United States 

Department of 

Agriculture

Marketing and 

Regulatory 

Programs

Animal and 

Plant Health 

Inspection 

Service

Proposed Field Release of 

Laricobius osakensis 

(Coleoptera: Derodontidae), 

a Predatory Beetle for 

Biological Control of 

Hemlock Woolly Adelgid 

(Adelges tsugae), in the 

Continental United States 

Environmental Assessment,

June 2010
2

Proposed Field Release of 

Laricobius osakensis (Coleoptera: 

Derodontidae), a Predatory Beetle 

for Biological Control of Hemlock 

Woolly Adelgid (Adelges tsugae), in 

the Continental United States 

Final Environmental Assessment, 

June 2010

Agency Contact:

Shirley A Wager-Page, Chief, Pest Permitting Branch

Plant Protection and Quarantine

Animal and Plant Health Inspection Service

U.S. Department of Agriculture

4700 River Road, Unit 133

Riverdale, MD 20737–1236

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Follow recommended practices for the disposal of surplus pesticides and pesticide containers.
3

Table of Contents

I. Background and Introduction ..................................................... 4

II. Purpose and Need for the Proposed Action............................... 5

III. Alternatives ............................................................................... 5

IV. Affected Environment ............................................................. 11

V. Environmental Consequences ................................................. 17

VI. Other Issues ........................................................................... 27

VII. Agencies, Organizations, and Individuals Consulted............. 28

VIII. References ............................................................................ 29

Appendix 1 .................................................................................... 38
4

I. Background and Introduction

The hemlock woolly adelgid (HWA) (Adelges tsugae Annand) is an

introduced insect pest destructive to forest and ornamental hemlock trees 

(Tsuga spp.) in the eastern United States. The adelgid feeds at the bases of 

needles, causing them to dry out and resulting in needle loss. This prevents 

trees from producing new buds for the next year’s growth, and leads to 

branch dieback and often eventual death of the tree. Heavy infestations 

have killed trees in as little as four years, but some survive longer with 

only a sparse amount of foliage at the very top of the crown (McClure et 

al. 2001). HWA has become a very important pest of eastern hemlock, 

Tsuga canadensis, and Carolina hemlock, T. caroliniana in the eastern 

United States because of the damage and mortality to trees ranging from 

landscape shrubs to old, large, forest trees. This pest has impacted federal 

parks, recreation areas, and forests; state-managed forest lands; 

commercial and private landowners; and urban and suburban 

communities.

The first report of HWA in eastern United States came from the Virginia 

Department of Agriculture and Consumer Services in 1951 on planted 

eastern hemlock in Richmond, VA (Stoetzel 2002). HWA now infests 18 

states and it is estimated that approximately 40 percent of the T. 

canadensis range and 100 percent of the T. caroliniana range within the 

United States is infested (Tighe et al. 2005). Because HWA is adapted to 

high elevations in Japan where winter temperatures commonly drop below 

-35°C (-63°F), it should continue to spread in eastern North America until 

it occupies the entire range of T. canadensis (see Appendix 1).

HWA infestation is fatal to eastern hemlocks of all ages, regardless of 

health prior to infestation (McClure 1990), with tree mortality occurring

between four and ten or more years after infestation, depending on 

environmental conditions (Orwig and Foster 1998, McClure et al. 2001). 

Modes of dispersal for HWA include birds, deer, humans (via movement 

of nursery stock), or wind (McClure 1990, McClure et al. 2001).

Existing management options for HWA are ineffective, expensive, 

temporary, or have nontarget impacts. For these reasons, forest managers 

and the United States Department of Agriculture (USDA) Forest Service

have sought to identify an effective, host specific biological control 

organism and release it into the environment for the control of HWA. 
5

II. Purpose and Need for the Proposed 

Action

The USDA Animal and Plant Health Inspection Service (APHIS) is 

proposing to issue permits for the release of a predatory beetle, 

Laricobius. osakensis (Coleoptera: Derodontidae). The agent would be 

used by the applicant for the biological control of HWA in the continental 

United States. Before permits are issued for release of L. osakensis, 

APHIS must analyze the potential impacts of the release of this agent into 

the continental United States.

The applicant’s purpose for releasing L. osakensis is to reduce the 

populations and the severity of infestations of HWA where it occurs in the 

United States. The HWA is a nonnative invasive pest in eastern North 

America on eastern hemlock and Carolina hemlock causing damage and 

mortality to the trees.

This environmental assessment1(EA) has been prepared, consistent with 

USDA, APHIS' National Environmental Policy Act (NEPA) 

implementing procedures (Title 7 of the Code of Federal Regulations 

(CFR), part 372). It examines the potential effects on the quality of the 

human environment that may be associated with the release of L. 

osakensis to control infestations of HWA within the continental United 

States. This EA considers the potential effects of the proposed action and 

its alternatives, including no action

III. Alternatives

This section will explain the two alternatives available to APHIS: no 

action, and the action to issue permits for environmental release of L.

osakensis. Although APHIS’s alternatives are limited to a decision on 

whether to issue permits for release of L. osakensis, other methods 

available for control of HWA are also described. These control methods 

are not decisions to be made by APHIS and are likely to continue whether 

or not permits are issued for environmental release of L. osakensis. These 

are methods presently being used to control HWA by public and private 

entities. 

 

1

Regulations implementing the National Environmental Policy Act of 1969 (42 

United States Code 4321 et seq.) provide that an environmental assessment “[shall include brief 

discussions of the need for the proposal, of alternatives as required by section 102(2)(E), of the 

environmental impacts of the proposed action and alternatives, and a listing of agencies and persons 

consulted.” 40 CFR § 1508.9. 
6

A third alternative was considered, but will not be analyzed further. 

Under this third alternative, APHIS would have issued permits for the 

field release of L. osakensis, but the permits would contain special 

provisions or requirements concerning release procedures or mitigating 

measures. Due to the small size of L. osakensis, and the probability that it 

may disperse on its own after release, mitigating measures for containment 

or retrieval would not be feasible. No issues have been raised that would 

indicate that special provisions or requirements are necessary.

A. No Action alternative

Under the “No Action” alternative, APHIS would not issue permits for the 

field release of L. osakensis, so the release of this agent would not take 

place in the United States. 

The following methods are presently being used to control HWA, and 

these methods will continue under the no action alternative and will likely 

continue even if permits are issued for release of L. osakensis.

1. Chemical control

Hemlock woolly adelgid infested hemlocks in the urban environment can 

be chemically controlled by thoroughly spraying infested trees with an 

application of insecticidal soap, horticultural oil, or any one of numerous 

other insecticides specifically labeled for this use. Oil and soap have been 

commonly used and are highly effective in killing adelgids but two spray 

treatments each year are usually necessary (McClure et al. 2001) and not

economically practical on larger scales. For example, the hydraulic 

application equipment required to spray larger trees cannot be used in 

rural forest situations without adequate access roads. 

More recently, systemic treatments of the insecticide imidacloprid, using 

either soil drench, soil injection or trunk injection techniques have been 

frequently adopted, with combinations of soil and trunk injections being 

most effective over both short and long term (Doccola et al. 2008). The 

soil or truck injection techniques do not require large equipment and

applications of imidacloprid have been performed on specific high value 

forested sites in many areas. 

An integrated approach in the Great Smokey Mountain National Park was 

employed on approximately 2,700 combined acres using foliar 

applications in developed areas (roads, campgrounds picnic areas, and 

drench applications in undeveloped sites, applied based on a priority 

system including site and infestation factors (Johnson et al. 2008).
7

2. Silvicultural control

Silviculture involves the management of forest areas or stands using 

techniques aimed at controlling the establishment, growth, composition, 

and quality of trees and other forest vegetation for certain objectives such 

as timber, wildlife, or other ecological attributes. Hemlocks are slow 

growing and their value is mainly environmental and not economic. Thus,

for most hemlock stands, silvicultural objectives are designed to ensure 

long term health of the associated ecological aspects of the site rather than 

for the production of timber. With essentially no ability to control the 

various modes of HWA dispersal, infestation cannot be prevented. 

Furthermore, HWA feeds on all ages of hemlock trees, and virtually all 

trees are susceptible to damage by the insect, regardless of age or site 

condition category. Therefore the options for using silvicultural techniques

to specifically mitigate HWA infestations are limited. Silviculture for 

HWA simply emphasizes good tree care, in as much as it can be 

accomplished, by maintaining healthy trees on individual sites. 

3. Biological control

Biological control efforts against HWA began in the early 1990’s. 

Typically, searches for natural enemies begin with seeking available and 

new parasitoids (organisms that are parasitic on just one host, eventually 

killing it as the parasitoid completes development). However, there were 

no parasitoids known worldwide, and in eastern United States, only 

generalist predators were observed to feed on HWA, and there were 

occasional fungal infections, also by non-specific species. Foreign 

exploration for natural enemies of HWA began in 1992 in Japan), then 

continued in China in 1995, and included western Canada starting in 1997 

(Cheah et al. 2004) as depicted in Figure 1 below. 
8

Figure 1 Worldwide occurrence of Hemlock (red) with arrows showing where 

biological control agents were collected for importation to the United States.

More than 60 species of lady beetles (Coccinellidae) were eventually 

collected in China (Yu and Montgomery 2008), with most being in the 

subfamily Scymninae, the largest subfamily of lady beetles. These

predatory beetles are quite small (less than 3 millimeters) and are 

“specialized predators” in that they attack only certain groups of sucking 

insects (Homoptera) such as scales, aphids, mealybugs - and adelgids. 

This group of tiny lady beetles contains the genera Sasajiscymnus and 

Scymnus. Both genera are found naturally only in Asia. Sasajiscymnus 

tsugae (Sasaji and McClure) (formerly Pseudoscymnus tsugae)

(Coleoptera: Coccinellidae) was collected in Japan, and three species of 

Scymnus were brought to the United States from China. The Scymnus 

species were studied in quarantine and proved to be very specialized 

adelgid predators – the adults fed on aphids to some extent but otherwise 

they fed on all stages of adelgids (such as HWA) and the larvae could not 

survive unless fed adelgid eggs (Cheah et al. 2004). 

L. nigrinus, from the beetle family Derodontidae, was collected in 

western Canada. This is also a very small predatory beetle that appears to 

be a specialized predator. 

L. nigrinus, Sasajiscymnus tsugae, and Scymnus sinuanodulus have been

released at numerous locations in eastern United States starting with S. 

tsugae in 1995, and after 2000 for the other two species. Establishment 

has been achieved by all three species, although establishment and buildup of S. tsugae has been very limited despite the release of over two 

million individuals of different stages (Salom et al. 2008). The degree to 

which these predators will suppress HWA populations has yet to be 

determined, however, since the majority of releases have been relatively 

recent (during just the last 5 years). 
9

Other biological control efforts include additional species of predatory 

beetles, and are in various stages of evaluation and research. Current 

efforts also include the development of effective fungus-based pesticide 

formulations using Lecanicillium muscarium (formally Vericillium 

lecanii) and Beauveria bassiana (Cheah et al. 2004, Gouli et al. 2008).

B. Second Alternative: Issue permits for

environmental release of Laricobius osakensis

Under this alternative, APHIS would issue permits for the field release of 

L. osakensis. These permits would contain no special provisions or 

requirements concerning release procedures or mitigating measures.

1. Description and Taxonomy of Laricobius osakensis

Laricobius osakensis Montgomery and Shiyake is a newly described 

species (see Montgomery et al. in press, for additional information). 

Traditional morphological and molecular techniques have been used to 

identify L. osakensis. Voucher specimens are currently located at the 

Osaka Museum of Natural History in Osaka, Japan, the USDA Forest 

Service, Northern Research Station in Hamden, CT, and the Beneficial 

Insects Quarantine Laboratory at Virginia Tech in Blacksburg, VA.

2. Life history

Based on weekly field sampling that has been conducted for the past year

in Japan, adults emerge from the ground in the fall and go to hemlock 

trees. Adults feed on HWA throughout the fall and winter months. Egg 

laying begins in December and continues through March. Larvae are 

active and feeding on HWA eggs from January through April. As 

prepupae, they drop to the ground, and bury into the soil for pupation. As 

adults, they enter diapause (dormancy) for the summer months. 

The life histories of L. osakensis and HWA are synchronized, although 

HWA has two generations per year and L. osakensis just one. The life 

history of HWA is characterized by the aestivation (summer dormancy) of 

the first stage nymphs during the summer (approximately June through 

September), with growth resuming in the fall, and continuing through 

winter and spring. HWA eggs are present typically from March into May 

and again in June (McClure et al. 2001). Laricobius larvae are likewise 

present during late February through May (see Figure 2). Larval 

development is completed and adults emerge by June, but the adults go 

into a period of dormancy during the summer as well, then resume activity 

and feed during the fall and winter on all stages of HWA which are 

present. 
10

Figure 2 Summarized presence of L. osakensis life stages from sampling HWAinfested hemlock in the Osaka region of Japan 2007 and 2008.

3. Native geographical range

L. osakensis has been recorded from only eight of Japan’s 72 prefectures

(provinces). It has been collected from well below 34° N latitude to just 

above 36° in Japan and at altitudes ranging from 300 to almost 7000 ft.

Given the latitudes and altitudes from which this species has been 

recorded, it is predicted that it will survive throughout most of the HWAinfested range of Tsuga spp. in the eastern United States. Furthermore, lab 

rearing indicates that L. osakensis is capable of surviving very low 

temperatures; as it lays eggs at 0°C and continues to feed at -7°C (A.

Lamb, personal observation).

4. Impact on HWA

HWA is not a pest in the areas of Japan where L. osakensis has been 

collected. As explained below, L. osakensis has an observable direct 

effect on the target host A. tsugae. Exclusion cages deployed throughout 

the winter months in Japan show a large decrease of HWA on branches 

exposed to L. osakensis compared to caged branches where HWA 

remained, but predators were excluded. A field study was conducted 

during the winter months in Japan at three locations with sufficient HWA 

populations. The stage and number of adelgids, as well as dead adelgids 

and the cause of death was recorded (i.e., caused by a chewing insect, 

sucking insect, fungus, or during aestivation). During that time, L. 

osakensis was the only predator present on the hemlock trees, and predator 
11

abundance was positively correlated to percent mortality on a site by site 

basis (Lamb et al. 2008). In the lab, L. osakensis appears to feed more 

voraciously on HWA than L. nigrinus, and also larval development rates 

are faster, with only 75 percent and 62 percent as much time in the larval 

stage as L. nigrinus at 9°C and 12°C, respectively (Lamb et al. 2008). 

IV. Affected Environment

A. Native North American Species

1. Species related to the Hemlock woolly adelgid

There are 13 described species of Adelgidae known to be native to North 

America (Havill and Foottit 2007), and at least three introduced species

besides HWA, including two known pests, the balsam woolly adelgid 

(Adelges piceae) and the eastern spruce gall adelgid (Adelges abietis)

(Johnson and Lyon 1991). Identified hosts of these 16 species are spruce, 

pine, fir, Douglas-fir, larch, and hemlock. The HWA is the only adelgid 

species in North America, and possibly the world, which utilizes hemlock. 

Adelgids have complex life cycles which can be divided into two types: 

species with only parthenogenetic (no sexual reproduction) cycles; and 

holocyclic species, which are species with both parthenogenetic and 

sexual cycles. Havill and Foottit (2007) provide the following description 

of adelgid life cycles and habits:

Five generations make up the typical adelgid holocycle. Three are 

produced on the primary host, where sexual reproduction and gall 

formation occur; two are produced on the secondary host that supports 

a series of asexual generations. The entire cycle takes two years to 

complete. Spruce (Picea spp.) is always the primary host and another 

conifer genus (Abies, Larix, Pseudotsuga, Tsuga, or Pinus) is always 

the secondary host. Adelgids are highly host specific: A given species 

can survive and reproduce only on certain tree species within a single 

primary and secondary host genus. For example, Pineus orientalis can 

alternate between Picea orientalis and Pinus silvestris, but it cannot 

survive on Picea abies, Pinus strobus, or Pinus cembra.

The primary hosts for HWA in Japan appear to be the spruce species 

Picea jezoensis hondoensis and P. polita, neither of which occurs in 

eastern north America, so HWA cannot complete the sexual cycles in the 

eastern United States.

2. Hemlock Woolly Adelgid
12

a. Native range of hemlock woolly adelgid

HWA is native to Asia and likely also western North America (Cheah et 

al. 2004, Havill et al. 2006). The population of HWA in the Pacific 

Northwest of North America was first described on western hemlock by 

Annand (1924). Havill et al (2006) determined that this population is 

molecularly distinct from populations in Asia and the eastern United 

States, and thus likely native to the region. It is present throughout this 

region of western North America, but at typically harmless densities 

(Furniss and Carolin 1977, Tait et al. 1985). 

b. Present distribution of HWA in eastern North America

In eastern North America, HWA has spread gradually from the 

introduction in Richmond VA and presently is known to occur in 18 states 

from Maine to Georgia (see Appendix 1). Approximately 40 percent of 

the T. canadensis range within the United States and 100 percent of the T. 

caroliniana range is infested (Tighe et al. 2005). 

c. HWA life history in eastern United States

Basically, there are three parthenogenetic generations of HWA each year 

on hemlock in eastern United States: an overwintering generation that 

occurs from July through April in the northeast, and two spring 

generations that occur simultaneously from April through June. All three 

of these generations have six stages of development: the egg; four 

nymphal instars (size stages); and the adult. One spring generation 

remains on hemlock, the other migrates to spruce, but the nymphs that 

hatch and begin to feed on spruce in July all die within a few days; none 

develop beyond the first instar on any of 15 different north American 

spruce species (McClure 1987, 1991). The adults from the spring 

generation (all female) each lay a cottony egg sack sometime in June or 

July. The crawlers (first stage nymphs) that hatch migrate to new growth 

on the tree and settle to feed but enter aestivation that lasts until October 

when they resume feeding (McClure 1996). 

3. Species related to Laricobius osakensis

Species in the genus Laricobius (Coleoptera: Derodontidae) feed only on

Adelgidae. The remaining species of Derodontidae in North America feed 

on various species of fungus during their entire life cycle. Laricobius is 

represented in North America by 4 species: L. erichsonii Rosenhauer, L. 

laticollis Fall, L. nigrinus Fender and L. rubidus LeConte. L. erichsonii, 

was introduced from Europe as a biological control agent of the balsam 

woolly adelgid, Adelges piceae (Ratzeburg). L. laticollis has been 

infrequently collected in the northwest and host associations are not 

known (Zilahi-Balogh et al. 2003b). The remaining two species of 

Laricobius, L. rubidus (eastern North America) and L. nigrinus (western 
13

North America), have been noted feeding on HWA. Laricobius rubidus

completes development, and survives well on a diet of HWA (ZilahiBalogh et al. 2005). It is present in Connecticut (Montgomery and Lyon 

1996), North Carolina, Virginia (Wallace and Hain 2000), Maine, New 

Hampshire, Massachusetts, District of Columbia, Pennsylvania, New 

York, Michigan, Quebec, Ontario, and New Brunswick (Lawrence 1989, 

Downie and Arnett 1996). The primary host of L. rubidus is the pine bark 

adelgid, Pineus strobi Hartig (Clark and Brown 1960), and is not 

commonly observed feeding on HWA.

The known distribution of L. nigrinus ranges from northern California to 

British Columbia, Alberta, and northern Idaho (Furniss and Carolin, 1977;

Lawrence 1989). An extensive 2 year survey of predators of HWA in 

Washington and British Columbia resulted in the collection of 55 species 

of predators. Just three species, Laricobius nigrinus, Leucopis 

argenticollis Zetterstedt, and Leucopis atrifacies (Aldrich) (Diptera: 

Chamaemyiidae) comprise 59 percent of all the predators collected, with 

L. nigrinus being the most abundant (Kohler et al. 2008). 

Laricobius nigrinus has one generation per year which is very well 

synchronized with HWA throughout the year (Zilahi-Balogh et al. 2003a).

Both the predator and prey are active in the fall, winter, and spring, and 

both diapause in the summer. Adults emerge from the soil in the fall, 

disperse to hemlock branches, feed on HWA nymphs, adults, and eggs 

(available during early-mid spring), and then die. In the laboratory tests 

conducted at Virginia Tech, L. nigrinus completed development on HWA 

but not on several other eastern adelgids and aphids tested. Because of its 

specificity to HWA, L. nigrinus was released from quarantine by USDAAPHIS (Zilahi- Balogh et al. 2002), and has subsequently been released 

in 16 eastern states where HWA is present.

B. Hemlock Resources in North America

Eastern hemlocks, T. canadensis, are long-lived, late successional climax 

trees that, if left undisturbed, eventually dominate stands. Eastern 

hemlock, may take 250-300 years to reach maturity, live for 800 years, 

and attain heights of 150-175 feet. Eastern hemlock is the most shade 

tolerant tree species in North America, capable of surviving underneath a 

shaded forest canopy for as long as 350 years (Quimby 1996). Because it 

is so shade tolerant and long-lived, hemlock is a late successional (or 

"climax") tree that can dominate a forest for centuries. 

Eastern hemlock forests create distinctive microclimates and provide an 

important habitat for a wide variety of wildlife. In the Northeast, 96 bird 

and 47 mammal species are associated with hemlock forests (Yamasaki et 

al. 2000). Of these, at least eight species of birds and ten species of 
14

mammals have strong ecological linkages with hemlock forest habitat. In 

Connecticut alone, almost 90 species of birds use hemlock as a food 

source, nesting site, roost site, or winter shelter (McClure et al. 2001). 

Examples of birds include black-throated green warbler, blackburnian 

warbler, blue-headed vireo, winter wren, red-breasted nuthatch, ruffed 

grouse, and the northern goshawk. Examples of mammals include black 

bear, bobcat, snowshoe hare, red squirrel, and southern red-backed vole. 

Hemlock is an important winter habitat for white-tailed deer. Many native 

plant species thrive in hemlock stands, including leatherwood, rattlesnake 

plantains, bunchberry, goldthread, bluebeard, Canada mayflower, wood 

sorrels (Evans et al. 1996, McClure et al. 2001). 

Hemlock forests are often a critical factor in supporting native brook trout

populations, by maintaining cool stream temperatures and stable flows. A 

study conducted by Snyder et al. (2001) in the Delaware Water Gap 

National Recreation Area showed that small streams in hemlock forests 

are three times more likely to support native brook trout populations than 

similar streams in hardwood forests in the park. The study showed that 

small streams in hemlock forests are typically 1-2

°C (2-3.5°

F) cooler in the 

summer than similar streams in hardwood forests. Furthermore, hemlock 

forest streams typically support about 65 species of aquatic insects, 

compared to only about 35 species in hardwood forest streams. About 15 

species of aquatic insects seemed to occur almost exclusively in hemlock 

forest streams in this park (Snyder et al. 2001).

For these and other reasons, hemlock stands are very popular recreational 

sites for fishing, hiking, hunting and bird watching. Hemlock is not a 

valuable timber species, but it is used widely for pulpwood and utilitarian 

uses (such as pallets). Hemlocks are valued landscape plants, however: 

with 274 cultivars of eastern hemlock, it is one of the most cultured and 

cultivated landscape trees in the United States (McClure 2001).

C. Relationship of HWA with eastern hemlocks

1. Continued spread of hemlock woolly adelgid

McClure and Cheah (1999) reported that from 1985 to 1999, the rate of 

spread of HWA averaged nearly 30 km (19 miles) per year. A later report 

by Evans and Gregoire (2007) calculated an average rate of spread of 12.5 

km (7.8 miles) per year since 1990. However, several factors influenced 

this rate of spread, the most important being exposure of the HWA 

nymphs to temperatures of around -25°C (-13°F). Thus the average rate of 

spread is only 8 km (5 miles) per year for Pennsylvania and north, and 

15.6 km (9.7 miles) per year for areas further south. Winter mortality of 
15

HWA has been observed on many occasions. The lowest temperature 

tolerated by a sample of individuals from both northern and southern US 

sites appears to be approximately -18°C (0°F), with some variation 

between individuals, and more individuals in northern sites tolerating 

temperatures slightly lower than 18°C (Costa et al. 2008). Nevertheless, it 

is widely considered that HWA will eventually occupy all of the natural 

range of eastern hemlocks (see Appendix 1)

2. Impact on hemlock resources

a. Tree decline and mortality

Eastern hemlock is classified as highly susceptible to HWA (Hoover et al. 

2008). HWA has caused significant mortality of hemlock trees over the 

last 20+ years. As HWA infestations rapidly spread to other states in the 

1980’s, and these HWA outbreaks had steadily grown in size, impacts 

from HWA infestation appeared to be worsening and by the mid 1990’s 

tree mortality was being reported from at least four states. 

Tree decline and mortality is highly variable site to site and year to year, 

often showing cycles of decline and regrowth and decline for individual 

trees and stands, mainly in response to HWA induced changes in 

nutritional quality of the tree on which they feed (McClure et al. 2001). 

Site and weather factors (i.e., drought) plus secondary pests attacking the 

weakened trees, are thought to influence when and where mortality occurs 

(Souto et al. 1996). For example, in Shenandoah National Park, some 

sites experienced a rise in mortality from 8 percent to 48 percent in just 

two years, with several site factors deemed to be important including, 

elevation and which cardinal direction a slope faces (Blair 2002). 

By about 2005, hemlock mortality and logging in anticipation of mortality 

had become so widespread that there was concern about the future 

viability and preservation of the species. However, there appears to be 

some innate resistance in a small minority of surviving hemlocks from 

devastated stands, based on propagating and then challenging these 

apparently resistant trees with HWA infestation (Casswell et al. 2008).

b. Economic, Social and Recreational Impacts

Landowners today have several options for monitoring and management

HWA and tree mortality (Ward et al. 2004, Orwig and Kittredge 2005, 

Costa and Onken 2006). However, no practical options are available to 

prevent hemlock decline in forest settings, and thus, these stands are 

transitioning to hardwoods and invasive plants (Orwig and Foster 1998, 

Orwig et al. 2002, Eschtruth et al. 2006).

Loss of hemlock landscape trees due to HWA infestations in residential 

properties has been estimated at $2,000 – $7,000 per home (Holmes et al. 
16

2005). Hemlock losses as a forest product resource have not been 

estimated due to the fact that hemlock is not an especially valuable or 

unique forest product resource. 

Hemlock mortality in the forest does have significant impact on 

recreational use, and large federal parks have engaged in integrated pest 

management (IPM) programs to address the varied recreational and 

ecosystem needs on their properties. For example, long term monitoring, 

ecosystem studies, and management efforts were begun at the Delaware 

Water Gap National Recreation Area in 1993 (the Park was originally 

infested in 1989). Monitoring has shown a rapid decline and mortality and 

as of 2006, 28 percent of originally healthy plot trees had died and none of 

the remaining trees were in healthy condition (Evans and Shreiner 2008). 

The Great Smokey Mountains National Park has engaged in an aggressive 

IPM program to respond to the infestation which threatens over 35,000 

acres of hemlock dominated forest (Johnson et al. 2008).

3. Ecosystem impacts of HWA

Richard Evans (2002) of the National Park Service commented that the 

“decline and loss of our remaining eastern hemlock stands could be more 

ecologically significant than the loss of American chestnut (Castanea 

dentata) in the early 1900s due to chestnut blight” due to the fact that 

hemlock would not be replaced by ecological equivalent species as 

occurred with the loss of the American chestnut. The large scale removal 

of hemlock trees due to HWA caused mortality, and in some cases the 

resulting salvage logging of stands is well documented (Kizlinski et al. 

2002, Orwig et al. 2002, Foster and Orwig 2006)

Impacts include negative effects on brook trout (reversal of cooler summer 

and warmer winter stream temperatures), carbon cycling (Nuckolls et al. 

2009), soil and water chemistry (Yorks et al. 2003). Loss of foliage and 

tree mortality in hemlock dominated stands often results in the invasion of 

exotic and native species which provide less shade and cover during the 

summer and winter seasons, significantly impacting temperature and 

moisture microhabitats.

Reduction in biodiversity after tree mortality due to HWA has been 

reported extensively (Yamasaki et al. 2000, Brooks 2001, Evans 2002, 

Snyder et al. 2002, Tingley et al. 2002, Ross et al. 2003, Ross et al. 2004, 

Buck et al. 2005, Ellison et al. 2005, Lishawa et al. 2007). Hemlock 

mortality is also changing ecosystem processes, structure, and function 

(Jenkins et al. 1999, Stadler et al. 2005, Cobb et al. 2006, Stadler et al. 

2006), water quality (Yorks et al. 2003).
17

V. Environmental Consequences

A. No action

The infestation and damage caused by HWA in urban and forest 

landscapes has received considerable attention from landowners and 

landmanagers, both public and private. Several management tactics have 

been implemented to reduce the infestation level of HWA and the damage 

and mortality it causes. The use of chemical insecticides and biological

controls at current levels would be expected to continue if the “no action” 

alternative is chosen. These environmental consequences may also occur 

even with the implementation of the biological control alternative, 

depending on the efficacy of L. osakensis to reduce infestations HWA and 

levels of damage to eastern hemlocks. 

Similarly, the current rate of spread, and levels and trends of eastern 

hemlock mortality and other environmental consequences from infestation 

by HWA are expected to continue if the “no action” alternative is chosen. 

Likewise, these environmental consequences may also continue at some 

level even with the implementation of the biological control alternative

1. Impact from use of other control methods

a. Chemical control

In recent years chemical control of HWA in both ornamental and forest 

situations has predominantly utilized imidacloprid applied as a soil drench, 

soil injection or trunk injection. The injection techniques use a Kioritz 

injector (soil) or any of a variety of injection systems for trunk injection. 

Some proprietary designs have been specifically developed for application 

against HWA (Doccola et al. 2008). Imidacloprid acts systemically (taken 

up by the hemlock tree and is translocated via the plants vascular system). 

Typically pest suppression is evident for more than one year after

application (Webb et al. 2003). 

It appears that very little to no run off occurs from properly applied soil 

injections (Churchel et al. 2008). Further, hemlocks frequently grow in 

stream-side locations and in steep, rocky ravines with little intact soil, and 

trunk injection is used instead of soil injection in these situations. Another

avenue for imidacloprid entry into the environs outside of the live tree is 

via leaf fall in deciduous trees. However with the needle retention of 

hemlock, this is less of a concern. Other insecticides will have different 

environmental fate scenarios.

Predatory organisms feeding on HWA on treated plants have the potential 
18

to be exposed to insecticides, including imidacloprid, through ingestion of 

contaminated prey. For example, predator poisoning was observed in one 

laboratory trial that investigated this issue. However, a strong feeding 

preference for healthy (untreated) adelgids was shown by L. nigrinus and 

Sasajiscimnus tsuga (Eisenback et al. 2008). A secondary impact could 

result from ingesting poorer quality prey items (i.e., less preferred and less 

suitable prey species) in treated areas.

b. Biological control

Information from surveys of native parasites and predators of HWA, 

indicates there are no parasites, and that the predators attacking HWA are 

generalist species, most of which were predatory flies in the families 

Cecidomyiidae, Syrphidae, and various lacewings (Chrysopidae, and 

Hemerobiidae). Only two coleopteran predators were noted, the invasive 

ladybeetle, Harmonia axyridis, and Laricobius rubidus. However,

predator abundance was not great enough to exert any controlling effect 

(Montgomery and Lyon 1996; Wallace et al. 2000; Salom et al. 2008).

Three species of predators have been released in eastern United States 

against HWA: Laricobius nigrinus (from northwestern United States),

and Sasajiscimnus tsuga, and Scymnus sinuanodulus (both from Asia). 

Many of these releases have been in recent years, thus, recovery and 

establishment is limited or not yet confirmed in many areas (Grant 2008, 

McDonald, et al. 2008). Recovery of the Asian coccinellid predators has 

been limited despite widespread releases and the release of over 2 million 

S. tsugae. However, Laricobius nigrinus has been recovered in 60 per 

cent of release sites (Mausel et al. 2008). Population buildup of this 

species has been noted in a few sites, for example in northwestern North 

Carolina (McDonald et al. 2008). 

Research of other biological control agents continues, including release 

and recovery efforts for the three species mentioned above (Salom et al.

2008)

B. Issue permits for environmental release of L. 

osakensis

1. Effects on target non target prey species

a. Scientific literature and sources

The genus Laricobius is known to be specific to Adelgidae (Zilahi-Balogh 

et al. 2003b). Museum specimens at the Osaka Museum of Natural 

History were all collected on Tsuga sieboldii and T. diversifolia infested 

with HWA. Hundreds of adults, eggs, and larvae of L. osakensis have also 
19

been collected from HWA on T. sieboldii during 2006 and 2007 visits to 

Japan for research.

L. nigrinus likewise may have become somewhat specialized on HWA in 

western North America. Zilahi-Balogh et al. (2007) reported that L.

nigrinus highly preferred HWA over three other adelgid, two aphid and 

one scale species, and that it could not complete larval development on 

these alternate hosts yet was successfully reared on HWA. 

b. Field Observations

L. osakensis appears to be well adapted to this host, feeding specifically on 

it. The seasonal cycles of the life histories of the two species are tightly 

synchronized as is evident in several regions in Japan. For example,

during autumn 2008 in northern Japan, HWA became active on October

14 and predators were found feeding on it, while at the same time in the 

Kansai area, regular sampling had revealed that HWA was still in diapause 

on October 13 and no predators were found.

L. osakensis appeared to have an observable direct effect on HWA. This 

was shown by a field test in Japan in winter 2007-2008 using cages on 

hemlock branches which prevented the free living L. osakensis in the area 

from feeding on the HWA inside the cages. There was a large decrease of 

HWA on branches exposed to L. osakensis compared to caged branches. 

c. Host specificity testing

Host range testing was conducted using adelgid species and other related 

species available in North America. Several adelgid hosts were used, as 

well as two scale species, and a woolly aphid. These alternate hosts were 

chosen because they are closely related to HWA, or are on hemlock trees, 

or because they have a specific non-target concern. The results indicate 

that HWA, Adelges tsugae, is the preferred host. Following is additional 

information about these species and results from these tests.

i. Species tested

Adelgid species

Balsam woolly adelgid (BWA), Adelges piceae (Ratz.), is of European 

origin but is now distributed in eastern and western North America and 

attacks various firs trees (Abies spp.). Pine bark adelgid (PBA), Pineus 

strobi (Hartig), is native to the eastern United States, and mainly attacks 

eastern white pine, Pinus strobes, but occasionally attacks other species of 

pine (Pinus). Larch woolly adelgid (LWA), Adelges laricis Vallot, is 

native to Europe and attacks larch (Larix spp.) in North America. Eastern 

spruce gall adelgid (ESGA), Adelges abietis (Linneaus), introduced from 

Europe, primarily attacks white spruce (Picea abies) and Norway spruce 

(P. glauca). 
20

Woolly aphid and scales

Woolly alder aphid (WAA), Paraprociphilus tessellates (Fitch), is

generally considered a pest, but it may be an insect of concern for nontargets effects because it is the host of the only carnivorous Lepidopteran 

in North America, the harvester butterfly, Feniseca tarquinius (Fabricius).

WAA is found east of the Mississippi river and requires both alder and 

silver maple to complete its lifecycle. This aphid is woolly, therefore 

there has been some concern that Laricobius would be attracted to it.

Elongate hemlock scale (EHS), Fiorina externa Farris, is a scale of 

Japanese origin that is found in several eastern states where it has been 

introduced and spread. It attacks both eastern and Carolina hemlocks, T. 

canadensis and T. caroliniana, thus, it is frequently in the same areas as 

HWA. It is considered a pest and contributes to the decline in hemlock 

trees. Pine needle scale (PNS), Chionaspis pinifoliae (Fitch), is a native 

scale that is commonly a pest on coniferous trees.

ii. Tests conducted:

No-Choice Tests – Adult Feeding and Oviposition

Female L. osakensis were placed individually on HWA, BWA, or PBA for 

5 days at 12°C, and the number of host eggs eaten and the number of eggs 

laid was recorded (see Table 1). Female L. osakensis were placed 

individually with WAA for 7 days, and the number of aphids eaten was 

recorded. Adult feeding and oviposition (egg laying) was higher on HWA 

than either of the other hosts (Tables 1 and 2 )

Table 1. Mean (±SD) host eggs consumed and oviposition rate by 

L. osakensis when offered hemlock woolly adelgid (HWA), balsam 

woolly adelgid (BWA) or pine bark adelgid (PBA) during a 5-day nochoice test. 

Host n L. osakensis Feeding 

(host eggs/day) 

L. osakensis

Oviposition 

(eggs/day) 

HWA 8 17.3 ± 5.6 a_ 3.7 ± 1.9 a 

BWA 10 2.1 ± 2.7 c 0.1 ± 0.1 b 

PBA 11 7.1 ± 3.8 b 0.5 ± 0.8 b 

Table 2. Mean (±SD) number of woolly alder aphids eaten in 7 

days when given no choice.

Host n Feeding 

WAA 10 0.7 ± 0.82 

Choice Tests – Adult Feeding

A series of choice tests measuring feeding and oviposition on HWA and 

one alternate host were conducted at 10°C for 7 days. For each test, a 

single adult was placed in each of 10 petri dishes with a sufficient amount 

each HWA and the alternate host. In each test, the number of HWA eaten 
21

was significantly greater than the number of alternate hosts eaten (Table 

3.)

Table 3. The mean number of hosts eaten in a 7-day choice test using hemlock 

woolly adelgid and an alternate host. Alternate hosts include pine needle scale 

(PNS), balsam woolly adelgid (BWA), woolly alder aphid (WAA), elongate 

hemlock scale (EHS), and pine bark adelgid (PBA).

Test n Mean HWA Eaten Mean Alternate Host Eaten

HWA vs PNS 10 6 +/- 0.68a 0 b

HWA vs BWA 10 6 +/- 0.92a 1.7 +/- 0.21 b

HWA vs WAA 10 7.9 +/- 1.18a 1.3 +/- 0.45 b

HWA vs EHS 10 3.6 +/- 0.27a 0.5 +/- 0.22 b

HWA vs PBA 10 3.8 +/- 0.39a 2.0 +/- 0.47 b

Means with the same letter within a row are not significantly different 

(p=0.05 Student T-test).

No-Choice Tests - Larval Development

L. osakensis eggs were placed on HWA and 5 alternate hosts, BWA, PBA, 

LWA, ESGA, and WAA. Individuals were held at 9°C and survival of 

each individual was assessed every 2-3 days (Table 4). L. osakensis was 

able to complete development from the egg stage through all larval stages

to adult only on HWA (see trail #1). There was no survival beyond the 

first larval stage (no feeding) when fed LWA and WAA (Trail #1). 

Cohort survival to prepupal stage was below 20% on BWA (7%), and 

PBA (see Trials #1 and #3), while cohort survival on HWA exceeded 50% 

in two of three trials. Trail #2, (average 43%). L. osakensis survival from 

egg to prepupal stage averaged 31% on PBA, and was 43% for ESGA.

Despite limited data, it is clear that there was no development on the only 

non-adelgid species tested (WAA), while development to prepupa 

occurred on four of the five adelgid species tested. Regarding 

development being restricted to adelgids, these data are consistent with

results from similar trials with L. nigrinus and three other adelgids (BWA, 

ESGA, PBA), and two aphid species (Zilahi-Balogh et al. 2002).
22

Table 4. The number and percentage of individuals of L. osakensis surviving to 

each life stage for each test prey species in No Choice conditions.

Trial #1

Stage HWA LWA WAA 

n % survival 

from egg 

stage

n % survival

from egg 

stage

n % survival

from egg 

stage

Egg 9 20 20 

L1 9 100 20 100 20 100 

L2 8 88 0* 0 0* 0 

L3 7 78 0 0 0 0 

L4 7 78 0 0 0 0 

Prepupae 5 56 0 0 0 0 

Pupae ? ? 0 0 0 0 

Adults 4 44 0 0 0 0 

*L1 larvae did not feed on LWA and WAA and did not develop to L2

Trial #2

Stage HWA ESGA PBA 

n % survival

from egg 

stage

n % survival 

from egg 

stage

n % survival 

from egg 

stage

Egg 28 14 29 

L1 28 100 14 100 29 100 

L2 24 86 14 100 26 89 

L3 11 39 12 86 21 72 

L4 7 25 8 57 18 62 

Prepupae 5 18 6 43 13 44 

Pupae ? ? ? ? ? ? 

Adults 0 0 0 0 0 0 

Trial #3

Stage HWA BWA PBA 

n % survival 

from egg 

stage

n % survival 

from egg 

stage

n % survival 

from egg 

stage

Egg 11 14 18 

L1 11 100 14 100 18 100 

L2 10 91 2 14 12 67 

L3 9 82 1 7 12 67 

L4 9 82 1 7 10 56 

Prepupae 6 55 1 7 3 17 

Pupae ? ? ? ? ? ? 

Adults 0 0 0 0 0 0 
23

iii. Summary and Discussion: Host specificity of L. osakensis

The life history pattern of L. osakensis indicates that it is naturally 

synchronized with the life history pattern of HWA, including a period of 

aestivation in the summer followed by active feeding and development in the 

colder months of September to June, which itself is synchronized with the 

annual pattern of growth and transpiration of the hemlock hosts (very high 

rates in the early spring). The literature shows that Laricobius species are 

specialist predator on adelgids. Results from the laboratory tests on L.

osakensis and the native L. nigrinus demonstrate a very narrow host range. 

L. osakensis is not expected to be able to survive on a diet of prey of other 

North American species related to HWA. Although L. osakensis adults may 

feed on these other adelgids, the results from paired choice test show they 

are not preferred. The synthesis of this information– specialized life history, 

and high degree of prey choice preference among the alternate hosts tested, 

coupled with the inability to survive on prey other than HWA, suggest very 

minimal direct impact on other potential prey species in the environment in 

North America.

d. Competition with other predators

The life history of Laricobius osakensis appears to be similar to L. 

nigrinus. This was confirmed by weekly field sampling conducted in 

2007-2008, and is summarized as follows. In the fall, after the summer 

aestivation ends, the adult L. osakensis emerge from the ground and go to 

hemlock trees, where they feed on HWA throughout the fall and winter 

months. Female L. osakensis begin begin laying eggs in December and 

continue through March. Beginning in January, larvae hatch and feeding 

on HWA eggs through April. The larvae finish their growth and drop to 

the ground during late March and April and bury into the soil for pupation. 

Adults emerge from the pupal stage by early summer, but remain in the 

soil in aestivation for the summer and into early fall when they become 

active and start the cycle again.

Since this species is active in the winter, and aestivates in the summer, it 

does not interact or compete with other predators on hemlock except 

perhaps the biological control agent L. nigrinus which has been introduced

and established in the eastern United States. This species may also 

interact with the native L. rubidus that feeds on pine bark adelgid but is 

known to occasionally feed on HWA. The potential interactions of all 

three species are currently being studied at Virginia Tech. Laboratory

studies of adult beetle interaction among all three species show no

negative interactions to the impact on the target host (see Fig. 3 below) 

and in the number of predator eggs deposited in HWA ovisacs (egg 

clusters) (Fig. 4). Additionally, survivorship among the three species 

appears unaffected (Fig. 5).
24

Figure 3. Mean number of HWA ovisacs disturbed by adult Laricobius spp. 

when placed in groupings by themselves or all together in the laboratory. All 

treatments contained a total of 3 adult beetles. “L. sp. N.” = L. osakensis. 

Treatments denoted by different letters are significantly different from each other 

(Tukey’s studentized test; p <0.05).

Figure 4. Mean number of eggs deposited by Laricobius spp. when placed in 

groupings by themselves or all together in the laboratory. All treatments 

contained a total of 3 adult beetles. “L. sp. N.” = L. osakensis. Treatments 

denoted by different letters are significantly different from each other (Tukey’s 

studentized test; p <0.05).
25

Figure 5. Survivorship of each predator species when placed in groupings by 

themselves or all together in the laboratory after 6 days. “L. sp. n.” = L. 

osakensis. No differences in treatments were observed (ANOVA; p > 0.05)

Based on these results with high but typical density of host ovisacs, no 

negative interactions are apparent. Under lower densities, preliminary 

results show no statistical differences at densities 1⁄2 and 1⁄4 of the tests 

depicted above. There is some tendency for each species to consume their 

own and competitor’s eggs. Again preliminary results show a trend (not 

significant) where L. nigrinus may prefer L. osakensis eggs somewhat to 

their own, but both L. osakensis and L. rubidus seemed to prefer their own 

eggs. In summary, there is no evidence of negative interspecific 

competition among these three specialized predators.

2. Uncertainties regarding the environmental release of L. 

osakensis

Once a biological control agent such as Laricobius osakensis is released 

into the environment and becomes established, there is a slight possibility 

that it could move from its preferred prey (HWA) to preferentially attack 

other nontarget prey, such as PBA, or native woolly aphids. Prey shifts by 

predators are not uncommon, especially opportunistic feeding on very 

abundant prey items in the environment. However, adaption to other prey 

by larval L. osakensis would require both nutritional as well as life history 

shifts in order to successfully survive on other prey, which significantly 

lowers the likelihood of such an occurrence.
26

If other insect species were to be attacked by L. osakensis, the resulting 

effects could be environmental impacts that may not be easily reversed. 

Biological control agents such as L. osakensis generally spread without 

intervention by man. In principle, therefore, release of this biological 

control agent at even one site must be considered equivalent to release 

over the entire area in which potential hosts occur and in which the 

climate is suitable for reproduction and survival.

In addition, these agents may not be successful in reducing HWA

populations in the continental United States. Approximately 12 percent of 

the introductions of biological control agents against pests have led to 

“complete” control of the target pests (Greathead and Greathead 1992). 

Actual impacts on HWA populations by L. osakensis will not be known 

until after release occurs and post-release monitoring has been conducted. 

The environmental consequences discussed under the “no action” 

alternative may occur even with the implementation of the biological 

control alternative, depending on the efficacy of those agents to reduce 

HWA populations in the continental United States

3. Cumulative impacts

“Cumulative impacts are defined as the impact on the environment which 

results from the incremental impact of the action when added to other past, 

present and reasonably foreseeable future actions regardless of what 

agencies or person undertakes such other actions” (40 CFR 1508.7).

Many states and counties, as well as individual federal, state and local and 

private property ownerships conduct their own programs to manage HWA

as well as other invasive forest pests. Chemical, mechanical, and 

biological controls, as described previously in this document are used in a 

wide range of habitats.

Release of L. osakensis is not expected to have any negative cumulative 

impacts in the continental United States because of its specificity to HWA. 

Effective biological control of HWA will have beneficial effects for forest 

and ornamental pest management programs, and may result in a long-term, 

non-damaging method to assist in maintaining native hemlock trees and 

hemlock stands in good health.

4. Endangered Species Act

Section 7 of the Endangered Species Act (ESA) and ESA’s implementing 

regulations require Federal agencies to ensure that their actions are not 

likely to jeopardize the continued existence of federally listed threatened 

endangered species or result in the destruction or adverse modification of 

critical habitat. 
27

APHIS has determined that based on the host specificity of Laricobius 

osakensis, and since there are no listed species related to HWA, or 

dependent on HWA, there will be no effect on any listed species or 

designated critical habitat in the continental United States 

VI. Other Issues

Consistent with Executive Order (EO) 12898, “Federal Actions to Address 

Environmental Justice in Minority Populations and Low-income 

Populations,” APHIS considered the potential for disproportionately high 

and adverse human health or environmental effects on any minority 

populations and low-income populations. There are no adverse 

environmental or human health effects from the field release of L.

osakensis and will not have disproportionate adverse effects to any 

minority or low-income populations. 

Consistent with EO 13045, “Protection of Children From Environmental 

Health Risks and Safety Risks,” APHIS considered the potential for 

disproportionately high and adverse environmental health and safety risks 

to children. No circumstances that would trigger the need for special 

environmental reviews is involved in implementing the preferred 

alternative. Therefore, it is expected that no disproportionate effects on 

children are anticipated as a consequence of the field release of L.

osakensisi.

EO 13175, ―Consultation and Coordination with Indian Tribal 

Governments, was issued to ensure that there would be “meaningful 

consultation and collaboration with tribal officials in the development of 

Federal policies that have tribal implications....”.

Consistent with EO 13175, APHIS sent letters of notification and requests for 

comment and consultation on the proposed action to tribes in Connecticut, 

Florida, Maine, Massachusetts, Michigan, Minnesota, Mississippi, New York, 

North Carolina, Rhode Island, South Carolina and Wisconsin. APHIS will 

continue to consult and collaborate with Indian tribal officials to ensure that 

they are well-informed and represented in policy and program decisions that 

may impact their agricultural interests, in accordance with EO 13175.
28

VII. Agencies, Organizations, and 

Individuals Consulted

North American Plant Protection Organization (NAPPO). 

A petition for consideration of release ref. NAPPO Standard RSPM No. 

12 (available at: http://www.nappo.org/Standards/Std-e.html) to APHIS 

and forwarded to the AAFC Biological Control Review Committee fro 

review and recommendation. The Committee recommended that release 

of Laricobius osakensis be approved with the conditions that: 1) a detailed 

post-release monitoring plan be provided; and 2) authoritatively identified 

voucher specimens of the L. osakensis populations released are

deposited in the national entomological collections in North America. 

Agencies and organizations represented on the committee are:

Agriculture and Agri-Food Canada, Research Centre, Ottawa, ON (Chair);

Centro Nacional de Referencia de Control Biológico, Enasica, Colima, 

Mexico;

Pest Management Regulatory Agency, Ottawa, ON;

Canadian Forest Service, Victoria, BC;

North Carolina State University, Raleigh, NC

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Plant Protection and Quarantine 

Registrations, Identifications, Permits and Plant Safeguarding

4700 River Road, Unit 133

Riverdale, MD 20737

U.S. Department of Agriculture

Forest Service, Northeast Area, State and Private Forestry

Forest Health Protection 

Morgantown Field Office

180 Canfield Rd.

Morgantown, WV 26505

Virginia Polytechnic Institute and State University (Virginia Tech)

Department of Entomology

Blacksburg, VA 24060
29

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Shenandoah National Park. pp. 61-66 in Onken, B., R. Reardon, and J. 

Lashomb (eds.), Proceedings, Symposium on Hemlock Woolly Adelgid in 

the Eastern United States, February 5-7, 2002, East Brunswick, NJ. New 

Brunswick, NJ: Rutgers University.

Brooks, R. T. 2001. Effects of the removal of overstory hemlock from 

hemlock dominated forests on eastern redback salamanders. Forest 

Ecology and Management 149:197-204.

Buck, L., P. Lambdin, D. Paulsen, J. Grant and A. Saxton. 2005. Insect 

species associated with eastern hemlock in the Great Smoky Mountains 

National Park and environs. Journal of the Tennessee Academy of Science 

80: 60-69.

Caswell, T., R. Casagrande, B. Maynard, and E. Preisser. Production and 

Evaluation of Eastern Hemlocks Potentially Resistant to the Hemlock 

Woolly Adelgid. Pp. 124 – 134. In B. Onken and R. Reardon [eds.], 

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Cheah, C.A.S.-J., M.E. Montgomery, S. Salom, B.L. Parker, S. Costa, and 

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Churchel, M. A., J. Hanula, C. W. Berisford, and J. M. Vose. 

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30

Costa, S. and B. Onken. 2006. Standardizing sampling for detection and 

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Doccola, J. J., B. I. Cruz, P. M. Wild, J. J. Aiken, R. N Royalty, and W. 

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Downie, N. M. and R. H. Arnett. 1996. The Beetles of Northeastern North

America. The Sandhill Crane Press, Gainesville, FL. 1721 pp.

Eisenback, B. M., S. M. Salom, and L. T. Kok. Laboratory Studies of 

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and Sasajiscymnus tsugae. Pp. 95 – 98. In B. Onken and R. Reardon 

[eds.], Fourth Symposium on Hemlock Woolly Adelgid in the Eastern 

United States. USDA Forest Service, Hartford, CT. FHTET-2008-01.

Ellison, A. M., J. Chen, D. Díaz, C. Kammerer-Burnham and M. Lau. 

2005. Changes in ant community structure and composition associated 

with hemlock decline in New England. pp. 280-289. . In B. Onken and R. 

C. Reardon [eds.], Third Symposium on Hemlock Woolly Adelgid in the 

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Appendix 1

Map of hemlock woolly adelgid infestations 2008

Map shows current and recently infested counties and native range of eastern hemlock (Tsuga 

canadensis)

Source: http://na.fs.fed.us/fhp/hwa/maps/distribution.shtm.