 5 mg/m3 

BASIC MANUFACTURER 

There are several manufacturers of products in this category. 

REFERENCES 

References for the information in this PIP can be found on the website, 

http://extoxnet.orst.edu/pips/pyrethri.htm) (Reference List Number 2) 

DISCLAIMER: The information in this profile does not in any way replace or supersede the 

information on the pesticide product label/ing or other regulatory requirements. Please refer to the 

pesticide product label/ing. 
APPENDIX K8. California Mosquito-Borne Virus 

Surveillance and Response Plan 

CALIFORNIA 

MOSQUITO-BORNE VIRUS 

SURVEILLANCE 

& 

RESPONSE PLAN 

Edmund G. Brown Jr., Governor 

California Department of Public Health 

Mosquito & Vector Control Association of California 

University of California

For further information contact: 

Vector-Borne Disease Section 

California Department of Public Health 

(916) 552-9730 

May 2012 http://westnile.ca.gov 

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CALIFORNIA MOSQUITO-BORNE VIRUS 

SURVEILLANCE AND RESPONSE PLAN 

TABLE OF CONTENTS 

Objectives.................................................................................................................. 3 

Introduction .............................................................................................................. 3 

Background .............................................................................................................. 3 

Education .................................................................................................................. 4 

Surveillance .............................................................................................................. 4 

Climate Variation .......................................................................................... 5 

 Mosquito Abundance .................................................................................... 5 

Mosquito Infections ...................................................................................... 5 

Avian Infections ............................................................................................ 6 

Tree Squirrel Infections ................................................................................ 7 

Equine Infections .......................................................................................... 7 

Human Infections ......................................................................................... 7 

Mosquito Control ..................................................................................................... 8 

Response Levels ........................................................................................................ 9

Characterization of Conditions and Responses .................................................... 16 

Key Agency Responsibilities ................................................................................... 18 

References ................................................................................................................. 21

Appendices 

Appendix A: Guidelines for Adult Mosquito Surveillance .............................. 22 

Appendix B: Procedures for Processing Mosquitoes for Arbovirus Detection 28 

Appendix C: Procedures for Maintaining and Bleeding Sentinel Chickens .. 30 

Appendix D: Procedures for Testing Dead Birds and Squirrels ..................... 34 

Appendix E: Procedures for Testing Equines and Ratites............................... 40 

Appendix F: Protocol for Submission of Specimens from Humans ................ 45 

Appendix G: West Nile Virus Surveillance Case Definition ............................. 46 

Appendix H: Compounds Approved for Mosquito Control in California ...... 48 

Appendix I: Adult Mosquito Control in Urban Areas .................................... 54 

Appendix J: Websites Related to Arbovirus Surveillance in California ........ 57 

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Objectives 

The California Mosquito-borne Virus Surveillance and Response Plan was developed to meet 

several objectives. Specifically, the Plan: 

 Provides guidelines and information on the surveillance and control of mosquito-borne 

viruses in California, including West Nile, St. Louis encephalitis, and western equine 

encephalomyelitis viruses; 

 Incorporates surveillance data into risk assessment models; 

 Prompts surveillance and control activities associated with virus transmission risk level; 

 Provides local and state agencies with a decision support system; and 

 Outlines the roles and responsibilities of local and state agencies involved with mosquitoborne virus surveillance and response. 

This document provides statewide guidelines, but can be modified to meet local or regional 

conditions. 

Introduction 

California has a comprehensive mosquito-borne disease surveillance program that has monitored 

mosquito abundance and mosquito-borne virus activity since 1969 (Reeves et al. 1990) and is an 

integral part of integrated mosquito management programs conducted by local mosquito and 

vector control agencies. Surveillance and interagency response guidelines have been published 

previously by the California Department of Public Health formerly known as the California 

Department of Health Services (Walsh 1987) and the Mosquito and Vector Control Association 

of California (Reisen 1995). The detection of West Nile virus (WNV) in New York, a virus not 

recognized in the Western Hemisphere prior to 1999, prompted the review and enhancement of 

existing guidelines to ensure that surveillance, prevention, and control activities were appropriate 

for WNV. From New York, WNV spread rapidly westward and by 2004 had been detected in all 

48 states in the continental United States. In addition to WNV, California is vulnerable to 

introduction of other highly virulent mosquito-borne viruses of public and veterinary health 

concern, such as Japanese encephalitis, dengue, yellow fever, Rift Valley fever, chikungunya and 

Venezuelan encephalitis viruses. If an existing or introduced virus is detected, it is critical that 

local and state agencies are prepared to respond in a concerted effort to protect people and 

animals from infection and disease. The current document describes an enhanced surveillance 

and response program for mosquito-borne viruses in the State of California. Its contents 

represent the collective effort of the California Department of Public Health (CDPH), the 

Mosquito and Vector Control Association of California (MVCAC), and the University of 

California at Davis (UCD). 

Background 

Mosquito-borne viruses belong to a group of viruses commonly referred to as arboviruses (for 

arthropod-borne). Although 12 mosquito-borne viruses are known to occur in California, only 

WNV, western equine encephalomyelitis virus (WEE) and St. Louis encephalitis virus (SLE) are 

significant causes of human disease. WNV is having a serious impact upon the health of 

humans, horses, and wild birds throughout the state. Since 2004, there have been 3,146 WNV 

human cases with 110 deaths and 1,167 horse cases. Consequently, the California Arbovirus 

Surveillance Program emphasizes forecasting and monitoring the temporal and spatial activity of 

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WNV, WEE, and SLE. These viruses are maintained in wild bird-mosquito cycles that do not 

depend upon infections of humans or domestic animals to persist. Surveillance and control 

activities focus on this maintenance cycle, which involves primarily Culex mosquitoes, such as 

the western encephalitis mosquito, Culex tarsalis, and birds such as house finches and house 

sparrows. 

Immature stages (called larvae and pupae) of Culex tarsalis can be found throughout California 

in a wide variety of aquatic sources, ranging from clean to highly polluted waters. Most such 

water is associated with irrigation of agricultural crops or urban wastewater. Other mosquito 

species, such as Culex pipiens, Culex quinquefasciatus, and Culex stigmatosoma, play an 

important role in WNV, and possibly SLE, transmission cycles in urban and suburban areas. 

Historically, Aedes melanimon, a floodwater mosquito, played a role in a secondary transmission 

cycle of WEE involving rabbits. Additional mosquitoes such as Aedes vexans and Culex 

erythrothorax also could be important bridge (i.e. bird to mammal) vectors in transmission. 

Mosquito control is the only practical method of protecting the human population from infection. 

There are no known specific treatments or cures for diseases caused by these viruses and vaccines 

are not available for public use. Infection by WEE virus tends to be most serious in very young 

children, whereas infections caused by WN and SLE viruses affect the elderly most seriously. 

WNV also kills a wide variety of native and non-native birds. There are WEE and WNV vaccines 

available to protect horses since both viruses can cause severe disease in horses. Mosquito-borne 

disease prevention strategies must be based on a well-planned integrated pest management (IPM) 

program that uses real-time surveillance to detect problem areas, focus control, and evaluate 

operational efficacy. The primary components of an IPM program include education, surveillance, 

and mosquito control. 

Education 

Residents, farmers, and duck club owners can play an important role in reducing the number of 

adult mosquitoes by eliminating standing water that may support the development of immature 

mosquitoes. For instance, residents can help by properly disposing of discarded tires, cans, or 

buckets; emptying plastic or unused swimming pools; and unclogging blocked rain gutters 

around homes or businesses. Farmers and ranchers can be instructed to use irrigation practices 

that do not allow water to stand for extended periods, and duck club owners can work with 

mosquito control agencies to determine optimal flooding schedules. Educating the general 

public to curtail outdoor activities during peak mosquito biting times, use insect repellents, and 

wear long-sleeved clothing will help reduce exposure to mosquitoes. Clinical surveillance is 

enhanced through education of the medical and veterinary communities to recognize the 

symptoms of WEE, SLE, and WNV and to request appropriate laboratory tests. Public health 

officials need to be alerted if a mosquito-borne viral disease is detected, especially if the public 

health risk is high. 

Surveillance 

Surveillance includes the monitoring, visualization, and analysis of data on climatic factors, 

immature and adult mosquito abundance, and virus activity measured by testing mosquitoes, 

sentinel chickens, wild birds (including dead birds for WNV), horses, and humans for evidence 

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of infection. Surveillance must focus not only on mosquito-borne viruses known to exist in 

California, but be sufficiently broad to also detect newly introduced viruses. 

Climate Variation 

The California Mediterranean climate provides ideal opportunities for forecasting mosquito 

abundance and arbovirus activity, because most precipitation falls during winter, as rain at lower 

elevations or as snow at higher elevations. Spring and summer temperatures then determine the 

rate of snow pack melt and runoff, mosquito population growth, the frequency of blood feeding, 

the rate of virus development in the mosquito, and therefore the frequency of virus transmission. 

In general, WEE virus outbreaks have occurred in the Central Valley when wet winters are 

followed by warm summers, whereas SLE and WN virus outbreaks seemed linked to warm dry 

conditions that lead to large populations of urban Culex. Although climate variation may 

forecast conditions conducive for virus amplification, a critical sequence of events is required for 

amplification to reach outbreak levels. 

Mosquito Abundance 

Mosquito abundance can be estimated through collection of immature or adult mosquitoes. The 

immature stages (larvae and pupae) can be collected from water sources where mosquitoes lay 

their eggs. A long-handled ladle (“dipper”) is used to collect water samples and the number of 

immature mosquitoes per "dip" estimated. In most local mosquito control agencies, technicians 

search for new sources and inspect known habitats for mosquitoes on a 7 to 14-day cycle. These 

data are used to direct control operations. Maintaining careful records of immature mosquito 

occurrence, developmental stages treated, source size, and control effectiveness can provide an 

early warning to forecast the size of the adult population. 

Adult mosquito abundance is a key factor contributing to the risk of virus transmission. 

Monitoring the abundance of adult mosquito populations provides important information on the 

size of the vector population as it responds to changing climatic factors and to larval control 

efforts. Four adult mosquito sampling methods are currently used in California: New Jersey 

light traps, carbon dioxide-baited traps, gravid (egg-laying) traps, and resting adult mosquito 

collections. The advantages and disadvantages of these sampling methods, and guidelines for the 

design, operation, and processing of the traps have been discussed in Guidelines for Integrated 

Mosquito Surveillance (Meyer et al. 2003) and are summarized in Appendix A. 

Mosquito Infections 

Virus activity can be monitored by testing adult mosquitoes for virus infection. Because Culex 

tarsalis is the primary rural vector of WNV, SLE, and WEE, and Culex quinquefasciatus and 

Culex pipiens are important urban vectors of WNV and SLE, surveillance efforts emphasize the 

testing of these species. Another species that should be tested is Culex stigmatosoma, which is a 

highly competent but less widely distributed vector of WNV and SLE that feeds on birds and is 

probably important in enzootic transmission where it is found in high abundance. Female 

mosquitoes are trapped, usually using carbon dioxide-baited or gravid traps, identified to species, 

and counted into groups (pools) of 50 females each for testing at the Center for Vectorborne 

Diseases (CVEC) at UC Davis. Procedures for submitting and processing mosquitoes for 

detecting virus infection are detailed in Appendix B. The current surveillance system is designed 

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to detect and measure levels of infection with WNV, SLE, and WEE. Although generally less 

sensitive than sentinel chickens, mosquito infections may be detected earlier in the season than 

chicken seroconversions and therefore provide an early warning of virus activity. Testing adult 

mosquitoes for infection is one of the best methods to detect newly introduced or emerging 

mosquito-borne viruses. Testing mosquito species other than Culex may be necessary to detect 

the introduction of viruses that do not have a primary avian-Culex transmission cycle. 

Avian Infections 

Detection of arboviral transmission within bird populations can be accomplished by 1) using 

caged chickens as sentinels and bleeding them routinely to detect viral antibodies 

(seroconversions), 2) collecting and bleeding wild birds to detect viral antibodies 

(seroprevalence), and 3) testing dead birds reported by the public for WNV. 

In California, flocks of ten chickens are placed in locations where mosquito abundance is known 

to be high or where there is a history of virus activity. Each chicken is bled every two weeks by 

pricking the comb and collecting blood on a filter paper strip. The blood is tested at the CDPH 

Vector-Borne Disease Section for antibodies to SLE, WEE, and WNV. Some agencies conduct 

their own testing, but send positive samples to CDPH for confirmation and official reporting. 

Because SLE cross-reacts with WNV in antibody testing, SLE or WNV positive chickens are 

confirmed and the infecting virus is identified by western blot or cross-neutralization tests. 

Frequent testing of strategically placed flocks of sentinel chickens provides the most sensitive 

and cost-effective method to monitor encephalitis virus transmission in an area. Because 

chickens are continuously available to host-seeking mosquitoes, they are usually exposed to 

more mosquitoes than can be collected by trapping, especially when adult mosquito abundance 

or viral infection rates are low. Sentinel housing, bleeding instructions, and testing protocols are 

provided in Appendix C. 

Virus activity in wild bird populations can be monitored by bleeding young (hatching year) birds 

to detect initial virus infection or by bleeding a cross-section of birds in an area and comparing 

seroprevalence among age strata to determine if the prevalence of the virus in the region has 

changed. Elevated seroprevalence levels (“herd immunity”) among key species during spring 

may limit virus transmission and dampen amplification. New infections also can be detected by 

bleeding banded birds in a capture-recapture scheme. In contrast to the convenience of using 

sentinel chickens, the repeated collection and bleeding of wild birds generally is too labor 

intensive, technically difficult, and expensive for most local mosquito control agencies to 

perform routinely. In addition, the actual place where a wild bird became infected is rarely 

known, because birds may travel over relatively long distances and usually are collected during 

daylight foraging flights and not at nighttime roosting sites where they are bitten by mosquitoes. 

Unlike WEE and SLE, WNV frequently causes death in North American birds, especially those 

in the family Corvidae (e.g. crows, ravens, magpies, jays). Dead bird surveillance was initiated 

by CDPH in 2000 to provide early detection of WNV. Dead bird surveillance has been shown to 

be one of the earliest indicators of WNV activity in a new area. Birds that meet certain criteria 

are necropsied at the California Animal Health and Food Safety Laboratory and kidney snips 

tested for WNV RNA by RT-PCR at CVEC or oral swabs of American crows tested by rapid 

antigen tests by local agencies. Dead birds are reported to CDPH’s dead bird hotline (1-877-

WNV-BIRD) or via the website, http://westnile.ca.gov. Beginning in 2010, results from RTK8-6
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PCR testing at CVEC distinguished between WNV recent and chronic positive birds based on 

cycle threshold (Ct) values. In general, birds tested by RT-PCR with a Ct value of <30 and those 

positive by antigen tests are considered to be recently infected, whereas those with Ct values >30 

are considered to have been chronically infected and the time since infection unknown. Chronic 

positive birds did not likely die from WNV infection and are of limited value for surveillance. 

The communication and testing algorithm for the dead bird surveillance program is detailed in 

Appendix D. 

Tree Squirrel Infections 

In 2004, tree squirrels were included as a WNV surveillance tool, based upon evidence that they 

were susceptible to WNV and could provide information on localized WNV transmission 

(Padgett et al. 2007). In conjunction with dead birds, tree squirrels were reported to the 

California WNV hotline, necropsied at the California Animal Health and Food Safety Laboratory 

and kidney tissue was tested by RT-PCR at CVEC. Tree squirrels will continue to be tested for 

WNV in 2012 and are included in the submission protocol in Appendix D. 

Equine Infections 

Currently, equine disease due to WEE and WNV is no longer a sensitive indicator of epizootic 

activity (unusually high incidence of infections in animals other than humans) in California 

because of the widespread vaccination or natural immunization of equids (horses, donkeys, and 

mules). Nevertheless, confirmed cases in horses can indicate that WEE or WNV has amplified to 

levels where tangential transmission has occurred and risk to humans is elevated in that region of 

the State. Each year, CDPH and the California Department of Food and Agriculture (CDFA) 

alert veterinarians of the risk of WNV to horses, advocate for vaccination, and provide 

information on diagnostic services that are available for suspected cases of WEE or WNV 

encephalitis. Other mosquito-borne viruses may also cause encephalitis in horses and testing of 

equine specimens for these other viruses is available (see Appendix E). 

Human Infections 

Local mosquito control agencies rely on the rapid detection and reporting of confirmed human 

cases to plan and implement emergency control activities to prevent additional infections. 

However, human cases of arboviral infection are an insensitive surveillance indicator of virus 

activity because most persons who become infected develop no symptoms. For those individuals 

who do become ill, it may take up to two weeks for symptoms to appear, followed by additional 

time until the case is recognized and reported. No human cases of SLE or WEE have been 

reported in California in recent years. However, a total of 3,146 cases of WNV have been 

reported in California from 2003-2011. 

To enhance human WNV testing and surveillance efforts throughout the state, a regional public 

health laboratory network was established in 2002. The laboratory network consists of the state 

Viral and Rickettsial Disease Laboratory (VRDL) as well as 26 county public health laboratories 

that are able to conduct WNV testing. Providers are encouraged to submit specimens for suspect 

WNV cases to their local public health laboratories. Specimens for patients with encephalitis 

may also be submitted directly to Neurologic Surveillance and Testing, which is based in the 

VRDL and offers diagnostic testing for many agents known to cause encephalitis, including 

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WNV and other arboviruses. In addition, VRDL collaborates with reference laboratories such as 

the regional laboratories of Kaiser Permanente to ascertain additional suspect WNV cases. 

In accordance with Title 17 of the California Code of Regulations (Sections 2500 and 2505), 

physicians and laboratories are required to report cases of WNV infection or positive test results 

to their local health department. Positive WNV or other arbovirus test results are investigated by 

local health department officials to determine whether a patient meets the clinical and laboratory 

criteria for a WNV diagnosis. If so, the local health department collects demographic and 

clinical information on the patient using a standardized West Nile virus infection case report, and 

forwards the report to the state health department. The local health department also determines 

whether the infection was acquired locally, imported from a region outside the patient’s 

residence, or acquired by a non-mosquito route of transmission such as blood transfusion or 

organ transplantation. Appendix F contains the protocol for submission of specimens to the 

regional public health laboratory network for WNV testing. Appendix G provides the national 

surveillance case definition for arboviral disease, including WNV infection. 

Mosquito Control 

Problems detected by surveillance are mitigated through larval and adult mosquito control. 

Mosquito control is the only practical method of protecting people from mosquito-borne 

diseases. Mosquito control in California is conducted by approximately 80 local agencies, 

including mosquito and vector control districts, county environmental and health departments, 

and county agriculture departments. Agencies applying pesticides directly to a water of the 

United States, or where deposition may enter a water of the United States, must obtain a National 

Pollutant Discharge Elimination System (NPDES) Permit for Biological and Residual Pesticide 

Discharges to Waters of the United States from Vector Control Applications (Vector Control 

Permit). Agencies must comply with provisions of the permit, including use of approved 

pesticides, pesticide use reporting, and visual, chemical, and toxicity monitoring requirements 

included in the permit. http://www.swrcb.ca.gov/water_issues/programs/npdes/aquatic.shtml 

Compounds currently approved for larval and adult mosquito control in California are listed in 

Appendix H. Please refer to the Vector Control Permit, Attachments E and F, for a list of vector 

control pesticides that may be applied to waters of the United States, unless the receiving water 

has an existing impairment from a pesticide with the same active ingredient. Please review the 

California State Water Resources Control Board listing of impaired water bodies (303d list) prior 

to applying any pesticide. 

http://www.swrcb.ca.gov/rwqcb4/water_issues/programs/303d_list.shtml 

Additional considerations regarding adult mosquito control in urban areas are described in 

Appendix I. 

Larval Control 

Mosquito larval and pupal control methods are target-specific and prevent the emergence of 

adult female mosquitoes which are capable of transmitting pathogens, causing discomfort, and 

ultimately producing another generation of mosquitoes. For these reasons, most mosquito 

control agencies in California target the immature stages rather than the adult stage of the 

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mosquito. Larval mosquito control has three key components: environmental management, 

biological control, and chemical control. 

Environmental management decreases habitat availability or suitability for immature mosquitoes, 

and may include water management, such as increasing the water disposal rate through 

evaporation, percolation, recirculation, or drainage. Laser-leveling of fields minimizes pooling 

at low spots, allows even distribution of irrigation water, and precludes standing water for long 

periods. Controlled irrigation or the careful timing of wetland flooding for waterfowl can reduce 

mosquito production or limit emergence to times of the year when virus activity is unlikely. 

Environmental management may include vegetation management because emergent vegetation 

provides food and refuge for mosquito larvae. Management strategies include the periodic 

removal or thinning of vegetation, restricting growth of vegetation, and controlling algae. 

Biological control uses natural predators, parasites, or pathogens to reduce immature mosquito 

numbers. Mosquitofish, Gambusia affinis, are the most widely used biological control agent in 

California. These fish are released annually in a variety of habitats, such as rice fields, small 

ponds, and canals. 

There are several mosquito control products that are highly specific and thus have minimal 

impact on non-target organisms. These include microbial control agents, such as Bacillus 

thuringiensis israelensis (Bti) and Bacillus sphaericus, and insect growth regulators, such as 

methoprene, that prevent immature mosquitoes from developing into adults. Surface films are 

very effective against both larvae and pupae, but also may suffocate other surface breathing 

aquatic insects. Organophosphate pesticides are used infrequently because of their impact on 

nontarget organisms and the environment. 

Adult Control 

When larval control is not possible or more immediate control measures are needed, adult 

mosquito control may be required to suppress populations of infected mosquitoes and interrupt 

epidemic virus transmission. Adult mosquito control products may be applied using groundbased equipment, fixed wing airplanes, or helicopters. Products applied in ultralow volume 

[ULV] formulations and dosages include organophosphates, such as malathion and naled, 

pyrethroids, such as resmethrin, sumithrin, and permethrin, and pyrethrins such as Pyrenone crop 

spray. Factors to consider when selecting an adulticide include: 1) efficacy against the target 

species or life cycle stage, 2) resistance status, 3) pesticide label requirements, 4) availability of 

pesticide and application equipment, 5) environmental conditions, 6) cost, and 7) toxicity to 

nontarget species, including humans. 

For more information about mosquito control please see “Best Management Practices for 

Mosquito Control in California”. http://www.westnile.ca.gov/resources.php 

Response Levels 

The California Mosquito-borne Virus Surveillance and Response Plan was developed to provide 

a semi-quantitative measure of virus transmission risk to humans that could be used by local 

mosquito control agencies to plan and modulate control activities. Independent models are 

presented for WEE, SLE and WNV to accommodate the different ecological dynamics of these 

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viruses (Barker et al. 2003). SLE and WN viruses are closely related, require similar 

environmental conditions, and employ the same Culex vectors. Seven surveillance factors are 

measured and analyzed to determine the level of risk for human involvement and thereby gauge 

the appropriate response level: 

1. Environmental or climatic conditions (snowpack, rainfall, temperature, season) 

2. Adult Culex vector abundance 

3. Virus infection rate in Culex mosquito vectors 

4. Sentinel chicken seroconversions 

5. Fatal infections in birds (WNV only) 

6. Infections in humans 

7. Proximity of detected virus activity to urban or suburban regions (WEE only) 

Each factor is scored on an ordinal scale from 1 (lowest risk) to 5 (highest risk). The mean score 

calculated from these factors corresponds to a response level as follows: normal season (1.0 to 

2.5), emergency planning (2.6 to 4.0), and epidemic (4.1 to 5.0). Table 1 provides a worksheet 

to assist in determining the appropriate rating for each of the risk factors for each of the three 

viruses. Appendix J shows sources of data useful in the calculation of risk in Table 1. 

For surveillance factor 2 (vector abundance), abundance is scaled as an anomaly and compared 

to the area average over 5 years for the same preceding two week period. The area typically 

encompasses the boundaries of a local mosquito and vector control district. The mosquito virus 

infection rate should be calculated using the most current data (prior two week period) and 

expressed as minimum infection rate (MIR) per 1,000 female mosquitoes tested. Calculations 

can also use maximum likelihood estimate (Biggerstaff 2003), which accounts for varying 

numbers of specimens in pools and the possibility that more than one mosquito could be infected 

in each positive pool when infection rates are high. For WNV and SLE, risk may be estimated 

separately for Cx. tarsalis and the Cx. pipiens complex, respectively, because these species 

generally have different habitat requirements and therefore spatial distributions (e.g., rural vs. 

urban). 

Each of the three viruses differs in its response to ecological conditions. WEE activity typically 

is greatest during El Niño conditions of wet winters, excessive run-off and flooding, cool 

springs, and increased Culex tarsalis abundance. Historically, WEE virus spillover into a 

secondary Aedes-rabbit cycle was common in the Central Valley, but has not been detected for 

the past 25 years. In contrast, SLE and perhaps WNV activity appears to be greatest during La 

Niña conditions of drought and hot summer temperatures and both SLE and WNV transmission 

risk increases when temperatures are above normal. Abundance and infection of the Culex 

pipiens complex are included in both SLE and WNV estimates of risk because these mosquito 

species are important vectors, particularly in suburban/urban environments. The occurrence of 

dead bird infections is included as a risk factor in the WNV calculations. For surveillance 

factors 4-6 (chickens, birds, humans), specific region is defined as the area within the agency’s 

boundary and the broad region includes the area within 150 miles (~241 km) of the agency’s 

boundary. 

Proximity of virus activity to human population centers is considered an important risk factor for 

all three viruses of public health concern. In the risk assessment model in Table 1 this was 

accommodated in two different ways. WEE virus transmitted by Culex tarsalis typically 

amplifies first in rural areas and may eventually spread into small and then larger communities. 

A risk score was included to account for where virus activity was detected. WNV and SLE virus 

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may be amplified concurrently or sequentially in rural and urban cycles. The rural cycle is 

similar to WEE virus and is transmitted primarily by Cx. tarsalis, whereas the urban cycle is 

transmitted primarily by members of the Culex pipiens complex. If the spatial distributions of 

key Culex species differ within an area (e.g., rural vs. urban), it may be advantageous to assess 

risk separately by species for abundance and infection rates in Cx. tarsalis and the Cx. pipiens 

complex. This would result in two estimates of overall risk for the areas dominated by each 

species. 

Each of these surveillance factors can differ in impact and significance according to time of year 

and geographic region. Climatic factors provide the earliest indication of the potential for 

increased mosquito abundance and virus transmission and constitute the only risk factor actually 

measured from the start of the calendar year through mid-spring when enzootic surveillance 

commences in most areas. Climate is used prospectively to forecast risk during the coming 

season. Other factors that may inform control efforts as the season progresses are typically, in 

chronological order: mosquito abundance, infections in non-humans (e.g., dead birds for WNV, 

mosquitoes, sentinel chickens), and infections in humans. Enzootic indicators measure virus 

amplification within the Culex-bird cycle and provide nowcasts of risk, whereas human 

infections document tangential transmission and are the outcome measure of forecasts and 

nowcasts. Response to the calculated risk level should consider the time of year; e.g., epidemic 

conditions in October would warrant a less aggressive response compared to epidemic conditions 

in July because cooler weather in late fall will contribute to declining risk of arbovirus 

transmission. 

The ratings listed in Table 1 are benchmarks only and may be modified as appropriate to the 

conditions in each specific region or biome of the state. Calculation and mapping of risk has 

been enabled by tools included in the CalSurv Gateway. Roles and responsibilities of key 

agencies involved in carrying out the surveillance and response plan are outlined in “Key 

Agency Responsibilities.” 

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 Table 1. Mosquito-borne Virus Risk Assessment. 

WNV Surveillance Factor Assessment 

Value Benchmark Assigned Value 

1. Environmental Conditions 

High-risk environmental conditions 

include above-normal temperatures 

with or without above-normal 

rainfall, runoff, or snowpack. 

Weather data link: 

http://ipm.ucdavis.edu 

1 Avg daily temperature during prior 2 weeks ≤ 56 oF 

2 Avg daily temperature during prior 2 weeks 57 – 65 oF 

3 Avg daily temperature during prior 2 weeks 66 – 72 oF 

4 Avg daily temperature during prior 2 weeks 73 – 79 oF 

5 Avg daily temperature during prior 2 weeks > 79 o F 

Cx tars Cx pip 

2. Adult Culex tarsalis and Cx. 

pipiens complex relative 

abundance*

Determined by trapping adults, 

enumerating them by species, and 

comparing numbers to those 

previously documented for an area 

for the prior 2-week period. 

1 Vector abundance well below average (≤ 50%) 

2 Vector abundance below average (51 - 90%) 

3 Vector abundance average (91 - 150%) 

4 Vector abundance above average (151 - 300%) 

5 Vector abundance well above average (> 300%) 

3. Virus infection rate in Culex 

tarsalis and Cx. pipiens complex 

mosquitoes* 

Tested in pools of 50. Test results 

expressed as minimum infection 

rate per 1,000 female mosquitoes 

tested (MIR) for the prior 2-week 

period. 

1 MIR = 0 

2 MIR = 0.1 - 1.0 

3 MIR = 1.1 - 2.0 

4 MIR = 2.1 - 5.0 

5 MIR > 5.0 

4. Sentinel chicken seroconversion

Number of chickens in a flock that 

develop antibodies to WNV during 

the prior 2-week period. If more 

than one flock is present in a region, 

number of flocks with seropositive 

chickens is an additional 

consideration. Typically 10 

chickens per flock. 

1 No seroconversions in broad region 

2 One or more seroconversions in broad region 

3 One or two seroconversions in a single flock in specific 

region 

4 

More than two seroconversions in a single flock or two 

flocks with one or two seroconversions in specific 

region 

5 More than two seroconversions per flock in multiple 

flocks in specific region 

5. Dead bird infection 

Number of birds that have tested 

positive (recent infections only) for 

WNV during the prior 3-month 

period. This longer time period 

reduces the impact of zip code 

closures during periods of increased 

WNV transmission. 

1 No positive dead birds in broad region 

2 One or more positive dead birds in broad region 

3 One positive dead bird in specific region 

4 Two to five positive dead birds in specific region 

5 More than five positive dead birds in specific region 

6. Human cases

Do not include this factor in 

calculations if no cases are detected 

in region. 

3 One or more human infections in broad region 

4 One human infection in specific region 

5 More than one human infection in specific region 

Cx tars Cx pip

Response Level / Average Rating: 

Normal Season (1.0 to 2.5) 

Emergency Planning (2.6 to 4.0) 

Epidemic (4.1 to 5.0) 

TOTAL 

 

AVERAGE 

 

* Calculation of separate risk values for Cx. tarsalis and the Cx. pipiens complex may be useful if their spatial distributions 

(e.g., rural vs. urban) differ within the assessment area. 

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SLE Surveillance Factor Assessment 

Value Benchmark Assigned Value 

1. Environmental Conditions 

High-risk environmental conditions 

include above-normal temperatures 

with or without above-normal 

rainfall, runoff, or snowpack. 

Weather data link: 

http://ipm.ucdavis.edu 

1 Avg daily temperature during prior 2 weeks ≤ 56 oF 

2 Avg daily temperature during prior 2 weeks 57 – 65 oF 

3 Avg daily temperature during prior 2 weeks 66 – 72 oF 

4 Avg daily temperature during prior 2 weeks 73 – 79 oF 

5 Avg daily temperature during prior 2 weeks > 79 o F 

Cx tars Cx pip

2. Adult Culex tarsalis and Cx. 

pipiens complex relative 

abundance*

Determined by trapping adults, 

enumerating them by species, and 

comparing numbers to those 

previously documented for an area 

for the prior 2-week period. 

1 Vector abundance well below average (≤ 50%) 

2 Vector abundance below average (51 - 90%) 

3 Vector abundance average (91 - 150%) 

4 Vector abundance above average (151 - 300%) 

5 Vector abundance well above average (> 300%) 

3. Virus infection rate in Culex 

tarsalis and Cx. pipiens complex 

mosquitoes* 

Tested in pools of 50. Test results 

expressed as minimum infection 

rate per 1,000 female mosquitoes 

tested (MIR) for the prior 2-week 

collection period. 

1 MIR = 0 

2 MIR = 0.1 - 1.0 

3 MIR = 1.1 - 2.0 

4 MIR = 2.1 - 5.0 

5 MIR > 5.0 

4. Sentinel chicken seroconversion

Number of chickens in a flock that 

develop antibodies to SLEV during 

the prior 2-week period. If more 

than one flock is present in a region, 

number of flocks with seropositive 

chickens is an additional 

consideration. Typically 10 

chickens per flock. 

1 No seroconversions in broad region 

2 One or more seroconversions in broad region 

3 One or two seroconversions in a single flock in specific 

region 

4 

More than two seroconversions in a single flock or two 

flocks with one or two seroconversions in specific 

region 

5 More than two seroconversions per flock in multiple 

flocks in specific region 

5. Human cases

Do not include this factor in 

calculations if no cases are detected 

in region. 

3 One or more human cases in broad region 

4 One human case in specific region 

5 More than one human case in specific region 

Cx tars Cx pip

Response Level / Average Rating: 

Normal Season (1.0 to 2.5) 

Emergency Planning (2.6 to 4.0) 

Epidemic (4.1 to 5.0) 

TOTAL 

 

AVERAGE 

 

* Calculation of separate risk values for Cx. tarsalis and the Cx. pipiens complex may be useful if their spatial distributions 

(e.g., rural vs. urban) differ within the assessment area. 

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WEE Surveillance Factor Assessment 

Value Benchmark Assigned Value 

1. Environmental Conditions 

High-risk environmental conditions 

include above normal rainfall, snow 

pack, and runoff during the early season 

followed by a strong warming trend. 

Weather data link: 

http://ipm.ucdavis.edu 

1 Cumulative rainfall and runoff well below average 

2 Cumulative rainfall and runoff below average 

3 Cumulative rainfall and runoff average 

4 Cumulative rainfall and runoff above average 

5 Cumulative rainfall and runoff well above average 

2. Adult Culex tarsalis abundance 

Determined by trapping adults, 

enumerating them by species, and 

comparing numbers to averages 

previously documented for an area for the 

prior 2-week period. 

1 Cx. tarsalis abundance well below average (≤ 50%) 

2 Cx. tarsalis abundance below average (51 - 90%) 

3 Cx. tarsalis abundance average (91 - 150%) 

4 Cx. tarsalis abundance above average (151 - 300%) 

5 Cx. tarsalis abundance well above average (> 300%) 

3. Virus infection rate in Cx. tarsalis

mosquitoes 

Tested in pools of 50. Test results 

expressed as minimum infection rate per 

1,000 female mosquitoes tested (MIR) 

for the prior 2-week collection period. 

1 Cx. tarsalis MIR = 0 

2 Cx. tarsalis MIR = 0.1 - 1.0 

3 Cx. tarsalis MIR = 1.1 - 2.0 

4 Cx. tarsalis MIR = 2.1 - 5.0 

5 Cx. tarsalis MIR > 5.0 

4. Sentinel chicken seroconversion 

Number of chickens in a flock that 

develop antibodies to WEEV during the 

prior 2-week period. If more than one 

flock is present in a region, number of 

flocks with seropositive chickens is an 

additional consideration. Typically 10 

chickens per flock. 

1 No seroconversions in broad region 

2 One or more seroconversions in broad region 

3 One or two seroconversions in a single flock in 

specific region 

4 

More than two seroconversions in a single flock or two 

flocks with one or two seroconversions in specific 

region 

5 More than two seroconversions per flock in multiple 

flocks in specific region 

5. Proximity to urban or suburban 

regions (score only if virus activity 

detected) 

Risk of outbreak is highest in urban areas 

because of high likelihood of contact 

between humans and vectors. 

1 Virus detected in rural area 

3 Virus detected in small town or suburban area 

5 Virus detected in urban area 

6. Human cases 

Do not include this factor in calculations 

if no cases found in region or in agency. 

3 One or more human cases in broad region 

4 One human case in specific region 

5 More than one human case in specific region 

Response Level / Average Rating: 

Normal Season (1.0 to 2.5) 

Emergency Planning (2.6 to 4.0) 

Epidemic (4.1 to 5.0) 

TOTAL 

AVERAGE 

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15 

General suggestions for applying the risk assessment model locally 

 Use a consistent time period for environmental conditions, adult mosquito abundance, 

mosquito infection rates, and human cases. If you use a period that differs from the prior 

two-week period defined in the risk assessment -- such as the prior month -- use the same 

period for all other relevant measures. Note that sentinel seroconversions and dead bird 

infections may need special treatment to accommodate bleeding schedules and zip code 

closures, respectively. For sentinel seroconversions, use the sentinel seroconversions 

from the most recent collection. 

 If you have multiple trap types in your surveillance program, determine the vector 

abundance anomaly for each trap type and species and use the most sensitive trap type’s 

value in the risk assessment. 

 When determining the vector abundance anomaly, there should be at least two and 

preferably five years of prior data to provide a comparative baseline for the particular trap 

type. Ideally, the prior years should be contiguous and immediately precede the time 

period being evaluated. 

Risk assessment as implemented by the CalSurv Gateway (http://gateway.calsurv.org)

 Assessment reports will be generated and delivered to the primary contacts of each 

agency by email every Monday. 

 The time frame of each assessment report will be for the prior two-week period ending on 

the previous Saturday. 

 Only those agencies with active Gateway accounts and active surveillance programs will 

receive the reports. 

 All calculations are done at the agency level, thus the specific region is the area within 

the agency’s boundary and the broad region includes the area within 150 miles (~241 km) 

of the agency’s boundary. 

 Due to privacy concerns and delays in detection and reporting, human cases are not part 

of the Gateway’s risk assessment. 

 All of the general suggestions from the prior section are used in the Gateway’s 

implementation. 

 Risk estimates based on mosquito abundance and infection rates will be calculated 

separately for the key mosquito species, Cx. tarsalis and the Cx. pipiens complex. 

 For sentinel seroconversions, flavivirus positives are treated as WNV positives. If SLE is 

found, this will be adjusted accordingly. 

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Characterization of Conditions and Responses 

Level 1: Normal Season 

Risk rating: 1.0 to 2.5 

CONDITIONS 

 Average or below average snowpack and rainfall; below or average seasonal temperatures (<65F) 

 Culex mosquito abundance at or below five year average (key indicator = adults of vector species) 

 No virus infection detected in mosquitoes 

 No seroconversions in sentinel chickens 

 No recently infected WNV-positive dead birds 

 No human cases

RESPONSE 

 Conduct routine public education (eliminate standing water around homes, use personal protection 

measures) 

 Conduct routine mosquito and virus surveillance activities 

 Comply with National Pollutant Discharge Eliminations System (NPDES) permit if applying pesticides 

to waters of the United States 

 Conduct routine mosquito control, with emphasis on larval control 

 Inventory pesticides and equipment 

 Evaluate pesticide resistance in vector species 

 Ensure adequate emergency funding 

 Release routine press notices 

 Send routine notifications to physicians and veterinarians 

 Establish and maintain routine communication with local office of emergency services personnel; obtain 

Standardized Emergency Management System (SEMS) training

Level 2: Emergency Planning 

Risk rating: 2.6 to 4.0 

CONDITIONS 

 Snowpack and rainfall and/or temperature above average (66-79F) 

 Adult Culex mosquito abundance greater than 5-year average (150% to 300% above normal) 

 One or more virus infections detected in Culex mosquitoes (MIR / 1000 is <5) 

 One or more seroconversions in single flock or one to two seroconversions in multiple flocks in 

specific region 

 One to five recently infected WNV-positive dead birds in specific region 

 One human case in broad or specific region 

 WEE virus detected in small towns or suburban area 

RESPONSE 

 Review epidemic response plan 

 Enhance public education (include messages on the signs and symptoms of encephalitis; seek 

medical care if needed; inform public about pesticide applications if appropriate) 

 Enhance information to public health providers 

 Conduct epidemiological investigations of cases of equine or human disease 

 Increase surveillance and control of mosquito larvae 

 Increase adult mosquito surveillance 

 Increase number of mosquito pools tested for virus 

 Conduct or increase localized chemical control of adult mosquitoes as appropriate 

 Contact commercial applicators in anticipation of large scale adulticiding 

 Review candidate pesticides for availability and susceptibility of vector mosquito species 

 Ensure notification of key agencies of presence of viral activity, including the local office of 

emergency services 

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Level 3: Epidemic Conditions 

Risk rating: 4.1 to 5.0 

CONDITIONS 

 Snowpack, rainfall, and water release rates from flood control dams and/or temperature well above 

average (>79F) 

 Adult vector population extremely high (>300%) 

 Virus infections detected in multiple pools of Culex tarsalis or Cx. pipiens mosquitoes (MIR / 1000 > 

5.0) 

 More than two seroconversions per flock in multiple flocks in specific region 

 More than five recently infected WNV-positive dead birds and multiple reports of dead birds in 

specific region 

 More than one human case in specific region 

 WEE virus detection in urban or suburban areas 

RESPONSE 

 Conduct full scale media campaign 

 Alert physicians and veterinarians 

 Conduct active human case detection 

 Conduct epidemiological investigations of cases of equine or human disease 

 Continue enhanced larval surveillance and control of immature mosquitoes 

 Broaden geographic coverage of adult mosquito surveillance 

 Accelerate adult mosquito control as appropriate by ground and/or air 

 Coordinate the response with the local Office of Emergency Services or if activated, the Emergency 

Operation Center (EOC) 

 Initiate mosquito surveillance and control in geographic regions without an organized vector control 

program 

 Determine whether declaration of a local emergency should be considered by the County Board of 

Supervisors (or Local Health Officer) 

 Determine whether declaration of a “State of Emergency” should be considered by the Governor at 

the request of designated county or city officials 

 Ensure state funds and resources are available to assist local agencies at their request 

 Determine whether to activate a Standardized Emergency Management System (SEMS) plan at the 

local or state level 

 Continue mosquito education and control programs until mosquito abundance is substantially 

reduced and no additional human cases are detected 

For more detailed information on responding to a mosquito-borne disease outbreak, please refer 

to: 

Operational Plan for Emergency Response to Mosquito-Borne Disease Outbreaks, California 

Department of Public Health (supplement to California Mosquito-Borne Virus Surveillance and 

Response Plan). http://www.westnile.ca.gov/resources.php

K8-17
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Key Agency Responsibilities 

Local Mosquito and Vector Control Agencies 

 Gather, collate, and interpret regional climate and weather data. 

 Monitor abundance of immature and adult mosquitoes. 

 Collect and submit mosquito pools to CVEC for virus detection. 

 Maintain sentinel chicken flocks, obtain blood samples, and send samples to VBDS. 

 Pick-up and ship dead birds for necropsy and WNV testing, or test oral swabs from American 

crows locally via rapid antigen screening assays. 

 Update CDPH weekly of all birds that are independently reported and/or tested by VecTest, 

RAMP or immunohistochemistry. 

 Update the surveillance gateway weekly with mosquito pool results that are independently 

tested by RAMP or PCR. 

 Conduct routine control of immature mosquitoes. 

 Comply with NPDES permit if applying pesticides to waters of the United States 

 Conduct control of adult mosquitoes when needed. 

 Educate public on mosquito avoidance and reduction of mosquito breeding sites. 

 Coordinate with local Office of Emergency Services personnel. 

 Communicate regularly with neighboring agencies 

Mosquito and Vector Control Association of California 

 Coordinate purchase of sentinel chickens. 

 Receive, track, and disperse payment for surveillance expenses. 

 Coordinate surveillance and response activities among member agencies. 

 Serve as spokesperson for member agencies. 

 Establish liaisons with press and government officials. 

California Department of Public Health 

 Collate adult mosquito abundance data submitted by local agencies; provide summary of data 

to local agencies. 

 Maintain a WNV information and dead bird reporting hotline, 1-877-WNV-BIRD, and a 

WNV website: http://westnile.ca.gov. 

 Coordinate submission of specimens for virus testing. 

 Provide supplies for processing mosquito pool and sentinel chicken diagnostic specimens 

 Test sentinel chicken sera for viral antibodies. 

 Test human specimens for virus. 

 Distribute a weekly bulletin summarizing surveillance test results. 

 Send weekly surveillance results to the UC Davis interactive website. 

 Immediately notify local vector control agency and public health officials when evidence of 

viral activity is found. 

 Conduct epidemiological investigations of cases of human disease. 

 Coordinate and participate in a regional emergency response in conjunction with California 

Emergency Management Agency. 

 Conduct active surveillance for human cases. 

K8-18
19 

 Provide oversight to local jurisdictions without defined vector-borne disease control 

program. 

 Maintain inventory of antigens and antisera to detect exotic viruses. 

 Provide confirmation of tests done by local agencies. 

University of California at Davis 

 Conduct research on arbovirus surveillance, transmission of mosquito-borne diseases, and 

mosquito ecology and control. 

 Test mosquito pools and dead birds for endemic and introduced viruses. 

 Provide a proficiency panel of tests for identification of viruses from human, equine, bird, or 

arthropod vectors to local agencies to ensure quality control. 

 Maintain an interactive website (http://gateway.calsurv.org) for dissemination of mosquitoborne virus information and data. 

 Maintain inventory of antigens, antisera, and viruses to detect the introduction of exotic 

viruses. 

 Provide confirmation of tests done by local or state agencies. 

California Department of Food and Agriculture 

 Notify veterinarians and veterinary diagnostic laboratories about WEE and WNV and testing 

facilities available at UCD Center for Vectorborne Disease Research. 

 Provide outreach to general public and livestock and poultry producers on the monitoring and 

reporting of equine and ratite encephalitides. 

 Facilitate equine and ratite sample submission from the field. 

 Conduct investigations of equine cases. 

California Animal Health and Food Safety Laboratory 

 Identify species of dead birds submitted for WNV testing. 

 Conduct necropsies and testing on dead birds. 

 Submit bird tissues to CVEC for testing. 

 Test equine specimens for WNV. 

Local Health Departments and Public Health Laboratories 

 Test human specimens for WNV. 

 Refer human specimens to CDPH for further testing. 

 Notify local medical community, including hospitals and laboratories, if evidence of viral 

activity is present. 

 Collect dead birds and ship carcasses to testing laboratories when needed. 

 Test American crows via rapid assay or RT-PCR as resources allow. 

 Participate in emergency response. 

 Conduct epidemiological investigations of cases of human disease. 

 Report WNV cases to CDPH. 

 Conduct public education. 

K8-19
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California Emergency Management Agency 

 Coordinate the local, regional, or statewide emergency response under epidemic conditions 

in conjunction with CDPH via the Standardized Emergency Management System (SEMS).

 Serve as liaison with the Federal Emergency Management Agency (FEMA) in the event that 

a federal disaster has been declared.

Federal Centers for Disease Control and Prevention 

 Provide consultation to state and local agencies in California if epidemic conditions exist. 

 Provide national surveillance data to state health departments. 

State Water Resources Control Board 

 Review NPDES permit applications and respond in a timely manner. 

 Review vector control pesticides registered by the California Department of Pesticide 

Regulation for inclusion on the Vector Control NPDES permit. 

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References 

Barker, C. M., W. K. Reisen, and V. L. Kramer. 2003. California State Mosquito-borne Virus 

Surveillance and Response Plan: A retrospective evaluation using conditional 

simulations. Am. J. Trop. Med. Hyg. 68: 508-518. 

Eldridge, B.F. 1987. Strategies for surveillance, prevention, and control of arbovirus diseases in 

western North America. Am. J. Trop. Med. Hyg. 37:77S-86S. 

Eldridge, B.F. 2000. The epidemiology of arthropod-borne diseases. pp. 165-185 in B. F. 

Eldridge and J. Edman, Eds. Medical entomology: a textbook of public health and 

veterinary problems caused by arthropods. Kluwer Academic Publications. Dordrecht, 

the Netherlands. 

Eldridge, B.F. 2000. Surveillance for arthropod-borne diseases. pp. 515-538 in B. F. Eldridge 

and J. Edman, Eds. Medical entomology: a textbook on public health and veterinary 

problems caused by arthropods. Kluwer Academic Publications. Dordrecht, Netherlands. 

Hui, L.T., S.R. Husted, W.K. Reisen, C.M. Myers, M.S. Ascher, V.L. Kramer. 1999. Summary 

of reported St. Louis encephalitis and western equine encephalomyelitis virus activity in 

California from 1969-1997. Proc.Calif. Mosq. Vector Control Assoc. 67: 61-72. 

Meyer, R. P., W. K. Reisen and Vector and Vector-borne Disease Committee. 2003. Integrated 

mosquito surveillance guidelines. Mosq. Vector. Contr. Assoc. Calif. 

Padgett, K.A, W.K. Reisen, N. Kahl-Purcell, Y. Fang, B. Cahoon-Young, R. Carney, N. 

Anderson, L. Zucca, L. Woods, S. Husted, and V.L. Kramer. 2007. West Nile virus 

infection in tree squirrels (Rodentia: Sciuridae) in California, 2004-2005. Am. J. Trop. 

Med. Hyg. 76: 810-813. 

Reeves, W. C., M. M. Milby and W. K. Reisen. 1990. Development of a statewide arbovirus 

surveillance program and models of vector populations and virus transmission. pp.: 431-

458. In: W. C. Reeves, (ed.) Epidemiology and control of mosquito-borne arboviruses in 

California, 1983-1987 Sacramento, Calif. Calif. Mosq. Vector Control Assoc., Inc. 

Reeves, W.C. 1990. Epidemiology and control of mosquito-borne arboviruses in California, 

1943-1987. California Mosquito Vector Control Association, Sacramento. 

Reeves, W.C. 2000. The threat of exotic arbovirus introductions into California. Proc. Calif. 

Mosq. Vector Control Assoc. 68: 9-10. 

Reisen, W.K. 1995. Guidelines for surveillance and control of arbovirus encephalitis in 

California. pp. 1-34 in: Interagency guidelines for the surveillance and control of 

selected vector-borne pathogens in California. California Mosquito Vector Control 

Association, Inc., Sacramento. 

Reisen, W.K., R.P. Meyer, S.B. Presser, and J.L. Hardy. 1993. Effect of temperature on the 

transmission of western equine encephalomyelitis and St. Louis encephalitis viruses by 

Culex tarsalis (Diptera: Culicidae). J. Med. Entomol. 30: 151-160. 

Theophilides, C. N., S. C. Ahearn, S. Grady and M. Merlino. 2003. Identifying West Nile virus 

risk areas: the Dynamic Continuous-Area Space-Time System. American Journal of 

Epidemiology 157:843-854. 

Theophilides, C. N., S. C. Ahearn, E. S. Binkowski, W. S. Paul and K. Gibbs. 2006. First 

evidence of West Nile virus amplification and relationship to human infections. 

International Journal of Geographic Information Science 20:1:103-115. 

Walsh, J.D. 1987. California's mosquito-borne encephalitis virus surveillance and control 

 program. California Department of Health Services, Sacramento. 

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Appendix A 

22 

Appendix A: Guidelines for Adult Mosquito Surveillance 

 The objective of Appendix A is to standardize mosquito sampling and reporting procedures 

to provide comparable and interpretable abundance measures among collaborating mosquito 

control agencies in California. This section summarizes information from Integrated Mosquito 

Surveillance Program Guidelines for California that has been adopted by the Mosquito and 

Vector Control Association (MVCAC) (Meyer et al. 2003). The MVCAC guidelines 

recommend stratifying the use of different sampling methods in rural, small town, and urban 

environments for each of the major biomes of California and provide a listing of target vector 

and nuisance mosquito species. The stratified sampling approach monitors vector populations 

and virus activity in rural enzootic foci, agricultural or suburban amplification sites, and densely 

populated urban centers to provide estimates of early, eminent, and current epidemic risk. 

 The four sampling methods currently used by mosquito control agencies are: 1) New Jersey 

(American) light trap, 2) CDC/ EVS style, or other CO2-baited trap, 3) gravid trap, and 4) adult 

resting collections. Collection location sites should be geocoded and registered using the 

Surveillance Gateway [http://gateway.calsurv.org/]. Studies comparing trap design and 

efficiency for surveillance purposes have been published (Reisen et al. 2000; Reisen et al. 2002). 

These guidelines describe: 1) a comparison of the sampling methods, 2) equipment design, 3) 

operation, 4) specimen processing, 5) data recording and analysis, and 6) data usage. 

Advantages and Disadvantages of Mosquito Sampling Methods: 

New Jersey Light Trap 

Pros 

 All female metabolic states and males collected 

 Minimal collection effort (can be run nightly without 

service) 

 Long history of use in California 

Cons 

 Selective for phototactic nocturnally active mosquitoes 

 Ineffective in the presence of competing light sources 

 Sorting time excessive because of other insects in traps 

 Specimens dead; less useful for virus detection 

 Collects comparatively few specimens 

CDC/EVS CO2 Trap 

Pros 

 Samples biting population 

 Collects large numbers of virus vector species 

 Specimens alive; suitable for virus detection 

 Without light, collects mostly mosquitoes thus reducing 

sorting time 

 Battery operated, portable 

Cons 

 Collects >50% nullipars (females that have never blood fed 

or laid eggs) 

 Must be set and picked-up daily 

 Dry ice cost high; availability can be a problem 

 Does not collect males or bloodfed or gravid females 

Gravid Trap 

Pros 

 Collects females that have bloodfed and digested the 

blood meal; may have higher infection rate than CO2 trap 

 Specimens alive; suitable for virus detection 

 Extremely sensitive for Cx.quinquefasciatus in urban 

habitat 

 Bait inexpensive 

 Battery operated, portable 

Cons 

 Collects only foul-water Culex [mostly pipiens complex]

 Bait has objectionable odor 

 Must be set and picked-up daily 

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Appendix A 

23 

Resting Catches 

Pros 

 All metabolic states collected 

 Minimal equipment needed 

 Specimens alive; suitable for virus detection 

 Blooded and gravid specimens can be tested to improve 

sensitivity of virus surveillance 

Cons 

 Standardization is difficult due to: 

1. Variable shelter size and type 

2. Variable collector efficiency 

 Labor intensive; difficult to concurrently sample a large 

number of sites 

New Jersey (American) Light Trap (NJLT) 

Operation 

 At a minimum, one trap should be located in each principal municipality of a district or have 

a distribution of one trap/township (36 sq. mi.). Correct placement of the NJLT is a critical 

factor in its performance as an effective surveillance mechanism for measuring the relative 

abundance of phototaxic mosquitoes. Place the traps at six-foot height. This can be done by 

using a metal standard, or by hanging the traps from tree limbs or roof eaves. These distances 

should maximize attractancy over a 360 degree radius. The trap should be placed on the leeward 

side of a structure or tree line to decrease the influence of wind on trap catch. 

 Traps should be kept away from smoke or chemical odors that may be repellent to the 

mosquitoes. Traps should be away from buildings in which animals are housed and not be in the 

immediate vicinity of sentinel flocks to diminish attractancy competition. Traps should be 

placed away from street and security lights that may diminish attractancy of the trap bulb. A trap 

should be placed approximately 100-200 feet from each sentinel chicken flock when possible. 

 Traps should be operated from week 14 to week 44 of the calendar year for districts north of 

the Tehachapi Mountains and all year long for districts south of the Tehachapi. Ideally, the traps 

should run for four to seven nights before the collection is retrieved (Loomis and Hanks 1959). 

The trap should be thoroughly cleaned with a brush to remove spider webs or any other debris 

that may hinder airflow through the trap. A regular cleaning schedule should be maintained 

during the trapping season to maintain trap efficiency. 

Processing 

 Adult mosquitoes from the NJLT collection should be sorted from the other insects in an 

enamel pan before being identified and counted at 10x magnification under a dissecting 

microscope. Counting aliquots or subsamples of all specimen samples should be discouraged, 

because vector species may comprise only a small fraction of the total mosquito collection. 

CDC style CO2-baited trap 

Operation 

 Carbon dioxide-baited traps can be used for abundance monitoring or capturing mosquitoes 

for virus testing. Traps should be hung from a 6-foot tall standard (approximately 4 feet above 

ground level) to standardize trap placement for population and virus infection rate monitoring. 

Knowledge of the host-seeking patterns of the target species is essential in determining CO2-

baited trap placement in the habitat to enhance catch size and therefore sampling sensitivity. 

Culex tarsalis primarily bloodfeed on birds and hunt along vegetative borders and tree canopies 

where birds roost and nest. Culex erythrothorax are best collected within wetland areas near 

K8-23
Appendix A 

24 

dense stands of tules and cattails. In large, open breeding sources such as rice fields, CO2-baited 

traps could be hung on standards on the up-wind side of the source for Culex tarsalis and 

Anopheles freeborni collections. Aedes melanimon and Aedes nigromaculis are mammal feeders 

and typically seek hosts over open fields. 

 When used to supplement sentinel chickens for arbovirus surveillance, traps should be 

operated at different locations to enhance geographical coverage and thus surveillance 

sensitivity. Labor and time constraints determine the extent of sampling. When used to monitor 

population abundance, traps should be operated weekly or biweekly at the same fixed stations. 

Temperature, wind speed, wind direction, and rainfall should be recorded because these factors 

affect catch size. The mini-light may be removed, because it attracts other phototactic insects 

that may hinder sorting and/or damage female mosquitoes in the collection container and may 

repel members of the Culex pipiens complex. The CO2-baited trap should not be placed in 

immediate proximity to the sentinel chicken flock because it will compete with, and therefore 

lessen, exposure of the sentinel birds, but may be placed within a 100-200 foot radius of the 

sentinel flock site, but no closer than 100 feet from the flock. 

Processing 

 Mosquitoes collected for arbovirus surveillance should be processed according to the 

procedures outlined in Appendix B. If possible, ten pools of a species (Culex tarsalis, Culex 

pipiens, Culex quinquefasciatus, Culex stigmatosoma, Aedes melanimon, and Aedes dorsalis) 

should be submitted for virus testing from a given geographical location at a given time. Only 

live mosquitoes should be pooled for virus testing. Dead, dried specimens should be counted 

and discarded. Only whole specimens should be submitted; avoid including detached body parts 

(which may be from other mosquito species) or other Diptera (i.e., Culicoides, etc.) in the pool to 

prevent sample contamination. Avoid freezing specimens before sorting and counting. 

Mosquitoes collected for population monitoring should be anesthetized in a well-ventilated area 

or under a chemical hood using triethylamine, identified to species under a dissecting 

microscope, counted, pooled and immediately frozen at -80C or on dry ice for later virus testing. 

Reiter/Cummings gravid traps 

Trap design and components

 The Reiter/Cummings gravid traps consist of a rectangular trap housing [plastic tool box] 

with an inlet tube on the bottom and an outlet tube on the side or top. The rectangular housing is 

provided with legs to stabilize the trap over the attractant basin containing the hay-infusion 

mixture. (Cummings 1992). The oviposition attractant consists of a fermented infusion made by 

mixing hay, Brewer’s yeast and water. The mixture should sit at ambient temperature for a 

minimum of three to four days prior to allow fermentation and increase attractancy. New 

solutions should be made at least biweekly to maintain consistent attractancy. 

Operation

 The Reiter/Cummings gravid trap is primarily used in suburban and urban residential 

settings for surveillance of gravid females in the Culex pipiens complex. The trap is placed on 

the ground near dense vegetation that serves as resting sites for gravid females. Specimens may 

be retrieved on a one to three day basis. 

K8-24
Appendix A 

25 

Processing

Culex pipiens complex females collected with the gravid trap for arbovirus surveillance 

should be retrieved daily and the protocol for mosquito pool submission as outlined in Appendix 

B should be followed. For population monitoring of the Culex pipiens complex, collections may 

be retrieved every third day. The females are killed, identified and counted before being 

discarded. Autogenous females may also be attracted to the gravid trap. 

Adult resting collections 

Trap design and operation 

 A flashlight and mechanical aspirator can be used to collect adult mosquitoes resting in 

habitats such as shady alcoves, buildings, culverts, or spaces under bridges. Highest numbers 

usually are collected at humid sites protected from strong air currents. Adults resting in 

vegetation may be collected using a mechanical sweeper such as the AFS (Arbovirus Field 

Station) sweeper (Meyer et al. 1983). For quantification, time spent searching is recorded and 

abundance expressed as the number collected per person-hour. 

 Red boxes were developed to standardize collections spatially. Different researchers have 

used red boxes of varying dimensions. Largest catches are made in semi-permanent walk-in red 

boxes which measure 4’ x 4’ x 6’ (Meyer 1985). Smaller 1’ x 1’ x 1’ foot boxes typically collect 

fewer specimens, but are readily portable. The entrance of the walk-in red box should be left 

open, draped with canvas, or closed with a plywood door. The canvas or plywood door should 

have a 1 or 2 ft gap at the bottom to allow entry of mosquitoes, while affording some protection 

from the wind and decreasing the light intensity within the box. The box entrance should not 

face eastward into the morning sun or into the predominant wind direction. 

Processing

 Mosquitoes should be anesthetized with triethylamine, identified under a dissecting 

microscope, sorted by sex and female metabolic status (i.e., empty or unfed, blood fed or gravid), 

and counted. Females may be counted into ten pools of approximately 50 females per site per 

collection date for virus monitoring (see Appendix B). Only living females should be used for 

arbovirus surveillance. Data on metabolic status may indicate population reproductive age as 

well as diapause status. 

Data recording and analysis 

 Counts from NJLTs, EVS, and gravid traps and information on pools submitted for testing 

or tested locally should be entered directly in electronic format through the California 

Vectorborne Disease Surveillance Gateway ( http://gateway.calsurv.org/). Import from local or 

proprietary data systems is available. For comparisons of abundance over time, space, or 

collection methods, refer to Biddlingmeyer (1969). 

Data usage 

Mosquito collections from some or all of the four sampling methods collectively can be used to: 

 1. Assess control efforts. 

K8-25
Appendix A 

26 

 2. Monitor arbovirus vector abundance and infection rates. 

 3. Compare mosquito abundance from collections with the number of service requests from the 

public to determine the tolerance of neighborhoods to mosquito abundance. 

 4. Determine proximity of breeding source(s) by the number of males present in collections 

from the NJLTs and red boxes. 

 5. Determine age structure of females collected by CO2 traps and resting adult collections; such 

data are critical to evaluating the vector potential of the population. 

References 

Barr, A.R., T.A. Smith, M.M. Boreham, and K.E. White. 1963. Evaluation of some factors 

affecting the efficiency of light traps in collecting mosquitoes. J. Econ. Entomol. 56:123-

127. 

Biggerstaff,BJ. 2003. Pooled infection rate. 

http://www.cdc.gov/ncidod/dvbid/westnile/software.htm : 1-5. 

Bidlingmeyer, W.L. 1969. The use of logarithms in analyzing trap collections. Mosq. News 

29:635-640. 

Cummings, R.F. 1992. The design and use of a modified Reiter gravid mosquito trap for 

 mosquito-borne encephalitis surveillance in Los Angeles County, California. Proceedings 

and Papers CMVCA 60:170-176. 

Loomis, E.C. and S.G. Hanks. 1959. Light trap indices of mosquito abundance: a comparison of 

operation for four and seven nights a week. Mosq. News 19:168-171. 

Komar, N., S. Langevin, S. Hinten, N. Nemeth, E. Edwards, D. Hettler, B. Davis, R. Bowen, and 

M. Bunning. 2003. Experimental infection of North American birds with the New York 

1999 strain of West Nile virus. Emerg. Infect. Dis. 9: 311-322. 

 Meyer, R.P., W.K. Reisen, B.R. Hill, and V.M. Martinez. 1983. The “AFS sweeper”, a battery 

powered backpack mechanical aspirator for collecting adult mosquitoes. Mosq. News 

43:346-350. 

Meyer, R.P. 1985. The “walk-in” type red box for sampling adult mosquitoes. Proc. New 

Jersey Mosq. Control Assoc. 72:104-105. 

Meyer, R.P. 1996. Mosquito surveillance and sampling methods in The Biology and Control of 

Mosquitoes in California (S. Durso, Ed.). Calif. Mosq. and Vector Control Assoc., Inc. 

Sacramento 

Meyer, R. P., W. K. Reisen and Vector and Vector-borne Disease Committee. 2003. 

 Integrated mosquito surveillance guidelines. Mosq. Vector. Contr. Assoc. Calif. 

Meyer, R. P., W.K.Reisen and Vector and Vector-borne Disease Committee. 2003. Integrated 

mosquito surveillance guidelines. Sacramento, California: MVCAC. 

Mulhern, T.D. 1953. Better results with mosquito light traps through standardizing 

 mechanical performance. Mosq. News 13:130-133. 

Pfuntner, A.P. 1979. A modified CO-baited miniature surveillance trap. Bull. Soc. Vector 

Ecol. 4:31-35. 

Reeves, W. C., M. M. Milby and W. K. Reisen. 1990. Development of a statewide arbovirus 

surveillance program and models of vector populations and virus transmission. pp.: 431-458. 

In: W. C. Reeves, (ed.) Epidemiology and control of mosquito-borne arboviruses in 

California, 1983-1987 Sacramento, Calif. Calif. Mosq. Vector Control Assoc., Inc. 

K8-26
Appendix A 

27 

Reisen, W. K., B. F. Eldridge, T. W. Scott, A. Gutierrez, R. Takahashi, K. Lorenzen, J. 

DeBenedictis, K. Boyce, and R. Swartzell. 2002. Comparison of dry ice-baited CDC and NJ 

light traps for measuring mosquito abundance. J. Am. Mosq. Control Assoc. 18: 158-163. 

Reisen, W. K., H. D. Lothrop, R. E. Chiles, M. B. Madon, C. Cossen, L. Woods, S. Husted, V. L. 

Kramer, and J. D. Edman. 2004. West Nile Virus in California. Emerg. Infect. Dis.8: 1369-

1378. 

Reisen, W. K., R. P. Meyer, R. F. Cummings, and O. Delgado. 2000. Effects of trap design and 

CO2 presentation on the measurement of adult mosquito abundance using CDC style 

miniature light traps. J. Am. Mosq. Control Assoc. 16: 13-18. 

Reiter, P. 1987. A revised version of the CDC gravid mosquito trap. J. Am. Mosq. Control 

Assoc. 3:325-327. 

K8-27
Appendix B 

28 

Appendix B: Procedures for Processing Mosquitoes for Arbovirus Detection 

1. Collect mosquitoes alive and return them immediately to the laboratory. Collections should 

be kept humid during transport with moist toweling to prevent desiccation. Females should 

be offered 5-10 percent sucrose if held overnight or longer before processing. 

 2. Anesthetize mosquitoes by cold, carbon dioxide, or triethylamine (TEA). TEA is 

recommended because specimens are permanently immobilized with minimal mortality and 

with no loss of virus titer. TEA should be used either outdoors or under a chemical hood. 

Collections can be anesthetized outdoors using a few drops of TEA, the specimens 

transferred to Petri dishes, and then taken into the laboratory for processing. If refrigerated 

and kept humid, mosquitoes will remain alive in covered Petri dishes for one or two days 

without additional anesthesia. If mosquitoes are frozen before processing, sorting to species 

and enumeration must be done on a chill table to prevent virus loss. 

 3. Sort mosquito collections to species under a dissecting microscope at 10X to ensure correct 

identification and to make sure that extraneous mosquito parts (i.e., legs, wings) or other 

small insects such as chironomids or Culicoides are not inadvertently included in the pools. 

This is extremely important because diagnostics have transitioned from virus isolation to 

sensitive RT-PCR methods of viral detection. Count and discard dead and dried mosquitoes. 

Lots of 50 females per pool of each vector species from each collection site are then counted 

into individual polystyrene vials with snap caps containing two 5mm glass beads. 

Recommended sampling effort is ten pools of 50 females of each species from each site per 

week to detect minimum infection rates (MIRs) ranging from 0 to 20 per 1,000 females 

tested. Vials with pools should be labeled sequentially starting with #1 each year after the 

site code; e.g., KERN-1-12; where 12 refers to year 2012. Data on each pool can be entered 

directly in electronic format through the California Vectorborne Disease Surveillance 

Gateway ( http://gateway.calsurv.org/). POOLS MUST BE ACCOMPANIED BY 

“MOSQUITO POOLS SUBMITTED FORM MBVS-3” AND CAN ONLY BE TESTED 

FROM REGISTERED SITES. Surveillance sites should be registered online at: 

http://gateway.calsurv.org/. Faxed registration forms (MBVS-1) will be accepted from 

agencies without adequate internet access. 

List the site code for each pool that consists of a designated four-letter agency code followed 

by six digits identifying the site, i.e., KERN000001. Keep the pool numbers in sequence for 

the whole year regardless of the number of site codes: e.g., pool #1 may be from 

KERN000001, and pool #2 may be from KERN000004. 

4. Freeze pools immediately at -70C either on dry ice in an insulated container or in an ultra-low 

temperature freezer. Pools should be shipped frozen on dry ice to CVEC for testing by real 

time multiplex RT-PCR. Pools received by noon on Wednesday will be tested and reported 

by Friday or sooner using the Gateway website and automated email notification, in addition 

to the routine reporting within the weekly Arbovirus Surveillance Bulletin. Each pool is 

screened for WNV, SLE, and WEE viruses by a multiplex assay, with positives confirmed 

by a singleplex RT-PCR. Pools from selected areas also are screened for additional viruses 

using Vero cell culture with isolates identified following sequencing. Care must be taken 

K8-28
Appendix B 

29 

not to allow pools to defrost during storage or shipment, because each freeze-thaw cycle 

may result in a 10-fold decrease in viral titer, and all virus will be lost if the specimens sit at 

room temperature for extended periods. Address shipment to: Ying Fang, Center for 

Vectorborne Diseases, VM: // PMI, 3336 VetMed 3A, University of California, Davis, , 

Davis CA 95616. Pools received by Wednesday will be tested and reported through the 

Gateway the same week. 

 5. Local agencies that conduct their own testing by RT-PCR or RAMP® tests need to complete 

and pass a proficiency panel each year for the results to be reported by CDPH. 

K8-29
Appendix C 

30 

Appendix C: Procedures for Maintaining and Bleeding Sentinel Chickens 

1. Procure hens in March or when they become available as notified by MVCAC when the 

chickens are 14-18 weeks of age to ensure minimal mortality during handling. Hens at this 

age have not yet begun to lay eggs, but they should have received all their vaccinations and 

been dewormed. 

2. Ten sentinel chickens can be housed in a 3Wx6Lx3H ft coop framed with 2x2 and 2x4 inch 

construction lumber and screened with no smaller than 1x1 inch welded wire. It is critical 

that the wire mesh be large enough to allow the mosquitoes to easily enter the coop and the 

coops be placed in locations with a history of arbovirus transmission and/or high mosquito 

abundance. The site of and band numbers located at each coop must be registered online at: 

http://gateway.calsurv.org/. Faxed registration forms (MBVS-1) will be accepted from 

agencies without adequate internet access. Coops should be at least two feet off the ground 

to reduce predator access, facilitate capture of the birds for bleeding, and allow the free 

passage of the feces through the wire floor to the ground. A single, hinged door should be 

placed in the middle of the coop, so that the entire coop is accessible during chicken 

capture. After construction, the lumber and roof should be protected with water seal. A 

self-filling watering device should be fitted to one end of the coop and a 25 lb. feeder suspended in the center for easy access. In exchange for the eggs, a local person (usually the 

home owner, farm manager, etc.) should check the birds (especially the watering device) 

and remove the eggs daily. If hung so the bottom is about four inches above the cage floor 

and adjusted properly, the feeder should only have to be refilled weekly (i.e., 100 lb. of feed 

per month per flock of ten birds). Therefore, if proper arrangements can be made and an 

empty 55-gallon drum provided to store extra feed, sentinel flocks need only be visited biweekly when blood samples are collected. 

3. Band each bird in the web of the wing using metal hog ear tags and appropriate pliers. This 

band number, the date, and site registration number must accompany each blood sample 

sent to the laboratory for testing. 

4. Bleed each hen from the distal portion of the comb using a standard lancet used for human 

finger "prick" blood samples. The bird can be immobilized by wedging the wings between 

the bleeder's forearm and thigh, thereby leaving the hand free to hold the head by grabbing 

the base of the comb with the thumb and forefinger. Use alcohol swabs on comb before 

bleeding. Blood samples are collected on half-inch wide filter paper strips, which should be 

labeled with the date bled and wing band number. The comb should be "pricked" with the 

lancet and blood allowed to flow from the "wound" to form a drop. Collect the blood by 

touching the opposite end of the pre-labeled filter paper strip to the wound. THE BLOOD 

MUST COMPLETELY SOAK THROUGH ON A 3⁄4 INCH LONG PORTION OF THE 

STRIP. Place the labeled end of the strip into the slot of the holder (or "jaws" of the clothes 

pin) leaving the blood soaked end exposed to air dry. 

5. Attach the completely dry filter paper strips to a 5x7 card in sequential order, from left to 

right by stapling the labeled end towards the top edge of the card, and leaving the blood 

soaked end free so that the laboratory staff can readily remove a standard punch sample. 

Write the County, Agency Code, Site, and Date Bled onto the card and place it into a zip 

lock plastic bag. Do not put more than one sample card per bag. It is important that 

blooded ends do not become dirty, wet, or touch each other. VERY IMPORTANT: 

CHICKEN SERA MUST BE ACCOMPANIED BY SENTINEL CHICKEN BLOOD 

K8-30
Appendix C 

31 

FORM (MBVS- 2) OUTSIDE THE ZIP-LOCK BAG. Do not staple the form to the bag. 

Samples from each bleeding date then can be placed into a mailing envelope and sent to: 

Department of Public Health, Richmond Campus 

Specimen Receiving Unit Room B106 (ATTN: ARBO)

850 Marina Bay Parkway 

Richmond, CA 94804 

 Specimens will be tested within 1-3 days upon receipt by the laboratory. 

6. In the laboratory, a single punch is removed from the blooded end of the paper and placed 

into one well of a 96-well plate with 150 l of diluent. Specimens are allowed to soak for 2 

hours on a rotator and the eluate is tested for WEE, SLE, and WNV IgG antibody using 

ELISA. Positive specimens are tested further with an indirect fluorescent antibody test and 

confirmed with a Western blot. Inconclusive SLE or WNV positives are confirmed and 

identified by cross-neutralization tests. Test results are made available online at: 

http://gateway.calsurv.org/. 

Reference 

Reisen, W.K. 1995. Guidelines for Surveillance and Control of Arboviral Encephalitis in 

 California, In: Interagency Guidelines for the Surveillance and Control of Selected 

 Vector-borne Pathogens in California, Mosquito and Vector Control Association of 

 California, Sacramento. 

K8-31
Appendix C 

32 

California Procedure for Testing Sentinel Chickens for the 

Presence of Antibodies to Flaviviruses (SLE and WNV) and WEE 

MVCD collects blood from 

comb of each chicken onto 

filter paper approx. every 

other week and enters data 

into Surveillance Gateway 

Local labs that test their 

own flocks send positive 

samples to CDPH for 

confirmation 

MVCD sends filter paper 

strips and submission 

report form to CDPH for 

arbovirus testing by EIA 

Local labs that test their 

own flocks send negative 

results to CDPH 

EIA positive samples 

tested by IFA and 

Western blot at CDPH 

Negative results 

reported immediately to 

submitting agency via 

Surveillance Gateway 

Inconclusive results may 

warrant CDPH request 

for whole blood sample 

Final test results reported 

immediately to submitting 

agency via Surveillance 

Gateway and listed in 

weekly bulletin 

Key: 

EIA: Enzyme immunoassay test 

IFA: Indirect fluorescent antibody test 

MVCD: Local Mosquito and Vector Control District/Health Dept. 

SLE: St. Louis encephalitis 

CDPH: CDPH Vector-Borne Disease Section, Richmond 

WEE: Western equine encephalitis 

WNV: West Nile virus encephalitis 

K8-32
Appendix C 

33 

Surveillance for Mosquito-borne Viruses 

Registration of Agencies and Sites 

1. Participation of agencies 

Agencies interested in participating in the statewide surveillance program for mosquito-borne 

viruses should place orders for mosquito pool testing by UC Davis Center for Vectorborne 

Diseases (CVEC) through the Mosquito and Vector Control Association (MVCAC). Sentinel 

chicken testing should be ordered through the California Department of Public Health (CDPH). 

Agencies will be billed in advance for the number of samples to be tested. 

Agencies are responsible for registering and maintaining updated information for their sites 

online at: http://gateway.calsurv.org/. 

2. Registration of sentinel flock sites and wing band numbers 

Agencies must use the unique band numbers assigned to their district by CDPH each year. Prior 

to submitting any sentinel chicken blood samples to CDPH, each agency must ensure that each 

flock site and accompanying band numbers are registered online at: http://gateway.calsurv.org/. 

CDPH will only test samples if they are accompanied by the form “SENTINEL CHICKEN 

BLOOD – 2012” (MBVS-2) for each flock site, which includes the registered agency code, the 

registered site code (assigned by local agency), the wing band numbers assigned to that site, and 

date bled. Also, the form should indicate any changes made and match the sample card 

exactly. 

3. Registration of mosquito sampling sites 

Registration of new sites used for collection of mosquitoes for virus testing may be accomplished 

by accessing the California Vectorborne Disease Surveillance Gateway 

http://gateway.calsurv.org/. Since 2010, the CalSurv Gateway has included enhanced spatial 

capabilities that allow users the option of directly entering geographic coordinates for sites or 

interactively selecting the location using a new Google Maps-based interface. The laboratory 

will test the pools provided that adequate information is provided on the “MOSQUITO POOL 

SUBMISSION” form (MBVS-3, revised 01/12/06), including your agency code, your site code 

for the site and geographic coordinates. 

The geographic coordinates will be used to generate computer maps that show all registered sites 

and test results for each site. Also, as part of a collaborative effort, CVEC will host real-time 

maps in ArcGIS format at http://maps.calsurv.org. In addition to these maps, agencies can 

access maps using Google Earth through the California Vectorborne Disease Surveillance 

Gateway (http://gateway.calsurv.org) that provide enhanced functionality and detail.

K8-33
Appendix D 

34 

Appendix D: Procedures for Testing Dead Birds and Squirrels 

In 2000, CDHS initiated a dead bird surveillance program in collaboration with other public 

agencies. CDPH annually notifies about 600 agencies, organizations, and veterinarians involved 

with wildlife, including rehabilitation centers, about the program. The public is also notified 

about the program through the media and outreach materials. Dead birds and squirrels are 

reported to CDPH or data entered electronically through the Surveillance Gateway 

[http://gateway.calsurv.org/] and shipped to the California Animal Health & Food Safety 

(CAHFS) laboratory at UC Davis for screening and removal of kidney tissue (an oral swab is 

taken instead if the bird is an American Crow), which is then sent to the UC Davis Center for 

Vectorborne Diseases (CVEC) for WNV RNA detection via RT-PCR. Beginning in 2010, 

results from RT-PCR testing at CVEC distinguished between WNV recent and chronic positive 

birds based on cycle threshold (Ct) values. Chronic positive birds did not likely die from WNV 

infection and are of limited value for surveillance. Overviews of the dead bird reporting and 

testing algorithms are provided below. 

Sick / Dead Bird Reporting Protocol for Public and Local Agencies 

Dead Bird Sick Bird 

CDPH Hotline / Web 

Wild Bird

CDFG

Disposal 

MVCA or local 

pick-up (AC etc.) 

AI testing 

(CAHFS)

WNV testing 

Wild Bird 

Local agency (AC, 

Rescue Group, 

CDFG, etc.) 

Domestic 

Poultry 

CDFA

B.I.R.D. System AUTOMATED 

EMAIL REPORTS

*

**

* domestic poultry, designated spp. 

** ≥ 5 birds, designated AI spp., water birds, shorebirds 

AC Animal Control 

AI Avian Influenza 

BIRD Bird Information Reporting Database (CDPH SQL Server) 

CAHFS CA Animal Health & Food Safety Laboratory 

CDFA California Department of Food & Agriculture: 

 California Bird Flu Hotline: 1-866-922-BIRD

CDFG California Department of Fish & Game 

 http://www.dfg.ca.gov/regions/index.html

CDPH California Department of Public Health 

West Nile virus & Dead Bird hotline: 1-877-968-BIRD

 website: www.westnile.ca.gov

MVCA Mosquito & Vector Control Agency 

K8-34
Appendix D 

35 

Procedures for Testing Dead Birds: RT-PCR

For multiple bird die-offs, VBDS 

contacts CDFG. 

Found within 24 hours of death 

and meets testing criteria; zip 

code “open” for testing. 

Dead Bird Found: 

Call CDPH Vector-Borne Disease 

Section (1-877-WNV-BIRD) or go to 

http://www.westnile.ca.gov for more 

information. Enter into Surveillance 

Gateway 

[http://gateway.calsurv.org/] 

Local agency obtains 

dead bird and delivers or 

ships on blue ice to 

CAHFS. 

VBDS contacts local agency to pick up 

dead bird, or coordinates for public dropoff when appropriate. Information on 

dead bird is faxed/emailed to local 

agency and CAHFS. VBDS reports 

submission by county in weekly 

Arbovirus Bulletin. CAHFS screens specimen to verify 

carcass is in a testable condition, 

then notifies VBDS of status. 

CAHFS removes kidney 

tissue/takes oral swab for RT-PCR 

testing by CVEC. 

Report will be recorded 

and noted in weekly 

bulletin, forwarded to 

agencies. 

Key: 

CAHFS: CA Animal Health and Food Safety Laboratory 

CD: Local Agency Communicable Disease Office 

CDFA: CA Dept. of Food and Agriculture 

CDFG: CA Dept. of Fish and GameCVEC: UC Davis 

Center for Vectorborne Diseases 

MVCD: Local Mosquito and Vector Control District 

USFWS: US Fish and Wildlife Service

VBDS: CDHS Vector-Borne Disease Section, Richmond 

VPHS: CDHS Veterinary Public Health Section, Sacramento 

IHC: Immunohistochemistry 

Negative Results: 

Submitting agency, 

CAHFS, local CD, 

local MVCD, 

CDFG, and other 

public agencies. 

Dead > 24hrs (e.g. 

stiff, presence of 

maggots); not a 

species targeted for 

testing. 

Laboratories enter test results into 

Surveillance Gateway 

VBDS sends dead bird 

results to: 

Positive Results: 

Submitting agency, CAHFS, 

VPHS, local CD, USFWS, 

CDFA, local MVCD, CDFG, 

and other public agencies. 

K8-35
Appendix D 

36 

Public reports dead bird to VBDS:

Is bird acceptable for 

West Nile virus (WNV) testing? 

Bird assigned state number 

and picked up by local agency or 

dropped off by public 

Dead bird reports available 

to agencies on request 

VBDS assigns primary identification 

Corvid or Non-Corvid? 

Corvid 

Send carcass to CAHFS; 

Tissue to CVEC; 

Results to CDPH

Has local vector control agency 

 passed proficiency panel for VecTest or 

RAMP? 

Test oral swab 

by VecTest 

or RAMP 

Send 

carcass 

to CAHFS 

STOP, submit results to 

VBDS by Friday by 

4:00pm 

STOP, submit results to 

VBDS by Friday by 

4:00pm 

No

Yes 

Non-corvid 

Yes No 

Negative 

Negative 

Crow Positive 

CVEC = Center for Vectorborne Disease Research 

VBDS = Vector-Borne Disease Section, California Department of Public Health 

CAHFS = California Animal Health and Food Safety Laboratory 

VBDS 

Local Agencies 

Procedures for Testing Dead Birds: Rapid Assays

K8-36
Appendix D 

37 

Dead Bird and Tree Squirrel Reporting and Submission Instructions for Local Agencies 

California West Nile Virus (WNV) Dead Bird & Tree Squirrel Surveillance Program 

California Department of Public Health (CDPH) 

Division of Communicable Disease Control 

When your agency receives a call from the public about a dead bird (especially recently dead 

crows, ravens, magpies, jays, or raptors) or dead tree squirrel, or one of your staff finds any dead 

bird, please immediately refer them to the CDPH West Nile Virus and Dead Bird Hotline at 

1-877-968-BIRD (2473). 

The Dead Bird Hotline is monitored 8am - 5pm, 7 days a week. CDPH will assess the 

suitability of the dead bird or tree squirrel for testing and contact your agency only if the carcass 

is approved for pickup. Any carcasses sent without prior notification will not be tested. 

Only agencies listed under the permit issued to CDPH from the California Department of Fish & 

Game are authorized to pick up dead birds and tree squirrels. The agencies covered include local 

mosquito abatement districts, environmental health departments, and other designated agencies.

Members of the public may salvage dead birds found on their property or place of residence. The 

public must first call the Dead Bird Hotline and obtain a Dead Bird Number; a 

corresponding public salvage submission form will then be faxed to the appropriate agency. The 

public will be instructed by the hotline staff to double-bag the carcasses and drop them off at the 

designated agency within 24 hours, between 9 am - 3 pm, Monday – Friday, and only in areas 

where local agencies are not picking up dead birds (e.g., closed zip codes), unless otherwise 

requested by the local agency. Note: only dead birds may be brought in by the public to local 

agencies for shipping. We discourage public salvage of all squirrels because ground 

squirrels, which could be infected with plague, may be misidentified as tree squirrels. 

web links: bird and tree squirrel ID chart (pdf) tree squirrel surveillance Q&A (pdf)

Once the submission is approved, your agency can ship the carcass to the California Animal 

Health & Food Safety laboratory at UC Davis (CAHFS Central). CAHFS Central removes 

specific tissues and forwards the samples to the UC Davis Center for Vectorborne Diseases 

(CVEC) for WNV testing. Shipping and testing expenses will be paid by CDPH. Carcasses are 

considered Category B, Biological Substances. This replaces the old designation, “Diagnostic 

Specimen”. 

To ensure the carcass arrives at CAHFS in a testable condition, to protect your safety, and to 

comply with shipping regulations, please follow these instructions: 

 

 Only dead birds and tree squirrels can be picked up under our permit. 

K8-37
Appendix D 

38 

 Wear rubber or latex gloves when handling all carcasses. If gloves are not available, use 

a plastic bag -- turned inside out -- over your hand and invert the bag to surround the 

carcass. Do not touch a carcass with bare hands. 

 Collect fresh carcasses. Badly decomposed or scavenged carcasses are of limited 

diagnostic value. Signs that a bird or squirrel has been dead for too long (over 24-48 

hours) are the presence of maggots, an extremely lightweight carcass, missing eyes, skin 

discoloration, skin or feathers that rub off easily, strong odor, or a soft, mushy carcass. 

 If upon pick-up the carcass is found to be unacceptable (e.g. a species your agency 

or CDPH is not accepting or a badly decomposed specimen), please collect the 

carcass, double-bag it, and dispose of it in a secure garbage can or dumpster. 

California Department of Fish & Game prefers that you burn or bury the carcass, but 

disposing of it in a dumpster is also acceptable. Please call CDPH immediately and 

notify us that the animal will no longer be submitted.

 Place each carcass into two sealed (zip-locked) plastic bags. Double-bagging prevents 

cross-contamination and leakage. There should always be two bags separating the 

carcass from shipping documents. 

 Enclose the shipping documents into a SEPARATE ZIP-LOCK BAG. The primary 

shipping document is a copy of the dead bird submission form which contains the dead 

bird number and which is located on the Surveillance Gateway 

[http://gateway.calsurv.org/] or faxed by CDPH. CAHFS prefers that you put this 

separate zip-lock bag inside the outer bag containing the dead bird or squirrel.

 Pack the carcass with blue ice packs. Please limit the number of ice packs to the 

number required to keep the carcass fresh, as the weight of extra ice packs add to the 

shipping charges. In accordance to shipping regulations, an absorbent material such as 

newspaper must be included in the box to prevent any leakage.

 Ship the carcass in a hard-sided plastic cooler or a styrofoam cooler placed in a cardboard 

box. Unprotected styrofoam containers cannot be shipped without an outer box or 

container, as they may break into pieces during shipment. Contact UPS/GSO directly to 

arrange for carrier pickup Monday through Thursday; this guarantees arrival at 

CAHFS before the weekend. 

 Contact UPS to pick up carcasses either by web 

(https://wwwapps.ups.com/pickup/schedule?loc=en_US) or by phone 1-800-PICK UPS

(1-800-742-5877). Select “UPS Next Day Air” and estimate the weight of the box 

(generally 10 lbs for a single large bird packed with ice). Please DO NOT UNDERESTIMATE the weight of a package. For billing, the UPS account number is: 23219W.

K8-38
Appendix D 

39 

 Carcasses that need to be stored for an extended time period (over 2 days) should be put 

on dry ice or stored at -70oC. If it is not possible to store carcass at -70oC, a carcass may 

be stored at 0oC (regular freezer) for a short period of time. Refrigerating the carcass is 

recommended for overnight storage only (this slows virus deterioration, but does not 

stop it). 

 CDPH will provide prepared shipping boxes with appropriate labels. Any empty boxes 

shipped to your agency from CDPH will have its caution labels covered by a sheet of 

paper with “EMPTY BOX” printed on it. Please discard this sheet of paper before using 

the box to ship out a dead bird. If you need additional boxes, please contact VBDS at 

(510) 412-6251 or email arbovirus@cdph.ca.gov. 

 Once West Nile virus is found in an area, agencies may test corvids via VecTest or 

RAMP assays. While results can be entered directly into the Surveillance Gateway, 

please notify CDPH with results by 4:00pm Friday of each week to have results 

included in reports for the following week’s State WNV updates. Reporting forms 

can be found at (http://www.westnile.ca.gov/resources.php). Note: any positive bird 

must be disposed of as biomedical waste (incineration). 

Dead Bird Shipping List 

Please verify that your agency has the following items: 

 CAHFS Address (see below) 

 UPS preprinted labels 

 WNV hotline number (877-968-BIRD; manned 8am - 5pm, 7 days a week) 

 Crumpled newspapers or another absorbent material 

 Rubber or Latex Gloves 

 Packing tape 

 Dead Bird Shipping Boxes 

- inner zip-lock bag 

- outer zip-lock bag 

- inner styrofoam box 

- outer cardboard box 

- blue ice packs 

California Animal Health & Food Safety (CAHFS) laboratories: 

CAHFS Central (530) 754-7372 

ATTN: WNV 

Jacquelyn Parker 

University of California, Davis 

West Health Science Drive 

Davis, CA 95616 

K8-39
Appendix E 

40 

Appendix E: Procedures for Testing Equines and Ratites 

The California Departments of Public Health (CDPH) and Food and Agriculture (CDFA) 

developed a cooperative passive surveillance program for equine and ratite encephalomyelitis. 

Primary responsibility for equine and ratite West Nile virus (WNV) surveillance rests with 

CDFA. Equine encephalomyelitides are legally reportable to CDFA by veterinarians and 

diagnostic laboratories pursuant to Section 9101 of the Food and Agricultural Code. Venezuelan 

equine encephalomyelitis is an emergency animal disease that must be reported to CDFA by 

telephone within 24 hours. 

This appendix contains information sent to veterinarians, public health lab directors, local health 

officers, public health veterinarians, animal health branch personnel, and interested parties every 

spring to inform them about the California Equine and Ratite Arbovirus Surveillance Program. 

The mailing includes a case definition for equine encephalomyelitides and instructions for 

specimen collection and submission for both equine and ratite samples. The information is 

distributed to approximately 1,200 practitioners, equine organizations, and other interested 

parties. Specimen submission is coordinated through the California Animal Health and Food 

Safety Laboratory System’s (CAHFS) and other laboratories or individual veterinarians. Equine 

serum and cerebrospinal fluid are tested by CAHFS using the ELISA test to detect anti-WNV 

IgM. Equine neurologic tissue specimens are also sent to CAHFS for microscopic examination 

and, as indicated by clinical findings, forwarded to the USDA National Veterinary Services 

Laboratories (NVSL) for further arbovirus testing. All fatal cases of equine encephalitides are 

first evaluated for rabies at the local public health laboratory. An algorithm outlining the 

protocol for specimen submission and reporting is available for participants in the program and is 

included in this appendix. 

Outreach is an important component of the program. CDPH and CDFA have developed and 

distributed educational materials concerning the diagnosis and reporting of arboviruses in 

equines and ratites. 

Additional information on WNV for veterinarians, horse owners, and ratite owners, is available 

from CDFA, Animal Health Branch (916) 900-5002, and at the CDFA website: 

http://www.cdfa.ca.gov/AHFSS/Animal_Health/WNV_Info.html. Information on submission of 

laboratory samples is available from CAHFS (530) 752-8700 and at CAHFS website: 

http://cahfs.ucdavis.edu. A brochure containing facts about California WNV surveillance and 

general information about prevention and control is available from CDPH (916) 552-9730 and at 

CDPH’s website: http://www.westnile.ca.gov; a special section for veterinarians and horse 

owners is available at: http://www.westnile.ca.gov/resources.php.

K8-40
Appendix E 

41 

Algorithm for Submission of Specimens from 

Domestic Animals with Neurologic Symptoms

 

Submit horse 

brain to local 

public health 

lab for rabies

testing

If rabies negative and viral 

encephalitis still suspected, 

brain sent to CAHFS for 

microscopic examination and 

WNV testing. Some 

arboviruses will be tested at 

NVSL or other diagnostic lab. 

Questions/Shipping 

Information: Call CAHFS at 

(530) 752-8700 or CDPH/AHB 

at (916) 900-5002. CAHFS or other diagnostic lab 

reports results to submitter. 

Positive results reported by phone 

or email to CDFA. A copy of the 

report is sent to CDPH/VPHS. 

Species: 

Horse 

Emu 

Ostrich 

Other 

Alive Dead 

Send acute and convalescent sera or 

CSF to CAHFS or other diagnostic 

lab for arbovirus serologic testing 

including the WNV IgM Capture 

ELISA test. Some arboviruses will 

be tested at NVSL or other 

diagnostic lab. If questions, call 

CAHFS at (530) 752-8700. 

Submit carcass to CAHFS 

for necropsy / histopath. 

Questions/Shipping 

Information: Call CAHFS 

at (530) 752-8700. 

Key: 

AHB: Animal Health Branch 

CAHFS: California Animal Health and Food Safety Laboratory 

NVSL: National Veterinary Services Laboratory 

VBDS: CDPH Vector-Borne Disease Section 

VPHS: CDPH Veterinary Public Health Section 

CDFA: California Department of Food and Agriculture 

CDPH: California Department of Public Health 

CDFA conducts investigation of 

lab-positive case. CDPH/VPHS 

reports preliminary results to 

CDPH/VBDS for notification of 

local agencies. 

K8-41
Appendix F 

42 

SURVEILLANCE CASE DEFINITIONS FOR WEST NILE VIRUS 

DISEASE IN EQUINES 

CONFIRMED CLINICAL CASE: 

A horse with compatible clinical signs including ataxia (stumbling, staggering, wobbly gait, or 

in-coordination) or at least two of the following: fever, circling, hind limb weakness, inability to 

stand, multiple limb paralysis, muscle fasciculation, proprioceptive deficits, blindness, lip 

droop/paralysis, teeth grinding, acute death. 

Plus one or more of the following: 

 Isolation of West Nile (WNV) virus from tissues1

 Detection of IgM antibody to WNV by IgM-capture ELISA in serum or CSF 

 An associated 4-fold or greater change in plaque-reduction neutralization test (PRNT) 

antibody titer to WNV in appropriately timed2

, paired sera 

 Positive polymerase chain reaction (PCR)3 for WNV genomic sequences in tissues1

 Positive IHC for WNV antigen in tissue (Note: this test has low sensitivity in equids) 

SUSPECT CLINICAL CASE4

: 

 Compatible clinical signs 

EXPOSED EQUID: 

 Detection of IgM antibody to WNV by IgM-capture ELISA in serum or CSF without any 

observable or noted clinical signs. 

Assumptions on which case definition is based: 

 Antibody in serum may be due to vaccination or a natural exposure; additional testing 

must be done to confirm WNV infection in a vaccinated horse. 

 IgM antibody in equine serum is relatively short-lived; a positive IgM-capture ELISA 

means exposure to WNV or rarely a closely related flavivirus (SLE) has occurred, very 

likely within the last three months. 

1

 Preferred diagnostic tissue are equine brain or spinal cord; although tissues may include blood or CSF, the only known reports

of WNV isolation or positive PCR from equine blood or CSF have been related to experimentally infected animals. 2

 The first serum should be drawn as soon as possible after onset of clinical signs and the second drawn at least seven days after 

the first. 

3 For horses it is recommended that RT-nested polymerase chain reaction assay be used to maximize sensitivity of the test 

(Emerg. Infect. Dis. 2001 Jul-Aug; 7(4):739-41) 

4

An equine case classified as a suspect case should, if possible, undergo further diagnostic testing 

to confirm or rule out WNV as the cause of the clinical illness. 

NOTE: A HORSE WITH SIGNS OF ENCEPHALITIS MAY HAVE 

RABIES – TAKE PROPER PRECAUTIONS

K8-42
Appendix F 

43 

Protocol for Submission of Laboratory Specimens for 

Equine Neurological Disease Diagnosis and Surveillance 

1. Specimen collection and submission: 

A. Blood 

 Acute sample (5-10 ml) / no later than 7 days after onset 

 Convalescent sample (5-10 ml) / 14-21 days after onset 

Red top tubes of whole blood or serum (no preservatives or anticoagulants) 

should be submitted at ambient temperature to the California Animal Health 

and Food Safety (CAHFS) Laboratory* in your area. Do not freeze whole 

blood. 

 NOTE: For WNV, an acute sample only is required since the assay used 

detects IgM (and vaccine does not interfere). For the other encephalitis 

viruses, the acute sample should be submitted immediately, and a 

convalescent sample may be requested later to assist with the interpretation 

and differentiation of vaccine titers from active infection. 

B. Brain 

 The local health department and CDFA/Animal Health District Office should 

be contacted if rabies is suspected. 

 The animal or intact head should be submitted to a CAHFS laboratory in 

your area as quickly as possible. The intact head should be refrigerated, not 

frozen, immediately after removal using a leak-proof insulated transporting 

container with "cold packs" to keep the specimen at 4o

 C while in transit. 

When it is impossible for the CAHFS Laboratory to receive the carcass or 

chilled intact head within 48 hours, the submission protocol should be 

coordinated with the CAHFS Laboratory. Submission of the head intact is 

preferable to removal of the brain because: 1) the brain is better preserved 

(anatomically and virus titer) when left in the skull during transport, 2) 

specimens may be compromised if removal is not performed correctly, and 3) 

brain removal in field conditions may increase the risk of exposure to rabies. 

 All equine specimens submitted first to the CAHFS Laboratory will be 

forwarded to: 1) a Public Health Laboratory to initially confirm or rule out 

rabies, then to 2) The National Veterinary Services Laboratories (NVSL) for 

arboviral testing, in addition to a complete diagnostic work-up at the CAHFS. 

 All equine specimens submitted first to local public health laboratories for 

rabies testing and found to be negative should be forwarded to the local 

CAHFS Laboratory for arboviral testing. 

 C. Other specimens for differential neurological diagnoses 

 Protocol for submission of these specimens may be coordinated through the 

CAHFS Laboratory, and may include sampling for equine herpes virus, EPM, 

or other agents associated with clinical neurological presentations.

Complete information on specimen collection and submission is available on the CDFA 

website at: http://www.cdfa.ca.gov/ahfss/Animal_Health/WNV_Lab_Submission.html 

K8-43
Appendix F 

44 

2. Submission forms: Complete and include the transmittal forms supplied by the CAHFS 

Laboratory. See attached sample or download the form from their website: 

http://cahfs.ucdavis.edu/. The submittal form for each specimen should be placed in a leakproof plastic bag and attached to the corresponding container.

3. Imperative information to include on the submission forms if West Nile virus is 

suspected: Precision case reporting by the veterinary practitioner is critical to mosquito 

control efforts that prevent WNV infection in both horses and humans. It is very important 

that each laboratory submission form is completed in its entirety. More specifically, it is 

imperative to include and communicate to us: 

 The location(s) of the horse during the two weeks prior to the onset of clinical 

disease. (Please ensure that this information is included in addition to the 

“owner’s address”) 

 Detailed clinical signs. 

 The present condition of the horse (including dead and euthanized). 

 An accurate vaccination history. 

 4. Shipment: For information on sample shipping including regulations governing the 

transportation of infectious materials contact CAHFS at 530-752-7578. 

K8-44
Appendix F 

45 

Appendix F: Protocol for Submission of Laboratory Specimens 

for Human West Nile Virus Testing 

West Nile virus (WNV) testing within the regional public health laboratory network (i.e., the 

California Department of Public Health Viral and Rickettsial Disease Laboratory and 

participating local public health laboratories) is recommended for individuals with the following 

symptoms, particularly during West Nile virus “season,” which typically occurs from July 

through October in California: 

A. Encephalitis 

B. Aseptic meningitis (Note: Consider enterovirus for individuals  18 years of age) 

C. Acute flaccid paralysis; atypical Guillain-Barré Syndrome; transverse myelitis; or 

D. Febrile illness* 

- Illness compatible with West Nile fever and lasting  7 days 

- Must be seen by a health care provider 

------------------------------------------------------------------------------------------------------------ 

* The West Nile fever syndrome can be variable and often includes headache and fever 

(T ≥ 38°C). Other symptoms include rash, swollen lymph nodes, eye pain, nausea, or 

vomiting. After initial symptoms, the patient may experience several days of fatigue 

and lethargy. 

Required specimens: 

 Acute serum:  2cc serum 

If a lumbar puncture is performed and residual CSF is available: 

 Cerebral spinal fluid (CSF): 1-2cc CSF for further testing at CDC (N.B. these results 

may not be available for several weeks) 

If West Nile virus is highly suspected and acute serum is negative or inconclusive, request: 

 2nd serum:  2cc serum collected 3-5 days after acute serum 

Contact your local health department for instructions on where to send specimens. 

K8-45
Appendix G 

46 

Appendix G: Surveillance Case Definition for 

West Nile Virus Infection in Humans 

West Nile virus infection is reportable to local health departments under Title 17 of the 

California Code of Regulations. Below is the case definition for West Nile virus disease as 

summarized by the Centers for Disease Control and Prevention (CDC) [available at 

http://www.cdc.gov/ncidod/dvbid/westnile/clinicians/surveillance.htm#casedef]. Blood donors 

that test positive for West Nile virus through blood bank screening should also be reported to 

CDPH, regardless of clinical presentation. 

CASE DEFINITION: West Nile Virus 

NOTE: This definition is for public health surveillance purposes only. It is not intended for use 

in clinical diagnosis. 

Clinical Description

Arboviral infections may be asymptomatic or may result in illnesses of variable severity 

sometimes associated with central nervous system (CNS) involvement. When the CNS is 

affected, clinical syndromes ranging from febrile headache to aseptic meningitis to encephalitis 

may occur, and these are usually indistinguishable from similar syndromes caused by other 

viruses. Arboviral meningitis is characterized by fever, headache, stiff neck, and pleocytosis. 

Arboviral encephalitis is characterized by fever, headache, and altered mental status ranging 

from confusion to coma with or without additional signs of brain dysfunction (e.g., paresis or 

paralysis, cranial nerve palsies, sensory deficits, abnormal reflexes, generalized convulsions, and 

abnormal movements). 

Laboratory Criteria for Diagnosis 

 Fourfold or greater change in virus-specific serum antibody titer, or 

 Isolation of virus from or demonstration of specific viral antigen or genomic sequences in 

tissue, blood, cerebrospinal fluid (CSF), or other body fluid, or 

 Virus-specific immunoglobulin M (IgM) antibodies demonstrated in CSF by antibodycapture enzyme immunoassay (EIA), or 

 Virus-specific IgM antibodies demonstrated in serum by antibody-capture EIA and 

confirmed by demonstration of virus-specific serum immunoglobulin G (IgG) antibodies 

in the same or a later specimen by another serologic assay (e.g., neutralization or 

hemagglutination inhibition). 

Case Classification 

 Probable: An encephalitis or meningitis case occurring during a period when arboviral 

transmission is likely and with the following supportive serology: 1) a single or stable 

(less than or equal to twofold change) but elevated titer of virus-specific serum 

antibodies; or 2) serum IgM antibodies detected by antibody-capture EIA but with no 

available results of a confirmatory test for virus-specific serum IgG antibodies in the 

same or a later specimen. 

 Confirmed: An encephalitis or meningitis case that is laboratory confirmed. 

K8-46
Appendix G 

47 

Comment 

 Because closely related arboviruses exhibit serologic cross-reactivity, positive results of 

serologic tests using antigens from a single arbovirus can be misleading. In some 

circumstances (e.g., in areas where two or more closely related arboviruses occur, or in 

imported arboviral disease cases), it may be epidemiologically important to attempt to 

pinpoint the infecting virus by conducting cross-neutralization tests using an appropriate 

battery of closely related viruses. This is essential, for example, in determining that 

antibodies detected against St. Louis encephalitis virus are not the result of an infection 

with West Nile (or dengue) virus, or vice versa, in areas where both of these viruses 

occur. 

 The seasonality of arboviral transmission is variable and depends on the geographic 

location of exposure, the specific cycles of viral transmission, and local climatic 

conditions. 

Asymptomatic West Nile Virus Infection: Asymptomatic infection with WNV, which is 

generally identified in blood donors, is also reportable. WNV-positive blood donors detected by 

blood banks are reported directly to local health departments. Blood donors who test positive for 

WNV may not necessarily be ill, nor will they initially have positive IgM or IgG antibody test 

results. Local health departments should report blood donors who meet the following criteria for 

being a presumptively viremic donor to CDPH: 

A presumptively viremic donor (PVD) is a person with a blood donation that meets at least 

one of the following criteria: 

a) One reactive nucleic acid-amplification (NAT) test with signal-to-cutoff (S/CO) ≥ 17 

b) Two reactive NATs 

Additional serological testing is not required. Local health departments should follow up with the 

donor after two weeks of the date of donation to assess if the patient subsequently became ill. If 

the donor did become ill as a result of WNV infection, an updated case report form should be 

sent to CDPH so that the blood donor may be reclassified as a clinical case. 

---------------------------------------------------------------------------------------------------------------------

Note: Due to the continued risk of unintentional or intentional introduction of exotic arboviruses 

into the United States (e.g., Venezuelan equine encephalitis virus), or the reemergence of 

indigenous epidemic arboviruses (e.g., St. Louis encephalitis and western equine encephalitis 

viruses), physicians and local public health officials should maintain a high index of clinical 

suspicion for cases of potential exotic or unusual arboviral etiology, and consider early 

consultation with arboviral disease experts at state health departments and CDC. 

K8-47
Appendix H 

48 

Appendix H: Compounds Approved for Mosquito Control in California 

Label rates and usage vary from year to year and geographically; consult your County 

Agricultural Commissioner and the California Department of Fish and Game before application. 

Examples of products containing specific active ingredients are provided below, but this is not an 

inclusive list nor constitutes product endorsement. For more information on pesticides and 

mosquito control, please refer to the Environmental Protection Agency (EPA) Web site: 

http://www.epa.gov/opp00001/factsheets/westnile.htm 

Larvicides:

1. Bacillus thuringiensis subspecies israelensis (Bti: e.g. Aquabac 200G, VectoBac 12AS, 

Teknar HP-D) 

 Use: Approved for most permanent and temporary bodies of water. 

 Limitations: Only works on actively feeding stages. Does not persist well in the water 

column. 

2. Bacillus sphaericus (Bs: e.g. VectoLex CG) 

 Use: Approved for most permanent and temporary bodies of water. 

Limitations: Only works on actively feeding stages. Does not work well on all species. May 

persist and have residual activity in some sites. 

3. Spinosad (e.g. NatularTM G30) 

Limitations: Effective against all larval stages and moderately effective against pupal stage. 

Toxic via ingestion and contact. Some formulations approved for use in OMRI certified 

organic crops. 

4. IGRs (Insect Growth Regulators) 

 a. (S)-Methoprene (e.g. Altosid Pellets) 

 Use: Approved for most permanent and temporary bodies of water. 

 Limitations: Works best on older instars. Some populations of mosquitoes may show some 

resistance. 

 b. Diflurobenzamide (e.g. Dimilin25W) 

 Use: Impounded tail water, sewage effluent, urban drains and catch basins. 

 Limitations: Cannot be applied to wetlands, crops, or near estuaries. 

5. Larviciding oils (e.g.Bonide) 

 Use: Ditches, dairy lagoons, floodwater. Effective against all stages, including pupae. 

 Limitations: Consult with the California Department of Fish and Game for local restrictions. 

6. Monomolecular films (e.g. Agnique MMF) 

 Use: Most standing water including certain crops. 

 Limitations: Does not work well in areas with unidirectional winds in excess of ten mph. 

7. Temephos (e.g. Abate® 2-BG) 

 Use: Non-potable water; marshes; polluted water sites 

K8-48
Appendix H 

49 

 Limitations: Cannot be applied to crops for food, forage, or pasture. This material is an 

organophosphate compound and may not be effective on some Culex tarsalis populations in 

the Central Valley. May require sampling and testing per General Vector Control NPDES 

permit requirements if applied to waters of the United States. 

Adulticides:

1. Organophosphate compounds 

 Note: Many Culex tarsalis populations in the Central Valley are resistant at label OP 

application rates. 

 a. Malathion (e.g. Fyfanon ULV) 

Use: May be applied by air or ground equipment over urban areas, some crops 

including rice, wetlands.

Limitations: Paint damage to cars; toxic to fish, wildlife and bees; crop residue 

limitations restrict application before harvest. 

 b. Naled (e.g. Dibrom Concentrate, Trumpet EC) 

Use: Air or ground application on fodder crops, swamps, floodwater, residential areas. 

 Limitations: Similar to malathion. 

 

2. Pyrethrins (natural pyrethrin products: e.g. Pyrenone Crop Spray, Pyrenone 25-5, 

Evergreen) 

 Use: Wetlands, floodwater, residential areas, some crops. 

 Limitations: Do not apply to drinking water, milking areas; may be toxic to bees, fish, and 

some wildlife. Some formulations with synergists have greater limitations. 

3. Pyrethroids (synthetic pyrethrin products containing deltamethrin, cyfluthrin, permethrin, 

resmethrin, sumithrin or etofenprox: e.g. Suspend SC, Tempo Ultra SC, Aqua-Reslin, 

Scourge Insecticide, Anvil 10+10 ULV, Zenivex E20, and Duet – which also contains 

the mosquito exciter prallethrin) 

 Use: All non-crop areas including wetlands and floodwater. 

 Limitations: May be toxic to bees, fish, and some wildlife; avoid treating food crops, 

drinking water or milk production.

K8-49
Appendix H 

50 

PESTICIDES USED FOR MOSQUITO CONTROL IN CALIFORNIA 

Larvicides 

Active Ingredient Trade 

name 

EPA 

Reg. 

No. 

Mfgr. Formulation Application 

Pesticide 

classification 

Bacillus sphaericus, 

(Bs) 

VectoLex CG 

/ WSP 73049-20 Valent BioSciences 

Granule 

Water soluble 

packet 

Larvae Biorational 

Bacillus sphaericus, 

(Bs)

VectoLex 

WDG 73049-57 Valent 

BioSciences 

Water dispersible 

granule Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti)

VectoBac 

WDG 73049-56 Valent 

BioSciences 

Water dispersible 

Granules Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) 

VectoBac 

12AS 73049-38 Valent BioSciences Liquid Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) VectoBac AS 275-52 Abbott Labs Liquid Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) VectoBac G 73049-10 Valent 

BioSciences 

Granule 

Flake Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) VectoBac GS 73049-10 Valent BioSciences 

Granule 

Flake Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti)

VectoBac 

Tech. Pdr. 73049-13 Valent BioSciences Technical powder Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) 

Aquabac 

200G 62637-3 Becker 

Microbial Granule Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) Consume MP 62637-3 Spartan Chemical Granule Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) Aquabac XT 62637-1 Becker Microbial Liquid Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) 

Bactimos 

PT 73049-452 Valent 

BioSciences Granular flake Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti)

Teknar 

HP-D 73049-404 Valent 

BioSciences Liquid Larvae Biorational 

Bacillus thuringiensis 

var. israelensis (Bti) Fourstar SBG 85685-1 

Fourstar 

Microbials 

LLC 

Granule Larvae Biorational 

Bti / Bs combination Vectomax G, 

CG, WSP 73049-429 Valent BioSciences 

Granular and water 

soluble packet Larvae Biorational 

Bti / Bs combination Fourstar 

Briquettes 83362-3 

Fourstar 

Microbials 

LLC 

Briquette Larvae Biorational 

Spinosad Natular 2EC 8329-82 Clarke Liquid concentrate Larvae and 

pupae 

Biorational 

Spinosad Natular G 8329-80 Clarke Granule Larvae and 

pupae 

Biorational 

Spinosad Natural G30 8329-83 Clarke Granule Larvae and 

pupae 

Biorational 

Spinosad Natular T30 8329-85 Clarke Tablet Larvae and 

pupae 

Biorational 

Spinosad Natular XRT 8329-84 Clarke Tablet Larvae and 

pupae 

Biorational 

Monomolecular film Agnique 

MMF 53263-28 Cognis Corp. Liquid Larvae and 

pupae 

Surface film 

Monomolecular film Agnique 

MMF G 53263-30 Cognis Corp. Granular Larvae and pupae 

Surface film 

K8-50
Appendix H 

51 

Monomolecular film 

Agnique 

MMF G Pak 

35 

53263-30 Cognis Corp. Water soluble pack Larvae and 

pupae 

Surface film 

Petroleum oil Masterline 

Kontrol 73748-10 Univar Liquid Larvae and pupae 

Surface film 

Petroleum oil BVA 2 70589-1 B-V Assoc. Liquid Larvae and 

pupae 

Surface film 

Petroleum oil GB-1111 8329-72 Clarke Liquid Larvae and 

pupae 

Surface film 

Dimilin Dimilin 25W 400-465 Uniroyal 

Chemical Wettable powder Larvae IGR 

S-Methoprene Altosid 

ALLC 2724-446 WellmarkZoecon Liquid concentrate Larvae IGR 

S-Methoprene Altosid ALL 2724-392 WellmarkZoecon Liquid concentrate Larvae IGR 

S-methoprene Altosid 

Briquets 2724-375 WellmarkZoecon Briquet Larvae IGR 

S-methoprene Altosid 

Pellets / WSP 2724-448 WellmarkZoecon 

Pellet-type 

granules / water 

soluble packet 

Larvae IGR 

S-methoprene Altosid SBG 2724-489 WellmarkZoecon Granule Larvae IGR 

S-methoprene Altosid XR 

Briquets 2724-421 WellmarkZoecon Briquet Larvae IGR 

S-methoprene Altosid XR-G 2724-451 WellmarkZoecon Granule Larvae IGR 

Temephos Abate 2-BG 8329-71 Clarke Granule Larvae OP 

Temephos 5% Skeeter 

Abate* 8329-70 Clarke Granule Larvae OP 

Temephos Abate 4E 8329-69 Clarke Liquid Larvae OP 

K8-51
Appendix H 

52 

PESTICIDES USED FOR MOSQUITO CONTROL IN CALIFORNIA 

Adulticides 

Active Ingredient Trade 

name 

EPA 

Reg. No. Mfgr. Formulation Stage Pesticide 

classification 

Malathion Fyfanon ULV 67760-34 Cheminova Liquid Adults OP 

Naled Trumpet EC 5481-481 AMVAC Liquid Adults OP 

Prallethrin 

Sumithrin 

AquaDuet 

Adulticide 

1021-2562-

8329 Clarke Liquid Adults Pyrethroid 

Prallethrin 

Sumithrin 

Duet Dual 

Action 

Adulticide 

1021-1795 Clarke Liquid Adults Pyrethroid 

Deltamethrin Suspend SC 432-763 Aventis Liquid Adults Pyrethroid 

Cyfluthrin Tempo SC 

Ultra 432-1363 Bayer Liquid Adults Pyrethroid 

Permethrin Aqua-Kontrol 73748-1 Univar Liquid Adults Pyrethroid 

Permethrin Aqualeur 20-20 769-985 

Value 

Garden 

Supply 

Liquid Adults Pyrethroid 

Permethrin Aqua-Reslin 432-796 Bayer Liquid Adults Pyrethroid 

Permethrin Biomist 4+4 8329-35 Clarke Liquid Adults Pyrethroid 

Permethrin Biomist 4+12 

ULV 8329-34 Clarke Liquid Adults Pyrethroid 

Permethrin Evoluer 4-4 

ULV 769-982 

Value 

Garden 

Supply 

Liquid Adults Pyrethroid 

Permethrin Kontrol 2-2 73748-3 Univar Liquid Adults Pyrethroid 

Permethrin Kontrol 4-4 73748-4 Univar Liquid Adults Pyrethroid 

Permethrin Kontrol 30-30 73748-5 Univar Liquid Adults Pyrethroid 

Permethrin Permanone 

31-66 432-1250 Bayer Liquid Adults Pyrethroid 

Permethrin Permanone

Ready-To-Use 432-1277 Bayer Liquid Adults Pyrethroid 

K8-52
Appendix H 

53 

Permethrin Perm-X UL 4-4 655-898 Prentiss Liquid Adults Pyrethroid 

Pyrethrins Aquahalt 1021-1803 Clarke Liquid Adults Pyrethroid 

Pyrethrins Evergreen 60-6 1021-1770 MGK Liquid Adults Pyrethroid 

Pyrethrins Pyrenone 

25-5 432-1050 Bayer Liquid Adults Pyrethroid 

Pyrethrins Pyrenone

Crop Spray 432-1033 Bayer Liquid Adults Pyrethroid 

Pyrethrins Pyrocide

7453 1021-1803 MGK Liquid Adults Pyrethroid 

Pyrethrins Pyrocide

7395 1021-1570 MGK Liquid Adults Pyrethroid 

Pyrethrins Pyrocide

7396 1021-1569 MGK Liquid Adults Pyrethroid 

Pyrethrins Pyronyl Crop 

Spray 655-489 Prentiss Liquid Adults Pyrethroid 

Pyrethrins Pyronyl Oil 525 655-471 Prentiss Liquid Adults Pyrethroid 

Pyrethrins Pyronyl Oil 

3610A 655-501 Prentiss Liquid Adults Pyrethroid 

Resmethrin 

Scourge

Insecticide 

(4%) 

432-716 Bayer Liquid Adults Pyrethroid 

Resmethrin 

Scourge

Insecticide 

(18%) 

432-667 Bayer Liquid Adults Pyrethroid 

Sumithrin Anvil 2+2 ULV 1021-1687 Clarke Liquid Adults Pyrethroid 

Sumithrin Anvil 10+10 

ULV 1021-1688 Clarke Liquid Adults Pyrethroid 

Sumithrin AquaANVIL 1021-1807 Clarke Liquid Adults Pyrethroid 

Etofenprox Zenivex E4 

RTU 2724-807 Wellmark Intl. Liquid Adults Pyrethroid 

Etofenprox Zenivex E20 2724-791 Wellmark, 

Intl. Liquid Adults Pyrethroid 

Lambda-cyhalothrin Demand CS 100-1066 Syngenta Liquid Adults Pryethroid 

K8-53
Appendix I 

54 

Appendix I: Adult Mosquito Control in Urban Areas 

Adult mosquito control via ultra low volume (ULV) application is an integral part of an 

integrated mosquito management program. This response plan recommends the consideration of 

adult mosquito control to break local virus transmission cycles and reduce the risk of human 

infection. The following provides guidelines for local agencies considering ground or aerial ULV 

control of adult mosquitoes. Agencies should ensure they are complying with NPDES permit 

requirements. 

Preparatory steps for aerial application contracts 

 Send out request for proposals (RFP) to commercial applicators well in advance of any 

potential need for actual treatment. Specify required equipment and abilities in the RFP 

such as: 1) application equipment capable of producing desired droplet spectrum and 

application rate, 2) aircraft availability time frames, and 3) the demonstrated ability to 

apply the chosen product to the target area in accordance with label requirements. 

 Outline the desired capabilities and equipment within the RFP such as: 1) onboard real 

time weather systems, and 2) advanced onboard drift optimization and guidance software. 

 Determine in advance whether the vector control agency or contractor will secure and 

provide pesticides. If the contractor will supply the pesticide, verify their knowledge of 

and ability to comply with regulations regarding the transport, use, and disposal of all 

pesticide and containers. 

 Enter into a contingency contract with the commercial applicator. 

 Consider acquiring non-owned, multiple engine aircraft insurance with urban application 

endorsement for added protection. 

 Determine product and application rate to be used, along with a contingency plan. The 

product choice may be subject to change depending on product availability, the 

determination of resistance, labeling restrictions, environmental conditions, or other 

unforeseen factors. 

Preparatory steps for ground-based applications 

 Ensure that application equipment has been properly calibrated and tested for droplet size 

and flow rate. The vector control agency should have enough equipment, operators, and 

product available to finish the desired application(s) between sunset and midnight, or 

within 2-3 hours pre-sunrise (or when mosquitoes are demonstrated to be most active) to 

maximize efficacy. 

 Ensure that vehicles are equipped with safety lighting and appropriate identifying signs; 

use sufficient personnel. 

 Contact local law enforcement and provide them with locations to be treated and 

approximate time frames. 

 Consider using lead and trailing vehicles particularly if the area has not been treated 

before and personnel are available. 

K8-54
Appendix I 

55 

Implementing an aerial application contract 

 Contact commercial applicator and determine availability. 

 Review long-term weather forecasts. Ideally applications should be scheduled during 

periods of mild winds to avoid last minute cancellations. 

 Contractor should: 

o Contact Local Flight Standards District Office (FSDO) for low flying waiver. 

o Arrange for suitable airport facilities. 

o Contact local air traffic control. 

o Locate potential hazards prior to any application and implement a strategy to 

avoid those hazards during the application – often in darkness. 

o Provide equipment and personnel for mixing and loading of material (if 

previously agreed upon in contract). 

o Register with applicable County Agricultural Commissioners office. 

 Vector control agency should: 

o Delineate treatment block in a GIS format and send to contractor. 

o Identify areas that must be avoided during an application and include detailed 

maps of those areas to contract applicators (e.g. open water, registered organic 

farms, any area excluded by product label). 

o Send authorization letter to FSDO authorizing contractor to fly on the agency's 

behalf; contractor should provide contact information and assistance. 

o Send map of application area and flight times / dates to local air traffic control; 

contractor should provide contact information and assistance. 

o Consult with County Agricultural Commissioners office. Commissioner's office 

can provide guidance on contacting registered bee keepers and help identify any 

registered organic farms that may need to be excluded from application. 

o If vector control agency is providing material, ensure adequate quantity to 

complete mission and that the agency has means to transport material. 

Efficacy evaluation for aerial or ground based application 

 Choose appropriate method(s) for evaluating efficacy of application 

o Determine changes in adult mosquito population via routine surveillance. 

o Conduct three day pre and post-trapping in all treatment and control areas. 

o Set out bioassay cages with wild caught and laboratory reared (susceptible) 

mosquitoes during application. 

 Ensure adequate planning so surveillance staff is available and trained, equipment is 

available, and trap / bioassay cage test locations are selected prior to application. 

 Ensure efficacy evaluation activities are timed appropriately with applications. 

 Enlist an outside agency such as CDPH and/or university personnel to help evaluate 

efficacy of application as appropriate. 

K8-55
Appendix I 

56 

Actions at time of application 

 Confirm application rate with contractor. 

 Confirm treatment block. 

 Coordinate efficacy evaluations. 

Public notification 

Notification of the public prior to a mosquito control pesticide application by a vector control 

agency signatory to a Cooperative Agreement with CDPH, or under contract for such agency is 

not a legal requirement in California (California Code of Regulations – Title 3: Food and 

Agriculture: Division 6. Pesticides and Pest Control Operations: Section 6620a). However, 

public notification of pending adult mosquito control is recommended as early as possible prior 

to the treatment event. 

Basic notification steps 

 Provide notification of pending application as early as possible. 

 Post clearly defined treatment block map online or through appropriate media outlet. 

 Post product label and material safety data sheet (MSDS) online or through appropriate 

media outlet. 

 Post and/or have available scientific publications regarding the efficacy of aerial or 

ground based applications (as appropriate), including effects on non-target organisms and 

risk-assessments. 

Public relations considerations 

 Ensure staffing is adequate to handle a significant increase in phone calls. 

 Ensure website capability is adequate to handle a rapid increase in visitors. 

 Train personnel answering phones to address calls from citizens concerned about 

personal and environmental pesticide exposure. 

 Ensure adequate follow-through for calls related to sporting events, concerts, weddings, 

and other outdoor events that may be scheduled during the application and within the 

treatment block

K8-56
Appendix J 

57 

Appendix J: Websites Related to Arbovirus Surveillance, Mosquito Control, Weather 

Conditions and Forecasts, and Crop Acreage and Production in California 

Website URL Available information

California West Nile Virus Website http://westnile.ca.gov 

Up to date information on the spread of 

West Nile virus throughout California, 

personal protection measures, online dead 

bird reporting, bird identification charts, 

mosquito control information and links, 

clinician information, local agency 

information, public education materials. 

UC Davis Center for Vectorborne Diseases http://cvec.ucdavis.edu/ 

Frequently updated reports and interactive 

maps on arbovirus surveillance and 

mosquito occurrence in California. 

Mosquito and Vector Control Association of 

California http://www.mvcac.org 

News, membership information, event 

calendars, and other topics of interest to 

California’s mosquito control agencies. 

California Vectorborne Disease Surveillance 

Gateway http://gateway.calsurv.org Data management system for California’s mosquito control agencies. 

California Data Exchange Center http://cdec.water.ca.gov 

Water-related data from the California 

Department of Water Resources, including 

historical and current stream flow, snow 

pack, and precipitation information. 

UC IPM Online http://www.ipm.ucdavis.edu 

Precipitation and temperature data for 

stations throughout California; also allows 

calculation of degree-days based on userdefined data and parameters. 

National Weather Service – Climate Prediction 

Center 

http://www.cpc.ncep.noaa.gov

/products/predictions/ 

Short-range (daily) to long-range (seasonal) 

temperature and precipitation forecasts. 

Also provides El Niño-related forecasts. 

California Agricultural Statistics Service http://www.nass.usda.gov/Stat

istics_by_State/California 

Crop acreage, yield, and production 

estimates for past years and the current 

year’s projections. Reports for particular 

crops are published at specific times during 

the year – see the calendar on the website. 

State Water Resources Control Board 

http://www.swrcb.ca.gov/ 

water_issues/programs/npdes/

aquatic.shtml 

National Pollutant Discharge Elimination 

System (NPDES) permit for vector control 

information. 

US Environmental Protection Agency –

Mosquito Control 

http://www.epa.gov/pesticides

/health/mosquitoes 

Describes the role of mosquito control 

agencies and products used for mosquito 

control. 

US Centers for Disease Control and Prevention 

– West Nile Virus 

http://www.cdc.gov/ncidod/dv

bid/westnile/index.htm 

Information on the transmission of West 

Nile virus across the United States, viral 

ecology and background on WNV, and 

personal protection measures in various 

languages. 

K8-57

APPENDIX K9. Mosquito Management Maps 

Dumbarton Marsh S

Dumbarton Marsh N

Ideal Marsh

Newark GC South

South Marsh Munster

Newark GC North

West Vaco Marsh

Entry trangle

Hetch Hetchy Marsh

Newark Sewer Marsh

§ ̈¦880

UV84

84

Dumbarton Bridge

Jarvis

Legend

Refuge Boundaries

Mosquito Inspection Areas

Mosquito Management Areas

County Boundary

Don Edwards SF Bay NWR 

Mosquito Management Sites in Alameda County (Map 1 of 2)

Path: D:\GIS\SFB_DonEdwards\CCP\mosquito\DE_Alameda1of2.mxd

K9-1
Vernal Pools

Pintail Marsh South

Pintail Marsh North

Mowry Slough FWS

Bailey Ranch Vernal Pools

Warren Ranch

Newark GC South

Albrae Marsh

Cushing Marsh South

Stevenson Fields

Newark GC North

Cushing Marsh West

Mouse Pasture

Cushing Marsh Red Gate

West Vaco Marsh

Cushing Gun Club

Cushing Marsh Drawbridge

Cushing Rd

Entry trangle

Hetch Hetchy Marsh

Cushing Marsh East

Newark Sewer Marsh

Dumbarton Marsh S

§ ̈¦880

§ ̈¦680

UV262

UV84

UV262

84

Legend

Refuge Boundaries

Mosquito Management Areas

Mosquito Inspection Areas

County Boundary

Don Edwards SF Bay NWR - Mosquito Management Sites in Alameda County (Map 2 of 2)

Path: D:\GIS\SFB_DonEdwards\CCP\mosquito\DE_Alameda2of2.mxd

K9-2
Legend

Mosquito Mgmt Access Points

Mosquito Mgmt Transect Lines

Refuge Boundaries

Don Edwards SF Bay NWR - Mosquito Management Sites in Santa Clara County

Path: D:\GIS\SFB_DonEdwards\CCP\mosquito\DE_Santa Clara.mxd

K9-3
£¤101

UV82

El Camino Real

Don Edwards SF Bay NWR - Mosquito Management Sites in San Mateo County

Legend

Mosquito Mgmt Transect Lines

Refuge Boundaries

Path: D:\GIS\SFB_DonEdwards\CCP\mosquito\mosquito-ES\DE_San Mateo.mxd

K9-4
Appendix L. Wilderness Inventory

L-1 

Wilderness Inventory for Don Edwards San Francisco Bay National 

Wildlife Refuge 

Introduction 

A wilderness inventory is the process used to determine whether to recommend lands or 

waters in the National Wildlife Refuge System to Congress for designation as wilderness 

under the National Wilderness Preservation System (NWPS). The Service is required by 

policy to conduct a wilderness review for each refuge as part of the CCP process outlined 

in 602 FW 1 and 3, and according to the National Environmental Policy Act compliance. 

Lands or waters that meet the minimum criteria for wilderness are identified in a CCP 

and further evaluated to determine whether they merit recommendation for inclusion in 

the NWPS. 

There are three phases to the wilderness inventory process: (1) inventory, (2) study, and 

(3) recommendation. Land and waters that meet the minimum criteria for wilderness are 

identified in the inventory. These areas are called wilderness study areas (WSAs). In the 

study phase, a range of management alternatives are evaluated to determine if a WSA is 

suitable for wilderness designation or management under an alternate set of goals and 

objectives that do not involve wilderness designation. 

The recommendation phase consists of forwarding or reporting the suitable 

recommendations from the Director through the Secretary and the President to Congress 

in a wilderness study report. The wilderness study report is prepared after the record of 

decision for the final CCP has been signed. 

Areas recommended for designation are managed to maintain wilderness character in 

accordance with management goals. 

Evaluation Criteria 

According to Section 13 of the Service’s Director’s Order No. 125 (12 July 2000), in 

order for a refuge to be considered for wilderness designation, all or part of the refuge 

must: 

Be affected primarily by the forces of nature, with the human imprint 

substantially unnoticeable; 

Have outstanding opportunities for solitude or a primitive and unconfined type of 

recreation; 

Have at least 5,000 contiguous acres (2,000 ha) or be sufficient in size to make 

practicable its preservation and use in an unimpaired condition, or be capable of 

restoration to wilderness character through appropriate management, at the time 

of review; and 

Be a roadless island. 

Evaluation of the Size Criteria 

Roadless areas or roadless islands meet the size criteria if any one of the following 

standards applied: 
L-2 

An area with over 5,000 contiguous acres. State and private lands are not 

included in making this acreage determination. 

A roadless island of any size. A roadless island is defined as an area surrounded 

by permanent waters or that is markedly distinguished from the surrounding lands 

by topographical or ecological features. 

An area of less that 5,000 contiguous Federal acres that is of sufficient size as to 

make practicable its preservation and use in an unimpaired condition, and of a 

size suitable for wilderness management. 

An area of less than 5,000 contiguous Federal acres that is contiguous with a 

designated wilderness, recommended wilderness, or area under wilderness review 

by another Federal wilderness managing agency such as the Forest Service, 

National Park Service, or Bureau of Land Management. 

Evaluation of Naturalness Criteria 

In addition to being roadless, a wilderness area must meet the naturalness criteria. The 

area must appear natural to the average visitor rather than “pristine”; it should “generally 

appear to have been affected primarily by the forces of nature with the imprint of man’s 

work substantially unnoticeable.” The presence of historic landscape conditions is not 

required. An area may include some human impacts provided they are substantially 

unnoticeable in the unit as a whole. Significant human-caused hazards, such as the 

presence of unexploded ordnance from military activity, and the physical impacts of 

refuge management facilities and activities are also considered in evaluation of the 

naturalness criteria. An area may not be considered unnatural in appearance solely on the 

basis of the “sights and sounds” of human impacts and activities outside the boundary of 

the unit.

Evaluation of Outstanding Opportunities for Solitude or Primitive and Unconfined 

Recreation 

In addition to meeting the size and naturalness criteria, a wilderness area must provide 

outstanding opportunities for solitude or primitive recreation. The area does not have to 

possess outstanding opportunities for both solitude and primitive and unconfined 

recreation, and does not need to have outstanding opportunities on every acre. Further, 

an area does not have to be open to public use and access to qualify under this criteria; 

Congress has designated a number of wilderness areas in the Refuge System that are 

closed to public access to protect resource values. 

Opportunities for solitude refer to the ability of a visitor to be alone and secluded from 

other visitors in the area. Primitive and unconfined recreation means non-motorized, 

dispersed outdoor recreation activities that are compatible and do not require developed 

facilities or mechanical transport. These primitive recreation activities may provide 

opportunities to experience challenge and risk; self-reliance; and adventure. 

These two “opportunity elements” are not well defined by the Wilderness Act, but in 

most cases, can be expected to occur together. However, an outstanding opportunity for 

solitude may be present in an area offering only limited primitive recreation potential. 
L-3 

Conversely, an area may be so attractive for recreation use that experiencing solitude is 

not an option. 

Evaluation of Supplemental Values

Supplemental values are defined by the Wilderness Act as “...ecological, geological, or 

other features of scientific, education, scenic, or historical value.” These values are not 

required for wilderness. 

INVENTORY FINDINGS 

As documented below, none of the units of Don Edwards San Francisco Bay National 

Wildlife Refuge (Refuge) meet the criteria to warrant wilderness consideration. 

Therefore, inclusion of this Refuge in the NWPS will not be sought. 

Roadless Areas and Roadless Islands 

Many roads and highways cross through the Refuge units, and therefore does not meet 

the roadless island criteria. Major roadways include Interstate Highway 880, U.S. Route 

101, California State Route 237, and California State Route 84. 

Size Criteria

While the Service owns more than 5,000 acres of this Refuge in fee title, the Refuge is 

located in a highly urbanized area. Much of the Refuge lands have been altered by 

human development and much of the lands are in the process being restored. 

Naturalness Criteria 

The Refuge units have been substantially changed from their origins as tidal wetlands. 

The Gold Rush era in the 1800s heavily changed the region where the Refuge is located. 

Mining operations contributed to large amounts of sedimentation in the area. Later, most 

of the Refuge was diked and actively managed for salt production, farming, and 

development. Today, salt production and both residential and commercial development 

surround the Refuge. The Refuge is also surrounded by several million people that make 

the San Francisco Bay Area their home. For these reasons, the Refuge does not meet the 

naturalness criteria for wilderness designation. 

Opportunities for Solitude or Primitive and Unconfined Recreation

The major roadways described in the Roadless Areas and Roadless Islands section 

(described previously) can be heard or seen from many of the Refuge’s units. These 

roadways are heavily traveled everyday as they provide major travel arteries around the 

south San Francisco Bay. Furthermore, there is substantial nearby residential and 

commercial development. This Refuge also receives roughly 800,000-900,000 visitors 

annually with its plethora of wildlife-oriented recreation, interpretation, and 

environmental education programs. Based on this assessment, the Refuge does not fully 

provide opportunities for solitude or primitive and unconfined types of recreation that are 

characteristic of a wilderness area. 

Supplemental Values
L-4 

The location of the Refuge relative to the saline waters of the Pacific Ocean results in a 

unique and rich tidal environment that directly transition to uplands. Large contiguous 

expanses of pickleweed-dominated tidal marsh support high densities of the endangered 

salt marsh harvest mouse as well as provide habitat for the endangered California clapper 

rail and other sensitive species. Hundreds of thousands of shorebirds and waterfowl use 

the Refuge as they migrate along the Pacific Flyway. 
Appendix M. Applicable Laws and Executive Orders







Appendix N. Appropriate Uses 

la) Do we have iurisdiction over the use? {(b) Does the use comply with applicable laws and regulations (Federal, State, tribal, andlocal)? {(c) ls the use consistent with applicable Executive orders and Department and Service

policies? {

ld) ls the use consistent with oublic safetv? {

(e) ls the use consistent with goals and objectives in an approved management plan or otherdocument? {

(0 Has an earlier documented analysis not denied the use or is this the first time the use has

been orooosed? {

lol ls the use manaoeable within available budoet and staff? {

lh) W¡ll this be manaoeable in the future within existino resources? {

(i) Does the use contribute to the public's understanding and appreciation of the refuge'snatural or cultural resources, or is the use beneficial to the refuge's natural or cultural

resources?

{

(l) Can the use be accommodated without impairing existing wildlife-dependent recreationaluses or reducing the potential to provide quality (see section 1.6D, 603 FW 1, for

descriotion)- comoatible. wildlife-deoendent recreation into the future?

{

Where we do not have jurisdiction over the use ("no" to (a)), there is no need to evaluate ¡t further as we cannot

control the use. Uses that are illegal, inconsistent with existing policy, or unsafe ("no" to (b), (c), or (d)) may not be

found appropriate. lf the answer is "no" to any of the other questions above, we will generally not allow the use.

lf indicated, the refuge manager has consulted w¡th State fish and wildlife agencies. Ve -{ No - \Men the refuge manager finds the use appropriate based on sound professional judgment, the refuge manager

must justifo the use in writing on an attached sheet and obtain the refuge supervisor's concurrence.

Based on an overall assessment of these factors, my summary conclusion is that the proposed use is:

Not Appropriate- Appropriatey'

Refuge L 7-lf found to be Not Appropriate, the refuge supervisor does not need to sign concurrence if the use is a new use.

lf an existing use is found Not Appropriate outside the CCP process, the refuge supervisor must sign concurrence.lf found to be supervisor must sign concurrence.Refuge øÞ Lol1,

FWS Form 3-2319

02t06

A compatibility determination is required before the use may be allowed.

9

N-1
c. Service policy recognizes the importance of preventing the introduction and controlling

populations of invasive species as noted in 601 FW 3 3.16(A), Biological lntegrity, Diversity,

and Environmental Health. Grazing is a tool consistent with that policy that will reducecompetition from non-native species, allowing native vernal pool and grassland upland

vegetation to thrive.e. The grazing program will be directed and refined by a grazing plan for the Warms Springssub-unit, that will be completed in the life of the Refuge's comprehensive conservation plan.

The goal of the grazing plan will be to restore native grasslands and enhancing vernal pool

habitat to some degree through this use.

N-2
la) Do we have iurisdiction over the use? {

(b) Does the use comply with applicable laws and regulations (Federal, State, tribal, and

local)? {

(c) ls the use consistent with applicable Executive orders and Department and Servicepolicies? {ld) ls the use consistent with oublic safetv? {

(e) ls the use consistent with goals and objectives in an approved management plan or other

document? {

(D Has an earliqr documented analysis not denied the use or is this the first time the use hasbeen proposed? {lo) ls the use manaoeable within available budoet and staff? {

(h) Will this be manaoeable in the future within existino resources? {(i) Does the use contribute to the public's understanding and appreciation of the refuge's

natural or cultural resources, or is the use beneficial to the refuge's natural or cultural

resources?

{

0) Can the use be accommodated without impairing existing wildlife-dependent recreationaluses or reducing the potential to provide quality (see section 1.6D, 603 FW 1, for

description), compatible, wildlife-dependent recreation into the future?

{

\Mere we do not have jurisdiction over the use ("no" to (a)), there is no need to evaluate it further as we cannot

control the use. Uses that are illegal, inconsistent with existing policy, or unsafe ("no" to (b), (c), or (d)) may not be

found appropriate. lf the answer is "no" to any of the other questions above, we will generally not allow the use.

lf indicated, the refuge manager has consulted with State fish and wildlife agencies. V.s -{ No - \Men the refuge manager finds the use appropriate based on sound professional judgment, the refuge manager

must justify the use in writing on an attached sheet and obtain the refuge supervisor's concurrence.Based on an overall assessment of these factors, my summary conclusion is that the proposed use is:

NotAppropr¡ate- Appropriatey'

Refuge ¿ L 2. gulllf found to be Not Appropriate, the does not need to sign concurrence ifthe use is a new use.

lf an existing use is found Not Approprlate outside the CCP process, the refuge supervisor must sign concurrence.

lf found to be Approprlate, the supervisor must sign concurrencÆ.

Refuge Lo æ(v

FWS Form 3-2319

02/06

A compatibility determination is requlred before the use may be allowed.

1

N-3
g

a

d 

access to

and from the Refuge. This use encourages the public to access the Refuge and

appreciate the wildlife values found there.

N-4
la) Do we have iurisdiction over the use? {

(b) Does the use comply with applicable laws and regulations (Federal, State, tribal, and

locaD? {

(c) ls the use consistent with applicable Executive orders and Department and Servicepolicies? {(d) ls the use consistent with oublic safetv? {(e) ls the use consistent with goals and objectives in an approved management plan or other

document? {

(D Has an earlier documented analysis not denied the use or is this the first time the use has

been proposed? {

lo) ls the use manaqeable within available budoet and slaff? {(h) Will this be manaqeable in the future within existino resources? {(i) Does the use contribute to the public's understanding and appreciation of the refuge's

natural or cultural resources, or is the use beneficial to the refuge's natural or cultural

resources?

{

(j) Can the use be accommodated without impairing existing wildlife-dependent recreationaluses or reducing the potential to provide quality (see sect¡on 1 .6D, 603 FW 1, for

descriotion). comoatible. wildlife-deoendent recrealion into the future?

{

lMrere we do not have jurisdiction over the use ("no" to (a)), there is no need to evaluate it further as we cannotcontrol the use. Uses that are illegal, inconsistent with existing policy, or unsafe ("no" to (b), (c), or (d)) may not befound appropriate. lf the answer is "no" to any of the other questions above, we will generally not allow the use.

lf indicated, the refuge manager has consulted with State fish and wildlife agencies. Ve" -{ No 

When - the refuge manager finds the use appropriate based on sound professional judgment, the refuge manager

must justify the use in wr¡ting on an attached sheet and obtain the refuge supervisor's concurrence.

Based on an overall assessment of these factors, my summary conclusion is that the proposed use is:

NotAppropr¡ate- nppropriatey'

Refuge c- L Z"lalf found to be Not Appropriate, the refuge supervisor does not need to sign concurrence if the use is a new use.

lf an existing use is found Not Appropriate outside the CCP process, the refuge supervisor must sign concurrence.lf found to be Appropriate, the refuge supervisor must sign concurrence.Refuge 0o^t*- Nc tz

FWS Form 3-2319

02/06

A compatibility determination is required before the use may be allowed.

N-5
enhancement of habitat for endangered species (

, the western snowy p

, vernal p

tadpole shrimp, salt marsh harvest mouse, California clapper rail). Research and monitoring

provided by others support our efforts to effectively manage the Refuge. Research andmonitoring permitted on the Refuge are those that are geared toward improving management

or monitoring capabilities. Research and monitoring are appropriate tools to gain additional

knowledge for managing the Refuge.

N-6
la) Do we have iurisdiction over the use? {

{ (b) Does the use comply with applicable laws and regulations (Federal, State, tribal, and locaD?

{ (c) ls the use consistent with applicable Executive orders and Department and Service policies?

ld) ls the use consistent with oublic safetv? {(e) ls the use consistent with goals and objectives in an approved management plan or other

document? {

{ (f) Has an earlier documented analysis not denied the use or is this the first time the use has been orooosed?

lo) ls the use meneoeable within available budoet and staff? {lh) W¡ll this be manaoeable in the future within existino resources? {(i) Does the use contribute to the public's understanding and appreciation of the refuge'snatural or cultural resources, or ¡s the use beneficial to the refuge's natural or cultural

resources?

{

{ ü) Can the use be accommodated without impairing existing wildlife-dependent recreational uses or reducing the potential to provide quality (see section 1 .6D, 603 FW 1, for

description), compatible, wildlife-dependent recreation into the future?

ìÂ/here we do not have jurisdiction over the use ("no" to (a)), there is no need to evaluate it further as we cannot

control the use. Uses that are illegal, inconsistent with existing policy, or unsafe ('no" to (b), (c), or (d)) may not befound appropriate. lf the answer is "no" to any of the other questions above, we will generally not allow the use.

lf indicated, the refuge manager has consulted with State fish and wildlife agencies. V"s -y' No - WÏren the refuge manager finds the use appropriate based on sound professional judgment, the refuge manager

must justify the use in writing on an attached sheet and obtain the refuge supervisor's concurrence.

Based on an overall assessment of these factors, my summary conclusion is that the proposed use is:

Not Appropriate- lppropriatell

Refugelf found to be Not Appropriate, the supervisor does not need to signRefuge

Date: ?/Lt / z,"lz- - concurrence if the use is a new use. lf an existing use is found Not Appropriate outside the CCP process, the refuge supervisor must sign concurrence lf found to be Appropriate, the refuge supervisor must sign concurrence. æl2o¡"-

FWS Form 3-2319

o2t06

A compatibility determination is required before thE use may be allowed.

,

N-7
d. W¡th the spread of mosquito-borne diseases across the country, there is increasing

pressure to manage mosquito populations that occur on lands of the National Wildlife Refuge

System, especially in wetland areas such as the Refuge. There are six primary mosquito

species that breed on the Refuge: Aedes dorsalis, Aedes squamiger, Aedes washinoi, Culex

erythrothorax, Culex tarsalis, and Culiseta inornata. Culex tarsalis has the potential to be in

the area and shows the greatest potential to amplify and maintain West Nile Virus in

California. While mosquitoes are a natural component of wetlands, we recognize that theymay pose a threat to human and wildlife health (e.9., West Nile Virus).

e. No current approved management plan exists. However, the use is consistent with

the draft comprehensive conservation plan and the Service's Draft Mosquito and

Mosquito-Borne Disease Management Policy (601 FW 7).

g/h. Use will be conducted by local mosquito abatement districts.

i. This use could have adverse impacts on the Refuge's natural resources. However,

primary treatment of mosquitoes on the Refuge uses the least toxic pesticides (i.e., biological

controls such as Bti (larvacides) and methoprene (pupacides) with minimal environmental

impacts. lf these areas were not treated when needed, larger mosquito populations could be

produced resulting in the need to treat much larger areas with more toxic pesticides (such asadulticides) to minimize public health hazards.

j. Mosquito control is not expected to substantially impair wildlife-dependent recreational

uses on the Refuge because control is not likely to take place on a daily or regular

occurrence. Wildlife-dependent uses on the Refuge may be temporarily displaced, but are

not expected to be excluded by mosquito control activities. Mosquito controlwill benefit

wildlife-dependent recreational uses by providing a more pleasant visitor experience.

N-8
Appendix O. Persons Responsible for Preparing this 

Document, Core Team Members and Expanded Team Members

O-1 

Persons Responsible for Preparing this Document, Core Team Members and 

Expanded Team Members

Core Team Members

Eric Mruz Refuge Manager, Don Edwards San Francisco Bay NWR

Melisa Helton Wildlife Refuge Specialist, Don Edwards San Francisco Bay NWR

Winnie Chan Refuge Planner, San Francisco Bay NWR Complex

Jennifer Heroux Visitor Services Chief, San Francisco Bay NWR Complex

Genie Moore Environmental Education Center Director, Don Edwards Don Edwards 

San Francisco Bay NWR

Cheryl Strong Wildlife Biologist, Don Edwards San Francisco Bay NWR

Rachel Tertes Wildlife Biologist, Don Edwards San Francisco Bay NWR

Meg Marriott Wildlife Refuge Specialist (former), Don Edwards San Francisco Bay 

NWR

Ivette Loredo Wildlife Refuge Specialist, Don Edwards San Francisco Bay NWR

Tia Glagolev Instructional Systems Specialist, Don Edwards San Francisco Bay NWR

Carmen Leong-Minch Outdoor Recreation Planner, Don Edwards San Francisco Bay NWR

Kimby Wells Environmental Education Specialist, Don Edwards San Francisco Bay 

NWR

Paul Mueller Volunteer Coordinator, Don Edwards San Francisco Bay NWR

Eric McKee Slow the Flow Program Coordinator, Don Edwards San Francisco Bay 

NWR, Environmental Education Center

Debra King Interpretive Specialist/Watershed Watchers Program Coordinator, 

San Francisco Bay Wildlife Society, Don Edwards SF Bay NWR, 

Environmental Education Center

David Thomson San Francisco Bay Bird Observatory

Expanded Team Members

Sallie Hejl Regional Biologist, Pacific Southwest Region, USFWS

Brian Popper USDA Wildlife Services

Chindi Peavey San Mateo Mosquito and Vector Control District

James Counts San Mateo Mosquito and Vector Control District

Noor Tietze Santa Clara County Vector Control District

Nayer Zahiri Santa Clara County Vector Control District

John Rusmisel Alameda County Mosquito Abatement District

Erika Castillo Alameda County Mosquito Abatement District

Appendix P. Response to Comments

1. INTRODUCTION 

This appendix contains a summary of all comments that were received in response to the Draft 

Comprehensive Conservation Plan and Environmental Assessment (Draft CCP/EA) for Don 

Edwards San Francisco Bay National Wildlife Refuge (Refuge) during the official 30-day public 

comment period. Public comments on the Draft CCP/EA were accepted from May 16, 2012 to

July 2, 2012. Some comments received shortly after this closing date were also accepted and 

analyzed.

All comments were reviewed and organized so that an objective analysis and presentation of the 

comments could be made (Section 2). Refuge responses are included in Section 3. The names and 

affiliations of all of the people who commented are listed in Section 4. 

2. SUMMARY OF COMMENTS RECEIVED

The Refuge received a total of 18 comment letters (via fax, email, and letter) on the Don Edwards 

San Francisco Bay NWR CCP/EA during the comment period. Hardcopies and CDs of the Draft 

CCP/EA were mailed out to interested parties and available for the public to review at the San 

Francisco Bay NWR Refuge Complex, and the U.S. Fish and Wildlife Service, Pacific Southwest 

Region, Planning Office. 

Affiliation Type Numbers of Comment Letters Received

State Agencies 1

Local Agencies 5

Organizations 5

Public 5

Private Company 2

TOTAL 18

3. SUMMARY OF COMMENTS AND REFUGE RESPONSES

This section provides a summary of the individual comments received on the Draft CCP/EA, 

followed by the Refuges’ responses to those comments. The comments were organized into topic 

areas:

A. Cultural Resources

B. Habitat Management and Restoration

C. Wildlife Management

D. Public Access

E. Environmental Education

F. Staffing

G. Jurisdiction and Acquisition

H. Mosquito Management

I. Other Projects

J. Climate Change

Every effort was made to present all substantive comments in this summary; the specific 

comments presented here are a representative sample of all the comments received. A comment 

that addressed several issues was sometimes placed in a single bullet, in the section to which it 

P-1 
was most closely related. Therefore, there is some overlap between topics. The Refuge response 

follows each group of comments. A copy of all of the original comments received on the Draft 

CCP/EA is maintained on file at San Francisco Bay National Wildlife Refuge Complex (Complex).

A. Cultural Resources

A.1. Comment: I would like to see the plan address or identify coordination and support of 

activities for appropriate archaeological investigation, recording, and (if appropriate) 

preservation of these resources, especially those that are not to be (or may not be) 

preserved (e.g., Drawbridge, salt ponds, Oliver Salt Works [Archimedes Screw Pumps]). 

(Bamford)

Refuge Response: Some Refuge sites have been investigated, recorded, and preserved 

(as needed). Cultural assessments on areas of the Refuge not yet surveyed will be 

conducted as funding and priority permits. 

A.2. Comment: The draft CCP/EA should evaluate potential submerged cultural resources in 

the CCP tidelands. The California State Lands Commission (CSLC) maintains a 

shipwrecks database, available at http://shipwrecks.slc.ca.gov that can assist with this 

analysis. The database includes known and potential vessels located on the State's tide 

and submerged lands; however, the locations of many shipwrecks remain unknown. 

Please note that any submerged archaeological site or submerged historic resource that 

has remained in state waters for more than 50 years is presumed to be significant. 

(CSLC)

Refuge Response: A search of the shipwrecks database did not yield any shipwrecks in 

the Refuge. There was one shipwreck located near the Refuge, between Bair Island and 

Greco Island. We do not anticipate any tidal restoration or habitat enhancements in this 

area, and therefore do not expect there will be any impacts to this shipwreck site as a 

result of the CCP. We will update the shipwreck database and evaluate any submerged 

cultural resources within the Refuge as they become known. 

A.3. Comment: The draft CCP/EA should also mention that the title to all abandoned 

shipwrecks, archaeological sites, and historic or cultural resources on or in the tide and 

submerged lands of California is vested in the State and under the jurisdiction of the 

CSLC. The recovery of objects from any submerged archaeological site or shipwreck 

may require a salvage permit under Public Resources Code section 6309. CSLC staff 

requests that the USFWS consult with Senior Staff Counsel Pam Griggs at the contact 

information noted at the end of this letter, should any cultural resources be discovered 

during implementation of the CCP. (CSLC)

Refuge Response: If any submerged cultural resources are found during our CCP 

implementation, we will consult with CSLC (Pam Griggs) or Senior Staff. 

B. Habitat Management and Restoration

B.1. Comment: Alameda County Water District (ACWD) requests that the CCP/EA include 

the provision that field activities are coordinated with ACWD so that: a) ACWD can 

assist in identifying the location of abandoned wells, and b) any wells identified or 

discovered during construction activities are properly destroyed in accordance to ACWD 

P-2 
Well Ordinance 2010-01. In addition, ACWD requests that the CCP/EA include the 

provision that ACWD is notified of any future channel improvements and levee breaches, 

so that any abandoned wells in the area are located and properly destroyed before such 

improvements or breaches are implemented. (ACWD)

Refuge Response: The Refuge will coordinate with ACWD to identify and locate 

abandoned wells on the Refuge, as well as activities associated with any restoration work 

including levee breaches. 

B.2. Comment: As required by ACWD's Well Ordinance No. 2010-01, drilling permits are 

required prior to the start of any subsurface drilling activities for wells, exploratory 

holes, and other excavations. (ACWD)

Refuge Response: The Refuge will comply with needed drilling permits under ACWD 

Well Ordinance No. 2010-01 for any drilling that may occur on the Refuge. 

B.3. Comment: ACWD requests that the CCP/EA address maintaining access to ACWD's 

wells. (ACWD)

Refuge Response: The Refuge will continue to work with ACWD for access to existing 

monitoring wells.

B.4. Comment: When water system facilities were installed during the construction of the 

Complex in the late 1970s, the water main and appurtenances were installed by the 

Refuge. The General Services Administration (GSA), on behalf of the Refuge, entered 

into a 10-year agreement which provided for ACWD to use and maintain the water main 

as part of the public water distribution system. In the intervening decades, ACWD and 

the GSA have renewed the 10-year agreement. However, the most recent agreement 

has expired, and ACWD's roles and responsibilities, as well as those of the GSA and 

Refuge, for the water main and appurtenances to the Complex are unclear. (ACWD)

Refuge Response: The Refuge will coordinate with GSA and ACWD to find a solution 

for the expired 10-year agreement.

B.5. Comment: It is unclear as to whether the analysis is intended to be at a programmatic 

or project level. Upon review of the EA, (CSLC) staff finds that the level of detail and 

analysis in the EA is more consistent with a programmatic document. In addition, there 

are several references indicating that additional NEPA analysis would be conducted. 

For example, page B-51 of the EA states: "As site-specific designs are developed at these 

other marsh areas, further NEPA documentation will be completed." Therefore, CSLC 

staff assumes that more detail regarding proposed construction activities, and analysis of 

those activities, would be provided in subsequent NEPA documents prior to 

implementation of the CCP. (CSLC)

Refuge Response: The CCP is intended to be a programmatic document. Any future

restoration projects prescribed in the CCP will likely require the Refuge to comply with 

laws and regulations such as National Environmental Policy Act, Endangered Species 

Act Section 7 consultation, and CEQA.

P-3 
B.6. Comment: Page B-39 of the EA states that the EA and CCP identify measures that 

would avoid and minimize any environmental impacts that could occur during 

implementation of the CCP. However, the potential impacts have not been quantified 

and no formal mitigation measures are called out for impacts specific to the CCP. One 

example of how mitigation has been treated in the CCP/EA is provided on page B-41, 

under Water Quality and Contaminants, where it states that "Mitigation measures 

adopted in the Records of Decision for the Bair Island and SBSP projects incorporated 

best management practices that include the use of barriers to prevent sediment from 

flowing off the Refuge, thus minimizing impacts to water quality." As water quality 

impacts are anticipated outside of the Bair Island and SBSP project areas, this 

mitigation should be modified to reflect all potential impacts included under the CCP. In 

addition, per the Council on Environmental Quality (CEQ) NEPA Regulations, 

mitigation measures should be specific, tangible actions that will reduce a physical 

environmental effect. CSLC staff recommends that as details of the project components 

outlined in the draft CCP/EA are developed, specific, enforceable mitigation measures 

be included in subsequent environmental documents. (CSLC)

Refuge Response: Comment noted. More specific mitigation measures will be explored 

and prescribed as needed in future project-specific environmental documents.

B.7. Comment: CSLC staff recommends the inclusion of more detailed descriptions of the 

location and specifics of proposed activities in subsequent NEPA documents. (CSLC)

Refuge Response: See Refuge Response in B6. The Refuge will conduct NEPA 

analysis as needed on future construction activities that may occur.

B.8. Comment: The draft CCP/EA should detail and analyze the potential for construction 

activities to affect special-status plant or wildlife species that may occur in the Refuge 

area. In particular, the analysis should identify whether the proposed activities could 

adversely impact species such as Steelhead salmon that are likely to be present in 

associated marshes and small channels within the Refuge boundary where restoration or 

construction work would be conducted. The analysis should include a discussion of the 

potential turbidity, siltation, and other physical effects on all life stages of aquatic 

species. While CSLC staff recognizes that the Project is intended to conserve, enhance, 

and restore natural resources in the long-term, implementation of certain components of 

the CCP could nonetheless have effects that are adverse, either temporarily or 

permanently. If impacts to special-status species are found to be potentially significant, 

the EA should include feasible measures that could be implemented to avoid or 

substantially lessen the impact. (CSLC)

Refuge Response: Any construction or restoration activities which the Refuge conducts 

will need environmental permits and the assessment of biological impacts will be 

conducted and analyzed at that time.

B.9. Comment: Objective 1.1. Conduct standardized monitoring efforts and research 

projects in coordination with other regional efforts for salt marsh harvest mouse and 

California clapper rail within five years. Improve high tide refugia for these species. 

P-4 
Strategy 5 - "Expand high marsh and the ecotone/transition zone wherever possible to 

benefit these species." Does this pertain to acquisition of these habitats as well as 

expansion of existing habitat? The strategies for snowy plover expressly states, 

"Identify appropriate snowy plover habitat in approved acquisition boundary to prioritize 

for acquisition or protection." Acquisition of high marsh and ecotone/transition zone 

should be incorporated explicitly as a strategy for the salt marsh harvest mouse and 

California clapper rail. (CCCR)

Refuge Response: Comment noted. A strategy has been added regarding acquisition of 

habitat for the salt marsh harvest mouse and California clapper rail.

B.10. Comment: Suggested edits of CCP narrative:

p. 37 - We propose the following change to the text regarding salt ponds in Redwood 

City:

The remaining 1400 acres of ponds are located on the west side of San Francisco Bay in 

close proximity to the Refuge's Greco Island tidal marsh and Ravenswood complex. 

These ponds continue to function on a limited basis as salt-producing crystallizer and 

bittern ponds and multi-use areas under Cargill Salt ownership. Cargill Salt is in the 

process of determining the regulatory feasibility of developing some portion of this 

Redwood City salt pond site. Use of this site by thousands of migratory and wintering 

waterfowl for roosting and foraging is well-documented.

The rationale for making this change is that there are actually 1400 or 1436 acres of salt 

ponds at the Redwood City site and the description provided of the location of these 

ponds is confusing. The use of the site by waterbirds is well documented. (CCCR)

Refuge Response: The acreage for the salt ponds in Redwood City owned by Cargill 

Salt has been updated to 1400 acres. However, because these lands are not part of the 

West Bay Unit, the description of these lands has been moved to 3.6.1 Land Use, 

Existing Uses Surrounding the West Bay Unit. We have added a reference regarding 

known bird use on the site. We have revised the description of development plans for 

the site to, “Cargill Salt is in the process of preparing a development plan for these 

ponds”, per information from the Redwood City Planning web page.

B.11. Comment: p. 120 - The description of the Redwood City salt ponds should be revised as 

suggested above. 1,300 acres should be changed to either 1,400 or 1,436 acres - both 

figures have been cited. The current status should be revised to: "Cargill Salt is in the 

process of determining the regulatory feasibility of developing some portion of this 

Redwood City salt pond site." At this time we do not know whether restoration of the 

site will be proposed.

Refuge Response: See previous response to Comment B.10. 

B.12. Comment: p. 98 - The statement "In the South Bay, several waterfowl breeding areas 

occurs near, or adjacent to the Refuge. These include..." The former Whistling Wings 

and Pintail Duck Clubs in Newark should be added to the list of sites. (CCCR)

P-5 
Refuge Response: Comment added.

B.13. Comment: Preferred alternative:

The CCP describes three potential implementation alternatives. Alternative A, the no 

action alternative, represents the current level of management. Alternative B would 

provide moderate increases in wildlife and habitat management, visitor services and 

environmental education. Alternative C would provide substantial increases in the 

activities identified in Alternative B. The Refuge has identified Alternative B as the 

preferred alternative. In general we support the identification of Alternative B as the 

preferred alternative, however, we believe it is important that the following actions 

should be included in Alternative B:

• Monitor population density, presence/absence, abundance, and/or cover on focal 

plant and animal species every five years.

• Survey/monitor for Suisun thistle, salt marsh bird's beak, soft bird's beak, and 

California sea-blite distribution and abundance

• Further control of weeds; for example, reduce cover of invasive perennial 

pepperweed on the Refuge by 50 percent of 2010-2011 baseline inventory within 

threatened and endangered species habitat (high tide refugia, transition zone and 

tidal areas)

• Enhance and restore marsh-upland ecotone along all levees in the Ravenswood 

and Alviso pond systems through established dominance (>50%) of native plants.

(CCCR)

Refuge Response: With regard to bullet one and four above, these actions require a 

very high level of funding and staffing that we do not believe possible with budget 

projections. We have added the second bullet to the CCP. We will consider the third 

bullet after the implementation of the Weed Management Plan.

C. Wildlife Management

C.1. Comment: With respect to the non-lethal methods of avian predator mitigation, I did 

not see provisions for monitoring mortality and injury/recovery against acceptable 

levels. Acceptable levels and periodic measurement would appear to be necessary for 

ensuring that the trapping/relocation activities are achieving a desired balance between 

the adverse effects on predators and on prey. (Bamford)

Refuge Response: Birds that are removed via non-lethal methods (i.e., live-trapped and 

relocated) are handled as minimally as possible and quickly relocated (generally less 

than 48 hours) in order to reduce any risk to mortality (per Migratory Bird Treaty Act 

(MBTA) requirements). Biologists observe the bird after capture and prior to release to 

insure the bird is healthy and uninjured. These individuals are also banded should they 

be sighted or recaptured; some individuals have even returned to capture sites. While 

we do not have long-term monitoring of relocated individuals, there is a long history of 

trapping raptors safely and releasing them for research and rehabilitation around the 

world. We only use traps that have been approved in a MBTA permit issued by the 

Migratory Bird Division of the U.S. Fish and Wildlife Service. Further, only a few 

individual predators would be removed and is not anticipated to have a population-level 

effect on the species.

P-6 
There is currently no funding to track birds once they have been released. Monitoring 

these individuals requires considerable effort and resources. The Migratory Bird Treaty 

Act requires that migratory birds be relocated as the preferred method for removing a 

problem individual. 

Although being caught in a trap can stress a raptor, trapped birds rarely are injured 

physically. The most frequent causes of trap-related injury or death are predation and 

weather. Raptors may succumb to temperature extremes or predation if allowed to 

struggle in traps for long periods. Used properly, the traps discussed in this chapter 

should rarely result in severe injury or death. (Source: Bird, David and Bildstein, Keith. 

2007. Raptor Research and Management Techniques. Raptor Research Foundation. 

464pp.) 

C.2. Comment: We ask that the CCP 1) refer to the Burrowing Owl Conservation Strategy 

for updated information, 2) that management to enhance habitat for burrowing owls be 

included in the CCP, and 3) that Refuge expansion land acquisition strategy includes land 

for burrowing owls.

Specific recommendations:

• Please discuss burrowing owl habitat in the context of Grassland Habitat (CCP 

page 68).

• Please compare proposed methods for weed control in grassland and ruderal 

habitats for potential impacts to burrowing owls, and develop methods to avoid 

adverse impacts and to enhance the habitat for the owls (CCP page 151).

• Please add to the CCP an objective that aims to increase burrowing owl 

reproductive success at the Refuge (Alviso area, Warm Springs.)

• Please expand Objectives 2.1, 2.2 and 2.3 of the CCP to include surveys and 

habitat enhancement for burrowing owls.

• Nesting burrowing owls have been reported at Whistling Wings and Pintail duck 

clubs. This area is within the Refuge Expansion Boundary. Please consider it a 

high priority for acquisition.

• Dog walking in upland areas (EA page B-16) could conflict with the preservation 

of upland and grassland species, including ground-nesting birds. In Santa Clara 

County, burrowing owls have stopped nesting in remnant upland areas around the 

Bay where dogs are allowed (Palo Alto, Sunnyvale etc.). Only 2% of the refuge 

consists of grassland, and presence of dogs there can potentially be impactful. 

Please analyze potential impacts of dog walking activity on grassland species, 

including discussion of the potential to restore habitat and recover the burrowing 

owl population in the South Bay. (SCVAS)

Refuge Response: Burrowing owls are discussed in the “Landbirds” section of Wildlife 

(3.4.4) in the CCP. We will update the CCP with more current information on this 

species. Thank you for the reference of the Burrowing Owl Conservation Strategy in the 

Santa Clara County Habitat Conservation Plan. 

With regard to weed control efforts in grassland and ruderal habitats, all proposed 

methods for weed control will be further evaluated in our forthcoming Weed 

P-7 
Management Plan. At that time, proposed methods for weed control will discuss impacts 

to Refuge resources (Objective 2.2). 

With regard to a burrowing owl objective, surveying, habitat enhancement and predator 

control are some examples of how the Refuge can support burrowing owl reproductivity. 

Objective 2.1 does include burrowing owls in Strategy 4: Participate in and support 

national and regional monitoring efforts (i.e., San Francisco Bay shorebird surveys, 

mid-winter waterfowl surveys, burrowing owl, harbor seal, etc.). The Refuge would be 

pleased to be included in the local planning and conservation efforts and could 

participate in or facilitate surveys on Refuge lands. A strategy was added to Objective 

2.3 to survey burrowing owls on Warm Springs.

With regard to Objective 2.3, the specific strategies for habitat enhancement for any 

particular species will be covered in the step-down weed management plan by habitat 

type. The following parts of the CCP discuss management to enhance or create 

burrowing owl habitat:

• Mayhew’s Landing Restoration Planning (Section 4.2 Habitat Enhancement and 

Restoration).

• Enhancement and restoration of the marsh-upland ecotone, especially at FaberLaumeister, La Riviere Marsh, EEC, A6, A8, and 75 miles of levee (Objective 

2.5). 

With regard to acquisition for burrowing owl habitat, Objective 2.10 includes identifying 

and acquiring areas with the potential to be restored to burrowing owl habitat. 

We recognize the potential conflict between dogs and wildlife and for this reason the 

Refuge is closed to dog walkers, with the single exception of the hill around 

headquarters. If burrowing owl habitat enhancement is successful here, then dogs will 

have been an “existing condition.” All dogs in this area are required to be leashed 

because of its proximity to the office this is relatively easy to enforce. No new areas are 

proposed for access to dog walking. Areas that currently have burrowing owls include 

Warm Springs and New Chicago Marsh, neither of which is open to dogs.

C.3. Comment: Objective 2.1. Within ten years of plan approval, conduct baseline surveys 

for population density, presence/absence, and abundance and/or cover of priority native 

plants, fish, and wildlife to determine species diversity that will inform habitat 

enhancement actions. [emphasis added] The rationale for this objective states, 

"Monitoring changes in biotic and abiotic resources will help management make 

informed decisions or develop, refine, and evaluate achievement of fish, wildlife, and 

habitat management objectives." We fully support actions to obtain baseline data for 

populations, but are concerned that a deadline that may extend up to ten years from plan 

approval is too far into the future. The life of the current CCP is only fifteen years, which 

could mean that data necessary to make informed wildlife and habitat management 

decisions would not be available until the final five years of the CCP. We recognize that 

in the end staffing, workloads, and prioritization will influence how soon this information 

can be obtained. (CCCR)

P-8 
Refuge Response: Based on the best professional judgment of the Refuge staff and 

with a realistic increase in funds, the timeframe of ten years is most feasible given 

current survey abilities and efforts.

D. Public Uses

D.1. Comment: Continue to allow leashed dogs on the lower Tidelands Trail, but post new 

signage at the bridges re-stating the leash requirement and the penalty for noncompliance. If possible increase enforcement. (Breaud)

Refuge Response: Comment noted. In order to be consistent with the other lands we 

manage on the Refuge, we plan to prohibit dog-walking on most trails in close proximity 

to tidal marsh. Increased enforcement and additional signage will be necessary to 

ensure compliance with this change.

D.2. Comment: I would like to see the plan address or identify coordination and support of 

activities for appropriate archaeological investigation, recording, and (if appropriate) 

preservation of these resources, especially those that are not to be (or may not be) 

preserved (e.g., Drawbridge, salt ponds, Oliver Salt Works [Archimedes Screw Pumps]). 

I would also encourage limited access (e.g., guided tours, with appropriate fees as at 

Vasco Caves in East Bay). (Bamford)

Refuge Response: Interpretive tours that offer a cultural resource history of the area 

are offered from time to time at the Refuge, and new opportunities will be offered on a 

rotating basis. We will consider limited access to cultural resources when public safety 

and protection of cultural resources permits.

D.3. Comment: I didn't see any references to the effects of lead shot. Presumably it was 

investigated and determined to not affect this plan. If so, would it be appropriate to 

mentioned in that in the plan? (Bamford)

Refuge Response: Our hunting regulations state that steel shot is required to hunt 

waterfowl anywhere in California. You cannot possess lead shot while hunting 

waterfowl.” We do not allow possession of lead shot on the Refuge. 

D.4. Comment: Pond A6 should be opened to waterfowl hunting, as that would create 

additional hunter opportunity (only 7,500 acres out of a total of 30,000 acres are 

currently open to hunting), help to better disperse hunters throughout the Refuge and 

not conflict with other recreational uses (recognizing this particular pond is rarely used 

by the public). CWA also supports the creation of a new universally accessible blind to 

increase opportunity for disabled and other hunters, but advises the Service to solicit 

input from the local hunting community as to its specific location. (CWA)

Refuge Response: After some consideration, we determined that opening Pond A6 

would not be a viable long-term opportunity. Alviso Pond A6 restoration was completed 

in 2010 as a Phase 1 action of the South Bay Salt Pond Restoration Project. The goal for 

this restoration project is to create approximately 330 acres of tidal salt marsh and tidal 

channel habitat that will evolve over time. The elevation of Pond A6 is currently below 

mean tide level (3.3 feet NAVD) and below the elevation at which marsh vegetation 

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colonizes emerging mudflats. However, over time, Pond A6 restoration will initially 

create large areas of emergent mudflat habitat. In addition, tidal channel and vegetated 

salt marsh habitats are expected to develop in Pond A6 as tidal channels reform and as 

sediment accumulates and vegetation establishes on the emerging mudflats. Therefore, 

Pond A6 will not persist as a salt pond in the future to support the Refuge’s waterfowl 

hunting program. In addition, a number of applied research studies are being 

implemented as part of Phase 1 to answer questions regarding key SBSP Project 

uncertainties related to ecosystem restoration. These ongoing studies in Pond A6 also 

preclude the Refuge from opening Pond A6 to waterfowl hunting or any other public 

uses.

We are unaware of any significant conflicts between hunters and other recreational 

users at this time. Regarding your comment on the universally accessible blind, we plan 

to solicit input from the local hunting community on its design and location.

D.5. Comment: The Service should increase the number of hunt program meetings, data 

collection and hunter outreach in order to best adapt the hunt program to the needs of 

its users over time. In addition, developing brochures, signage and exhibits regarding 

hunting will appropriately help to educate the non-hunting public as to the historical 

importance and current contribution of waterfowl hunting to wildlife conservation.

(CWA)

Refuge Response: Comment noted. We plan to increase outreach to the hunting and 

non-hunting community on the Refuge hunt program.

D.6. Comment: Conversion of salt ponds to tidal marsh should be focused on those ponds 

which provide only marginal wildlife habitat value. Salt ponds which receive high 

waterfowl or shorebird use should be maintained as such, or enhanced by reducing 

salinity levels, for example. (CWA)

Refuge Response: There is an ongoing process via SBSPRP to determine the best mix 

of ponds, tidal marsh, and upland for the benefit of wildlife and people. We understand 

that this will be an adaptive process given what we learn as we restore/modify habitat.

D.7. Comment: Navigable water areas within the Refuge's boundaries should continue to be 

open for boat access and waterfowl hunting 7 days per week during waterfowl season. 

Due to a current limited number of boat ramps available adjacent to SF Bay, the 

addition of new boat ramps should be considered. The Service should also permit 

hunters to launch scull boats and other small, nonmotorized craft off Refuge land (e.g. 

levees) and into navigable sloughs in appropriate areas. (CWA)

Refuge Response: We concur, navigable waters within the Refuge boundaries will 

continue to remain open to boat access and waterfowl hunting per state regulations. For 

the Alviso Ponds, waterfowl hunting is only allowed on Wednesdays, Saturdays, and 

Sundays per Refuge regulation. Boat access is currently allowed at different off-Refuge 

locations (e.g., Alviso Marina, outside the HQ entrance). We will research boat ramps 

on-Refuge when resources and funds allow.

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D.8. Comment: Guided tours through the hunt zones, if not properly coordinated during 

hunt season, will likely cause conflicts between recreational users and decrease the 

quality of the hunting experience such as that which sometimes occurs at Bair Island and

the A2E Pond (adjacent to the Bay Trail). (CWA)

Refuge Response: We are unaware of any significant conflicts between hunters and 

other recreational users at this time. With any future public access to hunt areas, we

plan to coordinate tours as well as provide information and signage to self-guided tours 

so to avoid conflict with the hunt season and hunt areas.

D.9. Comment: A predator management plan should not just focus on protecting shorebirds 

or endangered species, but also any nesting waterfowl. Predators, including skunks and 

raccoons, may significantly reduce waterfowl nesting success, particularly in small or 

isolated habitat areas. Studies have shown that focused predator control programs can 

lessen this effect, in some cases substantially. (CWA)

Refuge Response: Both the Mammalian and Avian Predator Management Plans 

(appended to the CCP) benefit migratory birds, including waterfowl. However, because 

the majority of predator management is conducted during the breeding season, MarchSeptember, waterfowl are not a focal species. Waterfowl are most abundant and diverse 

on the refuge during the winter migration.

D.10. Comment: The creation of islands in managed ponds to benefit nesting and roosting 

waterfowl and shorebirds should be evaluated and implemented, where appropriate.

(CWA)

Refuge Response: Comment noted.

D.11. Comment: The Compatibility Determination for Wildlife Observation and Photography 

permits walking, hiking, jogging, and bicycling on Refuge Trails, including the Bay Trail. 

This determination uses old, general research instead of using up-to-date, local research 

from the Don Edwards National Wildlife Refuge and its vicinity. We ask that the 

determination be re-evaluated. Instead of a blanket compatibility determination, the 

CCP should create an appropriate trail use / public management plan based on local 

existing and predicted trail use patterns and on relevant local studies.

According to the Bay Trail website, the Bay Trail would also provide ”a commute 

alternative for cyclists” (see http://www.baytrail.org/overview.html). This is of concern 

since employers in the valley (Facebook, Google, Apple and others) are expecting 

thousands of their employees to commute daily on the Bay Trail, and even provide 

amenities and incentives to encourage this use of the trail.

Please adjust EA Table 3 (EA page 79) to reflect the expected increase in number of 

commuters through the refuge.

Recent, local studies by Dr. Lynne Trulio and Jana Sokale (see links below) show that 

trail walkers disrupted nesting snowy plovers, causing them to leave their nests. The 

plovers returned to their nest fairly quickly, but even a short disturbance can have 

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temperature impact on nest success and catch the attention of predators. Faster 

movement on the trail was more impactful than slow movement.

Local studies also indicate significant response to trail use from migratory waterfowl. 

Dr. Trulio and Ms. Sokale’s research indicates that trail use reduces the foraging area 

available to migratory waterfowl. Since each type of waterfowl has specific foraging 

needs, and given that the research focused on areas that have historically had high 

waterfowl counts, it is premature to conclude that trail use by the public is compatible 

with the mandate of the Refuge to protect wildlife. (SCVAS)

Refuge Response: We have not conducted or participated in any studies looking at the 

impacts of bicycling on wildlife response; the work by Trulio and Sokale is focused on 

people walking on the trails. Most of the trails located on the Refuge are less compatible 

with commuter bicycling due to the remote nature and lack of connectivity of these trails. 

Though, a notable exception to this is the Moffett Trail opened adjacent to pond A2W. 

In addition, commuters tend to prefer paved trails for ease of riding and the Refuge does 

not have any paved trails.

There is currently a trail already located along the levee at pond A16 and this area does 

not have a high use by bicycles. Even if the Bay Trail did include a connection to the A16 

trail, this would not be paved, nor would it be any more connected to an area where 

people really commute to or from. Another paved trail is located adjacent to Highway 

237 that is more convenient and connected for commuters.

Despite the connectivity of Refuge trails and in light of potential future increases of 

commuter bicycling as indicated on the Bay Trail website, we agree that further 

management planning and monitoring may be needed for the different uses on trails, but 

believe it would be better suited to a step-down planning process. We will consider 

revising existing or creating additional visitor services compatibility determinations 

during that step-down planning process, and have added a strategy to the CCP 

regarding the need to assess trail uses. During that process, we will consider the 

management tools that you suggest for reducing disturbance from trail uses.

Table 3 in the EA represents a 30 percent increase in nature trail use/wildlife 

observation between Alternative A (current management) and Alternative B. We 

believe this sufficiently includes the anticipated increases in nature trail use by 

commuters. Should monitoring or future reports show an increase in trail use greater 

than our estimate, we will revise these estimates and consider any management tools to 

reduce impacts to Refuge properties and resources.

 

D.12. Comment: Page 131, Section 3.6.2. Public Uses – Mowry Unit – The document states 

that the ponds are open to hunting seven days per week. Cargill has not been notified 

that these ponds are available for hunting. This is a safety issue for our employees and 

we would request a review of this refuge use. Cargill requests that the Refuge not open 

the Newark or Mowry Units for hunting because we continue to operate in these ponds 

and have a concern for employee safety, equipment, and levee maintenance. (Cargill)

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Refuge Response: We currently do not allow hunting within the Newark Ponds as the 

CCP states, “Newark Unit: All Refuge ponds are closed to hunting.” Tidal marsh areas 

outside the ponds are open to hunting and under the jurisdiction of the California 

Department of Fish and Game hunting regulations. 

Waterfowl hunting for the Refuge was opened on September 8, 2004 (69 FR 54375). We 

allow hunting in Mowry Ponds M1 – M6 as was published in the Code of Federal 

Regulations (50 CFR 32): http://cfr.regstoday.com/50CFR32.aspx#50_CFR_32p8. 

Since this comment letter, the Refuge, in coordination with Cargill, has placed tighter 

restrictions on hunting regulations in these ponds to address safety issues for hunters, 

Cargill staff, and Refuge staff. As a result, the Refuge made minor updates to our 2012-

2013 Waterfowl Hunting Regulations posted at: 

http://www.fws.gov/desfbay/Hunt/Hunt_Information.htm

We will continue to work with Cargill to ensure that the Refuge hunt program does not 

interfere with Cargill’s salt-making process or pose safety concerns for individuals.

D.13. Comment: Page 159, Figure 18. Public Uses by Management Unit – This figure 

shows the Mowry Unit as a Hunt Area. As noted above, Cargill requests that the 

Refuge not open the Newark or Mowry Units for hunting because we continue to 

operate these ponds and have a concern for employee safety, equipment, and levee 

maintenance. (Cargill)

Refuge Response: Please see response for “Comment: Page 131, Section 3.6.2. Public 

Uses – Mowry Unit”.

D.14. Comment: Page 161, Figure 19. Refuge Hunt Map - This figure shows the Mowry 

Unit as a Hunt Area. As noted above, Cargill requests that the Refuge not open the 

Newark or Mowry Units for hunting because we continue to operate these ponds and 

have a concern for employee safety, equipment, and levee maintenance. Also, Cargill’s 

lands are depicted in the color gray on this map. Although, these lands are not shown as 

part of the hunt area, the CCP falsely represents that they are part of the Refuge. 

Please color Cargill’s land in white on the map. (Cargill)

Refuge Response: We have revised the hunt map so it doesn’t show Cargill’s fee 

property in gray. It only identifies the areas that are open to hunting. Regarding 

hunting in the Mowry Ponds, please see response for “Comment: Page 131, Section 

3.6.2. Public Uses – Mowry Unit”.

D.15. Comment: One of the planning tools missing from the documents is a comprehensive 

Trails compatibility determination. Currently, the document preparers have treated 

trail use and management as a subtopic in the Wildlife Observation and Photography CD 

(WO&P CD) while, in fact, trails are key elements for all land-based priority uses, 

provide access for Refuge management and easement partners and are used informally 

for non-priority purposes. Even if trails were considered uniquely for each type of public 

uses and of operations there would be a need for cumulative review to assess the 

combined impacts from all types of trail use. (CCCR)

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Refuge Response: We agree that the Refuge needs to take a more proactive role in 

managing and monitoring its trails. The author of this comment has noted a number of 

issues that could be solved or better managed through a thoughtful planning process. 

These issues include involvement in regional trails systems, user conflicts, and rules and 

regulation enforcement. We will address these issues as part of the visitor services 

step-down planning process which follows the CCP. 

D.16. Comment: It is unknown if any other Refuges have comprehensive Trails CDs. Possibly 

such a CD would be first and unique. That would not be a surprise as this Refuge was 

unique as the first urban Refuge and urbanity will always be a factor of significance. 

Refuge trails repeatedly link with trail systems of the surrounding communities and 

particularly with the San Francisco Bay Trail (Bay Trail). These linkages have 

introduced non-priority uses mentioned previously. These are users for whom wildlife is 

secondary to access, are not the public users described in the 1997 Improvement Act and 

who value the Refuge primarily as a source of new managed trails.

Unfortunately, this people-value of Refuge trails is an impression that is currently 

presented to the public on maps of the Bay Trail. On its maps, in addition to agreed-to 

segments of Bay Trail on the Refuge (Marshlands Road, Tidelands Trail, Moffet/Bay 

Trail), a reader will see many miles of Refuge Trails incorrectly color-coded as the “Bay 

Trail.” [See South Bay-Bay Trail map attached.]

A Trails CD can establish use priorities for each segment of the Refuge’s 30 miles of 

trails and establish a basis against which trail traffic density, use type, user type, 

hour(s)-of-use, incidents of illegal or unsafe activity and maintenance requirements can 

be monitored to inform management. With habitat disturbance data for same/like areas, 

trail data can inform trail management, continuously monitoring compatibility status. 

Additionally a completed Trails CD, can inform agencies like ABAG/Bay Trail or 

community groups like bicycle coalitions.

To this end, modifications are needed for the CCP and EA Alternatives to incorporate 

the establishment of a Trail monitoring and management plan (Alternative B), per the 

stipulations of a Trails CD. (CCCR)

Refuge Response: Compatibility Determinations (CDs) are a tool for refuge managers 

to determine the compatibility of a use of refuge lands, such as hunting or wildlife 

photography, with the refuge purpose. CDs are not usually used to determine the 

compatibility of a thing, such as a trail, but the uses of the trail. The compatibility of the 

trail itself is determined by whichever standards were available at the time it was 

established. All new trails are reviewed either during the CCP planning process or 

under individual project NEPA evaluations. We agree that a systematic review and 

evaluation of uses on trails is needed, but believe it would be better suited to a step-down 

planning process. We will consider revising existing or creating additional visitor 

services compatibility determinations during that step-down planning process, and have 

added a strategy to the CCP regarding future assessment of trail uses.

D.17. Comment: It is true that some people use bicycles to move about the Refuge to 

participate in any of the prioritized uses. Even these bicyclists have responsibilities i.e. 

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to defer to other trail users to avoid disrupting their activity, to avoid bike-produced 

injuries and to move at low speed to avoid wildlife disturbance. Of greater concern for 

Refuge impact are bicycle-commuters, long-distance bicycle exercisers and large-group 

recreational bicyclists.

Throughout the San Francisco Bay Area, including the cities and counties in which the 

Refuge resides, agencies, businesses and local governments have initiatives underway 

encouraging thousands of residents to replace automobiles with bicycles. All indications 

are that those initiatives are succeeding. The routes that serve those initiatives include 

both roads and trails. For the Refuge, a particular impact is the Bay Trail. Adjoining 

that trail and the Refuge, or nearby, large businesses like Facebook and Google are 

funding Bay Trail improvements, for their own employee-bicycle commuters and those 

of numerous smaller businesses.

The WO&P CD, in a footnote, states: “The Bay Trail is a planned recreational corridor 

that, when complete, will encircle San Francisco and San Pablo Bays with a continuous 

500-mile network of bicycling and hiking trails.”[NOTE: italics added] While the Bay 

Trail website still states that the trail has a recreational purpose, there is undisguised 

evidence that the agency is actively working with partners to provide a trail that serves 

bicycle-commuting as well.

It is not surprising then that the newest Refuge trail, the Moffett/ Bay Trail, near 

Google and large industrial parks, is the Refuge’s busiest. On a recent day one visitor 

reported that she walked out on that trail with a small group to observe wildlife. To her 

great annoyance, the group cut short their visit to escape the unrelenting disruption of 

speeding bicyclists. That is just one example of a nonpriority use undermining a priority 

use. While this site is an official Bay Trail segment, its usage must be managed to 

enhance the priority use such that the public gets the values intended by Congress.

Commute hours often coincide with optimal wildlife watching hours i.e. dawn and dusk. 

Any Refuge trail that includes commuters will disrupt wildlife observation and 

photography at least five days a week. The Refuge needs a trails plan that ensures that 

all new trails are reserved for priority uses. (CCCR)

Refuge Response: The Refuge is committed to continuing its participation in the Bay 

Trail program. However, as a National Wildlife Refuge within that system, we will work 

with the Bay Trail to get our refuge trails and lands accurately represented on their map 

system. We feel that clearer designations on the maps will help to alert future uses to 

the special purpose of our trails. Also, as part of our step- down planning for visitor 

services, we will consider ways to encourage priority uses of the trails and to discourage 

or mitigate non-priority uses, whether they are from the Bay Trail or not.

D.18. Comment: For many years, the Visitor Center in Fremont has been a water and toilet 

stop for bike clubs out on large group rides, usually on weekends. Without notice, 

suddenly the facilities will become overcrowded by non-priority users. Members of these 

groups do not hang around to enjoy wildlife as the ride is the “thing” as they head off 

along Marshlands Road. As the Bay Trail expands, such large groups will follow its 

route wherever it goes or is said to go e.g. per the Bay Trail map. There is no doubt that 

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these large speeding groups would dramatically disturb wildlife. Just as all organized 

races are banned from the Refuge, these informally organized rides must be specifically 

banned as well. (CCCR)

Refuge Response: Marshlands Road is the property of Caltrans and any issues with 

through use of the road by bicyclists would fall under their jurisdiction. The issue of the 

use of Refuge trails by large groups, whether biking or hiking, will be considered as part 

of the step down planning process. 

D.19. Comment: The WO&P CD cites Federal Highway Administration 2001 standards for

sidewalks and trails as a guide to trail design for planning for trail-sharing. That 

reference may inform structural planning but is not sufficient for the determination of 

shared-use priorities on a Refuge trail.

In the WO&P CD it is suggested that trail sharing can be informed by signage that 

promotes trail etiquette e.g.: “...bicycles should give an audible warning before passing 

other trail users.” IF all trail users are moving in the same direction, there is space such 

that safety isn’t a concern, and there is no wildlife present that would be disturbed by the 

sound or bike speed, that “etiquette” would apply.

But the same etiquette cannot and should not apply if it would disrupt priority uses. If 

one birdwatcher is on a trail, moving along carefully in hopes of a good sighting, any 

audible warning from a bicyclist would disrupt the activity and very likely cause birds to 

flee or remain hidden from view. If a large group blocks the trail, gathered to hear an 

interpretative leader discuss adjoining habitat and wildlife, there should be no 

expectation that the group give way to a bicyclist. Refuge priority etiquette should 

require a bicyclist to quietly dismount and walk past as space allows.

This etiquette is particularly important for non-priority bicyclists or joggers to 

understand. While compatibility may or may not exclude their trail use, the individuals 

need to be aware that their use is secondary and that rapid movement and loud noises 

disturb wildlife. I recall watching a jogger on the Mallard Slough Trail as he threw 

rocks at nesting terns that arose to fly toward and above him. He clearly did not 

understand the birds’ action nor realize that he’d caused it.

A Trails CD needs to stipulate that priority-use bicycle riders on the Refuge have the 

responsibility to disrupt neither wildlife nor other trail users. It also should stipulate 

signage or other actions that educate non-priority users (e.g. exercisers) about the limits 

to their use of the facility and that the Refuge can prohibit their use if those limits are 

ignored. (CCCR)

Refuge Response: The National Wildlife Refuge System recognizes six priority uses of 

its lands: hunting, fishing, interpretation, environmental education, wildlife observation 

and wildlife photography. Hiking, biking, car touring, among others, are all potential 

methods for conducting these priority uses. Given the diversity of uses and ways of 

conducting these uses, there is the strong potential for conflicts between different user 

groups. As part of our step down planning process for visitor services, we will consider 

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ways to encourage priority uses of the trails and to discourage or mitigate non-priority 

uses. In addition, we will seek ways to manage trail user conflicts.

D.20. Comment: The WO&P CD and other documents stipulate that trail use will be 

monitored by periodic law enforcement with scheduled biological surveys used to report 

habitat disturbance. While there is every reason to praise the effort and intentions of 

Refuge staff, facts fly in the face of the effectiveness of this level of monitoring. In the 

years that the writer has worked with the Refuge, it is seldom that Refuge Law 

Enforcement (LE) is fully staffed and/or present, allowing for too frequent turnover and 

time given to training. Even so, and even with an added LE position, these particular 

30,000 acres are an overwhelming stretch to monitor. Additionally, biological surveys 

are generally annual and cover limited ground. Again, it is difficult to consider these 

surveys as effective trail monitoring resources. (CCCR)

Refuge Response: Comment noted.

D.21. Comment: The documents do propose training all members of staff to be able to be able 

to answer questions and otherwise inform members of the public they each encounter in 

their jobs. This action may develop a new “anywhere” resource that could also 

contribute to trail monitoring. (CCCR)

Refuge Response: Comment noted.

D.22. Comment: At some locations, remote cameras could be used, compiling data for 

periodic review. It is possible that one or more academic institutions or researchers 

might be interested in designing and implementing portions of a suitable monitoring 

program. Another method could be volunteer Trail Stewards, possibly people who walk 

the trails already and would respond to training to be able to answer questions while also 

gathering data about the trail uses encountered. [Please also see comments below 

regarding volunteers.] (CCCR)

Refuge Response: The issues raised about trail monitoring are noted. The use of 

cameras and volunteer Trail Stewards will be considered as part of our step down 

planning process.

D.23. Comment: It is something of a surprise then to see boating listed in the CCP as NonWildlife Dependent Recreation (4.12.9, p. 174). As the Recreational Boating CD (RB 

CD) has a finding of “Use is compatible with Stipulations” it seems the use should have 

been classified as wildlife-dependent. Similarly, the EA Alternatives public use entries 

include multiple boating actions. It would be helpful if these conflicting references were 

clarified for the final documents. (CCCR)

Refuge Response: The discussion on boating has been moved to the hunting, fishing, 

and wildlife observation sections under the Current Management, Public Uses section of 

the CCP (4.12) as boating is used to facilitate these priority uses.

D.24. Comment: It has been at least a year since the State Coastal Conservancy approved the 

final EIR for the Water Trail, a plan designed to support increased number of and 

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improved sites for small-craft access to the Bay. Its initial planning actions have already 

begun, very possibly leading to ever greater numbers of boating visits to the edges of the 

Refuge. On occasions of the highest tides I have seen such boaters navigating in the 

middle of Greco Island and the marshes along Newark Slough. The Water Trail can 

make such instances of disturbance more frequent and possibly involve more boats per 

disturbance instance. As these very sensitive habitats support endangered species and 

can have no fences, extensive signage and outreach will be needed to inform boaters that 

the marshes are closed at all times.

The Water Trail Plan is neither mentioned nor discussed in the RB CD discussion but it 

and Refuge actions to protect wildlife from more frequent disturbance must be 

discussed. (CCCR)

Refuge Response: As part of their EIR, the Water Trail identified impacts to natural 

resources due to disturbance from increased boating use of Bay waters, and they have 

proposed mitigations. As of the current plan, no new public launch sites are planned 

within the refuge or within non-motorized boating distance of the refuge. The increased 

boat traffic that the Water Trail may create will be mitigated by their proposed 

measures. It is expected that the Water Trail’s Educational, Outreach and Stewardship 

plan will help educate new and existing boaters to boating ethics with a strong emphasis 

on resource protection messages. The refuge has one representative on the Water Trail’s 

Advisory Team, and we are involved in crafting these messages, the educational 

materials and launch site signage. All new signage will occur at launch sites. The refuge 

will continue to post boundary signs where appropriate. In addition, the refuge has 

proposed to develop and implement its own outreach program to promote responsible, 

water-based recreation (Objective 3.4). 

D.25. Comment: It was startling to find no mention of harbor seals in the RB CD discussion 

of anticipated impacts and also to find no reference citations to scientific sources about 

Bay-resident seals. The annual spring closure of Mowry Slough (to protect the pupping 

site) is mentioned but without species-specific explanation. Harbor seals respond quite 

differently to boaters than do other species discussed in the RB CD, making it more 

important to include a thorough review of the anticipated impacts of boaters.

Refuge Biology staff have or have access to extensive South Bay harbor seal data and 

studies that must be considered as part of the RB CD. (CCCR)

Refuge Response: Comment noted. We have included additional details on harbor 

seals in the recreational boating CD.

D.26. Comment: As boating can be a vehicle for all of the priority public uses, the RB CD 

should review each of those uses, separately and cumulatively, if there may be 

anticipated impacts. For instance, it should consider impacts from fishing debris (fishing 

lines) and disturbance by photographers who may enter closed areas to get a better shot.

(CCCR)

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Refuge Response: Comment noted. The CDs for recreational boating, wildlife

observation and photography, fishing, and hunting have been reviewed to assess 

anticipated impacts through boating.

D.27. Comment: None of the documents mention the PA Dock but it should be included. 

Small craft leaving that site can easily paddle to the Faber-Laumeister unit or to the 

shoreline edging Pond A1. This site has been identified by the Water Trail as suitable 

for support to improve it as a boating launch site i.e., it could handle more boater traffic 

in the years ahead. (CCCR)

Refuge Response: Comment noted. The Palo Alto Baylands launch site is included.

D.28. Comment: Knowing how long it takes for Refuge airboats to navigate to/from the Jarvis 

ramp on Newark Slough for annual rail surveys, it was good to see the concept of a 

Dumbarton boat ramp included. That ramp idea is not mentioned in the Biological 

Alternatives but it should be. Survey time is money. For Alternative C, a possible new 

LE boat launch site is mentioned to provide faster Bay access. While the primary use of 

the proposed ramp is described as public use, it makes planning sense to use the CCP to 

describe how the ramp could provide greater efficiency for Refuge operations.

As this ramp is conceptual at this time, it would be expected that a more complete 

proposal would undergo its own environmental review. (CCCR)

Refuge Response: Comment noted.

D.29. Comment: For years it was curious to me that the bridges that cross Newark Slough 

near Headquarters did not have “No Wake Zone” signs. Each winter, hunters that 

stayed out until the tides were almost too low to return, drove full throttle past 

Headquarters to the Jarvis ramp, their wakes washing broadly through the marshes. I 

don’t know if those No Wake signs ever got posted but do understand that jurisdictional 

issues complicate most waterway signage situations.

One possible action is that the Refuge work with other agencies to seek means to 

streamline sign placement on behalf of sensitive habitats and do so under Alternative B. 

Better public education through signage may be helpful to other agencies as well.

(CCCR)

Refuge Response: We will investigate placement of no wake signs along Newark 

Slough. Also, as a member of the Water Trail Advisory Team, we will work with others 

on boating signage and education to reduce impacts to wildlife and habitat.

D.30. Comment: As two active fishing sites are informal and may disrupt some habitat, it 

would be better to provide a fishing pier at those locations. While Alternative B includes 

the objective of “...also design and install a small fishing platform at Coyote Creek and 

Faber-Laumeister.”, the documents do not provide any project descriptions of the 

proposed installations. That means that this EA cannot adequately review these 

projects and environmental review may be needed when design details are available.

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The documents also propose that a new boardwalk be built along the entire length of the 

interior levee at Faber-Laumeister. It raises the question of whether the boardwalk and 

fishing platform will be connected structures. The current access to the FaberLaumeister fishing shoreline was not described. If the two structures will be connected, 

under NEPA, they should be considered a single project for review purposes. (CCCR)

Refuge Response: In the CCP, one of the fishing platforms was incorrectly named 

“Coyote Creek.” The proposed action is to build a small fishing platform at Coyote Creek 

Lagoon in order to improve fishing access. Fishing is already permitted at the site. The 

fishing platform at Faber-Laumeister is to be part of the proposed boardwalk. Again, 

fishing is permitted activity at this location as well. 

D.31. Comment: One of the Refuge “learnings” over these decades is that the design of the 

Alviso Environmental Education Center building, while aesthetically attractive, was 

highly inefficient for heating and cooling. The design also failed to recognize the need 

for the building to serve as a secondary visitor center. (CCCR)

Refuge Response: Under Objective 3.1, Strategy 14, we have acknowledged that the 

EEC needs to be improved in order to provide visitor information and contact facilities.

D.32. Comment: The documents omit discussion and CD justification of the basis for 

remodeling. It is not at all sufficient to use repeated statements like “...green/LEED 

features” without explaining what problem resolution/benefits those features or others 

would provide. What is the measurement basis that will demonstrate the value of 

remodeling? Utility usage? EE program requests vs. actual usage? Current extent of 

contact services vs. future service in this building? Other? Please improve each of the 

documents to present that information. (CCCR)

Refuge Response: Under Executive Order 13514 (Federal government’s commitment 

to sustainability and reducing greenhouse gases) and the USFWS’ climate change policy 

and its mitigation plan, the Service has committed to reducing the carbon footprint of its 

facilities, vehicles and workforce and to become carbon neutral by 2020. As a result, the 

Refuge will seek to attain the highest possible standard that is realistically achievable in 

its new construction and facility remodels. The rationale for Objective 3.2 and 4.5 have 

been augmented to reflect these goals. We have decided to use the LEED standard, 

which is a widely accepted standard system. There are many variables within the LEED 

model, and it is not practical at this time to determine which elements are possible and 

what the cost savings may or may not be.

D.33. Comment: The documents also omit discussion about how the final decisions of the ongoing South Bay Shoreline Study regarding final alignment of the proposed Alviso levee 

which may impact the EEC. That action could influence the remodeling plan and even 

involve the need to move the building. Please add this discussion and incorporate

appropriate contingencies plans to document discussion and findings. (CCCR)

Refuge Response: Any future remodels of the Environmental Education Center will be 

considered against the final proposed action of the Shoreline Study. 

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D.34. Comment: It was good to see proposals (Restoration Education, Slow the Flow 

programs) that expand programs suitable for college-level (adult) audiences. Other than 

the Slow the Flow program, for too long programs suited to adults have been largely in 

the interpretative program which lack the planned structure of the EE program. This is 

unfortunate because much of the curriculum of the EE programs is upgradable for use 

with adults. Adults like mud labs too!

Environmental Education for Refuge Volunteers: [Please also see comments below 

about the Volunteer Program.] While it is valuable to make EE curricula available to a 

broader public, the Refuge should not continue to overlook the adults with whom it will 

get the most “bang for the buck.’

For years, the best-informed Refuge volunteers, this writer among them, became wellqualified through self-driven education. Unfortunately such individuals represent only a 

small portion of the potential world of volunteers. As was learned during development of 

the original Salt Pond Docent program, very well qualified volunteers, often nonretirees, made the decision to volunteer only after they knew there would prepare 

through an in-depth, habitat-topical training program. Another tier of volunteers are 

willing to give their time but, especially if they will fill public-contact roles, need the 

same kind of topical training. For similar reasons, the Refuge has recognized in the 

CCP the importance of training all members of its staff for public contact.

The Refuge needs to modify its adult-level programs to enhance the capabilities of 

volunteers, current and new, and of all members of staff. (CCCR)

Refuge Response: The refuge will continue to seek a balance of programming for its 

diverse user groups. In Objective 4.1, Strategy 3, we will be seeking different ways to 

convey the main messages of the refuge, and as part of this process, we will consider the 

suggestion of education programs for adult audiences.

D.35. Comment: Often Interpretative programs are led by either volunteers or by partner 

organizations, actions that expand Refuge offerings. When these presenters are wellinformed and qualified for the task, this is an exceptional way to build the program. As a 

former and sometime still leader of such programs, it is unfortunately clear that the 

Refuge does not (perhaps cannot) monitor these programs for quality or content. On 

occasion and in my observation, a presenter may misrepresent the Refuge, include 

inaccurate content or may not provide a program deserving of a visitor’s time, 

representing the Refuge poorly. That outcome reduces the likelihood that a visitor will 

return. (CCCR)

Refuge Response: The refuge agrees and has identified the need for better and 

increased training for its volunteers. We have included a commitment to improve this in 

Objective 5.1, Strategy 4, “Establish a quality training program that will allow 

volunteers to conduct biological, environmental education, and interpretation 

activities...”

D.36. Comment: It is of great concern that the Alternatives propose green/LEED building 

programs with no explanation of how that curriculum is suited to the Refuge. In local 

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communities today, sustainability themes pervade all planning activities including the 

use of LEED standards. Universally, the missing component in the sustainability 

statements is wildlife and its habitats. Again and again, these descriptions fail to 

consider outdoor wildlife-impacting issues like pesticide use, pest-control, invasive 

plants, bird-safe windows, predator perching and other problems. At the Refuge, 

wildlife and their habitats need to be central to each and every program. Any buildinggreen content included needs to stress the issues that developers consistently omit – 

wildlife.

The CCP/EA/CDs need to present its plans for EE and Interpretative programs to give 

voice to sustainable wildlife. The programs could be called “Sustainable Wildlife.” As a 

Refuge advocate, I would take great pleasure in handing material about that program to 

any developer! (CCCR)

Refuge Response: The refuge’s public programs are, and will continue to be, based on 

the USFWS mission, the refuge purpose, and current (and future) FWS initiatives. Any 

future programming based on our building remodels or green technologies and 

construction will be tied to the same goals. The commenter’s specific suggestions are 

noted for future planning.

D.37. Comment: Because sufficient resources have never been given to volunteer labor, the 

Refuge perpetually struggles to sustain adequate numbers and quality of its volunteer 

workforce. The documents refer to this problem, in part, in the Alternative B proposal 

to “Separate visitor center roles from the volunteer coordinator roles.” In effect, and for 

many years on a daily basis, the Volunteer Coordinator fulfills an interpretative, contact 

station management function, directly undercutting his/her ability to serve as volunteerrecruiter and employer-in-chief on behalf of ALL Refuge functions. In fact, the 

Volunteer Coordinator role may contribute more effectively to all Refuge activity if it 

was an administrative arm, not a unit of Visitor Services. Please keep this role-change in 

the Refuge Alternative B plan! (CCCR)

Refuge Response: Comment noted.

D.38. Comment: While the goals presented in Alternative B for this program are admirable 

(build a larger volunteer corps, expand docent program, establish stewardship programs 

at remote units), none can be achieved unless the program provides new benefits to the 

new recruits. Sadly, few consider recognition for total hours served as a significant 

benefit.

The most effective benefit will be a substantive training program. The current volunteer 

development mode today often requires almost one-on-one training of staff to volunteer, 

even to the basic topics of the Refuge’s mission. That one-on-one emphasis burns staff 

time i.e. is inefficient. From a staff perspective, it would be more helpful if a volunteer 

came to a job with at least an introduction to the wildlife/habitat issues involved.

The science-run nature of Refuge management is particularly attractive to individuals 

who enjoy science even if only as an avocation. Science, by its nature, is about 

continuous learning. As such the most likely volunteer recruits are people who will be 

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attracted to a program that helps them expand their knowledge. That makes training 

the best reward the Refuge can provide.

Training does not have to be limited to classroom-style teaching but there should be a 

tracking mechanism by which training can be tracked by topic, date and time involved. 

That data can become a basis for matching volunteers to the jobs required.

Alternate training forms can include materials of EE programs, DVD recordings, online 

access to programs like those at USGS about the salt pond restoration, a lending library 

of recommended books and other training methods. There could be a Volunteer training 

workstation for individual, computer-based training. Training hours would count as 

volunteer hours and credit would be given credit for off-Refuge trainings such birdwatching classes or attendance at related public meetings or symposia. For some, 

walking-in-the-visitors shoes with a Family Discovery Pack or Refuge Geocaching can be 

a form of training as well.

Year-end rewards can recognize volunteers for personal investment in training. With 

each and every bit of training, a volunteer returns to family, friends and neighborhood as 

a better Refuge spokesperson and is more likely to continue as an active volunteer.

The CCP/EA/CDs need to include a major training program to attract and keep more 

volunteers and to improve the quality and contribution of the volunteer program overall.

(CCCR)

Refuge Response: The refuge agrees and has identified the need for better and 

increased training for its volunteers. We have included a committed to improving this in 

Objective 5.1, Strategy 4, “Establish a quality training program that will allow 

volunteers to conduct biological, environmental education, and interpretation 

activities...” Commenter’s specific suggestions are noted and will be considered during 

the training program planning. 

D.39. Comment: Why is there no trail between Marsh and Seaport? I have never seen the 

area behind the buildings (commercial and trailer parks) except in Google maps satellite 

view and from Bayfront Park, but I would think that would be a potential location for a 

trail. Is it because Cargill wouldn't agree to it because they have dreams of development 

someday and don't want to provide trail access now? (Jones)

Refuge Response: There is no Refuge trail between Marsh Road and Seaport 

Boulevard because the Refuge does not own any properties between those two roads.

D.40. Comment: At Coyote Slough I observed several people in a motorized boat with rifles.. 

They threw bottles into the water and shot them. This was in front of the Harbor Seal 

haulout side on the north bank. 

 

Several times at Coyote Slough the 2 shrimp boats from Alviso stopped in front of the 

seal haulout site and emptied their nets. Their motors were noisy.

 

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There was no mention in the Plan about the impact of these shrimp boats. There are 2 

boats from Alviso and sometimes one from Redwood City and a big one from San 

Francisco that I have seen going up and down the bay dragging nets.

 

Several times at Coyote Slough fishermen in motor boats anchored in front of the 

haulout site and fished for an hour or more. If I was able to get CF numbers from the 

boats I reported it to law enforcement but of course there was no action.

 

At Newark Slough where it enters the bay I have seen jet skiers come out of Newark 

slough and go out into the bay and make big circles and a great amount of noise near the 

Harbor Seal haulout side.

 

At Newark Slough where it enters the bay I have seen hunters hunting from the marsh 

with dogs running thru the marshes. This has occurred on the north bank near the 

haulout site and on the spit of land at the junction of Newark Slough and Plummer 

slough.. 

 

If I was able to get CF numbers from the boats I reported it to law enforcement but of 

course there was no action.

 

At Mowry slough near the mound which is the major Harbor Seal pupping site for the 

entire bay I have seen a hunter hunting from the marsh with a simulated duck with 

spinning wings on poles stuck in the marsh. He was shooting at ducks that landed in the 

slough. The hunter was very close to an open area where the seals usually haul out.

 

At Mowry slough near the mound I have seen a shrimp boat go up past the mound 

dragging a net. These boats usually stay in the deeper bay so this was very unusual.

(Bell)

Refuge Response: Thank you for the information. It has been relayed to the refuge 

manager.

D.41. Comment: I have suggested several times in writing to Clyde and others that Mowry 

Slough be closed to boating all year and to hunting because Harbor Seals have been 

known to abandon haulout sites after disturbances. If this happens it may impact the 

number of Harbor Seals. As many as 300 seals and pups have been observed at Mowry 

Slough at the pupping season. See http://userwww.sfsu.edu/~halmark/seals.htm (Bell)

Refuge Response: Mowry Slough is closed to boats March 15-June 15 to protect the 

harbor seal haulout during their breeding season.

D.42. Comment: Here are a few comments about the Compatible Determination for 

Recreational Boating- 

 

I served in the Coast Guard Auxiliary for several years. We patrolled the south bay on 

weekends aiding boaters in distress. This experience taught me much about hazard in 

the bay. The afternoon winds in the summer make it very hazardous for small kayakers 

and canoers. Immersion in cold water for more than a few minutes without a good thick 

P-24
wet suit means death! The shallow bay makes it likely that kayaks and canoes will run 

aground and get stuck until the tide rises. I used to have a sea kayak and I would launch 

at Palo Alto and paddle to Newark Slough where my wife would pick me up with the car. 

Several times I got stuck in the mud while exiting from Palo Alto and trying to find the 

entrance to Newark Slough. When in the Coast Guard several times we had to call for a 

helicopter to rescue boaters that were stuck in the mud. Several times high winds in the 

afternoon prevented me in my kayak from returning to the Palo Alto launch site until the 

winds died down in the evening. Boating stores are now pushing the sales of inexpensive 

and light weight sit-on kayaks. These expose boaters to the cold water and are hard to 

manage in winds.

 

Kayaking and canoeing in the open bay can be very hazardous. 

If launch sites and use of non-motorized boats are publicized there will be more incidents 

requiring USFWS and Coast Guard assistance. There will be people trying to walk thru 

the marsh after being stuck in the mud. These rescue attempts will have an impact on 

the marshes. 

 

Corkscrew Slough at Bair Island is being used by kayaks and canoes to circle inner Bair 

Island. I have paddled it and observed Harbor Seals and pups there. If small boating is 

popularized this will impact the Harbor Seals there. (Bell)

Refuge Response: Any recreational boating promoted by the Refuge will include an 

outreach and education component to address wildlife disturbance and boater safety. 

Should new recreational boating opportunities promoted by the Refuge result in adverse 

impacts to wildlife, habitat, and human safety, we will reconsider these opportunities. 

We are also involved as an advisory member of the San Francisco Bay Area Water Trail. 

Through this Trail development, we will continue to encourage wildlife/habitat 

appropriate and safe non-motorized small boat recreation.

D.43. Comment: The map of launch sides omitted the floating ramps for launching of small 

boats at Redwood City and at Palo Alto. (Bell)

Refuge Response: Thank you for the information on the ramps at Redwood City and 

Palo Alto. They have been added to the map.

D.44. Comment: We support Alternative B, including expansion of opportunities for NMSB 

launch sites, as stated in Section 2.7 (Development of Alternatives). We would also like to 

see the expansion of opportunities for NMSB destination sites. Destination sites are 

sites at which non-motorized boats may land and re-launch, but are usually not 

accessible by car. They provide NMSB users with an opportunity to rest, picnic (with 

appropriate packing out of trash), or find refuge during emergencies. Providing specified 

destination locations for users to disembark can prevent potential problems with boaters 

landing in unauthorized sensitive areas and may also provide a location suitable for 

educational messages about boating and wildlife. Water Trail staff are available to assist 

Refuge staff with providing the boater perspective and input on the suitability of a site 

as a launch or destination. (SFBAWT)

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Refuge Response: As a member of the Water Trail Advisory Team, we will consider 

wildlife-compatible destination sites in your planning process and have included this in 

the CCP Objective 3.3.

D.45. Comment: Thank you for specifically mentioning that the Refuge public use 

opportunities are expected to support the San Francisco Bay Trail and Water Trail Plan 

goals of providing access around the entire Bay (Goal 3, Objective 3.1, 3.3 and 3.4). The 

Water Trail supports the strategies identified under Objective 3.3 to promote waterbased wildlife observation programs and under Objective 3.4 to implement a public 

outreach program to promote responsible, water-based recreation in order to decrease 

wildlife disturbance. The strategies under Objective 3.4 mention partnering with waterbased recreation organizations to promote wildlife disturbance reduction messages and 

the distribution of prepared outreach materials. The Water Trail is currently developing 

education, outreach, and stewardship materials to increase boater awareness about 

wildlife disturbance and is working to disseminate this information regionally to ensure a 

consistent message. We would be interested in partnering with the Refuge to develop 

and disseminate boater education materials. (SFBAWT)

Refuge Response: Comment noted. We look forward to working with you on boater 

education through our participation in the Water Trail Advisory Team.

E. Environmental Education

E.1. Comment: Could Goal 4 be expanded beyond environmental education to incorporate 

historical interpretation? This could tie into the Partnerships in Paragraph 6.7 (e.g., 

universities and Ohlone for history). (Bamford)

Refuge Response: Comment noted. New interpretive programs will include historical 

interpretation. We will work with partners to facilitate these programs.

F. Staffing

F.1. Comment: Levels of staffing should be increased to meet the growing demands for 

monitoring/research, environmental education and enforcement. (CCCR)

Refuge Response: Comment noted. Increased staffing levels are necessary to keep up 

with existing activities as well as new actions prescribed in the CCP.

G. Jurisdiction and Acquisition

G.1. Comment: The Refuge site includes intertidal and subtidal lands subject to CSLC 

jurisdiction... Therefore, the CSLC should be named as both a trustee and a responsible 

agency for the Project see (see page 2 of this letter under CSLC Jurisdiction) (CSLC)

Refuge Response: We have updated the CCP to include CSLC jurisdiction in sections 

1.5.3 and 3.2. 

G.2. Comment: Page 9, Table 1. Don Edwards SF Bay NWR Timeline of Property 

Acquisition

a) Acreage - The document repeatedly mentions that the DESFBNWR is 

approximately 30,000 acres. Table 1, listing the acreage in the DESFBNWR, 

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cumulatively adds-up to 35,742.26 acres – a variance of nearly 20% from the 

30,000 acre figure. 

b) Donation - With regards to the 9,600 acres transferred by Cargill Salt to the 

DESFBNWR in 2003, the table incorrectly shows this transaction as a 

“Purchase” when in fact a majority of the land (more than 50% of the value) 

was donated by Cargill Salt (See Exhibit A – Statement of Just Compensation). 

Please include the word “donation” on this line. 

c) Labeling - There is also an inconsistency in the labeling of properties in Table 

1. Approximately 14,000 of the 15,437 acres acquired by the Refuge in 1979 

were salt ponds. Pond A6 was also leased and used by the salt company as a 

salt pond along with Pond SF2. (Cargill)

Refuge Response: We have revised this table to accurately reflect our acreage 

according to our Realty Office records. We understand that Cargill lands acquired 

include a combination of purchase and donation. We have included this in the revised 

Table 1. 

G.3. Comment: Page 9-10, Section 1.5.4. Land Protection – This discussion is misleading 

because it suggests that Congress approved the particular acquisition boundary depicted 

on the maps included throughout this document. In fact, that is not the case. This 

section needs to be expanded in order to clarify what in fact Congress approved in 1988. 

The 1988 legislation authorizing expansion of the Refuge boundaries beyond those 

originally approved by Congress in 1972, authorized the inclusion of “[u]p to 20,000 acres 

in the vicinity of the areas described [in the 1972 legislation] and similar to the areas 

described [in the 1972 legislation], which the Secretary determines are necessary to 

protect fish and wildlife resources.” San Francisco Bay National Wildlife Refuge, 

Enlargement of the San Francisco Bay National Bay Refuge, Pub. L. No. 100-556, 102 

Stat. 2780 (1988). However, no map depicting expanded boundaries was included as part 

of that legislative authorization. On Tuesday, July 12, 1988, at the U.S. House of 

Representatives, Subcommittee on Fisheries and Wildlife Conservation and the 

Environment, Committee on Merchant Marine and Fisheries, Dean of California Hon. 

Don Edwards testified in front of the subcommittee:

“H.R. 4272 will do only one thing: give these property owners the option, which they do not 

now have, to donate or sell wetlands and wildlife habitat to the wildlife refuge. Because 

the bill requires that land be purchased only from willing sellers, only those local 

landowners who have express an interest in selling or donating their land to the refuge will 

be affected by the scope of the legislation.”

On Tuesday, July 12, 1988, at the U.S. House of Representatives, Subcommittee on 

Fisheries and Wildlife Conservation and the Environment, Committee on Merchant 

Marine and Fisheries, Paul Shepherd, Vice President and Land Manager, Leslie Salt 

Company expressed concerns which ultimately led to the elimination of a map depicting 

the proposed expanded boundaries for the refuge: 

P-27
“Our company strongly supports responsible expansion of the San Francisco Bay 

National Wildlife Refuge. But, for the reasons that I will outline for you, we must 

just as strongly oppose the approach used by the bill, H.R. 4272, which is the 

subject of this hearing.

. . .

Mr. Chairman, our specific problem with the bill is the incorporation of the map 

prepared by the U.S. Fish and Wildlife Service. As the boundaries are proposed, 

Leslie Salt Company has a major stake in this legislation.

. . .

The map was prepared by a single-purpose Federal agency, outside the procedures 

set forth in NEPA, the National Environmental Protection Act. It has been 

represented as a conceptual map only, but that is not the case. Specific parcels are 

included or excluded. The map’s boundaries are anything but general or 

conceptual in nature. 

. . .

The incorporation of the map, in other words, is tantamount to a Federal lien on 

the properties included within its boundaries.

. . .

We encourage the Federal Government to negotiate fairly with property owners

for any parcels in which the government may be interested. However, we do not 

believe it is fundamentally fair for the Government to attempt to stack the deck in 

its favor by intimidating other potential buyers with legislated maps. This is the 

practical effect of the map and completely contradicts the legislation’s concept of a 

willing seller.” 

Hearing on H.R. 4272 A Bill to Enlarge the San Francisco Bay National Wildlife Refuge 

Before the H. S. Comm. On Fisheries and Wildlife Conservation and the Environment, 

100th Cong. 2d Sess 11-12, 16 (1988) (statement of Paul Shepherd, Vice President and Land 

Manager, Leslie Salt Company).

The congressional record from the Senate hearings on the bill reflects that the map 

originally proposed for inclusion was not adopted by Congress as part of the final 

legislation:

“As introduced, the House and Senate bill to expand the refuge, H.R. 4272 and S. 

2710, respectively, referred to a proposed map entitled “San Francisco Bay 

National Wildlife Refuge Additions – Proposed,” dated March 1988, depicting 

lands and water for inclusion in San Francisco Bay Wildlife Refuge. This reference 

is no longer included in Section 201 of S. 1986.” 

Excerpt from October 14, 1988 Senate Hearing on S. 1986, S16373 (1988) (emphasis added). 

This inaccurate depiction of Cargill’s fee-owned lands as being within the “Approved Refuge 

Boundary” or “Approved Refuge Acquisition Boundary” and included within the Refuge’s 

Planning Units pervades the Draft CCP including, without limitation, the following... (Cargill)

Refuge Response: We have revised section 1.5.4 Land Protection, to articulate what 

Congress approved in the 1988 legislation (Public Law 100-556) and what Congress gave 

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the Service the authority to do regarding additional land acquisition. Based on the 1988 

legislation, the Service prepared a 1990 Environmental Assessment with a map titled, 

“San Francisco Bay National Wildlife Refuge Potential Additions.” This map was 

developed for Refuge planning purposes and we have since referred to the map as the 

approved acquisition boundary, as defined by Service policy. Development of the map 

based on the 1990 EA does not need to be “approved” by Congress in order for the 

Refuge to use it as a planning tool. However, we have better articulated that we only 

wish to acquire land from willing sellers based on certain criteria (i.e., refuge goals & 

opportunities). In addition, we have revised Figure 3 of the CCP to reflect the 1990 

Environmental Assessment.

G.4. Comment: Page 22, Section 2.4.1. Issues, Concerns, and Opportunities – Cargill’s 

comment of “Do not include Cargill Salt’s fee-owned lands in the CCP process” should 

be dually noted. This is a clear indication that currently Cargill is not a willing seller and 

does not want its lands included in the planning document. (Cargill)

Refuge Response: We understand that currently Cargill is not a willing seller. 

G.5. Comment: Page 27, Figure 4. South Bay Salt Pond Restoration Project and Refuge 

Boundaries – This exhibit is grossly mislabeled showing most of Cargill’s fee-owned 

lands as within an “Approved Refuge Acquisition Boundary”. This was not authorized 

by Congress and therefore, not “approved”. Please remove this reference from the map.

(Cargill)

Refuge Response: This map was replaced with a Refuge Boundary Map that shows 

only Refuge lands that are either owned in fee title, leased, has an existing easement, or 

agreement. It also shows the footprint of the South Bay Salt Pond Restoration Project. 

G.6. Comment: Page 28, Figure 5. Refuge Units and Vicinity Map – This exhibit is 

grossly mislabeled showing most of Cargill’s fee-owned lands as part of the “Don 

Edwards S.F. Bay National Wildlife Refuge” and the Refuge planning units. Cargill’s 

lands are not part of the Refuge nor should they be represented as part of the planning 

units. Please remove Cargill’s properties and this reference from the map. (Cargill)

Refuge Response: This map was replaced with a Refuge Boundary Map that shows 

only Refuge lands that are either owned in fee title, leased, has an existing easement, or 

agreement. 

G.7. Comment: Page 29, Figure 6. Refuge Map – This exhibit is grossly mislabeled showing 

most of Cargill’s fee owned lands as within the “Approved Refuge Boundary”. This was 

not authorized by Congress and therefore, not “approved”. Please remove this reference 

from the map. (Cargill)

Refuge Response: This map was removed from this section as it was not necessary in 

the CCP. We refer to the Refuge Boundary Map, which only show Refuge lands that are 

either owned in fee title, leased, has an existing easement, or agreement. 

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G.8. Comment: Page 30, Figure 7. Newark and West Bay Units – This exhibit is grossly 

mislabeled showing most of Cargill’s fee owned lands within the “Approved Acquisition 

Boundary”. This was not authorized by Congress and therefore, not “approved”. Please 

remove this reference from the map. Also, shown in white on the legend of the map 

under “Ownership Status” is the phrase “in holding”. This falsely indicates that all 

properties on this map shown in white are “in holding” for the Refuge. Please remove 

this reference from the map. (Cargill)

Refuge Response: We have removed the references to “Approved Acquisition 

Boundary” and “in holding” from the map. 

G.9. Comment: Page 34, Figure 8. Alviso and Mowry Units – This exhibit is grossly 

mislabeled showing most of Cargill’s fee owned lands with the “Approved Acquisition 

Boundary”. This was not authorized by Congress and therefore, not “approved”. Please 

remove this reference from the map. Also, shown in white on the legend of the map 

under “Ownership Status”, is the phrase “in holding”. This falsely indicates that all 

properties on this map shown in white are “in holding” for the Refuge. Please remove 

this reference from the map. (Cargill)

Refuge Response: We have removed the references to “Approved Acquisition 

Boundary” and “in holding” from the map.

G.10. Comment: Page 52, Figure 12. Predicted 100-year Floodplain for the South San 

Francisco Bay Region - This exhibit is grossly mislabeled showing most of Cargill’s feeowned lands as part of the “Don Edwards S.F. Bay National Wildlife Refuge”. Cargill’s 

lands are not part of the Refuge. Please remove this reference from the map. (Cargill)

Refuge Response: Comment noted. This floodplain map was obtained by the Corps and 

it inaccurately identifies Cargill fee-owned lands as part of the Refuge. We have 

replaced the map with a correct version. 

G.11. Comment: Page 62, Figure 15. Distribution of Habitat Categories within the 

Approved Acquisition Boundary – Since no “boundary” exists as part of the 

Congressional Record, Figure 15 has no basis for the breakdown it was given. Figure 15 

should be removed from the plan. (Cargill)

Refuge Response: We use the term and associated map “approved acquisition 

boundary” because it has undergone NEPA review and has been approved by the 

Service and is the appropriate title per Service policy. This map does not need to be 

approved by Congress to be used by the Service as a planning tool. Public Law 100-556 

did not specify a boundary for expansion, but gave the Service discretion to which lands 

it could acquire. The Service then conducted a formal planning and NEPA process to 

determine which lands to consider for additions to the Refuge. We have left this figure 

as is in the CCP to identify habitat types with the approved acquisition boundary. 

G.12. Comment: Page 66, Figure 16. Habitat Map - This exhibit is grossly mislabeled 

showing most of Cargill’s fee-owned lands as part of the “Don Edwards S.F. Bay 

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National Wildlife Refuge”. Cargill’s lands are not part of the Refuge. Please remove 

this reference from the map. 

This map also incorrectly shows one of Cargill’s parcels in the City of Fremont as 

Agricultural. This property is zoned and General Planned in the City of Fremont as 

“Tech Industrial” – please label it as such. This exhibit also incorrectly labels two hills 

owned by Cargill as Active Salt Ponds. Lastly, the small insert map depicting the 

Refuge units is incorrect. It is similar to Figure 5, which incorrectly includes Cargill’s 

lands as part of the Refuge Units. Please make the appropriate corrections by removing 

references to Cargill’s property. (Cargill)

Refuge Response: We have removed any references to Cargill lands as being part of 

the Refuge. However, some Cargill lands continue to be identified as within the 

approved acquisition boundary as described in the 1990 EA. We have re-labeled 

Cargill’s parcel from “agricultural” to “developed.” We do not have the ability to add the 

layer titled, “Tech Industrial. The parcel of two hills owned by Cargill is already 

designated as “Upland /Grassland.” We have removed the small inset map from this 

figure. 

G.13. Comment: In order to properly set the tone of the CCP document and eliminate 

misguided figures and text, it is important to inform the reader that; although Congress 

approved the expansion of the Refuge to 43,000 acres, it did not approve a map as an 

exhibit of the law. Therefore, there is no legal map showing an “Approved Refuge 

Acquisition Boundary” as part of the Congressional Record. This message has been 

previously conveyed to Refuge staff, but unfortunately they have failed to include it. 

With that said, all figures showing properties labeled as “Approved Refuge Acquisition 

Boundary” or “Approved Acquisition Boundary” need to be removed. (Cargill)

Refuge Response: We have revised section 1.5.4 Land Protection and Figure 3, to 

articulate what Congress approved in the 1988 legislation (Public Law 100-556) and what 

Congress gave the Service the authority to do regarding additional land acquisition. 

Based on the 1988 legislation, the Service prepared a 1990 Environmental Assessment 

with a map titled, “San Francisco Bay National Wildlife Refuge Potential Additions.” 

This map was developed for Refuge planning purposes, as per Service policy, and we 

have since referred to the map as the approved acquisition boundary. Development of 

the map based on the 1990 EA does not need to be “approved” by Congress in order for 

the Refuge to use it as a planning tool. Public Law 100-556 did not specify a boundary 

for expansion, but gave the Service discretion to which lands it could acquire. The 

Service then conducted a formal planning and NEPA process to determine which lands 

to consider for additions to the Refuge. However, we have better articulated that we 

only wish to acquire land from willing sellers based on certain criteria (i.e., refuge goals 

& opportunities).

G.14. Comment: Page 63, Table 7. Habitat Types within the Approved Acquisition 

Boundary – How are these acreages derived when there is no congressionally approved 

map? The CCP should focus on the Refuge – land that is currently owned – in order to 

develop a useful table. Also, since no “boundary” exists as part of the Congressional 

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Record, Table 7 has no basis for the breakdown it was given. Table 7 should be removed 

from the plan. (Cargill)

Refuge Response: We use the term and associated map “approved acquisition 

boundary” because it has undergone NEPA review by the Service. This map does not 

need to be approved by Congress to be used by the Service as a planning tool. We have 

left this table in the CCP.

G.15. Comment: Page 69, Developed Habitats and Pond Habitats – Incorrectly refers to 

Approved Acquisition Boundary as if there were a map as part of the Congressional 

Record, which there is not. Please remove this reference from these sections. (Cargill)

Refuge Response: We use the term and associated map “approved acquisition 

boundary” because it has undergone NEPA review and has been approved by the 

Service and is the appropriate term defined in Service policy. This map does not need to 

be approved by Congress to be used by the Service as a planning tool. We have left 

these references in the CCP.

G.16. Comment: Page 116, Section 3.6.1. Land Use – Although the Refuge has the 

authorization to acquire up to 43,000 acres, there is no congressionally approved map 

depicting a boundary. What should be noted in this section is that although not all of the 

lands are under ownership of the Refuge, most of the lands listed as “Potential Additions 

to the San Francisco Bay National Wildlife Refuge” are already under public ownership 

and are managed to preserve and enhance significant wildlife habitat, protect migratory 

waterfowl and other wildlife, and provide an opportunity for wildlife-oriented recreation 

and nature study. (Cargill)

Refuge Response: The purpose of this section is to identify current land use (existing 

conditions) within the Refuge Units and land use in areas surrounding the Refuge. This 

provides context for CCP readers regarding habitats adjacent to the Refuge. Although 

some lands may be under public ownership and managed for conservation, the Refuge 

has no ability to ensure these lands will remain as such. No changes have been made to 

the section because our goal is to provide context, not planning goals. 

G.17. Comment: Page 117, Section 3.6.1. Land Use – Mowry Unit – Incorrectly includes 

Cargill’s lands within this planning unit. Please exclude Cargill’s lands (acreage) from 

this section. (Cargill)

Refuge Response: Cargill lands (acreage) are not included in this section. We have 

included only the acreage that is fee-owned or managed by the Refuge. These lands 

include: Mowry Ponds M1-M6, M12, M13, and adjacent marshes, sloughs, and vernal 

pool areas. These areas total approximately 6,000 acres. We added a sentence to clarify 

Cargill’s salt-making rights in perpetuity per the 1979 agreement. 

G.18. Comment: Page 120, Section 3.6.1. Land Use – West Bay Unit - There is a 

misrepresentation of Cargill’s Redwood City Plant Site operations where the document 

states it functions “on a limited basis”. The Redwood City Plant Site is an operating salt 

plant. Please make this correction and remove all references of “on a limited basis”. 

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This section also incorrectly includes Cargill’s lands within this planning unit. Please 

exclude Cargill’s lands (acreage) from this section. (Cargill)

Refuge Response: We have removed all references of “on a limited basis.” We have not 

included Cargill lands (acreage) as part of the West Bay Unit. 

G.19. Comment: Page 15, Table 2. Habitat Goals for the San Francisco Bay Joint 

Venture – This table is extremely confusing on how the acreages were derived. Since 

this document, the Draft Comprehensive Conservation Plan, is to be focused on Refuge 

lands, I recommend removing this table as it adds no value to the document. (Cargill)

Refuge Response: This table was created by SFBJV and we use it, in part, to guide our 

habitat management and restoration. The purpose for including it in the CCP is to 

identify that the Refuge’s CCP goals contribute to overall regional habitat goals. We 

have kept the table in this section. 

G.20. Comment: Page 37, Section 3.2. Regional and Historic Setting – West Bay Unit – 

There is a misrepresentation of Cargill’s Redwood City Plant Site where the document 

states it functions “on a limited basis”. The Redwood City Plant Site is an operating salt 

plant. Please make this correction and remove all references of “on a limited basis”.

Also, the Redwood City Plant Site is not part of the West Bay Unit as depicted on 

Figure 5 nor is the property “in holding” as depicted on Figure 7. Please remove the 

Redwood City Plant Site from the West Bay Unit. (Cargill)

Refuge Response: We have removed the phrase “on a limited basis” in the sentence of 

concern. We have removed the Redwood City Plant Site from the two maps as 

requested. 

G.21. Comment: Page 115, Section 3.5.5. Historic Resources, 1st full paragraph – The 

statement, “Given the social and economic significance of the salt industry in the South 

Bay, it is possible that the salt pond complexes would qualify as an historic district for 

the NRHP” is completely speculative and outside the scope of the CCP process. Remove 

this sentence from the plan. (Cargill)

Refuge Response: We have removed the two sentences in that paragraph. 

G.22. Comment: Page 31, Section 3.2. Regional and Historic Setting – It should be noted in 

both the Newark Unit and the Mowry Unit that Cargill Salt retains the salt making 

rights to these ponds in perpetuity, and that Cargill plans on continuing its rights in 

these ponds. Therefore, no planning will be conducted in these ponds that would 

interfere with Cargill’s perpetual salt making rights as per the Declaration of Taking 

dated June 30, 1977. (Cargill)

Refuge Response: In the Newark and Mowry Unit paragraphs, we have added a 

sentence that reads, “Under a 1979 agreement between Cargill and the Service, Cargill 

Salt retains the salt making rights in the Newark Ponds in perpetuity. Cargill plans to 

continue salt making in these ponds.”

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G.23. Comment: Page 134, Section 3.6.4. Public Utilities/Easements – There are several 

rights/easements inadvertently left out of the Newark Unit and Mowry Unit – i.e.: 

Cargill’s perpetual salt making rights need to be shown over both units, Cargill’s 

drainage and utility easement through the Coyote Tract, Tracts 102 and 103, Caltrans 

drainage easement through the Coyote Tract, Tract 103, etc. (Cargill)

Refuge Response: We will review the lease agreements we have on file and include all 

rights/easements within the Newark and Mowry Units. 

G.24. Comment: Page 188, Section 5.4. Refuge Goals, Objectives, and Strategies – 

Objective 2.4 – Please rephrase the statement “It is important to note that the Mowry 

and Newark Ponds are still active salt making ponds” to read “It is important to note 

that Cargill retains perpetual salt making rights on the Mowry and Newark Ponds; 

therefore, no change in use will be planned for these areas that would interfere with 

Cargill’s rights as per the Declaration of Taking dated June 30, 1977.” (Cargill)

Refuge Response: We have replaced the sentence to read, “It is important to note that 

Cargill retains perpetual salt making rights on the Mowry and Newark Ponds; therefore, 

no change in use will be planned for these areas that would interfere with Cargill’s rights 

as per the Declaration of Taking dated June 30, 1977.”

G.25. Comment: Page 14, Section 1.6. Related Project - It should be noted that North Creek 

was entirely donated by Cargill to CDFG. Cargill also supplied its dredge, The Mallard, 

at cost, to reconstruct the creek channel and banks. (Cargill)

Refuge Response: This is referring to the CDFG property near Eden Landing. Adding 

the recommended language regarding Cargill’s donation of land and use of the Mallard 

is irrelevant to our CCP process. The purpose of this paragraph is to identify other 

restoration projects in the vicinity of the refuge that help accomplish our mission not to 

identify donors. Such language may already be included in CDFG documents. 

G.26. Comment: Page 71, Section 3.4.2 – Summary of Habitat Categories within the 

Refuge – Developed Habitats – the reference to “two large parcels containing 

agricultural lands (876 acres total)..., offering potential restoration sites adjacent to 

freshwater marsh and tidal wetlands” includes Cargill’s Fremont Coyote Tract. This 

tract of land is approximately 91 acres that is completely isolated from any hydrology, 

separated by Coyotes Hills to the west, Hwy 84 to the south, Paseo Padre Parkway to 

the east and a dirt access road to the north. The property is Zoned and General Planned 

within the City of Fremont as Tech Industrial. Please make the appropriate corrections.

(Cargill)

Refuge Response: We have kept the reference to the “two large parcels...” in this 

section and it remains under Developed Habitats. We have removed the phrase 

“offering potential restoration sites to freshwater marsh and tidal wetlands” since that is 

speculative. 

G.27. Comment: It should be noted that, except for Pond 3C in Baumberg, all salt evaporator 

ponds are under public ownership. All the parcels listed below are now in public 

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ownership and some of them are cooperatively managed to preserve and enhance 

significant wildlife habitat, protect migratory waterfowl and other wildlife, and provide 

an opportunity for wildlife-oriented recreation and nature study:

• Pond A4 – 321 acres

• Pond A18 – 856 acres

• Baumberg Tract – 850 acres

• Baumberg Ponds – 5450 acres

• Northern Channel – 16 acres

• A8 Peninsula Parcel – 16 acres

As mentioned above, the acreage total on Table 1 is 35,742.26 acres. With the addition of 

the properties listed immediately above, the total is 43,251 acres. Also to note is the 

approved Patterson Ranch Project which will transfer approximately 270 acres into 

perpetual open space, thereby bringing the total acreage for the DESFBNWR or its 

partners in cooperative management to 43,521 acres. The acreage in the DESFBNWR 

should be consistently and accurately referred to throughout the CCP document. 

Although not all of the lands listed above are under ownership of the Refuge, it is 

understated throughout this document that most of the lands listed as “Potential 

Additions to the San Francisco Bay National Wildlife Refuge” are already under public 

ownership and are managed to preserve and enhance significant wildlife habitat, protect 

migratory waterfowl and other wildlife, and provide an opportunity for wildlife-oriented 

recreation and nature study. (Cargill)

Refuge Response: We have revised Table 1 to reflect accurate acreages. We cannot 

include the above properties in our total acquisition under purchase, lease, or agreement 

at this time since they are not owned or managed by the refuge. We can only manage 

the land we currently own in fee title, lease, or have an agreement. Therefore, we cannot 

include the above properties as part of the refuge in the CCP. We also cannot guarantee 

that the above listed properties will be managed to preserve and enhance significant 

wildlife habitat, protect migratory waterfowl and other wildlife, and provide an 

opportunity for wildlife-oriented recreation and nature study in perpetuity. 

G.28. Comment: Additional Comment: Neither Congress Nor FWS Has Adopted Any Map 

designating “Approved Refuge Boundary Maps." Such Maps, as used in the Draft CCP, 

Must Therefore be Removed.

The San Francisco Bay National Wildlife Refuge was established in 1972 by Public Law 

92-330. This law incorporated the first definition as to the boundary associated with the 

Refuge:

Sec. 2. There shall be included within the boundaries of the refuge those lands, marshes, 

tidal flats, salt ponds, submerged lands, and open waters in the south San Francisco Bay 

area generally depicted on the map entitled "Boundary Map, Proposed San Francisco 

Bay National Wildlife Refuge", dated July 1971, and which comprise approximately 

twenty-one thousand six hundred and sixty - two acres within four distinct units to be 

known as Fremont (five thousand five hundred and twenty acres), Mowry Slough (seven 

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thousand one hundred and seventy-five acres), Alviso (three thousand and eighty acres), 

and Greco Island (five thousand eight hundred and eighty-seven acres). Said boundary 

map shall be on file and available for public inspection in the offices of the Bureau of 

Sport Fisheries and Wildlife, Department of the Interior.

Sec. 3. (a) ... The Secretary may from time to time make corrections in the boundaries of 

the refuge, but the total area within the boundaries shall not exceed twenty-three 

thousand acres of land, marshes, tidal flats, salt ponds, submerged lands, and open 

waters.

Pub. L. No. 92-330 (1972) (emphasis added). Thus, the enabling legislation for the 

Refuge established its potential boundaries by reference to a map dated July 1971 

showing a "general" depiction of the boundaries, a description of four units totaling 

approximately 21,662 acres, and a limit of23,000 acres on the total acreage of lands to be 

included within the Refuge.

On March 29, 1988, Congressman Don Edwards introduced H.R. 4272, which proposed 

an expansion to the boundary of the Refuge through incorporation of a map depicting 

certain properties as lying within the Refuge boundary.

Following introduction of H.R. 4272, Paul Shepherd, then Vice President and Land

Manager for Leslie Salt Company, testified before at a House Subcommittee Hearing on 

July 12, 1988. Mr. Shepherd expressed the concerns of Leslie Salt Company, now 

Cargill, about the inappropriate designation of privately owned land as within an 

"approved" boundary for the Refuge:

[O]ur specific problem with this bill is the incorporation of a map prepared by the U.S. 

Fish and Wildlife Service. As the boundaries are proposed, Leslie Salt Company has a 

major stake in this legislation.

Leslie Salt owns well over 17,000 acres of the 20,850 acres that are the subject of the 

map. That comes to approximately 85 percent of the land authorized for acquisition 

under this bill. Moreover, the line drawn on the map takes in almost all of our 

developable lands.

[The map] has been represented as a conceptual map only, but that is not the case. 

Specific parcels are included or excluded. The map's boundaries are anything but 

general or conceptual in nature.

The targeting of so much of our land holdings for the expansion proposed by this 

legislation threatens our company with real economic harm. Regardless of the good 

intentions behind this bill, the practical effect of the inclusion of the map in H.R. 4272 

has been to cast a cloud over the land parcels that are located within its boundaries. The 

mere existence of the map in an unreported bill already has reduced the value of these 

lands.

The incorporation of the map, in other words, is tantamount to a Federal lien on the 

properties included within its boundaries.

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We encourage the Federal Government to negotiate fairly with property owners for any 

parcels in which the Government may be interested. However, we do not believe it is 

fundamentally fair for the Government to attempt to stack the deck in its favor by 

intimidating other potential buyers with legislated maps. This is the practical effect of 

the map and completely contradicts the legislation's concept of a willing seller.

Hearing on H.R. 4272 A Bill to Enlarge the San Francisco Bay National Wildlife Refuge 

Before the H. S. Comm. On Fisheries and Wildlife Conservation and the Environment, 

1OOth Cong. 2d Sess 11-13 (1988) (statement of Paul Shepherd, Vice President and Land 

Manager, Leslie Salt Company).

The congressional record from the Senate hearings on Senate Bill 1986, the corollary to 

H.R. 4272, confirms that all references to the proposed 1988 map were intentionally 

excluded by Congress from the final bill that ultimately became law:

 

As introduced, the House and Senate bills to expand the refuge, H.R. 4272 and S.

2710, respectively, referred to a proposed map entitled "San Francisco Bay National 

Wildlife Refuge Additions-Proposed," dated March 1988, depicting lands and waters for 

inclusion in San Francisco Bay Wildlife Refuge. This reference is no longer included in 

section 201 of S.1986. However, the lack of any reference to the March 1988 map in this 

legislation should not be interpreted as an expression of opposition either to the 

acquisition of any of the lands and waters depicted on that map, or to the preparation by 

the U.S. Fish and Wildlife Service of a map depicting those or other proposed additions 

of lands and waters of the refuge.

Excerpt from October 14, 1988 Senate Hearing on S. 1986, S16373 (1988) (emphasis 

added).

The final text of Public Law 100-556, which in conjunction with the original 1972 

legislation, governs FWS's authority regarding land that may be acquired for inclusion 

within the Refuge, reflects the fact that Congress rejected the proposed inclusion of the 

1988 map originally proposed in connection with H.R. 4272. Rather than reference a 

map, Public Law 100-556 expanded the maximum acreage that can be included within 

the Refuge boundary by 20,000 acres (that is, from 23,000 acres up to 43,000 acres) 

without adoption of any map showing a specific geographic boundary for the expansion 

designated by Congress:

Sec. 2. There shall be included within the boundaries of the refuge the following: 

(1) Those lands, marshes, tidal flats, salt ponds, submerged lands, and open waters in the 

south San Francisco Bay area generally depicted on the map entitled "Boundary Map, 

Proposed San Francisco Bay National Wildlife Refuge", dated July 1971, and which 

comprise approximately twenty-one thousand six hundred and sixty -two acres within 

four distinct units to be known as Fremont (five thousand five hundred and twenty 

acres), Mowry Slough (seven thousand one hundred and seventy-five acres), Alviso 

(three thousand and eighty acres), and Greco Island (five thousand eight hundred and 

eighty-seven acres). Said boundary map shall be on file and available for public 

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inspection in the offices of the Bureau of Sport Fisheries and Wildlife, Department of the 

Interior.

(2) Up to 20,000 acres in the vicinity of the areas described in paragraph (1), and similar 

to the areas described in paragraph (1), which the Secretary determines are necessary 

to protect fish and wildlife resources.

San Francisco Bay National Wildlife Refuge, Enlargement of the San Francisco Bay 

National Bay Refuge, Pub. L. No. 100-556, 102 Stat 2780 (1988) (emphasis added).

 

Congress, therefore, specifically rejected inclusion of the original 1988 map proposed 

with H.R. 4272 when it provided the Refuge with expansion authority of up to 20,000 

additional acres in 1988. This is contrary to typical practice within the refuge system, 

wherein Congress has typically included an "approved refuge boundary" map when 

authorizing the expansion of any particular refuge. The decision by Congress not to do 

so when it passed expansion authority for the Don Edwards Refuge emphasizes that the 

acquisition authority in this particular Refuge is markedly different than it is for other 

FWS refuges.

A 1990 Environmental Assessment conducted for the Refuge confirms the significantly 

different treatment set by Congress in connection with any future establishment of an 

expanded Refuge boundary:

Because of the nature of the 1988 legislation, any interests acquired under the 

authorized expansion is flexible and dependent on many factors. The boundaries, and 

thus the lands now desired for acquisition for wildlife habitat, is not firmly established as 

is often the case in other acquisition projects. Hence, Congress has given the Service 

discretion as to which parcels it may acquire. Obviously, the acquisition of some parcels 

may be more desirable and thus, may be more actively pursued than others.

Until lands are acquired, they do not become part of the refuge. Lands identified herein 

as possible for acquisition may or may not be acquired depending on price, state of 

development or proposed development, character modification, opportunities to protect 

through other mechanisms, and other considerations. This environmental assessment is 

not intended to be used to influence general plan, zoning, or other land use 

determinations by State and local government.

"Final Environmental Assessment, Potential Additions to San Francisco Bay National 

Wildlife Refuge Alameda, San Mateo, and Santa Clara Counties, California" ("EA'') at 2 

(FWS 1990) (emphasis added).

Since passage of the 1988 legislation, the Secretary (including his/her designee, to the 

extent that such authority has been designated) has never promulgated approval of any 

map designated as an "Approved Refuge Boundary Map" for the Refuge.

Cargill is particularly concerned that the Draft CCP contains arbitrary maps and figures 

that are labeled as "approved refuge boundary" or "approved refuge acquisition 

boundary" and encompass lands owned in fee simple by Cargill. These maps were never 

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authorized by Congress or otherwise promulgated by the Secretary. In other portions of 

the Draft CCP, lands that are owned in fee simple by Cargill appear to be included 

directly within Refuge planning units- incorrectly indicating that private property is 

"within" the Refuge. These depictions erroneously suggest that FWS has either 

acquired private property for inclusion in the Refuge or that the designated property is 

effectively slated for acquisition, when neither inference is correct. These arbitrary 

designations will mislead the public and decision makers by suggesting that the 

properties may not be freely transferrable or, at minimum, the existence of significant 

restrictions on their use. As a result, the marketability of Cargill's property is 

significantly impacted by these unapproved and arbitrary designations.

As such, adoption of the current Draft CCP, incorrectly describing Cargill's private 

property as lying within an approved boundary and/or inferring ownership directly by 

the Refuge would be "arbitrary, capricious, an abuse of discretion, [and] otherwise not in 

accordance with law" in violation of the federal Administrative Procedures Act. 5 U.S.C. 

§ 706(2)(A). We request that the relevant figures and maps be removed or redrafted 

prior to finalization of the CCP. (Barg, Coffin, Lewis and Trapp)

Refuge Response: In 1972, Public Law 92-330 authorized and directed the Secretary of 

Interior to establish a refuge and acquire up to 23,000 acres in South San Francisco Bay 

by June 30, 1977. Further, it authorized a refuge composed of four units (Mowry Slough, 

Fremont, Greco Island, and Alviso). Congress approved a refuge boundary map and 

authorized the Secretary, “...from time to time to make corrections in the boundaries of 

the refuge...” (PL 92-330) 

In 1988, Public Law 100-556 increased the Service’s acquisition authority from 23,000 

acres to a total of 43,000 acres. Unlike the original legislation (PL 92-330), Congress did 

not specify a boundary for the 20,000 acre expansion. However, in PL 100-556, 

Congress did specify that the 20,000 acres be “. . . in the vicinity of . . . and similar to . . .” 

the existing refuge units, and that they be “ . . .necessary to protect fish and wildlife 

resources.” Hence, Congress gave the Service discretion as to which parcels it may 

acquire. 

Following PL 100-556, the Service began a formal planning process to determine which 

lands would be considered for additions to the Refuge. This Service’s planning process 

was conducted pursuant to NEPA and included opportunities for public comment. In 

1990, the Service issued the Final Environmental Assessment, Potential Additions to the 

San Francisco Bay National Wildlife Refuge, Alameda, San Mateo, and Santa Clara 

Counties, California (Final EA). The preferred alternative in the Final EA included a 

map and a boundary in which the Refuge could expand to include the additional 20,000 

acres authorized by PL 100-556. The map and boundary depicted in the 1990 Final EA 

identified 24,500 acres as “potential additions” because not all of the lands would be 

added to the Refuge for the following reasons: 1) no more than 20,000 acres out of the 

24,500 acres identified would be added to the refuge under existing authorities; 2) 

Service plans for acquisitions do not preclude lawful, environmentally sound 

development, as determined by local government; 3)the acquisition cost of some of the 

lands may be prohibitive; 4) the amount of available funding for acquisition is unknown; 

and 5) some landowners indicated that they would not be willing sellers. On March 5, 

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1990, the Service selected the preferred alternative for implementation in a Finding of 

No Significant Impact (USFWS 1990). 

This map boundary is now known as the approved acquisition boundary for the Refuge. 

According to our national policies, an approved acquisition boundary encloses “those 

lands that we have authority to acquire, in whole or in part. This boundary often 

encompasses both public and private land, but does not imply that all private parcels 

within the boundary are targeted for our acquisition. The approved acquisition 

boundary can originate from a variety of means (e.g., Executive Order, Congressional 

Order, Secretarial Order, Public Land Order, Service Director, Regional Director, and 

Migratory Bird Conservation Commission)” (343 FW 3). The Service has authority to 

acquire and/or manage lands within the approved acquisition boundary through various 

agreements, based upon planning and environmental compliance processes. Approval of 

an acquisition boundary does not grant the Service jurisdiction or control over lands 

within the approved acquisition boundary, and it does not make lands within the 

acquisition boundary part of the National Wildlife Refuge System. In fact, to date, many 

lands within the approved 1990 boundary have already been converted to urban 

developments. 

We acknowledge that some maps in the Draft CCP erroneously included some of 

Cargill’s fee title lands within the refuge boundary. These mistakes have been rectified.

G.29. Comment: The Scope of the Draft CCP Must Be Limited to Land Owned by the 

Refuge.

The Draft CCP, including its maps and figures, encompasses land owned by the Refuge 

and certain other private property owned by third-parties, including Cargill. This 

approach is overly broad and is not authorized under existing law; the CCP process must 

be limited to property owned by the Refuge and any discussion of adjacent, private 

property must be limited and specifically, and clearly identified.

The National Wildlife Refuge System Improvement Act of 1997 ("Act") requires that 

FWS "propose a comprehensive conservation plan for each refuge or related complex of 

refuges." 16 U.S.C. § 668dd(e)(l)(A)(i) (emphasis added). The term "refuge" is specifically 

defined as "a designated area of land, water, or an interest in land or water within the 

System, but does not include Coordination Areas." 16 U.S.C. § 668ee(11). The term 

"System""means the National Wildlife Refuge System ..." as defined in the Act and over 

which FWS has authority and control.

As such, the Act requires preparation of a plan applicable to the geographic scope of the 

property owned by the refuge actually being evaluated. In preparing a CCP, therefore,

Congress did not intend for FWS to evaluate, or otherwise include, properties outside of 

property owned and maintained by the federal government as a refuge.

This conclusion is further evidenced by the directive from Congress that FWS, in 

preparing a CCP, shall "consult with adjoining ... private landowners ..." 16 U.S.C. § 

668dd(e)(3)(A). The requirement indicates that Congress made a clear distinction 

between the scope of the CP -.which was limited to refuge property - and a need to 

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coordinate with adjoining private landowners during the planning process. Because of 

the overly broad reference to private properties - including erroneous maps that indicate 

private property is within the Refuge boundary - the Draft CCP is not in accord with the 

directive from Congress to limit evaluation to the actual Refuge.

If FWS adopts a final CCP containing these misrepresentations with respect to Cargill's 

property, it will have exceeded the scope of its authorization pursuant to the Act, 

because Congress did not provide for the comprehensive conservation planning process 

to extend to privately owned properties. For these reasons, finalization of the CCP in 

its current form would violate the Administrative Procedures Act because such an action 

would not be "in accordance with law." 5 U.S.C. § 706(2)(A). (Barg, Coffin, Lewis and 

Trapp)

Refuge Response: We acknowledge that some maps in the Draft CCP erroneously 

included some of Cargill’s fee title lands within the refuge boundary. These mistakes 

have been rectified. 

Public Laws 92-330 and 100-556 established the Refuge and gave discretion to the 

Secretary of the Interior to acquire up to 43,000 acres “for the conservation and 

management of wildlife and natural resource, the development of outdoor recreation 

opportunities, and interpretive education.” To date the Refuge, has acquired (by fee 

title, easement, or lease) 30,000 of the 43,000 acres allowed under Public Law 100-556. 

The Refuge plans to continue acquiring lands within the approved acquisition boundary 

from willing sellers. We recognize that Cargill is not a willing seller at this time.

The Draft CCP identifies current land use (existing conditions) within the refuge units 

and land use in areas generally in the approved acquisition boundary. This provides 

context for CCP readers and refuge staff regarding habitats adjacent to the Refuge, 

particularly those habitats that would fit with the Refuge purposes. However, this 

discussion does not specify any planning actions on those lands generally within the 

approved acquisition boundary other than to express our interest in acquiring lands that 

meet the Refuge purposes from willing sellers. 

For those lands which Cargill owns in fee simple as per the 1979 agreement between 

Cargill and the Service, we recognize that Cargill Salt retains the salt making rights in 

the Mowry and Newark Ponds in perpetuity. Therefore, no change in use will be 

planned for these areas that would interfere with Cargill’s rights per the Declaration of 

Taking dated June 30, 1977.

G.30. Comment: Erroneous Designation of Cargill Owned Property as "Within the Refuge" 

May Cause Cargill Economic Harm Constituting an Unlawful Take Under the Fifth 

Amendment.

Moreover, FWS's designation of Cargill's properties as being within an "approved

boundary" for the Refuge would constitute an unlawful take, in violation of the Fifth 

Amendment to the U.S. Constitution, for which Cargill must be compensated if the CCP 

is finalized without appropriate revision. FWS's improper inclusion of properties owned 

in fee simple by Cargill as lying within the Refuge boundaries imposes a cloud of 

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condemnation over Cargill's property. This is reflected in the comments made in 1988 by 

Mr. Shepherd, cited above and including the point that "[t]he targeting of so much of our 

land holdings for the expansion proposed by this legislation threatens our company with 

real economic harm."

As was raised by Mr. Shepherd in 1988, the continued and repeated reference to Cargill 

private property as being within some type of "approved refuge boundary" is erroneous 

and threatens Cargill with direct, and potentially serious, economic harm via diminution 

in value of its property and/or the inability to use its property freely. Failure to promptly 

correct this arbitrary and capricious representation of "approved" Refuge boundaries 

and the erroneous designation of Cargill property as ''within" the Refuge may entitle 

Cargill to just compensation under the Fifth Amendment. (Barg, Coffin, Lewis and 

Trapp)

Refuge Response: We acknowledge that some maps in the Draft CCP erroneously 

included some of Cargill’s fee title lands within the refuge boundary. These mistakes 

have been rectified. See response to the previous two comments.

G.31. Comment: Allowing Hunting on Property Owned by the Refuge, but on which Cargill 

Retains "Reserved Rights" for Salt Production, Violates the Final Judgment Associated 

with FWS's Acquisition of Certain Property

Leslie Salt, the predecessor to Cargill's salt manufacturing operations in the Bay Area, 

transferred thousands of acres to the Refuge in the 1970s. The Final Judgment related 

to FWS's acquisition of that property specifies that although the Refuge now owns the 

land Cargill retains specified "Reserved Rights." Exhibit CC to the Second Amendment 

to the Declaration of Taking, dated June 29, 1979. These "Reserved Rights" provide for 

the continuation of Cargill's unhindered and unobstructed salt production operations on 

certain parcels within the Refuge.

For example, the June 29, 1979 agreement includes the following key provisions 

delineating Cargill's Reserved Rights:

Leslie and the United States agree that Leslie's activities and operations on the 

Property shall conform to, and be governed by, the rules and regulations ... but only to 

the extent such rules, regulations, and restrictions are consistent with Leslie's exercise 

of its Reserved Rights. Should the United States, its agents, designees, and permittees 

take any action which interferes with or otherwise adversely affects Leslie's Reserved 

Rights then Leslie shall be entitled to compensation and other remedies as provided by 

law and this agreement, on account of impairment, interference with, or the taking of 

Leslie's Reserved Rights.

Agreement Between United States Fish and Wildlife Service and Leslie Salt Co. at 2 

(June 29, 1979) ("FWS Agreement'') (emphasis added).

The Draft CCP indicates that certain salt making ponds owned by the Refuge, but on 

which Cargill retains and exercises its Reserved Rights to manufacture salt, have been 

designated as open to the public for hunting seven days per week without Cargill's 

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approval. This is a major safety issue for Cargill's employees and may severely impede 

salt operations and necessary maintenance work in those ponds. The Refuge cannot 

designate locations, over which Cargill retains Reserved Rights, as approved for hunting 

without Cargill's explicit authorization. Doing otherwise, as the Draft CCP apparently 

does, is in direct violation of the FWS Agreement, could be enjoined by a court, and 

entitle Cargill to appropriate compensation for interference with its contractual rights.

Refuge Response: We currently do not allow hunting within the Newark Ponds as the 

CCP states, “Newark Unit: All Refuge ponds are closed to hunting.” Tidal marsh areas 

outside the ponds are open to hunting and under the jurisdiction of the California 

Department of Fish and Game hunting regulations. 

We do allow hunting in Mowry Ponds M1 – M6 as was published in the Code of Federal 

Regulations (50 CFR 32): http://cfr.regstoday.com/50CFR32.aspx#50_CFR_32p8. 

Since this comment letter, the Refuge, in coordination with Cargill, has placed tighter 

restrictions on hunting regulations in these ponds to address safety issues for hunters, 

Cargill staff, and Refuge staff. As a result, the Refuge updated our 2013-2013 Waterfowl 

Hunting Regulations posted at: 

http://www.fws.gov/desfbay/Hunt/Hunt_Information.htm

We will continue to work with Cargill to ensure that the Refuge hunt program does not 

interfere with Cargill’s salt-making process or pose safety concerns for individuals.

G.32. Comment: We take great exception to the text on page 191 under Objective 2.10 that 

suggests that the Refuge is only interested in acquiring some of the lands within the 

Refuge expansion boundary. Specifically, Objective 2.10 states, “Rationale: Some lands 

within the approved acquisition boundary have good potential to provide habitat or be 

restored for threatened and endangered species, and other Refuge purposes (bold 

emphasis ours.)” 

It is quite clear from the 1988 Refuge expansion legislation as well as from the 

accompanying Congressional Record that all of the lands found within the 

approved refuge expansion boundary shall have, “good potential to provide habitat 

or be restored for threatened and endangered species...” Otherwise, they would not 

be in the boundary.

The 1988 legislation allowing for the expansion of the Refuge bill states:

Sect. 2. There shall be included within the boundaries of the refuge the following...

(2) Up to 20,000 acres...which the Secretary determines are necessary to protect fish 

and wildlife resources.”

Furthermore, in the Congressional Record (Congressional Record-Senate, October 14, 

1988, S16373) Senator Mitchell states that, “the development pressures in the vicinity of 

the refuge continue to increase, threatening valuable wildlife habitat, as well as areas 

that have served to buffer the human impacts on the wildlife resources within the 

refuge...Under this legislation, the U.S. Fish and Wildlife Service 

should...determine which uplands, marshes, tidal flats, salt ponds, submerged 

lands, and open water should be added to the Refuge...[and] prepare a map 

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depicting proposed refuge additions...” and Senator Pete Wilson added, “...Land 

acquisition of the sort that is called for in this bill is the only way to ensure that this 

sensitive habitat will be protected for tomorrow’s wildlife and tomorrow’s visitors...”

These are clear statements. From this, one must conclude that, as required by the 

statute, all the lands that are included within the Refuge’s expansion boundaries, as 

depicted in the map and accompanying text found in the Final Environmental 

Assessment, Potential Additions to San Francisco Bay National Wildlife Refuge, 

Alameda, San Mateo and Santa Clara Counties, California, May 4, 1990 (Assessment),

are lands “necessary to protect fish and wildlife resources” and as such are lands 

appropriate and necessary for inclusion within the Refuge. If not, the Service failed to 

appropriately implement its legislative mandate.

For this reason, we believe that the CCP must emphasize in Objective 2.10 the need 

to acquire all of the lands identified in the Assessment that are still available for 

acquisition. (CCCR)

Refuge Response: Unlike the original legislation (PL 92-330), Congress did not specify 

a boundary for the 20,000 acre expansion. However, in PL 100-556, Congress did 

specify that the 20,000 acres be “. . . in the vicinity of . . . and similar to . . .” the existing 

refuge units, and that they be “. . . necessary to protect fish and wildlife resources.” 

Hence, Congress gave the Service discretion as to which parcels it may acquire. 

Following PL 100-556, the Service began a formal planning process to determine which 

lands would be considered for additions to the Refuge. The Service’s planning process 

was conducted pursuant to NEPA and included opportunities for public comment. In 

1990, the Service issued the Final Environmental Assessment, Potential Additions to the 

San Francisco Bay National Wildlife Refuge, Alameda, San Mateo, and Santa Clara 

Counties, California (Final EA). The preferred alternative in the Final EA included a 

map and a boundary in which the Refuge could expand to include the additional 20,000 

acres as authorized by PL 100-556. However, the 1990 map identified more than 20,000 

acres for potential additions to the Refuge (24,500 acres to be exact) because it was 

assumed that not all identified lands would be available for acquisition (e.g., some 

landowners may not be willing sellers). With the originally approved 23,000 acres, this 

additional acreage totals 47,500 acres and is more than the Service’s statutory 

acquisition authority of 43,000 acres. Therefore we cannot acquire all lands within the 

approved acquisition boundary.

Furthermore, we recognize that Service plans for acquisitions do not preclude lawful, 

environmentally sound development, as determined by local government. Some lands 

within the approved acquisition boundary have already been developed and have lost 

their wildlife values. We also recognize that other lands within the approved acquisition 

boundary have already been acquired by other public agencies or conservation 

organizations with similar conservation goals similar to our own. According to our 

national policies, an approved acquisition boundary encloses those lands that we have 

authority to acquire, in whole or part. This boundary often encompasses both public and 

private land, but does not imply that all private parcels within the boundary are targeted 

for our acquisition.

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G.33. Comment: In the Assessment the Service, when developing the actual maps 

required by Congress, identified as priorities, (1) Non-tidal, (2) Abandoned salt 

ponds and (3) endangered species habitat. This was further broken down into 7 

categories and acreages:

1. Salt ponds – 58%; 14,260 acres

2. Freshwater wetlands – 22%; 5,270 acres

3. Salt marsh – 7 %; 1,710 acres

4. Uplands – 6%; 1,480 acres

5. Mud flats – 3%; 810 acres

6. Farmed wetlands –2 %; 590 acre

7. Estuarine open water- 2%; 380 acres.

(Final Environmental Assessment, Potential Additions to San Francisco Bay National 

Wildlife Refuge, Alameda, San Mateo and Santa Clara Counties, California, May 4, 

1990).

All of these land types and habitats play a critical role in supporting the Refuge’s fish 

and wildlife species. 

We believe that the Refuge CCP should follow these priorities and identify possible 

acquisition lands. For example, the Redwood City abandoned salt ponds should be 

identified as a high acquisition priority as lands that currently support large numbers of 

shorebirds (the CCCR has video documentation of thousands of shorebirds using these 

ponds), as lands that traditionally supported the threatened Western snowy plover and 

as historic tidal marshes whose current elevation provides some of the best opportunities 

for tidal marsh restoration and for development of transition and upland ecotones. 

Area 4 in Newark provides rare Salt Marsh Harvest Mouse (SMHM) habitat. Its 

acquisition would allow the Refuge to restore nearly the entire Mowry Slough 

headwaters. This is a rare opportunity (perhaps the only in the south Bay) to restore an 

entire slough and its adjacent transition and upland habitats in a slough that provides 

habitat for the California clapper rail and the Harbor seal as well as the previously 

mentioned SMHM.

Both of these sites also address the increasing need to acquire lands that will allow for 

wetland migration in the face of climate change and sea-level rise. (CCCR)

Refuge Response: We agree that the habitat types identified in the 1990 EA play a 

critical role in the Refuge’s conservation of fish and wildlife species. As stated in 

Objective 2.10, we will begin a process of assessing remaining lands within the approved 

acquisition boundary with the potential to meet the Refuge’s purposes. We will acquire 

these lands from willing sellers, as our resources allow.

G.34. Comment: We recognize the importance of preserving burrowing owl habitat and agree 

with the emphasis given that species in Section 2.10 but believe that other acquisition 

needs, such as lands needed to address climate change and that can provide rare habitats 

deserve equal recognition in the Rationale statement for this Objective. We also believe 

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it appropriate to identify specific lands that might be of special importance for 

acquisition. (CCCR)

Refuge Response: Through our assessment process in Objective 2.10, Strategy 1, we 

anticipate prioritizing and identifying specific habitats, including rare habitats important 

for acquisition. We have added a strategy regarding prioritizing lands based on climate 

change implications in Objective 2.10. 

G.35. Comment: Finally, on this point, we were also disappointed to see acquisition listed as 

the last of the Section 2 goals. As clearly stated by Senator Pete Wilson in the 

Congressional Record, “...Land acquisition of the sort that is called for in this bill is the 

only way to ensure that this sensitive habitat will be protected for tomorrow’s wildlife 

and tomorrow’s visitors...” While the Refuge has acquired many of the lands identified 

in the Assessment, critical habitats remain unprotected and their acquisition should be 

among the Refuge’s highest priorities. Once developed, these lands are lost forever and 

with climate change pushing habitats to the urban border all these unacquired lands take 

on an even greater importance. This latter point, the impact of climate change and the 

need to acquire adjacent upland areas, is recognized in Objective 2.9, Strategy 5. This 

need should also be identified or at least referenced in Section 2.10, the section that 

directly addresses acquisition policy. (CCCR)

Refuge Response: Comment noted. See previous response.

G.36. Comment: We appreciate finding in Appendix B, Table 1, under Alternative B, the 

Proposed Action, that acquisition is a priority in the CCP. This is found under the 

category “Land Management Priorities”. However, in the actual text for Alternative B, 

as opposed to the Table, the discussion of acquisition is buried and nearly undetectable. 

It consists of only one sentence, and that is the last sentence in an extensive multiparagraph Habitat Management section (as opposed to Land Management in the Table). 

As far as I could detect, acquisition is not discussed at all in the text of Alternative A (if it 

is to be found under the same Land Management heading as in Alternative B) although 

it is found in Alternative A in Table 1.

Even more disturbing, the description of Alternative B found on page 24 in the CCP text 

does not even mention acquisition. Thus, for those who don’t read the Appendix, there is 

no indication that acquisition is a component of Alternative B, the Proposed Action. 

All this suggests again that one of the most important functions of the Refuge, to acquire 

and protect important fish and wildlife habitats, has received very little attention and 

this sadly suggests a lack of interest. (CCCR)

Refuge Response: Regardless of the alternatives proposed during the CCP process, the 

Refuge has always been committed to acquisition of lands within the approved 

acquisition boundary from willing sellers as our resources allow. We discuss the 

importance of acquiring lands with fish and wildlife benefits in Sections 1.5.4 and 1.5.5., 

Land Conservation Methods. We agree that acquisition is important to protect fish and 

wildlife habitats. The importance of land acquisition has been further elaborated in the 

EA.

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G.37. Comment: The CCP needs to better address the Congressional instruction to expand 

the Refuge by 20,000 acres. This should be represented as a high priority in the CCP. 

While acquisition is recognized as a Refuge Goal in Objective 2 (Objective 2.10) its 

location as the last objective in that section suggest a lack of interest. We suggest 

moving it up in the list of goals under Objective 2. (CCCR)

Refuge Response: Comment noted. See response previously in G.29. 

G.38. Comment: The failure to identify acquisition as a component of Refuge Management in 

the summary of Alternative B found in the main text of the CCP should be corrected. 

Thus, acquisition as a management activity should be added to the summary of 

Alternative B as found on CCP, pg. 24. It should also be added to the text of Alternative 

A in Appendix B. (CCCR)

Refuge Response: The importance of acquisition has been further elaborated in the 

CCP and EA.

G.39. Comment: Climate change should be included in the Rationale for acquisition in 

Objective 2.10. (CCCR)

Refuge Response: Comment noted. Climate change has been included in the rationale.

G.40. Comment: One of the Strategies in Objective 2.10 should be to identify lands within the 

Refuge expansion boundary that would help the Refuge address the impacts of sea level 

rise and climate change, investigate the feasibility of acquiring those lands and acquire 

them when feasible. (CCCR)

Refuge Response: Comment noted. A strategy has been added to Objective 2.10 to 

reflect this.

G.41. Comment: While we whole-heartedly support Objective 2.10. "Actively work with 

partners and willing sellers to acquire remaining lands within the approved acquisition 

boundary of the Refuge," we are puzzled by the language of the rationale, "Some of the 

lands within the approved acquisition boundary have good potential to provide habitat or 

be restored for threatened and endangered species, and other Refuge purposes." 

[emphasis added] If the word "some" was used because lands within the approved 

acquisition boundary have been developed and can no longer provide wildlife or habitat 

values, it would be more appropriate to provide a separate statement to that effect, 

rather than utilizing language that calls into question of the value of all of the lands 

within the approved acquisition boundary.

There should be no question that the lands identified in the approved acquisition 

boundary would be valuable additions to the Refuge. The Final Environmental 

Assessment (FEA) Potential Additions to San Francisco Bay National Wildlife Refuge 

Alameda, San Mateo, and Santa Clara Counties, California issued March 5, 1990 states:

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Through its planning process, including and incorporating other studies done by the 

Service and other entities, the Service identified tracts of land which are suitable for 

inclusion in the San Francisco Bay National Wildlife Refuge.

Under the description of the "Purpose and Need for Action" the FEA states:

The reason for proposing to expand the refuge by approximately 20,000 acres is to 

enhance the purposes for which the refuge was originally established. These purposes as 

stated in Public Law 92-330 are:

1. For the preservation and enhancement of highly significant wildlife habitat.

2. For the protection of migratory waterfowl and other wildlife, including species 

known to be threatened with extinction.

3. To provide an opportunity for wildlife-oriented recreation and nature study within 

the open space so preserved.

The proposed action is needed to preserve, enhance, or restore essential environments 

(or habitats) for wildlife and to provide for the enjoyment of wildlands and wildlife by 

the public. [emphasis added]

The language is quite explicit that the lands identified in the acquisition boundary were 

determined to be "highly significant wildlife habitat" and either possess or have the 

potential to possess "essential" environments (or habitats) for wildlife. The use of the 

word "some" in the rationale of Objective 2.10 disregards the painstaking, thoughtful, 

and thorough process by which the acquisition boundary was identified. This language 

must be revised to: "All of the lands within the approved acquisition boundary have 

good potential..." (CCCR)

Refuge Response: We concur that only some of the lands within the approved 

acquisition boundary have been developed and can no longer feasibly provide wildlife or 

habitat values. This has been clarified in the rationale for Objective 2.10. With 

discretion from Congress in Public Laws 92-330 and 100-556, the Service developed a 

map, “Potential Additions to the San Francisco Bay National Wildlife Refuge, Alameda, 

San Mateo, and Santa Clara Counties, California” pursuant to the National 

Environmental Policy Act and included opportunities for public comment. This map was 

developed for Refuge planning purposes and we have since referred to the map as the 

approved acquisition boundary, as defined by Service policy. However, the 1990 map 

identified more than 20,000 acres for potential additions to the Refuge (24,500 acres to be 

exact) because it was assumed that not all identified lands would be available for 

acquisition (e.g., some landowners may not be willing sellers). With the originally 

approved 23,000 acres, this additional acreage totals 47,500 acres and is more than the 

Service’s statutory acquisition authority of 43,000 acres. Therefore we cannot acquire all 

lands within the approved acquisition boundary. According to our national policies, an 

approved acquisition boundary encloses those lands that we have authority to acquire, in 

whole or part. This boundary often encompasses both public and private land, but does 

not imply that all private parcels within the boundary are targeted for our acquisition.

G.42. Comment: Continuing with the rationale for Objective 2.10:

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The Refuge is particularly interested in acquiring property that will benefit burrowing 

owls, migratory birds that are a Refuge trust species. The Refuge is committed to 

acquiring these lands from willing sellers as identified in the 1990 Final Environmental 

Assessment of Potential Additions to the San Francisco Bay National Wildlife Refuge. 

[emphasis added]

Is it the intent of this description to include lands that were described in Strategy 4, or 

only property that benefits burrowing owls and migratory birds? Strategy 4 states, "If 

feasible, acquire or protect currently unprotected high marsh, ecotonal, and uplands 

habitats by working with adjacent landowners, NGOs, and other Federal and State 

agencies." [emphasis added]

Why would the CCP make the distinction of being "committed" to acquiring burrowing 

owl habitat, but not "committed" to acquiring or protecting unprotected high marsh, 

ecotonal and upland habitats? Furthermore, Strategy 5 states the Refuge will, "Identify 

and acquire areas with the potential to be restored to burrowing owl habitat." [emphasis 

added]

Again, there is a distinction between "if feasible" and the more affirmative "identifying 

and acquire" areas. We do not disagree that burrowing owl habitat is under continued 

and serious threat by development and is worthy of protection, however, high marsh, 

ecotonal and uplands habitat has also been acknowledged by the CCP to be extremely 

rare and under serious and continued threat of being developed. The rationale of this 

objective should be reworded to clarify the Refuge is "committed" to acquiring 

unprotected high marsh, ecotonal and uplands habitats, and the strategy rewritten

to indicate the Refuge will "identify" and "acquire" such areas. (CCCR)

Refuge Response: Regarding Objective 2.10, Strategy 4, “if feasible” was removed. 

The intent of this objective is to acquire unprotected high marsh, ecotonal, and upland 

habitats within the approved acquisition boundary. We have little burrowing owl 

habitat, a species of concern, and have added a strategy particular to that species.

G.43. Comment: Strategy 1 - "Investigate remaining lands within the approved acquisition 

boundary with the potential to meet the Refuge's purposes." We are strongly opposed to 

the language of this strategy - it should be removed from the objective. Please refer to 

the discussions provided above and below regarding the values of the lands within the 

approved acquisition boundary.

Finally, the Refuge needs to actively and routinely express its interest in acquiring lands 

within the approved acquisition boundary to all owners willing, or unwilling. We are 

aware of at least three instances of lands located within the approved acquisition 

boundary, where the landowners have claimed the Refuge has not indicated an interest 

in acquiring the lands, and have used this perceived lack of interest on the Refuge's part 

to conclude the lands must have only limited habitat and wildlife values.

Interest in acquiring or protecting all lands within the approved acquisition boundary 

(that have not been developed) should regularly be expressed by Refuge staff. This 

action is consistent with the vision statement developed for the Refuge. There should be 

P-49
no question in any landowner's mind (who owns lands within the approved acquisition 

boundary) that their lands would be considered a valuable addition to the Refuge.

The CCP narrative provides four examples in which there are ongoing acquisition 

discussions. What is unclear from the description is whether these discussions were 

actually initiated by the Refuge, or by the landowner/project proponent. The CCP 

narrative describes acquisitions as a "method of increasing habitat for Refuge wildlife 

and habitat resources." The narrative goes on to state, "In addition, global warming and 

impending sea level rise may require that the Refuge seek lands adjacent to its current 

holdings to provide wildlife and habitat resources into the future." We concur and urge 

the Refuge to more actively pursue acquisition/protection of lands within the approved 

acquisition boundary. (CCCR)

Refuge Response: Regarding the comment on the remaining lands within the approved 

acquisition boundary, please refer to the response to G.38. Regarding the Refuge’s 

initiative to express interest in acquiring lands, we have expressed interest when our 

work priorities allow. Further, we are hindered by the availability of funds for acquiring 

such properties. We hope that additional staffing as prescribed in the CCP will allow us 

to take more of an active role on acquisition priorities.

G.44. Comment: Inadequate discussion of the values of the lands within the approved 

acquisition boundary:

The actual narrative of the CCP should be amended to describe the attributes of lands 

within the approved acquisition boundary. There is little to no discussion explaining the 

value of these lands - such information should be included within the narrative of the 

CCP to help inform future Refuge actions and to help the public and decision-makers 

understand why these lands must be acquired or protected. Examples of the types of 

information that would be useful to the public and decision-makers might include:

• the habitats that are supported by lands included in the approved acquisition 

boundary,

• the suite of species would benefit from acquisition of the lands,

• whether the lands in question mitigate the impacts of sea level rise or offset 

impacts of salt pond conversion to tidal marsh, etc. (CCCR)

Refuge Response: We disagree with the comment. The primary purpose of the affected 

environment section of the CCP is directed at describing the lands and resources within 

the refuge boundary that the Refuge manages or owns. Secondarily, we have described 

the general habitat types within the approved acquisition boundary and the general 

wildlife resources that are found there. We do not have complete information on lands 

within the approved acquisition boundary because we do not actively conduct surveys on 

lands that we do not manage or own. We have a general understanding of the habitats 

within the approved acquisition boundary through a habitat map in the CCP (Figure 16). 

This information, combined with our understanding of the habitat needs of our trust 

species, informs us of priority lands for acquisition.

G.45. Comment: There is a need to explicitly state throughout the CCP the value of lands 

within the acquisition boundary. This is important not only for internal planning 

purposes, it also serves to inform landowners that there is continued interest in their 

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lands, and to inform decision-makers and the public who may in turn provide support for 

acquisition efforts. (CCCR)

Refuge Response: We disagree. The CCP is intended primarily to guide management 

of lands that the Refuge owns and manages. The Refuge may also identify and prioritize 

habitat types that maybe beneficial in acquiring to meet the Refuge’s purposes.

G.46. Comment: p. 117 - The Description of the Patterson Ranch project is inaccurate and 

inconsistent with the description provided on p. 121. The description provided on p. 121 

accurately reflects the current status of the project. The Patterson Ranch project does 

not include any impacts to the Cargill owned Fremont-Coyote Tract. (CCCR)

Refuge Response: The description of the Patterson Ranch project has been deleted 

from p. 117 as this section only relates to properties owned or managed by the Refuge in 

the Newark Unit. The description on p. 121 is unchanged.

H. Mosquito Management

H.1. Comment: Pg. 4 (K-8) Last paragraph. “There were no humans cases of WNV 

reported in San Mateo County from available state reports (2007-2011).”

State reports are actually available for WNV data in California back to 2005. In 2005, 

San Mateo County did in fact have one human case of WNV. Since “historical health 

threat” is to be used as a factor in determining Threat Level, as defined in the Mosquito 

Management Plan’s (MMP) Table 2, it is imperative to document San Mateo County’s 

human case in this report.

The recently completed Final Mosquito Management Plan for the San Pablo Bay 

National Wildlife Refuge specifically cites a human disease case from Santa Clara 

County in 2004 (pg. G-31). We feel strongly that the proposed MMP should be at least as 

inclusive of local historical disease data.

State WNV activity summaries for all counties going back to 2005 have been included for 

your reference (Attachment 1). These documents were all retrieved on 6/27/12 as 

reports available on http://westnile.ca.gov. (SMCMVC)

Refuge Response: Comment noted. This information has been added to the MMP.

H.2. Comment: Pg. 5 (K-9) Table 1. Cases of West Nile Virus by County, 2007-2011.

Table 1 does not currently include cases of WNV in tree squirrels. As seen in 

Attachment 1, San Mateo County has had several squirrels test positive for WNV. The 

California state health department considers WNV cases in squirrels to be significant 

indications of local disease activity, stating that “tree squirrels, because they do not fly, 

provide evidence of highly localized WNV transmission to mammals.” (Attachment 2) 

On page 15 (K-19) of the MMP, birds and squirrels together are recognized as the “most 

sensitive method of detecting the presence of WNV.”

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Although we recognize that squirrel data was not recorded before 2006, all three MADs 

in this MMP have had squirrels test positive for WNV and these cases should be added 

to Table 1. (SMCMVC)

Refuge Response: Comment noted. Table 1 of the MMP has been updated with the 

information you have provided.

H.3. Comment: Pg. 5 (K-9) Mosquito Biology section, first paragraph. “Depending on 

seasonal and environmental conditions and the particular mosquito species involved, it 

generally takes from three to up to three months for a mosquito to complete its life from 

developed egg to early adult stage.”

Word missing; we believe the intended text was “...generally takes from three days to 

up to three months...”

Because no references are given for this sentence, the author’s intended statement is 

unclear. The MMP for the San Pablo Bay NWR includes the following statement in its 

analogous section on mosquito biology (pg. G-28): “In Northern California, it takes a 

mosquito from three to 12 days to complete a life cycle, depending on seasonal and 

environmental factors and the species of mosquito.” We find the upper limit of this 

estimate (12 days) to be low, in our experience. While is not apparent where the “three 

months” time frame appearing in the current draft MMP originates from, we do not 

object to this estimate. (SMCMVC)

Refuge Response: “Days” added. Reference included.

H.4. Comment: Pg. 11 (K-15) Threat Level 2 section. “Human health threats include the 

presence of a vector species and historical incidence of disease in the local area.” 

This statement seems to limit the term “human health threats” to only situations directly

involving “historical incidence of disease.” We contend that a severe biting nuisance or 

an emergent disease with no “historical incidence” in the local area may also be declared 

a health threat, if so designated by the “appropriate public health authority” (as 

designated in Table 2 of the MMR). We propose the sentence to be amended to read the 

following:

“Human health threats typically include the presence of a vector species and historical 

incidence of disease in the local area.” (SMCMVC)

Refuge Response: Comment noted, “typically” was added to this sentence in the 

Mosquito Management Plan. 

H.5. Comment: Pg. 11 (K-15) Threat Level 2 section. “Some areas may already be operating 

under Phase 2 if they have had recent and recurring presence of mosquito-borne 

disease.”

“Phase 2” should be replaced with “Threat Level 2” for consistency. (SMCMVC)

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Refuge Response: Comment noted. Change made.

H.6. Comment: Pg. 11 (K-15) Threat Level 3 section. “The preferred larvicide treatments 

are biorationals (biological agents) B.t.i., B.s., and methoprene because of limited nontarget effects (Appendix K3, K4). Chemical larvicides treatments (e.g. methoprene) 

would be the second preferred method for larvicides control.”

Methoprene seems to be indicated here as both the primary and secondary preferred 

material for control. We suggest rewording these sentences to clarify meaning.

(SMCMVC)

Refuge Response: Comment noted. Section was reworded to prescribe methoprene as 

a secondary preferred material for control.

H.7. Comment: Pg. 12 (K-16) Threat Level 5 section. “In this phase, mosquito-borne disease 

activity has been documented on the Refuge or within flight range of vector mosquito 

species present on the Refuge.”

For consistency, “phase” should be replaced with “threat level.” (SMCMVC)

Refuge Response: Comment noted. Change made.

H.8. Comment: Pg. 15 (K-19) Dead wildlife section. “Submission of dead birds by the public 

is also solicited by the MADs. Residents are directed to call the California Department 

of Health Services if they find a dead bird ((877) WNV-BIRD). This information is 

conveyed to the MADs, which collects the bird and submits it for testing.”

The paragraph correctly identifies both birds and squirrels as important testing 

specimens. Sentences cited above should also include references to squirrels. The 

California Department of Public Health has replaced the CDHS. We suggest the 

following wording of these statements:

“Submission of dead birds and tree squirrels by the public is also solicited by the MADs. 

Residents are directed to call the California Department of Public Health’s West Nile 

virus hotline if they find a dead bird or squirrel ((877) WNV-BIRD). This information is 

conveyed to the MADs, which collects the bird or squirrel and submits it for testing.”

(SMCMVC)

Refuge Response: Comment noted. Change made.

H.9. Comment: Pg. 15 (K-19) Mosquito pools section. “This method is not as efficient at 

detecting the presence of virus, but is used to supplement information gained by testing 

wild birds.”

Is there a reference the author can cite for this statement? While it is true that this 

method is not generally employed for county-wide monitoring for WNV in the same way 

as bird or squirrel testing, it is be misleading to state that the method is not efficient at 

detecting the presence of virus. Positive mosquito pools have indicated WNV presence 

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around the same time or earlier as the first positive birds of the season in many counties 

over the past several years. Mosquito testing is a valuable monitoring tool in its own 

right, as this method does not rely on the opportunistic and sporadic nature of public 

dead bird and squirrel reporting.

We would suggest omitting the statement altogether. Alternately, if the sentence is to 

be maintained, it should include a reference citation. (SMCMVC)

Refuge Response: This statement has been deleted.

H.10.Comment: Pg. 17 (K-21) Product name section. “VectoLex CG, VectoLex G Granules, 

VectoLex WDG, VectoLex WSP”

The authors should consider adding “Spheratax SPH” to this list, as Spheratax 

formulations of B.s. products have recently been brought to market by Advanced 

Microbiologics, LLC. The Spheratax products have comparable formulations to 

VectoLex products (Attachment 3). This may be addressed in future meetings between 

NWR and MAD staff. (SMCMVC)

Refuge Response: Approvals for use of pesticides on the Refuge are updated only at 

the end of the calendar year for use in the following year. Please request use of this 

product through the Pesticide Use Proposal (December 2012) for calendar year 2013.

H.11.Comment: Pg. 18 (K-22) Product name section. “Vectobac 12AS, Vectobac G”

Teknar HP-D should be added to this list, as it is already included in Table 5 and Table 6 

on pg. 20 (K-24). Summit B.t.i. Briquettes are also included in Table 6 and should be 

added to this list. (SMCMVC)

Refuge Response: Comment noted. Products added.

H.12.Comment: Pg. 20 (K-24) Table 5. Pesticides permitted for use on the Refuge in 2011 for 

San Mateo County

Will this table be updated for 2012 in the final permit? If so, we would like to substitute 

“BVA 2 Oil” for “Mosquito Larvicide GB-1111 (Clarke)” in this document. BVA 2 Oil is 

listed as an alternate Product Name for Golden Bear -1111 on pg. 22 (K-26), and is the 

only pupacide currently used by the San Mateo County MVCD. (SMCMVC)

Refuge Response: The tables have been updated with the Pesticide Use Proposals for 

2012 that were submitted in December 2011/January 2012. BVA 2 Oil was not included 

in the Proposal. Please request use of this product through the Pesticide Use Proposal 

(December 2012) for calendar year 2013.

H.13.Comment: Pg. 22 (K-26) Pupacide section.

The larvicide section is grouped by active ingredient, while the pupacide section is 

grouped by brand name. We suggest the header for the pupacide section be changed to 

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at least include the active ingredient, as the mineral oil larvicides are actually 

represented by two separate brand names, “Golden Bear Oil (GB1111),” and “BVA 2 

Oil.” Agnique is the only brand name under which the alcohol-based surfactant larvicide 

is sold, but the active ingredient name is Poly (oxy-1,2-ethanediyl), α-Isooctadecyl-ωhydroxyl. (SMCMVC)

Refuge Response: Comment noted. The Pupacide section has been categorized by 

active ingredient instead of brand name, for consistency with the other sections.

H.14.Comment: Pg. 25 (K-29) Reptiles and Amphibians section. “Because mosquito control 

is applied directly to vernal pools, VPTS and CTS may be directly affected.... The effects 

of pesticides on VPTS and CTS are unknown at this time. However, refuge surveys over 

the last several years indicate that there is continued, long-term presence of VPTS and 

CTS in these pools.” 

VPTS is not defined as an abbreviation until pg. 27 (K-31). Additionally, VPTS are not 

reptiles or amphibians and should not be included in this section. (SMCMVC)

Refuge Response: Comment noted and VPTS moved to the Endangered Species 

section.

H.15.Comment: Pg. 29 (K-33) Stipulations and Best Management Practices... section, second 

bullet point. “This information will be made available at or before the time of the annual 

meeting.”

No other reference is made to an annual meeting before this statement in the MMP. 

The MMP for the San Pablo Bay NWR includes a section on Annual Meeting/Training 

on pg. G-21, and this bullet point may be referring to a similar meeting not currently 

defined in the proposed Don Edwards NWR MMP. (SMCMVC)

Refuge Response: Chapter 2 of the MMP discusses annual coordination with the 

mosquito and vector control districts.

H.16.Comment: Pg. 30 (K-34) Motor Vehicle Operation section, fifth bullet point. “Aerial 

pesticide (larvicide or pupacide) application is required in lieu of ground-based 

application methods in areas with endangered species.” (Bullet point is repeated in 

Endangered Species Habitat section.)

This restriction will significantly hamper effective and efficient mosquito control 

operations. There may be instances where a small or pocketed treatment area can be 

effectively treated on foot with sensitivity to environmental concerns for a fraction of the 

material and cost of an aerial treatment. For instance, the San Mateo County MVCD 

has worked cooperatively in the field with biologists from the California State Coastal 

Conservancy for the past several years to treat specific tufts of invasive cordgrass while 

ensuring no harm or disturbance would come to California clapper rails or their habitat. 

We respect the need to protect endangered species, but making one-size-fits-all 

recommendations for control operations leads to imprecise and inefficient control 

activities.

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We suggest the following statement: “In areas with endangered species, special care will 

be taken to select application methods for larvicides or pupacides which minimize impact 

on the species of concern and their habitat. In these instances, pesticide application 

methods will be chosen in consultation with the Refuge manager before the application 

occurs.” (SMCMVC)

Refuge Response: We prefer the use of aerial mosquito control application as it is less 

physically impacting than ground application, particularly where we have endangered 

species. We have revised the language to add flexibility: “aerial mosquito control 

application in encouraged over ground-based application methods” in both the “Motor 

Vehicle Operation” and “Endangered Species Habitat” sections.

H.17.Comment: Pg. 30 (K-34) Endangered Species Habitat section, second bullet point. 

“Access (via foot or mechanized vehicle) to tidal marsh and muted tidal marsh for the 

purpose of mosquito management would not be allowed access February 1 to July 15 in 

areas that are inhabited by California clapper rails and along slough and channel edges 

(100 meter buffer).”

This restriction as written will prevent needed access to many known larval mosquito 

breeding sites in Bair Island. We share the desire to protect clapper rails and their 

nesting sites. However, exempting a 100-meter buffer of ALL slough and channel edges 

from mosquito management activities (including surveillance, a crucial part of IPM) will 

lead to massive unregulated mosquito breeding in these areas. The potential for 

mosquito fly-offs to neighboring communities from these areas will be greatly increased. 

This in turn raises the probability of increased Threat Levels, which may trigger 

otherwise preventable pupaciding and adulticiding events. Moreover, many of our 

potentially affected treatment areas have no recent history of clapper rail presence and 

consist of vegetative communities not associated with California clapper rails.

We suggest the following edited statement: “Access (via foot or mechanized vehicle) to 

tidal marsh and muted tidal marsh for the purpose of mosquito management would not 

be allowed from February 1 to July 15 in areas that are inhabited by California clapper 

rails.”

Alternately, if Refuge management would like to keep the 100-meter buffer as a default, 

we propose the following addition: “Access (via foot or mechanized vehicle) to tidal 

marsh and muted tidal marsh for the purpose of mosquito management would not be 

allowed from February 1 to July 15 in areas that are inhabited by California clapper rails 

and along slough and channel edges (100 meter buffer) without authorization of the 

Refuge manager.”

We believe the proper balance of environmental and public health stewardship can best 

be achieved by working cooperatively and actively with Refuge management to craft 

appropriate solutions to these complicated and site-specific issues. This change in 

wording gives the Refuge manager latitude to allow reasonable access for necessary 

mosquito surveillance activity. (SMCMVC)

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Refuge Response: This bullet has been changed to: “Access (via foot or mechanized 

vehicle) to tidal marsh and muted tidal marsh for the purpose of mosquito management 

would be not be allowed access February 1 to July 15 in areas that are inhabited by 

California clapper rails without authorization of the refuge manager”. 

H.18.Comment: Pg. 32 (K-35) First bullet point on the page. “Access (via foot or mechanized 

vehicle) to tidal marsh and muted tidal marsh for the purpose of mosquito management 

would not be allowed access February 1 to July 15 in areas used by nesting snowy 

plovers.” 

While this restriction does not currently prevent access to surveillance of known larval 

mosquito breeding sites in San Mateo County, it is impossible to anticipate how this will 

change as the salt pond areas are restored and evolve over time. We would like to keep 

some measure of flexibility in these guidelines, with an emphasis on working together 

with Refuge management to implement responsible, science-based solutions specific to 

individual and changing situations.

We suggest the following edited statement: “Access (via foot or mechanized vehicle) to 

tidal marsh and muted tidal marsh for the purpose of mosquito management would not 

be allowed from February 1 to July 15 in areas used by nesting snowy plovers without 

authorization of the Refuge manager.”

We also note that this mosquito management plan does not include a mandated Annual 

Meeting among Don Edwards NWR and MAD representatives. As regulations, 

available materials, restoration issues, and public health concerns change, it is important 

to provide a forum for open communication, updates, and proposed adjustments to 

mosquito management practices. Inclusion of an annual meeting will allow all parties to 

openly discuss and debate reasonable mosquito surveillance and treatment options 

rather than relying on rigid guidelines for overly broad categories of mosquito control 

situations. Modern MADs and Refuge managers both preferentially use science-based 

approaches to solve specific problems, and ongoing collaboration is crucial to 

communicate and enact these solutions. We suggest inclusion of a mandated Annual 

Meeting to discuss mosquito issues in the refuge and refer the authors to the meeting 

outlined in the recent San Pablo Bay NWR MMP (pg. G-21). (SMCMVC)

Refuge Response: Edit made to the bullet statement. Chapter 2 includes annual 

meetings between the Refuge and the mosquito and vector control districts.

H.19.Comment: More studies are warranted for food chain effects or how an ecosystem 

responds to lack of mosquitoes, before deciding on supporting the underlying premise.

(SCCVCD)

Refuge Response: We agree that more research is needed on food chain effects or 

ecosystem effects to lack of mosquitoes. We hope to work with you and other partners to 

analyze these questions. Until then, we must take a precautionary approach and 

conservatively limit mosquito control activities under the assumption that mosquitoes 

are part of the ecosystem.

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H.20.Comment: How is it that on the refuge, language protecting “non-arboviral” mosquitoes 

on refuge property is in direct conflict with California State Health and Safety Code 

regarding creating a public nuisance (2060)? According to this state code, “(b) The 

person or agency claiming ownership, title, or right to property or who controls the 

diversion, delivery, conveyance, or flow of water shall be responsible for the abatement 

of a public nuisance that is caused by, or as a result of, that property or the diversion, 

delivery, conveyance, or control of that water.” (SCCVCD)

Refuge Response: There is no waiver of sovereign immunity requiring the Refuge to 

comply with the California Health and Safety Code provisions relating to mosquito 

abatement. The Refuge recognizes that they have a responsibility to manage health 

threats from mosquitoes as set forth in Service policy and the 2005 Interim Guidance for 

Mosquito Management on National Wildlife Refuges. Based on these policies and 

guidance, as well as overarching Refuge goals, the Refuge has developed to the mosquito 

management plan to respond to pests that threaten human and wildlife health.

H.21.Comment: By far the greatest issue with this document was the apparent elimination of 

our capacity to control “nuisance mosquitoes”. (SCCVCD)

Refuge Response: The Service does not recognize nuisance mosquitoes because it is an 

arbitrary term with no quantifiable distinction between it and non-nuisance mosquitoes. 

There is no set, measurable criteria for nuisance mosquitoes making it arbitrary as to 

when each district can conduct control. Instead, a phased approach is used as a 

structure to provide a systematic method using disease history, disease presence, and 

mosquito population numbers to control mosquitoes to reduce the threat of mosquitoborne disease. 

H.22.Comment: It is confusing as to how there could be no documented health threat or 

mosquito management issues in phase 1 without the execution of mosquito surveillance. 

Mosquito surveillance needs to be included in phase 1. Mosquito and vector surveillance 

should be ongoing to identify potential and existing mosquito management issues. 

Mosquito and vector surveillance should also be performed as a component of a 

proactive, as opposed to a reactive, mosquito control program. The Districts cannot 

contact the refuge regarding a health threat in phase 2 without having performed 

mosquito surveillance on the refuge in phase 1. (SCCVCD)

Refuge Response: Given the history of mosquito-borne disease in the surrounding 

vicinity of the Refuge, we recognize that all the districts are in Phase 2 of the Mosquito 

Management Plan and should be conducting surveillance per stipulations in the Plan.

H.23.Comment: In the response section the plan states “increase the intensity and frequency 

of larvicides.” The language if appropriate should be added to the statement mentioned 

in phase 4. It may not always be appropriate to automatically increase the intensity and 

frequency of larvicides. (SCCVCD)

Refuge Response: Comment noted. Language in the MMP revised.

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H.24.Comment: As indicated in comments submitted by CDPH VBDS, a declaration of a 

public health emergency is not appropriate relative to mosquito-borne health issues. 

Conceptually, to have high risk of public health issues as criteria to initiate adult 

mosquito control constitutes a reactive approach and is problematic in several aspects 

(e.g., minimizing public health risk, efficacy, possible increased adulticide use and 

departure from sound IPM practices, etc.). This is a subject that warrants further 

discussion; perhaps phase 5 should be separated to address the issues of exceeding adult 

mosquito thresholds on the refuge in general, and then actually reaching a high risk 

public health situation. (SCCVCD)

Refuge Response: Initiating adult mosquito control is (Threat Level 5) is not triggered 

by the declaration of a public health emergency. Adult mosquito control would be 

permitted with documented mosquito-borne disease activity near or on the Refuge. 

Appropriate documentation of a high risk to public health and safety would include 

species-specific adult mosquito monitoring data from the Refuge, or areas near the 

Refuge, that show an increase in the rate of disease-infected mosquitoes, as well as a risk 

assessment as defined in the California Mosquito Surveillance and Response Plan.

H.25.Comment: As with the proposed phased approach, using a “public health emergency” 

as criterion to initiate larval and adult mosquito control operations is inappropriate and 

again constitutes reaction approach to vector control. The District recommends 

referring to the California Mosquito-borne Virus Surveillance and Response Plan and 

also considering and integrating established thresholds for “nuisance mosquito species”.

(SCCVCD)

Refuge Response: The mosquito management plan does not require a public health 

emergency in order to conduct larval and adult mosquito control operations. Historical 

presence of mosquito-borne disease in the area permits the use of larvicides for control 

of mosquito populations. Some larvicides have also been determined safe for aquatic 

environments that represent the Refuge. The use of adulticides in Refuge environments 

could have potential impacts to Refuge resources and the food sources they may depend 

upon. Therefore, we view that the use of adulticide should require a higher threshold for 

use, such as species-specific adult mosquito monitoring data from the Refuge, or areas 

near the Refuge, that show an increase in the rate of disease-infected mosquitoes, as well 

as a risk assessment as defined in the California Mosquito Surveillance and Response 

Plan. 

We recognize that nuisance mosquito species are an ongoing management concern of the 

local mosquito abatement districts. We believe that the actions outlined in the phased 

approach will be effective in preventing disease outbreaks and will also provide some 

ancillary benefits in controlling nuisance mosquitoes. However, we cannot allow the 

application of mosquito pesticides simply to control nuisance mosquitoes.

H.26.Comment: The draft plan acknowledges the significance of nuisance mosquito and 

mosquito populations in general, however it does not include provisions for controlling 

larval or adult populations of “nuisance” species. Requiring a “public health emergency” 

and the presence of a pathogen or arboviral disease to control adult mosquito 

populations severely limits the ability of the Districts to control mosquito vectors and 

P-59
minimize the potential for discomfort and injury to local residents. The California 

Health and Safety Code establishes that mosquito species capable of producing human 

discomfort and injury are indeed “vectors” (Section 2002). FIFRA section 2100 defines 

the term “vector” as “...any organism capable of transmitting the causative agent of 

human disease or capable of producing human discomfort or injury, including 

mosquitoes...” Restricting the application of adulticide to a one-time event is 

inappropriate in term of proper IPM practices, and can dramatically reduce the efficacy 

of adult mosquito control. Controlling large adult mosquito populations and breaking a 

disease transmission cycle commonly requires more than one ultra-low volume (ULV) 

adulticide application. (SCCVCD)

Refuge Response: With regard to nuisance mosquitos, please see response to the 

previous comment. We will consider additional adulticide applications in the event that a 

single treatment is not effective. Such applications must be coordinated with the Refuge.

H.27.Comment: The draft plan should allow for Refuge Managers and District staff to fully 

practice proper IPM, make adaptive management decisions and practice prudent 

mosquito control. For example, language within the plan could state: Refuge Managers 

and District staff shall work collaboratively utilizing an IPM strategy including 

mosquito surveillance, source reduction and larval control (if necessary) to achieve 

mosquito management and minimize the need for adult mosquito control operations on 

the refuge (this would include all vector species and nuisance and disease/arbovirus 

carrying species alike). (SCCVCD)

Refuge Response: We believe that the mosquito management plan does present a 

comprehensive IPM process for conducting mosquito control, based on historical and 

present data on mosquito-borne disease in the area. We view the plan as a living 

document that will require working and meeting collaboratively on an annual basis to 

allow all parties involved in mosquito control to manage lands adaptively.

H.28.Comment: Pg. 4, (K-8) 

Third paragraph. “By the mid-1980s most districts in the Bay area had replaced the 

majority of chemical controls materials that are relatively non-toxic with few ecological 

side-effects - with biorational methods.” The sentence is awkward and possibly missing 

a word making the meaning unclear. A possible revision would be to move the phrase 

“with biorational methods” after the word materials and make controls singular (By the 

mid-1980s most districts in the Bay area had replaced the majority of chemical control 

materials with biorational methods that are relatively non-toxic and have fewer

ecological side-effects). 

Last paragraph. The MMP West Nile Virus (WNV) case counts only go back to 2007. 

Since WNV was first introduced into California in 2003, a relatively short period of time, 

all local activity since then should be counted and reflected in Table 1 to accurately 

portray the WNV historical health threat. This would add two more human cases to 

Alameda County bringing the total number of WNV human cases to four. A WNV 

positive osprey was also found near refuge property in 2004.

P-60
In addition, squirrels have been used as a WNV surveillance tool since 2004 and are 

considered an indicator of “highly localized WNV transmission to mammals” (Tree 

Squirrels: A New Surveillance Tool for West Nile Virus) because they do not fly. 

Currently all squirrel data has been omitted from Table 1 when it should be included. 

Since 2004, Alameda County has had 15 WNV positive squirrels. WNV summaries 

dating back to 2003 for Alameda County are attached for reference. (ACMAD)

Refuge Response: The language on biorational methods has been revised accordingly. 

WNV summaries for all three districts have been updated with data since 2005 

(www.westnile.gov) and squirrels have been included in the summaries.

H.29.Comment: Pg. 9, (K-13) 

Bullet point #5. “At the beginning of the mosquito breeding season, the districts will 

provide a firm schedule of seasonal activities to the Refuge Manager. If activities are 

proposed that differ from the schedule, the districts will notify the Refuge Manager at 

least two business days prior to accessing the Refuge.” 

The Alameda County mosquito Abatement District operates under an Integrated Vector 

Management Program and adjusts its response to mosquito production according to 

environmental conditions and the presence of immature mosquitoes themselves. 

Therefore, it is impossible to provide a firm schedule for control activities in advance. 

Mosquitoes breed year round on Refuge lands and larval abundance and development is 

determined by several factors, including but not limited to: rainfall, high tides, ambient 

temperatures and intentional flooding. Natural factors such as rainfall and 

temperatures cannot be determined in advance, and a firm schedule of inspections and 

treatments for Aedes squamiger, Aedes washinoi, Culex erythrothorax, Culex tarsalis, 

and Culiseta inornata is impossible. The refuge managers do not have a set schedule for 

intentional flooding of the Mouse Pasture and ACMAD staff are usually given only a 

day’s notice before this occurs. A two business day advance notice prior to accessing 

the Refuge can be the difference between treating mosquitoes with a biorational 

product in their early larval stages versus pupaciding or adulticiding. The result of such 

a requirement will inevitably lead to daily calls to the Refuge Manager and the need to 

use more toxic materials to control mosquitoes. (ACMAD)

Refuge Response: We have revised this language to request a general schedule of 

activities and their locations. For any significant changes to the schedule, particularly in 

endangered species habitat, we continue to request that you contact us prior entering 

the Refuge.

H.30.Comment: Pg. 10, (K-14)

Table 2, Footnote 1. Definition of human health threat is “based on the presence of 

endemic or enzootic mosquito-borne diseases.” Page 3 (K-7) correctly identifies “public 

health risks from mosquito-borne diseases and significant nuisance.” The definition of 

human health threat should take into account the “historic documents concerning 

mosquitoes and mosquito-borne diseases in California focus on the presence of malaria 

and large nuisance populations of mosquitoes affecting the first immigrants and 

settlers” (pg. 3). In order to meet the “social obligation to protect the health and 

P-61
well-being of the human communities surrounding refuges,” (pg.1) nuisance 

mosquitoes must be considered a human health threat. (ACMAD)

Refuge Response: While we recognize that nuisance mosquito species are an ongoing 

management concern of the districts, the Service does not recognize nuisance 

mosquitoes because it is an arbitrary term with no quantifiable distinction between it 

and non-nuisance mosquitoes. There is no set, measurable criteria for nuisance 

mosquitoes making it arbitrary as to when each district can conduct control. We believe 

that the actions outlined in Threat Levels 1 through 5 of the Mosquito Management Plan 

will be effective in responding to mosquito-borne disease risks and will also provide some 

ancillary benefits in controlling nuisance mosquitoes. The phased approach is used as a 

structure to provide a systematic method using disease history, disease presence, and 

mosquito population numbers to control mosquitoes to reduce the threat of mosquitoborne disease.

H.31.Comment: Pg. 11, (K-15)

Threat Level 2. “Some areas may already be operating under Phase 2 if they have had 

recent and recurring presence of mosquito-borne disease.” The wording in this section 

has changed from “historical” (used earlier in the document) to “recent and recurring”. 

To remain consistent and not impose further restrictions we suggest the wording be 

changed to “historical incidence of mosquito-borne disease.”

Threat Level 3. “The preferred larvicide treatments are biorationals (biological agents) 

B.t.i., B.s., and methoprene because of limited non-target effects (Appendix K3, K4). 

Chemical larvicides treatments (e.g., methoprene) would be the second preferred 

method for larvicides control.”

Methoprene is listed as a primary, biorational, and a secondary, chemical, preferred 

material for larval control. For clarity, methoprene should be removed from the first 

sentence and only referenced as a chemical larvicide. (ACMAD)

Refuge Response: The term “historical” has been readded to Threat Level 2. However, 

we believe it is important to show that there is not only historical evidence, but recurring 

presence of mosquito-borne disease in an area in order to justify mosquito control 

activities.

H.32.Comment: Pg. 18, (K-22)

Product names (B.t.i section). The paragraph above this section lists six products, but 

only two appear in the product names section. VectoBac G, VectoBac 12AS, Teknar HPD, VectoBac WDG, Bactimos pellets, and Summit B.t.i. Briquettes should all be listed 

under product names in this table. (ACMAD)

Refuge Response: Comment noted. Product names added.

H.33.Comment: Pg. 19, (K-23)

Table 4. BVA 2 should be added to the table. This is the pupacidal oil currently used by 

ACMAD. (ACMAD)

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Refuge Response: Please discontinue use of this product until 2013. The tables have 

been updated with the Pesticide Use Proposals for 2012 that were submitted in 

December 2011/January 2012. BVA 2 Oil was not included in the Proposal. Please 

request use of this product through the Pesticide Use Proposal (December 2012) for 

calendar year 2013.

H.34.Comment: Pg. 22, (K-26)

Section 8.4.2 Pupacide. BVA 2 is should also be listed in this section.

Golden Bear-1111. This section covers both Golden Bear-1111 and BVA 2 so the 

heading should reflect that. We suggest changing the heading to “Surface Films.” In 

addition, a description of BVA 2 should also be included. (ACMAD)

Refuge Response: Please see previous comment regarding BVA 2. Heading has been 

changed to “Surface Oils and Films. 

H.35.Comment: Pg. 29, (K-33)

Contra Costa goldfield. “Motor vehicles would not be permitted to operate during 

the Contra Costa goldfields blooming season...Contra Costa goldfields may also be 

indirectly affected by MAD staff spreading non-native plant species by foot (no motor 

vehicles will be permitted in these areas) within the listed plant’s habitat.” 

These sentences are in conflict with the stipulations mentioned under endangered 

species habitat bullet points 4 and 5 (pg. 31, K-35), with which we agree. We would like 

the bolded phrases deleted or modified. (ACMAD)

Refuge Response: Comment noted. The language has been changed to reflect the 

bullet points 4 and 5 (K-35).

H.36.Comment: Section 10, General Stipulations

Bullet point #1. The phrase “minimize the use of pesticides” is too vague. For example, 

smaller quantities of more toxic pesticides might be used (e.g., adulticides) vs. using 

greater quantities of less toxic materials (biorationals). Does “minimize the use” mean 

fewer total applications or less amount of total material applied? Preferred wording 

would be “The MADS will be required to utilize an Integrated Management strategy and 

continually investigate...” (ACMAD) 

Refuge Response: “Minimize the use of pesticides” can include the factors mentioned, 

including less toxic materials and fewer applications. We request that the districts use 

their best professional judgment to effectively control mosquitoes while reducing the use 

of pesticides in order to reduce impacts to the environment.

H.37.Comment: Bullet point #9. States that “pesticide application should not occur within 

100 feet of natural sloughs and channels” is unacceptable for effective mosquito control. 

Many sloughs bifurcate into smaller branches and pockets that breed mosquitoes. 

Many/most of these smaller branches, as well as some isolated pools of water are within 

100 feet of a main channel or slough. Larvicides typically are not applied directly to a 

major channel or slough. But they are frequently used in smaller channels and pools 

next to these areas. (ACMAD)

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Refuge Response: This bullet point is intended to limit pesticide impacts to navigable 

waterways and open water where they can impact aquatic species. We request that 

pesticide application should not occur within 100 feet of major natural sloughs and 

channels that have the potential to disperse into major navigable waterways and open 

water. This bullet has been revised to reflect this point.

H.38.Comment: Bullet point #12. This sentence appears to be missing something. The 

sentence reads “ To reduce the spread of nonnative invasive plants all construction 

equipment, clean vehicles and personnel gear of any possible seeds, soil or plant material 

before arriving on site”. Suggest it be changed to “To reduce the spread of nonnative 

invasive plants, all construction equipment, vehicles and personnel gear will be cleaned 

of seeds, soil or plant material before arriving on site. (ACMAD)

Refuge Response: Changes made.

H.39.Comment: Pg. 30, (K-34)

Section 10, Motorized Vehicle Operation

Bullet point #5. “Aerial pesticide (larvicide or pupacide) application is required in lieu 

of ground-based application methods in areas with endangered species.”

Based on the maps showing the presence of endangered species, most parts of Refuge 

land would require aerial treatments. Aerial application of larvicides/pupacides has 

rarely been performed on refuge land in Alameda County because of the small size of 

most individual sources of mosquito development there. This type of application would 

only be performed under extreme circumstances, such as the presence of immature 

mosquitoes over a large area (greater than 50 acres), significant presence of mosquitoborne disease, or where access by other means is impossible, such as sources surrounded 

by sloughs which can only be accessed by air or boat. Treatment by aerial application is 

not part of the District’s treatment regimen because it is cost prohibitive, helicopter 

services must be contracted for at a cost of at least $1,200 per hour, plus transportation 

costs of $200 to $500 per application. In addition, liquid formulations of the biorational 

materials used on the refuge have no residual effect, so aerial applications would need to 

be performed every three weeks for during the summer season. We would prefer this 

statement to read, “In areas with known endangered species, extreme care shall be 

taken to avoid adverse impacts on species habitat and well-being. When possible, 

inspections and treatments shall be performed on foot. When not practical, mechanized 

equipment such as ATVs or ARGOs will be considered for use only with approval of the 

Refuge manager”. (ACMAD)

Refuge Response: This bullet was replaced with: “Aerial pesticide (larvicide or 

pupacide) application is encouraged over ground-based application methods in areas 

with endangered species.” Also, a bullet was added regarding endangered species 

habitat: “Inspections and treatments will be primarily performed on foot, when 

possible.”

Section 10, Endangered Species Habitat

H.40.Comment: Bullet point #1. “Aerial pesticide (larvicide or pupacide) application is 

required in lieu of ground-based application methods in areas with endangered species.” 

P-64
See above comments under Section 10, Motorized Vehicle Operation, Bullet point #5. 

(ACMAD)

Refuge Response: See previous response.

H.41.Comment: Bullet point #2. “Access (via foot or mechanized vehicle) to tidal marsh and 

muted tidal marsh for the purpose of mosquito management would be not be allowed 

access February 1 to July 15 in areas that are inhabited by California clapper rails and 

along slough and channel edges (100-meter buffer).” Based on the map, “Don Edwards 

SF Bay NWR Mosquito Management and Endangered Species Sites in Alameda 

County,” Alameda County has several marsh areas considered Clapper rail territory, 

including Mowry Sough and Pintail Marsh. These large areas can be significant 

producers of the salt marsh mosquito, Aedes dorsalis and Ae. Squamiger. Aedes 

dorsalis larvae develop year round, Ae squamiger larvae between November to March. 

Completely denying ACMAD staff access to these marshes from February to mid-July 

would result in large fly offs of adult mosquitoes. The only treatment option left would 

be adulticiding, which would have a much greater impact on non-mosquito species. 

Specific clapper rail habitat needs to be distinguished from those areas that breed 

mosquitoes, as typically these areas have minimal, if any overlap. In addition, the phrase 

“...and along slough and channel edges (100-meter buffer)” was addressed in Section 10, 

General Stipulations Bullet point #9, which mentioned a less restrictive buffer of 100 

feet. (ACMAD)

Refuge Response: This bullet has been modified to, “Access (via foot or mechanized 

vehicle) to tidal marsh and muted tidal marsh for the purpose of mosquito management 

would not be allowed access from February 1 to July 15 in areas that are inhabited by 

California clapper rails without authorization of the Refuge Manager. 

H.42.Comment: Pg. 31(K-35)

Section 10, Use of Pyrethrins

Bullet point #1. “Use of adulticides must meet the following criteria: (1) when 

mosquito-borne disease incidence has been documented on the Refuge or within flight

range of vector mosquito species present on the Refuge and (2) when there are no 

practical and effective alternatives to reduce a mosquito-borne, disease-based health 

threat.”

ACMAD would like to reserve the right to use adulticides in the event of a large fly off of 

Aedes species. In some cases these mosquitoes have been shown to transmit disease 

causing viruses. In addition the aggressive nature of these mosquitoes can result in 

large numbers of complaints from the public, and in some individuals, cause severe 

allergic reaction. To our knowledge, ACMAD has never performed an adulticiding 

operation on Refuge property. Regular access to Refuge land for larval surveillance and 

subsequent larviciding should obviate the need for adulticiding. (ACMAD)

Refuge Response: The use of adulticide on the Refuge would require conditions and 

procedures as indicated in Threat Level 5 of the Mosquito Management Plan, the risk 

assessment in the most recent Mosquito-borne Virus Risk Assessment in the California 

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Mosquito-borne Virus Surveillance and Response Plan, and approval from the Refuge 

Manager.

H.43.Comment: Letter appended to comment from ACMAD written by Bartkiewicz, 

Kronick, and Shanahan.

Refuge Response: 

California State Law

We wish to address a point made in the letter asserting that California law applies to the 

Service’s management of mosquitoes (California Health and Safety Code section 2060(b), 

2002(j)). There is no waiver of sovereign immunity requiring the Service to comply with 

the California Health and Safety Code provisions relating to mosquito abatement. 

Decisions regarding whether and how to manage mosquito populations on national 

wildlife refuges are guided by Service policy, which is discussed below. We believe the 

Refuge has made a good faith effort to develop a comprehensive integrated pest 

management plan in the form of the Mosquito Management Plan that meets both the 

Service’s policies for pest management and the overall State goals of mosquito 

management.

There are several sources of Service policy that provide guidance on the management of 

mosquito populations on refuge lands. The Fish and Wildlife Service Manual, at 569 FW 

1.6, directs the Service to manage pests if the “pest causes a threat to human or wildlife 

health or private property ... or Federal, State, or local governments designate the pest 

as noxious; the pest is detrimental to refuge management goals and objectives; and the 

planned pest management actions will not interfere with achieving [Refuge] 

management goals and objectives.” Service policy further provides that pest 

management methods are chosen based on ranked factors, with human safety being the 

most important factor. Environmental integrity, effectiveness and cost are also 

considered, in that order. (569 FW 1.7) 

In addition, the Service has issued interim guidance on the management of mosquito 

populations on Refuge lands. See, 2005 Interim Guidance for Mosquito Management 

on National Wildlife Refuges. The 2005 Interim Guidance provides that the Service 

“will allow populations of native mosquito species to function unimpeded unless they 

cause a wildlife and/or human health threat.” If the Service agrees that there is a 

“documented” health threat and the threat is “above action levels,” the 2005 Interim 

Guidance directs the Service to take appropriate action in coordination with federal, 

state and/or local agencies such as vector control districts. (See 2005 Interim Guidance, 

Table 1.) 

The determination of whether to undertake response actions on Refuge lands in

response to human health threats is guided by Service policy, which is informed by the 

qualified opinions of federal, state and/or local public health agencies. According to the 

2005 Interim Guidance, “the first step in addressing mosquito management on a refuge 

is notification by the appropriate Federal, State, or local public health authority of a 

potential mosquito-associated health threat.”1

 If a human health threat is documented 

1 The 2005 Interim Guidance provides that a “mosquito-associated health threat is defined as an adverse impact to the health 

of human, wildlife, or domestic animal populations from mosquitoes. A health threat determination will be made by the 

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by these agencies, the 2005 Interim Guidance encourages cooperation and consultation 

between the Service and public health agencies to determine whether on-Refuge 

interventions should occur. Before authorizing mosquito monitoring or abatement 

actions on refuge lands, the Service must ensure that there is sufficient documentation of 

the existence of a public health threat. Once a threat is established, the Service has an 

important role in deciding whether on-Refuge interventions should occur. A decision to 

take abatement action on Refuge lands is not solely in the province of local vector control 

agencies. The 2005 Interim Guidance sets forth a number of criteria for the Service to 

consider in deciding whether on-Refuge abatement actions should occur. (See, the 

Action Thresholds and Treatment Options sections of the 2005 Interim Guidance for a 

full explanation of when and how treatment options are considered.) 

Nuisance and the Phased Response Plan

The comment letter suggests that mosquito populations are currently causing a nuisance 

and must be addressed. In the absence of documentation of a health threat, the Service 

cannot determine whether to authorize control or abatement measures on refuge lands. 

We believe that the actions outlined in Threat Levels 1 through 5 of the Mosquito 

Management Plan will be effective in responding to mosquito-borne disease risks and 

will also provide some ancillary benefits in controlling nuisance mosquitoes. The phased 

approach is used as a structure to provide a systematic method using disease history, 

disease presence, and mosquito population numbers to manage mosquitoes to reduce the 

threat of mosquito-borne disease.

Mosquito Control as a Use

The term “use” refers to any activity on a National Wildlife Refuge that is not a 

management activity conducted by refuge personnel for the purpose of conservation of 

fish and wildlife resources. It does not imply an extractive activity. Because we do not 

conduct mosquito management operations ourselves, but allow it when necessary 

through agreements with mosquito control agencies, mosquito management must be 

considered a use.

I. Other Projects

I.1. Comment: Regarding the San Francisquito Creek Restoration Project (SFCP), 

preserve the channels and levee section being planned for removal. Please preserve 

these channels free of vegetation and from becoming dry as the City of East Palo Alto 

and the community does not have the monies needed to upgrade this system. These are 

the Purdue Street outlet and channel, Stevens Street outlet and channel, and the Illinois 

Street outlet and channel. (Huerta)

Refuge Response: The SFCP which is being planned by the Joint Powers Authority 

(JPA) to improve flood control along the San Francisquito Creek corridor is noted in the 

CCP as Related Projects. The Refuge is not part of the planning and design work 

needed for this project, but we have commented during public scoping meetings offered 

by the JPA. As you may know, the Faber Tract is owned by the City of Palo Alto, but 

appropriate Federal, State, or local public health authority that has the expertise and the official capacity to identify human, 

wildlife, or domestic animal health threats. Documentation of a specific health threat on a refuge by a Federal, State, or local 

public health agency must be based on local and current mosquito population and/or mosquito-borne disease monitoring 

data.”

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through a Memorandum of Understanding with the City, the property is managed as 

part of the Refuge. The Refuge is concerned with impacts related to the lowering of the 

levee on the Faber Tract adjacent to SFCP. The Faber Tract has one of the highest 

populations of breeding California clapper rails in the Bay area, and if this levee were to 

be lowered, we have concerns that increased sediment rates, changing hydrology 

dynamics, high tide refugia, changes in vegetation, and invasive could cause negative 

impacts to endangered species. The Refuge will continue to work with JPA as needed to 

insure that impacts to endangered species and their habitats are protected.

The Faber Tract, which has the Bay Trail on the west side, and a public trail to the 

North, is already providing public use for hikers and wildlife observation. The levee

adjacent to the SFCP will remain closed to the public in order to reduce impacts to 

endangered species from these activities. Cooley Landing is in the process of opening to 

the public and will provide additional trails for the public to enjoy. 

The storm drains channels located within the Faber/Laumeister Tracts will remain as is 

and the Refuge has no plans to change or discontinue the use of these drains.

J. Climate Change

J.1. Comment: The draft CCP/EA briefly notes the potential effects of sea level rise on the 

Refuge and the CCP's contribution to greenhouse gas (GHG) emissions; however, the 

effects associated with implementing the CCP are not quantified. Please note that when 

reviewing lease applications CSLC staff is directed to (1) request information concerning 

the potential effects of sea level rise on proposed projects, and (2) if applicable, require 

applicants to indicate how they plan to address sea level rise and what adaptation 

strategies are planned during the projected life of each project. (CSLC)

Refuge Response: Comment noted.

J.2. Comment: Please provide a comprehensive analysis of the impacts of expected Sea 

Level Rise on Transitional Upland Habitat and discuss the ways in which the CCP would 

contribute to the protection of these habitats. (SCVAS)

Refuge Response: The Refuge will be working with others to assess sea-level rise 

impacts on refuge properties and resources (Objective 2.9). 

The protection and creation/enhancement of transitional upland habitat is discussed in 

the following objectives and restoration plans:

Objective 1.1. Conduct standardized monitoring efforts and research projects in 

coordination with other regional efforts for salt marsh harvest mouse and 

California clapper rail within five years. Improve high tide refugia for these 

species.

Objective 2.2. Within two years of Plan approval, complete and implement a Weed 

Management and Re-vegetation plan on the Refuge. 

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Objective 2.5. Within the life of the Plan, enhance and restore marsh-upland 

ecotone, especially at Faber-Laumeister, La Riviere Marsh, EEC, A6, A8, and 75 

miles of levee by establishing a dominance (>50 percent) of native plants along the 

levees or transitional uplands of the Refuge.

J.3. Comment: Lack of time frame and clarity regarding Climate Change Objectives 

and Strategies:

The CCP is correct in identifying the threat posed by invasive species and devotes an 

appropriate and thoughtful discussion to this issue, i.e. invasions of non-native and 

nuisance species pose a significant threat to the long-term viability of the Refuge. 

Unchecked invasive species could substantially alter community structure, lead to 

significant declines in species biodiversity, and adversely affect listed and rare species. 

The consequences of inaction are clearly explained and the time frames developed for 

the Objectives and Strategies appropriately convey a sense of urgency and hence 

priority - "Objective 2.2. Within two years of Plan approval, complete and implement a 

Weed Management and Re-vegetation plan on the Refuge." This is also true for the issue 

of mammalian and avian predator management. Even the development of a visitor 

services plan, which does not deal with direct threats to the resources of the Refuge, has 

a specified time frame of five years.

In contrast, the discussion regarding climate change fails to impart any sense of 

urgency/prioritization and does not adequately disclose the ramifications of inaction. 

(CCCR)

Refuge Response: Comment noted. We have added a timeframe of five years to 

Objective 2.9. We do not have internal expertise of climate change assessments. We will 

need funding and external expertise to help us with this analysis.

J.4. Comment: "Collecting data on physical and biological changes" can help to inform how 

to proceed with the conversion of salt ponds to tidal marsh, but we remain extremely 

concerned the objectives and strategies pertaining to climate change fail to convey the 

urgent need to acquire and/or protect lands that can ameliorate the expected impacts of 

sea level rise.

There should be no need to investigate the dire need to provide for the upslope migration 

of tidal marsh species as sea level rises. (CCCR)

Refuge Response: Comment noted. We agree that areas higher than the tidal marsh 

plain provide migration benefits, but we still believe it is important to understand the 

physical and biological changes that are taking place in order to make informed 

management decisions and potentially mitigate for such changes (e.g., introduced 

species, hybridized species, conflicts between species in different habitat types).

4. LIST OF PEOPLE AND ENTITIES THAT PROVIDED COMMENTS

State Agency

California State Lands Commission (CSLC)

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Local Agency

Alameda County Mosquito Abatement District (ACMAD)

San Mateo County Mosquito and Vector Control District (SMCMVC)

Santa Clara Vector Control District (SCCVCD)

Alameda County Water District (ACWD)

San Francisco Bay Area Water Trail (SFBAWT)

Organizations

Citizens Committee to Complete the Refuge (CCCR)

California Waterfowl Association (CWA)

Santa Clara Valley Audubon Society (SCVAS)

Private Companies

Barg, Coffin, Lewis and Trapp, LLP

Cargill

Individuals

R. Bamford

N. Bell

B. and D. Breaud

B. Huerta

D. Jones

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