# Aquatic Pesticide Monitoring Program

Review of Alternative Aquatic Pest

Control Methods For California Waters

Ben K. Greenfield

Nicole David

Jennifer Hunt

Marion Wittmann Geoffrey Siemering

San Francisco Estuary Institute

7770 Pardee Lane, 2 nd 

# Floor Oakland, CA 94621

April 2004

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# i 

# Table of Contents:

Disclaimer and Acknowledgements ..................................................................................iii
Introduction......................................................................................................................... 2 Review Design.................................................................................................................... 4
Literature Review............................................................................................................ 5 Practitioner Survey.......................................................................................................... 5 Biological Control Methods................................................................................................ 6
Pros and Cons of Biocontrol........................................................................................... 6 Triploid Grass Carp......................................................................................................... 7
Other Herbivorous Fishes ............................................................................................. 11 Fish Biomanipulation.................................................................................................... 11
Terrestrial Herbivorous Mammals................................................................................ 13 Gastropod Mollusks...................................................................................................... 13

Insects ........................................................................................................................... 14 Predatory Animals For Mosquito Control .................................................................... 16 Commercially Available Biocontrol Agents................................................................. 17 Plant Pathogens Currently In Development.................................................................. 18 Pathogens For Mosquito Control.................................................................................. 20 Cyanobacteria Control Agents Currently in Development........................................... 20 Organic Material Amendment ...................................................................................... 21
Acetic Acid ................................................................................................................... 22 Management Considerations For Organic Material Amendment................................. 23 Plant Competition ......................................................................................................... 24 Physical and Mechanical Control Methods ...................................................................... 25 Mechanical Harvesting ................................................................................................. 25 Environmental Effects of Mechanical Harvesting........................................................ 29 Mechanical Cutting....................................................................................................... 31 Rotovation, Rototilling and Hydroraking ..................................................................... 34 Weed Rollers and Sweepers.......................................................................................... 36 Diver-operated Suction Dredging................................................................................. 37
Sediment Removal........................................................................................................ 37 Shading and Piping ....................................................................................................... 37
Bottom Barriers............................................................................................................. 38
Manual Removal........................................................................................................... 40 Water Level Manipulation ............................................................................................ 42 Channel Clearing or Excavation ................................................................................... 43 Exposure of Plants to Extreme Environmental Conditions (Heat, Steam, Flame, Cold, or Electricity) ................................................................................................................ 45 Aeration, Oxygenation, and Water Circulation ............................................................ 45
Nutrient Removal.......................................................................................................... 48
Non-conventional Chemical Controls............................................................................... 49
Calcium-based Products................................................................................................ 50 Aluminum based products ............................................................................................ 51
Nitrate ........................................................................................................................... 52

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# ii Aquashade..................................................................................................................... 52 Salt (Sodium Chloride) ................................................................................................. 53 NPDES Permitting Status of Non-Conventional Chemicals ........................................ 53
Preventive Measures ......................................................................................................... 54 Early Detection ............................................................................................................. 54 Quarantine and Regulation ........................................................................................... 55
Education and Outreach................................................................................................ 56 Riparian Buffer Strips................................................................................................... 56
Retention Pond or Wetland Construction ..................................................................... 57 Watershed Best Management Practices ........................................................................ 57
Relative Reliance on Conventional Pesticides vs. Alternative Methods .......................... 58 General Permitting Requirements For Non-Chemical Methods....................................... 60
General Discussion ........................................................................................................... 61
References......................................................................................................................... 62 Appendix A: Contractors/ Retailers That Specialize in Non-Chemical Control Methods79
Contractors who conduct Non-Pesticide Control Methods .......................................... 79Companies that Manufacture and Sell Aquatic Plant Harvesters or Other NonChemical Devices ......................................................................................................... 80 Appendix B: Practitioners Interviewed For Review......................................................... 82
California Practitioners ................................................................................................. 82
Out of State Practitioners.............................................................................................. 88 Appendix C: Feasibility Screening For Different Weed Control Methods ...................... 93 Appendix D: Peer Review .............................................................................................. 102

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# iii 

# DISCLAIMER AND ACKNOWLEDGEMENTS

This report is the result of feedback by some members of the Aquatic Pesticide

Monitoring Program Steering Committee that there is a need for thorough documentation

on alternative aquatic pest control methods for California waters. This work is intended

as an educational tool, including detailed discussion of alternative methods. This review

does not evaluate conventional chemical pesticides; therefore, it should not be considered

a guideline on all available aquatic pest control methods. No policy or regulation is

expressed or intended by this report.

We thank the APMP Steering Committee and Interested Parties for providing

feedback and direction on this literature review. Thanks are also due to all the aquatic

plant managers, scientists, regulators, and NGOs who agreed to be interviewed and

provide literature and unpublished reports for this review. Any errors or omissions in

presenting alternative pest control efforts are the responsibility of the authors, rather than

those interviewed. David Spencer, George Forni, Lars Anderson, and Robert Leavitt

provided constructive review comments on portions of this review, Joe DiTomaso and

John Madsen constructively reviewed the entire document, and Roger Mann assembled

some of that information in the Feasibility Screening (Appendix C). Amy Franz and Seth

Shonkoff assisted with document review and formatting. The California State Water

Resources Control Board is acknowledged for funding this review.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 2 

# INTRODUCTION

Aquatic plant and algae infestations can reduce the utility of water bodies for

irrigation, aquaculture, potable water, navigation, and recreation, as well as obstruct

drainage canals, which are needed for flood control prevention. Millions of dollars are

spent annually to control aquatic weeds and algae (Joyce 1992), and California agencies

invest heavily in programs to control nuisance aquatic plants (e.g., CDBW 2001; CDFA

2003a). Over the next several decades, with increasing human population growth,

demand for food and water will increase, exacerbating the need for efficient delivery of

usable water in California and worldwide (Van Vierssen et al. 2001).

The purpose of this review is to evaluate aquatic pest control methods that may

serve as alternatives to registered chemical pesticides (Table 1). These alternatives

include biological, mechanical, and physical control methods, as well as preventive

measures. The review also discusses chemicals not registered as pesticides, including

phosphorus-binding agents, acetic acid, and Aquashade.

Biological methods include the introduction of insect species and sterile grass

carp, as well as microbial biocontrol agents, enzymes, and the addition of organic

material. Mechanical control methods include harvesting, cutting, shredding, pulling,

rolling, rotovation, diver dredging, the placement of barriers to inhibit growth, and

excavation. Physical control methods include shading, aeration, and water level

drawdown. Manual cutting, pulling, and rolling are geared towards small-scale projects,

obstructed areas, or individual waterfronts. Harvesting, rotovation, excavation, and

dewatering are used in larger scale aquatic weed removal (Table 1).

This document was written to discuss plant management methods that may be

usable in California waters. Wherever possible, local case studies are described, and local

environmental conditions and regulations are referred to. For readers desiring further

information, several excellent reviews of aquatic plant control methods are readily

available on the World Wide Web. Madsen (2002) provides a general review. Gibbons et

al. (1999) provides recommendations for implementation of aquatic plant management

plans. Systma and Parker (1999) review methods that are appropriate for irrigation

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 3 canals. The identification of aquatic weeds and other information on their biology are

described in DiTomaso and Healy (2003).

Table 1. Methods available for control of aquatic pests in California waters.

Physical and Mechanical Control Methods Biological Control Methods Mechanical Harvesting Triploid Grass Carp Mechanical Cutting Other Herbivorous Fishes Rotovation and Rototilling Fish Biomanipulation Hydroraking Terrestrial Herbivorous Mammals Weed Rollers Gastropod Mollusks Lake Sweepers Insects Diver-operated Suction Dredging Non-Insect Crustaceans (for mosquito control) Sediment Removal Predatory fishes (for mosquito control) Shading Commercially Available Biocontrol Agents Piping Microbial Pathogens (e.g., cyanophages) Bottom Barriers Fungal Pathogens Manual Removal Organic Material Amendment Water Level Manipulation Acetic Acid Channel Clearing Plant Competition
Mechanical Excavation Exposure to Extreme Environmental Conditions Preventive Measures Aeration, Oxygenation, and Water Circulation Early Detection Nutrient Removal Quarantine Regulation

Non-conventional Chemical Controls Education and Outreach Calcium based Products Riparian Buffer Strips Aluminum based products Retention Pond or Wetland Construction Nitrate Watershed Best Management Practices Aquashade Salt (Sodium Chloride)



# Aquatic plant control typically involves a balance of multiple management

objectives. Different water body users may have varying definitions of how much

submerged aquatic vegetation is acceptable (Van Nes et al. 1999). This can be

particularly important because some management objectives can be incompatible. For

example, reducing macrophyte biomass can result in increased algal blooms, and vice

versa (Scheffer et al. 1993; Scheffer, 1999). Success of many control methods could be

improved by the timing of application to the nuisance species. For example, water

hyacinth control agents should be applied when the plant carbohydrate stores are at their

lowest which generally occurs in the spring. Eradication when plants are young and

shoots and leaves are small may also increase rates of success (Madsen et. al 1993).

This review synthesizes past and present knowledge of alternative management

options, providing a wide range of potential tools for controlling aquatic plants and algae.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 4 Nevertheless, each combination of plant species, water body, and stakeholder needs will

respond best to a particular set of management options. Often times, significant progress

can be achieved with alternative techniques on the control of relatively small infestations.

However, large infestations may be most effectively treated with conventional pesticides,

either alone or in combination with alternative plant control methods (Madsen 2002). It is

important to not limit the available options in vegetation management and to choose

carefully which ones are best applied for certain scenarios, considering the managed

species, ecological system, natural resource values, and stakeholder priorities.

To determine the best management options, aquatic resource managers are

encouraged to develop aquatic plant management plans that best address all user goals

(Gibbons et al. 1999). If a practitioner wishes to decide among a specific suite of

management options, they may want to formally compare their feasibility and cost

effectiveness, using the Aquatic Plant Management Economic Methodology prepared as

part of this project (Mann 2003).

Some of the methods described in this review are also used to control mosquito

larvae in California waters. Water level manipulation has a long use history in mosquito

control, as larva production is elevated in stagnant standing waters. Mechanical removal

of aquatic or wetland vegetation could reduce larval production in some cases.

Additionally, biological control is commonly used to control mosquito production;

mosquitofish ( Gambusia affinis ) and other animal species may be introduced to water

bodies, where they prey on larval mosquitoes.



# REVIEW DESIGN

An evaluation of plant control methods for potential use in California should

include all methods and technologies available throughout the United States. This study

includes a detailed evaluation of methods documented in scientific journal literature,

agency technical reports and grey literature. Additionally, telephone or in-person

interviews were conducted with 77 practitioners in California and other states to point out

methods currently successfully applied in specific management circumstances.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 5 Literature Review

An extensive review of recent literature and survey papers was conducted. This

included keyword searches using selected library search engines (e.g., the Web of

Science, Biosis) and review of relevant articles in the past several years of relevant

journals. For example, The Journal of Aquatic Plant Management

( http://www.apms.org/japm/japmindex.htm ) was reviewed since 1990, and Lake and

Reservoir Management since 1996. The World Wide Web was also surveyed for gray

literature using keyword searches on web search engines. An excellent source of gray

literature regarding plant management is the Aquatic Plant Information Retrieval Service

(APIRS) at the University of Florida ( http://plants.ifas.ufl.edu/search80/NetAns2/ )

. Additionally, papers available from the U.S. Army Corps of Engineers Waterways

Experiment Station Digital Archives were downloaded and reviewed. Finally, several

frequently published research scientists in the field were contacted with reprint requests.

Of the published papers, grey literature, and web documents evaluated, 177 were

included in this report and cited in the references section.

Practitioner Survey

To augment the findings of the literature review with late breaking information

from the field, practitioners were surveyed within California and other states.

Practitioners were asked whether they knew of any novel techniques for control of

aquatic pests that would serve as alternatives to application of chemical pesticides in

specific management circumstances. Interviews generally ranged in length from 15 to 60

minutes, depending on the time constraints of the interviewee and the information they

had to share.

Appropriate practitioners and experts for interviews were identified using

publications of articles regarding non-chemical plant control methods, relevant reports

and information on the World Wide Web, attendance at the Western Aquatic Plant

Management Society conference, listings on the APMS and NALMS websites and

recommendations through already established contacts. Contact information of all

practitioners interviewed is available in Appendix B

.

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# 6 

# BIOLOGICAL CONTROL METHODS

Biological control involves using plant, animal, or fungal species or components

to reduce the survival, growth, or reproduction of the nuisance species. This includes use

of herbivores, such as grass carp or insects that consume parts or all of the nuisance plant

species. Bacterial and fungal pathogens are also used. These cause disease to the nuisance

plant species, thereby reducing survival and recruitment. Additionally, biological

materials, such as bacteria, enzymes, barley straw, organic matter amendments, may be

added to the system to reduce growth of nuisance plants or algae, without preying on

them or causing disease. The proposed mechanisms for non-predatory biocontrol

methods include competition for resources, and production of natural substances that

inhibit the growth of the nuisance species. The development of biocontrol agents has

been limited due to production difficulties, unresolved regulatory questions, virulence

issues and lack of capital investment (Watson 2003).

Biological control is often more successful when multiple methods are integrated.

Plants weakened by insect damage or sublethal doses of chemicals are often more

susceptible to pathogens. In water hyacinth management, for example, multiple insect

species, insects combined with grass carp, or pathogens combined with chemical

treatment are often more effective than individual treatment methods alone (Gopal 1987).

Pros and Cons of Biocontrol

Biocontrol for reduction of nuisance plants in aquatic systems has both positive

and negative attributes (Charudattan et al. 2002). A positive aspect of biocontrol is that

control agents are often host specific, so effects to non-target species may be reduced.

Control agents can also reproduce in response to increases in nuisance species density

often without reapplication of the agent. Development and registration (where necessary)

of biocontrol agents is generally less expensive than chemical agents. Additionally, the

ecosystem impacts under biocontrol can be more gradual, thereby allowing the system to

adjust to loss of a species.

However, biocontrol can have many potential disadvantages. An important risk is

involved when new species are introduced as biocontrol agents. To be considered

successful, these species are expected to persist indefinitely in the environment where

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 7 they are used, and may spread to new locations. Therefore, if there are any adverse

effects resulting from the biocontrol agent, these effects may be difficult or impossible to

control. Adverse effects of biocontrol agents could include loss of habitat for some fauna,

competition with native species, and the production of toxic metabolites that are released

to the environment. Other drawbacks include unpredictable success and rates of control

that are slower than with chemical methods. Resistance in host species is unlikely to

develop but can occur. Finally, agents that work in one area may not be suitable in all

ecosystems. Climate, interference from herbicidal application, hydrological conditions,

and eutrophication of the system can influence the effectiveness of biocontrol agents (Hill

and Olckers 2001). The growth of nuisance weeds can be suppressed with the use of

biocontrol agents, but not fully eliminated.

Triploid Grass Carp

The grass carp, also known as the white amur ( Ctenopharyngodon idella ), feeds

on aquatic plants and can therefore be used as a biological tool to control nuisance

aquatic plant growth. To reduce the potential for unintended consequences, grass carp

must be sterilized for use in waters of the United States. Once grass carp are stocked in a

water body, it may take several years for them to control the plant growth and decrease

weeds to about 20% of the earlier plant cover (Washington State Department of Ecology

2001). If practitioners stock enough fish to achieve control within the first few years, this

can eventually result in detrimental effects to non-target plants, as the fish increase in size

(e.g., Colle and Shireman 1994). If possible, it would be more cost-effective to stock a

smaller number of fish, and wait for them to grow sufficient size to control the plant

problem (Stewart and Boyd 1999).

A wide range of field applications and scientific studies has demonstrated that

grass carp can effectively reduce growth and biomass of undesirable vegetation (e.g.,

Leslie et al. 1994; Pauley et al. 1994; Santha et al. 1994; Van Vierren et al. 2001).

However, success with grass carp may vary from site to site. Sometimes identical

stocking rates result in no control, adequate control, or even complete elimination of all

underwater plants. Therefore, before introducing grass carp to a water body, it must be

determined whether complete elimination of all submerged species could be tolerated.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 8 Many researchers and aquatic plant managers think that grass carp should only be

stocked when complete elimination of all submersed plant species could be tolerated.

As with any large-scale ecosystem manipulation, grass carp introduction may

cause significant environmental impacts to a water body. Elimination of submerged

plants by grass carp foraging could result in increased turbidity, water column nutrients,

and phytoplankton production (Scheffer et al. 1993; Colle and Shireman 1994; Scheffer

1999). If all aquatic vegetation is removed, waterfowl, amphibians and aquatic mammals

may also be adversely impacted (Brakhage 1994). In light of the fact that grass carp, once

introduced, are extremely difficult to remove from a water body (e.g., Colle and

Shireman 1994), caution should be exercised when considering new waters for grass carp

introduction.

Case study results vary widely in overall impacts of grass carp introduction to

native plant and animal communities. Overstocking can result in disturbance to the

existing fish community, resulting from vegetation habitat removal. In two Florida lakes

heavily stocked with grass carp, all submerged vegetation was wiped out, resulting in

impaired water quality and declines in sensitive native fish species (e.g., Colle and

Shireman 1994). In contrast, when grass carp were carefully stocked in eight Oregon and

Washington lakes, dissolved oxygen improved and other fish populations were not

affected (Pauley et al. 1994). By reducing dense monotypic vegetation, and increasing

underwater structural diversity, grass carp introduction may even increase abundance of

other fish species (Killgore and Kirk 1998; Killgore et al. 1998).

California Department of Fish and Game has implemented a number of

restrictions to reduce the probability of negative consequences of grass carp use. First of

all, grass carp may only be used in water bodies that are isolated from the 100-year

floodplain of major California rivers (Marty Muschinske, pers. comm. ). Due to the risk of

adverse impacts on adjacent water bodies, stocked water bodies should be isolated or

have screened inlets and outlets (Washington State Department of Ecology 2001).

Screens to inlets or outlets are generally only approved by CDFG where they do not

interfere with anadromous fishes, e.g. steelhead or salmon runs. Additionally, grass carp

must be sterilized, a process achieved by causing fertilized eggs to retain three sets of

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 9 chromosomes (triploidy). The risk of inadvertent release of fertile grass carp (e.g., Webb

et al. 1994) is reduced by testing the blood of juvenile fish to confirm triploidy.

In California waters, stocking costs include the purchase price of the fish

(generally about $8-15/fish), purchase cost for the permit ($100 application fee), a onetime stocking fee of 15$/fish paid to CDFG, and an annual regulatory fee of $7.50/fish

also paid to CDFG. Inquiries can be submitted to the local region office of CDFG or to

Marty Muschinske, of the Eastern Sierra/Inland Desert region, who currently has the

most experience with the program (Marty Muschinske, pers. comm. ). Applications are

evaluated by the local region office. Stocking rates for Washington lakes generally range

from 9 to 25 eight to eleven inch fish per vegetated acre. This number will depend on the

amount and types of plants as well as water temperatures (Washington State Department

of Ecology 2001). One-year-old fish (less than 225 grams body weight) have much lower

plant feeding rates than larger fish (Pine et al. 1990), so if small fish are stocked, foraging

rates may increase considerably with fish size.

For any given water body, it can be difficult to determine the optimal number of

grass carp to stock. In the 1980s and 1990s, stocking rates varied widely among U.S.

water bodies (Stewart and Boyd 1999). The optimal stocking rate is generally higher in

Oregon and Washington than in southeastern United States (Pauley et al. 1994),

suggesting that cooler water bodies in northern California would require higher stocking

rates than warmer southern California waters. Currently, a number of California

practitioners often report simply stocking a fixed number of fish per year, based on the

general observation of successful weed control (Paul Saunders, pers. comm. ; Ron Derma,

pers. comm. ).

For practitioners wishing to more accurately estimate the appropriate number of

fish to achieve adequate control, the Waterways Experiment Station (WES) of the United

States Army Corps of Engineers has developed a grass carp stocking rate computer

model called AMUR/STOCK (Madsen et al. 1998). AMUR/STOCK was developed to

help aquatic plant managers evaluate proposed stocking rate strategies. Practitioners

would input data on water body temperature, plant biomass and growth rate, number of

grass carp initially stocked, and grass carp feeding preference. The model would then

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 10 determine the required rate of restocking and the plant area controlled (Stewart and Boyd

1999). AMUR/STOCK is available as part of the Aquatic Plant Information System CDROM, which can be ordered for free from the U.S. Army Corps of Engineers Website

(U.S. ACE 2001; http://www.wes.army.mil/el/aqua/apis/apishelp.htm )

Grass carp are more effective at removing some plant species than others. Highly

preferred species include Egeria densa

, Hydrilla verticillata

, common elodea ( Elodea

canadensis ), and duckweeds ( Lemna spp. and Spirodela spp.). Non-preferred species

include coontail ( Ceratophyllum demersum ) and milfoils ( Myriophyllum spp.) (Stewart

and Boyd 1999). Success has been reported in controlling water hyacinth using a

combination of grass carp and weevils (Gopal 1987). Eurasian watermilfoil is not a

preferred food source and grass carp will consume most other aquatic species before

eating it (Washington State Department of Ecology 2001). Also, grass carp may consume

submerged species before eating floating species in the same water body (Santha et al.

1994).

A number of practitioners in California water bodies have reported positive

experiences with grass carp. Use of grass carp has been successful for southern California

irrigation district delivery channels, where the primary management objective is water

conveyance, and complete elimination of all vegetation is acceptable. For example, grass

carp have been an important tool in controlling Hydrilla verticillata (hereafter, hydrilla)

in the Imperial Valley, CA. In the Imperial Irrigation District, hydrilla infested areas have

been reduced from over 600 miles of irrigation canals, reservoirs, drains, private ponds

and deliveries to less than 0.75 miles in a single drain. While triploid grass carp remain

the main weapon against hydrilla, an integrated method of fish, mechanical, and manual

methods is being used to eliminate the final <1% of the hydrilla infestation (Mike

Mizumoto, pers. comm. ). A total of 13,908 triploid grass carp have been stocked into the

Imperial Valley waters. By 2000, hydrilla was reported to be eliminated from all sites

except one drain (Mizumoto 2001). The Bard Irrigation Districts and Coachella Valley

Water District also report very positive experiences using grass carp in irrigation canals

(Ron Derma, pers. comm. ; Paul Saunders, pers. comm. ). In the Bard Irrigation District,

recent set up costs for a six mile irrigation canal included the purchase and permitting for

300 fish, and the installation of a concrete grate to reduce the risk of fish escape (Ron

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 11 Derma, pers. comm. ). Finally, a number of southern California and Central Valley golf

courses have stocked grass carp to control vegetation in their ponds (Paul Beaty, pers.

comm. ). These include the Tulare County Recreation Department and the Woodridge

Golf Course (just outside of Lodi) (Marty Muschinske, pers. comm. ).

Grass carp have also been successfully employed in Arizona canals used for

drinking water conveyance, where chemical pesticide application was discontinued. The

Salt River Project (SRP) delivers a million acre-feet of water annually to 250,000 acres in

central Arizona through approximately 130 miles of canals and 120 miles of laterals.

Water usage in the SRP system has shifted from primarily agricultural use to use as a

drinking water source. As a result, environmental regulations prohibit the use of most

chemical herbicides. Magnacide H (acrolein) and chelated elemental copper are currently

the only used chemicals. SRP has used grass carp to control extensive aquatic weed

growth in most of the canal systems for ten years and has found them to be

“environmentally friendly and cost effective.” Weed growth and fish populations are

monitored and fish are moved to maintain effective weed control throughout the system.

Grass carp have been shown to adequately control aquatic weed growth in the SRP

(Maldonado 2001).

Other Herbivorous Fishes

In addition to triploid grass carp, common carp and tilapia have been added to

ecosystems to reduce aquatic vegetation. However, these species are not perceived to be

successful and are not recommended for use as biocontrol agents. Common carp stir up

the bottom of water bodies, and are generally considered to be a nuisance species.

Anecdotal reports of use of tilapia in the Coachella Irrigation District (southern

California) indicated that they did not control growth of aquatic plants and were

constantly getting stuck in irrigation drains (Paul Saunders, pers. comm. ). Tilapia is

prohibited in California north of Los Angeles County and CDFG does not recommend

they be used for aquatic vegetation control.

Fish Biomanipulation

In addition to the use of herbivorous fish, water resource managers can also

reduce aquatic plant growth by changing the abundance of fish higher in the food web.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 12 This method, often referred to as biomanipulation, is typically used to control growth of

nuisance planktonic algal blooms and has been most successful in small lakes when

combined with nutrient input control (John Madsen, pers. comm. ). Fish biomanipulation

may also be appropriate in water bodies characterized by large populations of small fish

that eat zooplankton. In these lakes, the heavy grazing by planktivorous fish can cause

low zooplankton abundance, and a consequent reduction in zooplankton grazing rates on

algae. In these circumstances, it may be possible to indirectly control algal production by

manipulating the “top” of the food web. Specifically, managers reduce the population of

smaller fish. Freed up from the predation pressure by the small fish, the zooplankton in

the lake increase in size and foraging rate. This greater grazing by zooplankton

consequently reduces the overall abundance of algae in the water body, improving water

clarity (Carpenter et al. 1987; Carpenter and Kitchell 1988). The water body manager can

reduce the small fish population either by directly removing the fish from the water body

(e.g., Annadotter et al. 1999) or by adding a large population of predatory fish, which are

expected to forage heavily on the smaller fish, thereby reducing their population (Kitchell

1992). This is most successful when omnivorous, benthivorous fish are controlled at the

same time (John Madsen, pers. comm. ).

Fish biomanipulation is a difficult management method to implement effectively.

It typically requires a good understanding of the community structure and chemistry of

the water body. It is only successful in water bodies with certain community structure

types. If predatory fish are added to the water body, severe fishing restrictions may be

necessary to maintain the high populations (Kitchell 1992). Additionally, many factors

can influence algae growth, causing success to vary considerably from year to year

(Carpenter et al. 1987). Nevertheless, biomanipulation has been reported to substantially

improve lake water quality in lakes where other methods have failed (e.g., Annadotter et

al. 1999).

We know of no examples of fish biomanipulation attempted in California waters.

It may be an appropriate method for consideration in drinking water reservoirs, where

human access and fishing are limited, and there is a good scientific understanding of the

limnology of the water bodies.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 13 Terrestrial Herbivorous Mammals

Terrestrial herbivores may be used to control emergent and riparian vegetation.

Goats may be corralled into an area where control is desired using electric fencing, and

allowed to forage there until vegetation is reduced. A number of private companies

currently offer goat grazing as a vegetation control option, and irrigation districts such as

Reclamation District 999 do include goat grazing in their control methods (Bob Weber,

pers. comm. ). Although terrestrial herbivores serve as alternatives to chemical pesticide

application, water quality may be adversely impacted by the movement of soil and

sediment following disturbance, as well as goat excretion. One of the Aquatic Pesticide

Monitoring Program demonstration projects evaluates the cost-effectiveness and water

quality impacts of goat grazing.

Gastropod Mollusks

Introduction of snails or sea slugs is a biocontrol option that has been researched

for certain aquatic infestations. Cooke et al. (2001) reported that small research

experiments indicate that snails grazing on biofilm algae may be useful for improving

growth of desirable aquatic plants. Presumably, the use of these grazing snails would

increase aquatic vascular plant biomass, thereby resulting in reduced nutrient availability

for floating nuisance algae, and ultimately improvement in water quality (Scheffer et al.

1993; Scheffer, 1999). Researchers are currently evaluating a number of sea slug species

for potential biocontrol of the marine invasive plant, Caulerpa taxifolia

. Although the

slug is very promising as a biocontrol agent, there is considerable political ambivalence

regarding the introduction of a non-native biocontrol species in marine waters (Meinesz

1999). Therefore, use of gastropods has not been developed for commercial biocontrol

application. Snails were extensively researched for biocontrol of hydrilla, but were found

to be an ineffective control method, and thus were not commercially developed (Bill

Haller, pers. comm. ). Interest in development of snails as a biocontrol agent has been

limited due to the environmental risk associated with purposeful introduction of prolific

generalized herbivores. Additionally, there is concern that snails can serve as vectors for

certain fish parasites (McCann et al. 1996). Thus, although gastropod mollusks may have

potential for use in biocontrol, there is yet to be an example of successful field-scale

application.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 14 Insects

Another alternative in biological control is the release of insects that specialize in

feeding on particular nuisance plant species. In other states and countries, insects have

been developed for biological control of a number of aquatic and emergent plants that

occur in California waters. These include hydrilla, Eurasian watermilfoil, water hyacinth,

giant salvinia, and purple loosestrife. In California, insects have been evaluated for

biological control of hydrilla and water hyacinth, but not for Eurasian watermilfoil or

purple loosestrife. Currently, the weevil, Cyrtobagous salviniae

, is being evaluated for

long-term control of giant salvinia ( Salvinia molesta ) on the Colorado River and adjacent

irrigation drains (Olson 2003).

Biological control using insects has had limited field application in California

waters, but has been reportedly successful for plant management in some other states. In

Florida and Louisiana, biological control of water hyacinth has been successful using two

weevil species of the genus Neochetina and one moth of the genus Sameodes

. However,

large-scale reduction of water hyacinth (50-70% reduction in plant growth) often took

years to occur (Bill Haller, pers. comm. ). Another concern is that even though plant

height and flowering might be reduced, the expansion of the plant mat could still occur

(John Madsen, pers. comm. ).

In California, insects have been tested for control of water hyacinth and hydrilla.

In an effort to control water hyacinth in the Sacramento-San Joaquin Delta, three species

of insects were released in 1982. Recent surveys have shown that one of the species

( Neochetina bruchi

, the water hyacinth-eating weevil) has spread throughout the Delta,

but the populations are not of sufficient size to effectively control the hyacinth. Currently,

a research collaboration among CDBW, CDFA, and the USDA is underway to

understand the factors limiting the success of insect biocontrol in the Delta (USDA and

CDBW 2003).

Two insect species have been evaluated for control of hydrilla in California, the

hydrilla tuber weevil ( Bagous affinis ) and the Asian hydrilla leaf mining fly ( Hydrellia

pakistanae ). Laboratory and field studies have determined that both species feed on

hydrilla tissue and have the potential to reduce hydrilla densities (Godfrey and Anderson

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 15 1994; Godfrey et al. 1994; Godfrey et al. 1995). However, hydrilla eradication in the state

is currently achieved using chemical application, grass carp, hand removal, and sediment

dredging for tubers.

Biological control has shown some success in controlling Eurasian watermilfoil in

other states, though the control agents have not been introduced in California. The milfoil

weevil ( Euhrychiopsis lecontei ) appears to be able to control Eurasian watermilfoil,

causing significant biomass reduction in the laboratory (Creed and Sheldon 1993) and in

the field (Creed and Sheldon 1995). This insect exposes vascular tissue of the stem when

feeding on Eurasian watermilfoil and causes the collapse of the plant. Sheldon and

O’Bryan (1996) have shown that the weevil preferred Eurasian watermilfoil. Their data

from the six years following a Eurasian watermilfoil decline in a Vermont lake show that

watermilfoil has not regained its dominance, while native plant density has increased.

The increase in native plant density may result from poor egg hatching and recruitment

on non-target plant species (Sheldon and Creed 2003).

Biological control using insects or other invertebrates does not appear to hold

much promise for Egeria densa

. Many organisms were tested to control Egeria densa

(including snails), but generally showed little success (Bill Haller, pers. comm. ).

Often times, insect population growth may not be sufficient to achieve biological

control in weed-infested areas. Evaluation of feasibility is often required on a sitespecific basis. For example, the milfoil weevil appears to have much lower densities in

waters with cooler temperatures, and might not be suitable for regions with colder

summer climates. Another important consideration is the potential for effects on nontarget species or other unintended consequences of the insect introduction (Sheldon and

Creed 2003). Non-native insect species, once introduced to a new region, could

potentially spread rapidly and adversely affect local ecosystems. They could potentially

impact non-target vegetation and cause loss of habitat for some fauna. Site-specific

research on the specific impacts of a particular biocontrol insect should be conducted

before that agent is introduced to California waters.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 16 Predatory Animals For Mosquito Control

A number of predatory fishes and invertebrates are available or in development

for controlling mosquitoes. These organisms prey upon mosquito larvae or pupae,

thereby reducing reliance on chemical pesticide application for mosquito control. In

California, mosquitofish ( Gambusia spp

. ) are readily available for mosquito control.

Gambusia are very effective predators on mosquito larvae, with some species even able

to reduce mosquito populations in dense beds of aquatic plants (Lounibos et al. 1992).

Additionally, a number of predatory fish and invertebrate species are currently being

applied on a pilot or local basis by various California Mosquito and Vector Control

Districts (Karl Malamud-Roam, pers. comm. ).

In addition to mosquitofish, at least three fish species are currently being studied

for biological control in California waters: guppies ( Poecilia reticulate ), Sacramento

perch ( Archoplites interruptus ), and three-spined stickleback ( Gasterosteus aculeatus )

(Miller 2003; Schon 2003a, b). The Sacramento-Yolo Mosquito and Vector Control

District (SYMVCD) has stocked guppies in 286 mosquito sources, comprising 670 acres.

Permitting for guppies was relatively easy for guppies in northern California waters,

because they do not survive the cold winters and are therefore unlikely to have long-term

adverse impacts on native wildlife. They are relatively easy to culture and more tolerant

of adverse environmental conditions than mosquitofish, making them appropriate for

stocking in dairy lagoons and acidic creeks (Schon 2003a). SYMVCD has had limited

success with three-spined stickleback. Although they can be cultured and do consume

mosquito larvae in the laboratory, the sticklebacks are not effective at consuming

mosquito larvae in many field conditions (Schon 2003b). Sacramento perch are still in the

development and testing phase for mosquito control by the Contra Costa Mosquito and

Vector Control District. They have been successfully raised and consume mosquito

larvae in the lab, but large-scale experiments or field applications have yet to be

conducted (Miller 2003).

An additional fish genera, the pupfish ( Cyprinodon spp.) has been proposed for

evaluation, but practical use for mosquito control is restricted due to special status (Su

2003a). In the Coachella Valley (southern California desert), a species of tadpole shrimp

( Triops newberryi ) has been extensively evaluated in laboratory studies. The tadpole

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 17 shrimp shows promise for mosquito control in ephemeral habitats. Tadpole shrimp have a

number of desirable traits for mosquito control in intermittently wetted habitats; they prey

on mosquito larvae, have a desiccation resistant life stage, grow quickly, and have high

reproductive capacity. Nevertheless, they have yet to be evaluated in large-scale field

applications (Su 2003b).

Commercially Available Biocontrol Agents

Biological agents such as bacteria, viruses, and enzyme solutions are

commercially available to aid in the improvement of water quality. These agents are

touted to increase water flow by reducing/eradicating algal, and to some extent,

macrophyte growth. Few field and lab experiments have been completed to test the

efficacy of commercial microbial products. Commercial microbial products generally

contain a mixture of bacteria and enzymes. The microbial products are typically applied

to the system to augment the system’s bacterial populations. The theory is that increased

bacterial concentrations will limit the availability of nutrients necessary for algal and

macrophyte growth and reproduction. The bacteria, theoretically, utilize the same

nutrients (nitrogen and phosphorus) as the photosynthesizers and therefore act as

competitors for growth.

Biocontrol agents are readily available as commercial formulations. Examples

include Aqua 5 TM 

# , 1998 LakePak TM



# , WSP R



# , Algae-Tron TM 

# , and PK-700, all of which

are relatively inexpensive to purchase. Nevertheless, the success of biocontrol agents to

reduce primary producer (planktonic) populations is not well established. Few studies

are available testing the effectiveness of these methods. The available peer-reviewed

studies indicate that microbial control methods are not effective for control. Some

laboratory research has piloted new methods, such as culturing and expanding the

bacterial fauna from individual lakes. But the practicality and cost-effectiveness of these

methods for field application remains to be tested. Mesoscale experiments are necessary

to see if laboratory results can be replicated in the field.

A recent laboratory and field study provided evidence that commercially available

biocontrol agents were generally not effective for control of algal growth (Duvall et al.

2001; Duvall and Anderson 2001). In the laboratory study, there was no significant

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 18 decrease in chlorophyll-a concentrations in the treated systems, compared to control

systems where no microbial product was added (Duvall et al. 2001). In the field study,

lake mesocosms treated with commercial microbial product were measured for bacteria

concentrations. One out of the three commercial products applied showed a significant

increase in bacteria concentrations when compared to the controls but none of the

commercially treated mesocosms showed a significant decrease in chlorophyll-a

concentrations when compared to controls (Duvall and Anderson 2001). A study by

Queiroz and Boyd (1998) also indicated no relationship between addition of bacterial

agents and chlorophyll concentration in the water body. Bacterial inoculate were added

to catfish aquaculture ponds. There was no significant difference in chlorophyll-a

concentrations between treated and control ponds and no difference in bacterial

populations between treated and control ponds. The treated ponds produced a higher net

production of catfish than the non-treated ponds, but the reason for this was unclear.

Plant Pathogens Currently In Development

Plant pathogens for the control of hydrilla and Eurasian watermilfoil have shown

progress over recent years but remain in the research phase. So far, only laboratory tests

in aquariums and small ponds have been conducted, and the methods are not available for

widespread application. The use of the pathogen Fusarium graminearum in control of

Egeria species is in the pre-commercial evaluation phase (Charudattan and Dinoor 2000).

The fungus Alternaria eichhorniae has shown some success in control of water hyacinth

in Africa but rapid colonization by the fungus is necessary for long-term control (Reeder

2003). Species of Rhizoctonia have the ability to kill plants but there is no host

specificity and non-target plants can also be affected.

Since the 1980s, the Corps of Engineers (USACE) has been researching plant

pathogens to control hydrilla in the Southeastern U.S. A fungal pathogen species from

Texas ( Mycoleptodiscus terrestris ) holds promise for future control but is not yet

commercially viable (Judy Shearer, pers. comm. ). So far, only laboratory testing in

aquariums (up to 67,000 l) and small pond testing have been conducted since the USACE

does not have the permit required for larger scale fieldwork. Whether these agents will be

successful in flowing waters or large-scale applications remains to be tested. New

methods have been developed to bind the organisms to plants. These new formulations

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 19 include flour or starch and oil that apply buoyancy and keep the fungus attached to

hydrilla. The USACE is working with the SePRO Corporation on patenting the microbial

herbicide (Judy Shearer, pers. comm. ).

Hydrilla has also been evaluated for integrative control combining fungal agents

with herbicides. Laboratory studies indicated that use of Mycoleptodiscus terrestris in

combination with the herbicide fluridone reduced hydrilla biomass by more than 90% and

was more efficacious than these treatments individually (Netherland and Shearer 1996;

Nelson and Shearer 2002). Mesocosm studies had similar results (Nelson et al. 1998).

Sublethal amounts of herbicide were applied which would also minimize the impact on

non-target species if used in natural environments. Shearer and Nelson (2002) found that

application of a combination of M. terrestris and the chemical herbicide endothall also

reduced hydrilla biomass in lab experiments. Shearer (2002) also noted that stressful

conditions, such as herbicidal application in non-lethal doses, may weaken a plant and

compromise a plant’s defenses, thereby making it more susceptible to infection by the

fungus.

Integrative control has been evaluated for water hyacinth using multiple insects or

insects in combination with bacterial pathogens (Gopal 1987). Co-introduction of

Neochetina eichhorniae and Orthogalumna terebrantis reduced plant density by 45%

and petiole length by 35% over a 50-week experimental period. Integrative control has

also been applied to water hyacinth management. The pathogen Cercospora rodmanii

and Neochetina eichhorniae eliminated 99% of water hyacinth (Charudattan 1984, as

reviewed in Gopal 1987).

The permitting process for plant pathogens is fairly extensive, which can delay

and limit development of these alternatives. Endemic plant pathogens need to be

registered with EPA before release in the environment. The registration process requires

intensive host specificity and toxicity testing. After that is accomplished, the pathogen

species gets a label, just like a chemical, with established maximum applications rates

and use restrictions. Costing about $2 million, plant pathogen registration is less costly

than chemical registration (about $20 million) (Judy Shearer, pers. comm. ). Further

development and registration of plant pathogens has been slowed by lack of funding and

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 20 interest on the part of major corporations or venture capitalists (Rahavan Charudattan,

Pers. comm. ; Judy Shearer, pers. comm. ).

Pathogens For Mosquito Control

Pathogens have also been studied for mosquito control. The microbial organism,

Lagenidium giganteum shows promise for reducing larval populations of Mansonia

mosquitoes. In a study by Cuda et al. (1997), L. giganteum reduced the emergence of

adult mosquitoes, and appeared to generate self-sustaining populations in test pools. This

pathogen has specific water quality requirements and is only likely to be effective in

relatively unpolluted water bodies.

Cyanobacteria Control Agents Currently in Development

In laboratory and microcosm experiments, specialized biological control agents

have shown success in the control of nuisance cyanobacterial blooms. Methods under

development include cyanophages, bacteria, and cell culture isolates (reviewed in Sigee

et al. 1999). However, many of these agents are still in the research phase, and it may be

years before they become available to practitioners.

Cyanophages (viruses) may be useful in controlling cyanobacterial blooms.

Cyanophages are host specific, so a variety of species would be necessary for biocontrol.

Ultimately, the cyanobacteria species may become resistant to the cyanophages,

rendering the control method ineffective in the long term. Bacteria can kill cyanobacteria

by producing extra cellular products that lyse cells (i.e., cause them to “blow up”). Some

fungal species can produce an antibiotic that also harm cyanobacteria, but physical

proximity between fungi and cyanobacteria is necessary. Isolates from cultures of the

aquatic fungus, actinomycetes, have shown inhibitory effects against cyanobacteria. The

isolates are collected from environmental samples and isolated in the lab. Streptomyces

exfoliatus was successful in lysing genera of major bloom species such as Anabaena,

Microcystis and Oscillatoria

. Microcosm studies show that S. exfoliatus was successful

in lysis of lake phytoplankton and a reduction of algal populations. Protozoans reduce

cyanobacterial cells by grazing. Lab experiments have shown that certain protozoan

species graze on genera of oscillatoria and anabaena. Microcosm experiments have

shown a reduction in algal populations.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 21 Organic Material Amendment

Organic materials, such as peat, and barley straw, have been used for control of

rooted aquatic plants and algae. Theoretically, control is achieved by reduction of nutrient

availability to the nuisance species or release of chemicals that impede growth. Organic

material amendment results tend to be system specific, creating a need for small-scale

pilots prior to widespread application in a specific water body.

Field studies have shown that sediment amendment with peat or barley straw may

reduce hydrilla production (Spencer et al. 1992). A number of laboratory studies have

demonstrated that natural or human-altered increases in sediment organic matter content

can reduce growth of Eurasian watermilfoil (Barko et al. 1986; Gunnison and Barko

1989). The chemistry of added organic materials can affect their ability to reduce aquatic

plant growth; organic material may inhibit plant growth or stimulate plant growth,

depending on the nitrogen content of the added organic materials (Spencer et al. 1992).

The use of organic additions, including barley straw, for the control of hydrilla has not

been widespread.

Barley straw has gained popularity in recent years for algae control via word-ofmouth successes, but research indicates that it only works in certain management

circumstances (Lembi 2002). The activity of barley straw is usually described as

preventing the new growth of algae, rather than killing algae already present. It is thought

that fungi decompose the barley in water, which causes lignin- and tannin-derived

polyphenolic compounds to be released, preventing the growth of algae. This method is

most successful in well oxygenated water bodies where the decomposition of barley is

not disrupted (Boylan and Morris 2003). Martin and Ridge (1999) and Terlizzi et al.

(2002) suggest that decomposing barley may inhibit the growth of a limited number of

algae and dinoflagellate species under both laboratory and field conditions. Barley straw

has also shown some success in the control of cyanobacterial growth (Barrett et al. 1996).

Because effectiveness of barley straw to control algae will vary from site to site, smallscale pilot studies should be conducted before investing significant time or effort in

whole-lake applications.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 22 Managers can also add barley straw to sediments, in an effort to control growth of

rooted aquatic plants. Other materials, including sand, gravel, and peat, have also been

added to sediments to alter plant growth (Barko et al. 1986; Spencer et al. 1992). Plants

grow best with a certain amount of nutrients in the sediment (Barko and Smart 1986).

Addition of barley straw, peat, or other organic material may inhibit aquatic plant growth

by bringing the nutrient density and concentration out of the ideal range (Systma and

Parker 1999). As with floating algae, the ability of barley straw to control growth of

rooted aquatic plants varies among studies and locations. Parker and Sytsma (1998)

found good evidence that addition of barley straw reduced Potamogeton growth in

Oregon irrigation canals. In contrast, Spencer et al. (1992) found that barley straw or peat

can actually increase hydrilla growth in California soils. Water hyacinth and other freefloating plants that prefer acidic water for nutrient uptake may also benefit from organic

additions to the water body (John Madsen, pers. comm. ). As with control of algae, smallscale pilot studies should be conducted to evaluate effectiveness before applying at a

management scale.

Although barley straw may be a viable algae control method, it has uncertain legal

status for use by public water body management practitioners (Lembi 2002). The EPA

states that a pesticide is “any substance or mixture of substances intended for preventing,

destroying, repelling, or mitigating any pest.” However, no company has ever registered

barley for use as a pesticide as it has not gone through the testing required for

registration. Therefore, barley cannot be sold as a pesticide to control algae. Its use in

private ponds or lakes is allowed under the facet that it qualifies as a “home remedy”, its

use as a commercial algaecide in larger or public bodies of water is not supported by the

EPA (Lembi 2002). Despite the non-qualification of barley straw as an official pesticide,

it is still widely sold on the commercial market, approved by the New York State as a

method to improve the quality of garden ponds (Lembi 2002).

Acetic Acid

The addition of dilute acetic acid to the propagules, root crowns, or tubers of

aquatic weeds has shown to be a successful growth inhibitor (Spencer and Ksander

1995a, 1995b, 1997, 1999; Parker and Sytsma 1998). Submersed aquatic plants, such as

hydrilla, rely on subterranean vegetative propagules, such as tubers, turions, or winter

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 23 buds for reproduction. These propagules enable the plant to survive periods of

unfavorable conditions. The addition of acetic acid to these propagules at the appropriate

time in their life cycles was shown to limit growth of these weeds. The growth of both

hydrilla and sago pondweed ( Stuckenia pectinatus ) can be decreased as a result of

exposure to dilute acetic acid (Spencer and Ksander 1995a, 1995b, 1997, 1999; Parker

and Sytsma 1998). Acetic acid sediment amendment will only be effective in channels

with little or no standing water; therefore, natural or artificial water level drawdown is

generally necessary for this method (Parker and Sytsma 1998).

At this time, we know of no California field practitioners who use acetic acid to

control growth of rooted aquatic plants. Field studies have shown that it was effective in a

Yuba County canal (Spencer and Ksander 1999), though cost effectiveness for

widespread application has not been determined (David Spencer, pers. comm. ).

Preliminary research trials by the USDA-ARS and the Invasive Spartina Project have also

shown that acetic acid may hold promise for killing rhizomes of smooth cordgrass

( Spartina alterniflora ) (Anderson 2003). A sanitary district in Humboldt County has been

evaluating acetic acid for control of floating vegetation in some of their treatment ponds.

An ongoing APMP demonstration project is underway to evaluate its effectiveness and

environmental impacts in control of duckweed ( Lemna spp.) growth (Mark Bryant, pers.

comm. ). In Kansas, acetic acid can be an effective contact herbicide for common weeds

in agricultural field plots (Lee DeHaan, pers. comm. ). As with barley products, acetic

acid has not been registered or formally tested for use as a pesticide, so it has uncertain

legal status. Increased acidity in the water body may have severe effects on non-target

aquatic organisms.

Management Considerations For Organic Material Amendment

All of the organic material amendment techniques can be difficult to apply at

large management scales. Barley straw added to the water column tends to float on the

surface, which can lead to homeowner complaints. Attempts to contain the barley straw

in sacks can reduce effectiveness (Tom Jordan, pers. comm. ). Commercial products, such

as barley pellets, barley straw bales, “pond pads”, and barley extract are readily available

(Jane Sooby, pers. comm. ). They can be purchased on the World Wide Web or ordered

through pond management magazines, such as Doctors Foster Smith

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 24 ( www.DrsFosterSmith.com ) or Water Gardening ( www.watergardening.com ). A half

pound of barley straw ranges in cost from $5-$15, and marketers claim this amount can

be used to treat 500 to 1000 gallons for approximately 6 months. Barley hay can also be

purchased in bulk from agricultural sources for only $1 - $3/bale. In urban areas, storage

may not be readily available for bulk quantities (Tom Jordan, pers. comm. ). Sediment

amendment is typically applied in dewatered systems, because materials like barley straw

tend to float. Development of techniques to produce barley straw slurries or other easily

spread materials may improve application efficiency and effectiveness (Parker and

Systma 1998; Systma and Parker 1999). Although acetic acid is relatively inexpensive to

purchase, it can be dangerous to handle in concentrated form. Concentrated acetic acid

can cause burns to skin and eyes, requiring protective clothing, and appropriate

environmental conditions for use (Parker and Sytsma 1998).

Plant Competition

Nuisance aquatic plant impacts may be reduced by introduction or augmentation

of other plant populations. The more desirable plants may compete with nuisance species,

thereby impeding their growth and spread. Nevertheless, the addition of competing plants

remains a highly experimental procedure with limited field applications or assessments of

effectiveness (Holdren et al. 2001). The best results will be seen when the nuisance plant

is controlled before the native plant is added in order to prolong the effectiveness of the

initial control technique (John Madsen, pers. comm. ).

In a Massachusetts lake, native Chara sp. was experimentally planted in areas

harvested for Eurasian watermilfoil. The researchers found that areas with transplanted

Chara plants remained resistant to milfoil invasions over the duration of the two-year

study (Monnelly et al. 2003). For selected Wisconsin water bodies, The Nature

Conservancy plants shoreline areas with wild rice, a native emergent plant. The

replanting efforts are perceived as successful methods of reestablishing native vegetation

(Hannah Spaul, pers. comm .). Spikerush ( Eleocharis spp.) has had some success in

crowding out nuisance plant species in many aquatic systems, including irrigation

drainage canals (Sytsma and Parker 1999). Spikerush has a low growth habit and

negligible effect on water flow, which are desirable characteristics. There is also some

evidence that these plants secrete a growth inhibitor that is absorbed by surrounding

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# 25 plants. Slender spikerush ( Eleocharis acicularis ) may be more suited for California

water bodies.



# PHYSICAL AND MECHANICAL CONTROL METHODS

This section includes all methods that involve destruction or removal of nuisance

plants by physical or mechanical methods. Mechanical methods include harvesting,

cutting, rotovation, weed raking, hand pulling, dredging, channel clearing, and

excavation. All of these methods involve direct damage to the target nuisance species

(typically aquatic plants) by physical removal or destruction. Physical methods also

involve physically manipulating the water body or immediate plant environment to

reduce survival or growth of the nuisance species.

Mechanical Harvesting

Mechanical harvesters are large machines which cut and collect aquatic plants.

They remove the upper portion of the plant and are able to cut five to ten feet below the

water surface. The weeds collected by the harvester can then be transferred to an upland

disposal site. Harvesting immediately removes surface mats of plants and opens up the

area, which can help maintain boat lanes. Due to the size of the machines, only larger

areas with a sufficient depth are suitable for this treatment. The same area may need to be

treated twice or more per growing season to maintain control of the nuisance weed

(Kimbel and Carpenter 1981; U.S. Army Corps of Engineers 2002).

Mechanical harvesters are currently available in California, with several

contractors offering these services and harvesters available for purchase from local and

national companies (Appendix A). Several companies commercially produce harvesters,

including Aquarius Systems ( http://www.aquarius-systems.com ) and Aquamarine

( www.aquamarine.ca ). PMC Production, a California based company, produces

harvesters commonly used by local contractors ( http://www.pmcproduction.com/ ). Miller

Aquatic Technologies actively markets some of their harvesters as cost effective for

management on canals, small ponds, and other narrow and shallow waterways

( http://www.milleraquatics.com/harvesters.html ).

In other parts of the country, harvester technology has developed to provide

specialized responses to local plant management concerns. For efficient control of plant

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# 26 problems in the very large waterways of Florida, large-sized harvesters have been

developed. Harvesters used in Florida reach up to 95 feet in length and work very

efficiently in large-scale projects (Bill Haller, pers. comm. ). Although such large

harvesters may not be appropriate for many California water bodies, they may be useful

for managing Salvinia molesta in the Colorado River.

A significant problem with mechanical harvesting is the often rapid regrowth of

the plant after harvesting. In a study of Eurasian watermilfoil control in a Minnesota lake,

total shoot biomass and plant abundance was only reduced for six weeks following the

harvest (Crowell et al. 1994). Plant growth rates were higher in the harvested areas than

unharvested areas. As a result of the rapid regrowth, harvesting must be conducted

multiple times in a growing season to achieve adequate control. For example, in a

Wisconsin lake, monthly or bi-monthly harvesting was most successful for controlling

Sago pondweed (Madsen et al. 1988), a plant common throughout California (DiTomaso

and Healy 2003). In some water bodies, multiple harvesters must be operated daily

during the growing season to fight off the constant plant regrowth (e.g., Lake

Minnetonka Conservation District 2002). Local municipalities, such as the City of

Oakland, often purchase and maintain their own harvesters to achieve this constant

control.

Sometimes, specialized mechanical harvesting innovations can increase control

efficiency, thereby reducing frequency of harvesting required. In particular, cutting at the

base of the plant stem can dramatically reduce regrowth rate. In Wisconsin, a mechanical

harvester was modified with a blade that could cut Eurasian watermilfoil to within 0.6 m

of the sediment surface (Unmuth et al. 1998). Long-term control was achieved in deep

waters (greater than three meters), where 46% of cut channels persisted for three years

after the study. Control was less effective in shallow waters (less than three meters), with

only four percent of channels remaining clear. One of the Aquatic Pesticide Monitoring

Program demonstration projects will evaluate a mechanical cutter designed to remove

plants at the root, which may also reduce plant regrowth rate (Ross Holton, pers. comm. ).

Timing and frequency of harvesting may also affect the regrowth of the nuisance

species. In Wisconsin, harvests in autumn are likely to cause strong reductions in

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 27 Eurasian watermilfoil total non-structural carbohydrates (carbohydrates used for future

growth), and consequent regrowth rate (Kimbel and Carpenter 1981). In a Florida study,

repeated clipping of hydrilla stems significantly reduced rate of producing reproductive

tubers. Tuber reduction was more pronounced when plants were clipped prior to

formation of a dense canopy. This result suggests that repeated harvesting during tuber

forming time-periods may reduce hydrilla recruitment (Fox et al. 2002).

Disposal is a very difficult issue with wide scale harvesting applications such as

the Sacramento-San Joaquin Delta (Cynthia Gause, pers. comm. ). Disposal costs

constitute almost 25% of the annual harvesting budget for control of Eurasian

watermilfoil in Tahoe Keys (Greg Tischler, pers. comm. ) In Florida, large harvesting

machines dispose the plant material in areas of the same water body since launching and

on-land disposal would dramatically increase cost (Bill Haller, pers. comm. ). CDBW has

met with substantial permitting difficulty in their efforts to dispose of plant material on

levees or other locations near Delta water bodies. For example, the Central Valley

Regional Water Quality Control Board (CBRWQCB) mandated that they obtain written

approval from individual landowners, prior to disposing of plant materials on levees. The

CBRWQCB also determined harvested plant materials to become waste discharges once

removed from the water, creating difficulties in NEPA and CEQA permitting (Cynthia

Gause and Marcia Carlock, pers. comm. ). Although not insurmountable, permitting issues

do delay the implementation of harvesting projects in sensitive areas like the Delta.

The Waterways Experiment Station (WES) of the Army Corps of Engineers has

developed computer programs to assist managers in developing effective mechanical

harvesting plans. The HARVEST program, developed by WES, will simulate the cutting,

collection and transport of a nuisance species in an aquatic system (Madsen et al. 1998).

It has been used in California to determine the current production capacity of harvesters

operating on Big Bear Lake, and to identify locations where new offloading sites could

be developed to increase harvesting efficiency (ReMetrix 2001). HARVEST is available

for free by ordering a CD-ROM copy of APIS (Aquatic Plant Information System) from

WES. APIS is an interactive CD-ROM that provides information on aquatic nuisance

species, their distribution, and the current control methods available (U.S. Army Corps of

Engineers 2001; http://www.wes.army.mil/el/aqua/apis/apishelp.htm ).

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 28 Peer reviewed studies are lacking on the cost-effectiveness and environmental

impacts of harvesting in California waters. However, a number of successful harvesting

programs currently exist in California. One example is mechanical harvesting of Sago

pondweed in Clear Lake, CA. At three locations in Clear Lake, mechanical harvesting

was conducted in a combined area of about eight acres. Approval was obtained from the

Lake County Department of Agriculture to assure that there would be no interference

with active hydrilla control. It was reported that a boat that followed the cutter retrieved

about 80% of the cut weeds. The only observed fish mortality was one small catfish. The

subsequent clean up was messy, as about 15 cubic yards of fragments were removed from

the shoreline. Overall, it was stated that mechanical harvesting was an effective method

for nuisance control with immediate results (Lake County Water Resource Division

1999). Mechanical harvesting programs are also actively employed by the Tahoe Keys

Property Owners Association (Greg Tischler, pers. comm .) and the City of Oakland (for

Lake Merritt; Richard Bailey, pers. comm. ). Many estuarine and inland water bodies,

such as Lake Van Ness (City of Visalia), Winchester Lake (Reclamation District 999),

Westlake Lake (City of Westlake), and San Mateo Lagoon (city of San Mateo) are

managed by contracts with private contractors (Dave Najara, pers. comm. ; Tom McNabb,

pers. comm. ; George Forni, pers. comm. ; Bob Weber, pers. comm. ).

Harvesting and removing cut plant material may be preferable to leaving plant

material in place in eutrophic (high nutrient) systems, because it may decrease the

amount of nutrients available for primary production. Carpenter (1980) predicted that

half of the flux of dissolved total phosphorus (DTP) and dissolved organic material

(DOM) from the littoral zone (shallow area) to the pelagic zone (open water) is from the

decay of aquatic plants. The prediction, based on a eutrophic hard water lake in

Wisconsin, suggests that aquatic plants can compose a substantial pool of nutrients that

mechanical cutting would free up for algal growth. Harvesting of macrophytes removed

37.4% of the annual phosphorous inputs and 16.4% of nitrogen inputs to a eutrophic lake

in Wisconsin during a late August harvest (Carpenter and Adams 1977). This may

decrease within-lake nutrient levels but does not decrease the external loading of

nutrients to a water body. Although harvesting may decrease within-lake nutrient levels,

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 29 algae production may continue to remain high due to high external loading or nutrient

release from sediments.

The price per acre of mechanical harvesting may range from $500-800, excluding

mobilization, and the cost for equipment purchase ranges from $35,000 to $110,000

(Washington State Department of Ecology 2001). Regular harvesters can remove plants

at rates of approximately one to four acres per day, depending on the size of the machine

and plant density (John Madsen, pers. comm. ). Larger water bodies with widespread

infestations may require several harvesters to achieve plant control (e.g., Lake

Minnetonka Conservation District 2002). Disposal options and fees are another

consideration. Sometimes permits have to be obtained to dispose the plant biomass and

disposal fees apply for landfill sites.

Environmental Effects of Mechanical Harvesting

Mechanical harvesting operations can have impacts on water quality, fish

survival, and future distribution of problem weeds. Unlike many mechanical control

methods, the environmental impacts of harvesting have been evaluated extensively in

numerous studies.

Water body nutrient concentrations may be reduced by the harvesting and

removal of plants (Carpenter and Adams 1977). Harvesting may initially increase the

turbidity and dissolved solid concentration of a system (Alam et al. 1996). In some cases,

harvesting may have no short-term impacts on water quality. For example, Carpenter and

Gasith (1978) found no significant difference in particulate phosphorus, total Kjeldahl

nitrogen, DOC, BOD or dissolved reactive phosphorus between control and cut plots in a

eutrophic lake. In the longer term, harvesting can reduce internal loading of dissolved

phosphorus that occurs via natural macrophyte senescence (Carpenter 1983).

Nevertheless, the amount of nutrients removed in a typical harvesting program is usually

much less than the total rates of internal nutrient recycling and external loading to a water

body (John Madsen, p ers. comm. ). In contrast, chemical application may increase internal

phosphorus loading by plant senescence (Carpenter and Adams 1978). Ultimately,

harvesting may slow succession of highly eutrophic lakes (Carpenter 1981).

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 30 Harvesting is not recommended for fast moving waters, due to the potential risk

of spreading an invasive plant species. Harvesting is also not advisable in water bodies

with early infestations of plants that spread by fragmentation. Plant species of particular

concern include Eurasian watermilfoil ( Myriophyllum spicatum ), parrotfeather

( Myriophyllum aquaticum ), hydrilla ( Hydrilla verticillata ), and Brazilian egeria ( Egeria

densa ) (John Madsen, pers. comm. ). There is evidence that standard harvesting

operations release viable fragments of Egeria densa in the Delta (Anderson et al. 2000).

If fragments of plants are not captured by the harvester, they can be hand collected to

eliminate the possibility of spreading the plant parts to new areas. If all available niches

are infested already, harvesting is an option to be considered to reduce plant biomass,

while leaving the bottom part of the plant intact for habitat as well as sediment

stabilization. In Clear Lake, permits from the Department of Food and Agriculture will

only be issued for harvesting in areas more than 1⁄4 mile away from sites infested with

hydrilla (Nate Dechoritz, pers. comm. ).

Mechanical harvesting can have both negative and positive effects on aquatic life.

Harvesting can result in direct mortality to and removal of fish, invertebrates, and turtles

(Mikol 1985; Booms 1999; Madsen 2002). Booms (1999) estimated that 39,000 fish and

700 turtles were removed during the harvesting of a Wisconsin lake from May thru mid

August. Unmuth et al. (1998) estimated that 36 fish/hectare were removed in a harvest.

Nevertheless, these removals of small fish and invertebrates may have limited impacts on

the overall populations. For example, Armitage et al. (1994) found no significant

difference in macroinvertebrate richness or abundance between stream areas treated with

chemicals or by harvesting. Monahan and Caffrey (1996) found that mechanical cutting

reduced macroinvertebrate community composition and abundance more than chemical

treatment but abundance increased rapidly after cutting and there were no observable

effects to fish.

Part of the effect of harvesting is the alteration of underwater habitat. Garner et al.

(1996) indicate that after cutting, reduction in available plant cover causes declines in fish

growth and Cladoceran densities. When applied to create habitat variation, harvesting

can positively affect growth of some fish species. For example, when channels are

created to enable access of predatory species, harvesting can reduce stunting of smaller

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 31 fish. Olson et al. (1998) found that creating deep lake channels by harvesting increased

the growth rates of some age classes of bluegill and largemouth bass. Another strategy to

create variation in habitat is to harvest in alternating sections of a water body with

alternating years. For example, in a river or canal where water delivery is needed, a

channel may be cut adjacent to opposite banks on alternating years (Garner et al. 1996).

Harvesting may also impact plant diversity in lake systems. Species diversity was

found to be greater in unharvested areas than harvested areas in Lake Wingra, Wisconsin

(Nichols and Lathrop 1994). Long-term monitoring of harvested lakes in Wisconsin

showed a decrease or no change in the number of native species and a decline or no

change in the watermilfoil frequency (Helsel et al. 1999).

Mechanical Cutting

Mechanical weed cutters can cut plants several feet below the water surface or

can cut emergent plants above the water surface. The distinction between mechanical

cutting and mechanical harvesting is that while harvesters remove cut plant material from

the water body, mechanical cutting machines do not remove the cut plant material.

Therefore, the cutters can operate demonstrably faster compared to harvesters. Generated

floating plant fragments may be removed from the water to prevent them from re-rooting

or drifting. Clean up can be accomplished using a weed rake or specially designed nets.

As with harvesting, areas may need to be cut several times during the growing season.

In limited circumstances, cut plants may be left in the water to decompose. This

significantly reduces control costs because removal, off-loading, and disposal are not

required in these situations. This method usually requires shredding of the plants into

small pieces. It is only appropriate for species not likely to spread by fragmentation, or in

dense infestations requiring rapid control. However, the cut vegetation may increase

water column nutrient concentrations and turbidity (James et al. 2002).

Recent mechanical cutting technologies not readily available in California waters

include “juicers” and highly efficient mechanical shredders. Several demonstration

models have been developed of the “juicer” or “grinder”, which grinds the cut plant

material to a fine pulp and thereby is believed to create non-viable fragments. The

addition of nutrients to the water column may be a concern (William Haller, pers. comm. ;

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 32 John Madsen, pers. comm. ). Most models of this system are prototypes that are not

widely available for commercial use. One model, “the Crusher,” will be evaluated as part

of an APMP (Aquatic Pesticide Monitoring Program) demonstration project in 2004.

Shredding machines may be a cost-effective, large-scale operating alternative to

harvesters. The shredded plant material is left in the water, and effects of decomposing

plants to the water chemistry have to be studied. Commercially available shredders

include the Swamp Devil (Aquarius Systems; http://www.aquarius-systems.com ) and the

Cookie Cutter. The Cookie Cutter is effective for destruction of extremely dense stands

of wetland or emergent vegetation. It is a barge with two hydraulically driven knifelike

blades, which spin rapidly, shredding a three-foot swath of vegetation in its path, and

even grinding through soft sediments. It may create access and available habitat for

shorebird nesting, but may also aid seed and fragment dispersal (U.S. Army Corps of

Engineers 2001). Additionally, a prototype shredder designed for water hyacinth control

(the Terminator; http://www.aquasolutionsusa.com/ ) can be hired for large projects. In

Vermont, a shredding approach was conducted to control waterchestnut ( Trapa natans

L.) and generally killed the plants without adversely affecting water chemistry or causing

nutrient problems (Ann Bove, pers. comm. ). The effects of shredding on water quality in

Delta water hyacinth stands is being evaluated by the APMP (NCAP Annual Report

2003, Greenfield et al 2003).

As with mechanical harvesting, mechanical cutting should not be conducted in

circumstances where infestations are likely to spread. This includes fast moving waters,

in addition to early infestations of species that spread by fragmentation. When shredding

machines are used on species that spread by fragmentation (e.g., Egeria densa, Eurasian

watermilfoil, hydrilla), there is substantial risk that the shredded material will spread to

other locations and actually increase infestation. Therefore, mechanical shredding

without removal is generally more appropriate for species that do not always spread by

fragmentation, such as water hyacinth. In closed water bodies with complete weed

coverage, shredding may be useful on any aquatic species for controlling plant biomass

and achieving boat access (Madsen 1997; John Madsen

, pers. comm. ).

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 33 As with mechanical harvesting, effects to other aquatic organisms should be

considered. Most literature to date has focused on effects of mechanical harvesting, with

little evaluation of effects on ecosystems where cut plants were not removed from the

water body. A mechanical shredding study found no significant difference in

macroinvertebrate benthic community density, diversity, or richness after shredding of

waterchestnut in a Vermont lake (Fiske 1999). Further research is warranted on the

effects of cutting operations to animal populations.

In California, mechanical cutting is frequently performed by resorts, marinas, and

other relatively small lakeshore recreation managers to maintain access to their site. An

example is the Soda Bay resort of Clear Lake, which performed cutting weekly from June

15 th 

# through September 29 th 

# 1999. The resort had cutting equipment that attached to a

boat and cut to a depth of five feet. After cutting, the fragments were removed from the

water with rakes and pitchforks, distributed for composting at another privately owned

location, and used for garden mulch (Lake County, Water Resource Division 1999). This

use of low-tech, relatively inexpensive, but labor-intensive methods, is typical of

mechanical cutting operations conducted by lakeshore commercial enterprises.

Many agencies and companies build their own mechanical cutting boats for plant

management in local ponds and canals. For example, Environmental Waterworks, an

Orange County contractor, has built and operates a mechanical cutter that is operated on a

boat 20’ long, 5’ wide, and weighing 600 pounds (Steve Walters, pers. comm. ). Solano

Irrigation District also constructed its own mechanical cutter, which it uses for weed

control in selected irrigation ponds. Small boat operated cutters are appropriate for

isolated small ponds such as those found in golf courses, where cut materials can be

pushed to the banks and removed manually. Specialized underwater weed cutters can also

cut weeds in water as shallow as ten inches and as deep as five feet.

Mechanical cutting by hand held brush cutters has also been used experimentally

on Spartina alterniflora in a Washington state bay. Cutting with herbicide application

was more effective than cutting or application alone. This method reduced stem density

and stem height when measured at the one-year post treatment mark but did not eradicate

the plant (Major et al. 2003). Spartina alterniflora is threatening the native Spartina

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 34 species in the marshes in and around San Francisco Bay, and integrated approaches, such

as mechanical cutting with herbicide applications, are currently in development for its

control (ISP 2003). Mechanical cutting was also utilized on the nuisance weed

waterchestnut ( Trapa natans L.) in lakes in New York state. Cutting experiments

reduced seed production, though some seeds were still produced (Madsen 1990; Methe et

al. 1993).

With the exception of specialty shredders like the Terminator, Swamp Devil, and

Cookie Cutter, manual cutting is relatively inexpensive. Portable boat-mounted cutting

units cost from $400 to $3,000. Specialized underwater cutters cost about $11,000. These

tools are commercially available but can also be constructed in homemade fashion. Since

no expertise is needed to operate these tools, costs can be limited to the purchase of

cutting implements. Disposal fees may apply (Washington State Department of Ecology

2001).

Rotovation, Rototilling and Hydroraking

Rotovation and rototilling are methods for chopping up and disturbing plants,

focusing on the base of the plant, including submerged portions. A rotovator is a bargemounted rototilling machine that lowers a tiller head about eight to ten inches into the

sediment to dislodge plant root crowns. Whereas rototilling could only be used with

emergent vegetation, rotovation can also be used to control submerged vegetation. Unlike

harvesters, rotovators do not have the capability to collect the uprooted plant material and

the buoyant root masses float to the surface. The plant material may then be removed by

a harvester following the rotovator, manually collecting plant material from the water

surface, or raking along the beaches. However, the risk of spreading the infestation due to

a large number of plant fragments is still high. Since the entire plant is removed from the

sediment, rotovation can often reduce plant biomass throughout the growing season,

sometimes even for two seasons (Gibbons et al. 1987).

Water bodies suitable for rotovation include larger lakes or rivers with sufficient

depth. Rotovation may not be appropriate in salmon-bearing waters, since it causes

increased short-term turbidity. Additional risks include the potential impact of

contaminants released from the sediment as well as the resuspension of various nutrients

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 35 to the water body. Rototilling can be used for control of emergent wetland vegetation,

such as Spartina

, cattails, and bulrush.

A rotovation attachment is available as part of the Aquamog mechanical system.

The Aquamog has an excavator arm which accepts a number of different attachments.

The rotovation attachment for the Aquamog is 10' wide, weighs about 2,000 pounds, and

has 4 rows of spring steel tines that are off-set to increase efficiency at dislodging aquatic

plants (BBMWD 2003).

In Washington, the Willapa National Wildlife Refuge uses rototilling, in

combination with targeted chemical spraying to control invasive Spartina alterniflora

. Spraying during low tide with rototilling during the winter appears to work well

(Jonathan Bates, pers. comm. ). Oregon has used rotovation to control Eurasian

watermilfoil (Sytsma and Parker 1999). Winter tilling to a sediment depth of 4-6 inches

reduced stem density by 80 – 90% for 2 to 3 years of control.

As with mechanical harvesting, the risk of spreading viable plant fragments must

be considered for rotovation and rototilling. For example, when Spartina stands are

rototilled, viable rhizomes may be released and wash out to other areas with tidal

movement (Vanessa Howard, pers. comm. ). The potential for spread of viable Spartina

fragments to new locations has not been studied for locations such as San Francisco Bay

.

Hydroraking is a similar method to rotovation. In hydroraking, a heavy-duty

metal rake is attached to a hydraulic arm, and then dragged across the lake bottom to

dislodge buried plant material. As with rotovation, management considerations include

disposal, and the potential for spreading of plant fragments, turbidity, and disturbance to

bottom habitat (Holdren et al. 2001; Ann Bove, pers. comm. ).

Costs for rototilling, rotovation, and hydroraking vary according to treatment

scale, density of plants, machinery used, and other site constraints. Contract costs for

rotovation range from $1,200 – $1,700 per acre. Disposal fees may also apply (Taylor

and Gately 1998).

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# 36 Weed Rollers and Sweepers

Weed rollers and sweepers are relatively new methods to control nuisance weed

infestations in small locations. Weed rollers include a long metal cylinder (up to 30’)

attached to a dock or piling on one end. A motor drives the cylinder forward and

backwards in a 270-degree arc from the attachment point. The cylinder compresses

young plants and soil in the area. Fin-like blades on the roller remove taller plants from

sediment and may remove roots. For weed control, use once per week should be

sufficient (Washington State Department of Ecology 2001).

The use of rollers may disturb bottom dwelling organisms and spawning fish.

Plant fragmentation of nuisance weeds may also occur (Washington State Department of

Ecology 2001). Furthermore, in soft bottom areas, sediment disturbance can be

significant (Terry McNabb, pers. comm. ). Concern has also been expressed about the use

of weed rollers on sediments high in organic matter. The Minnesota Department of

Natural Resources regulates management of aquatic vegetation and requires permits for

the use of weed rollers to protect littoral habitats (Minnesota Department of Natural

Resources 2004).

The Lake Sweeper is an automatic weed control device that may be used in

similar areas to the weed roller. Like weed rollers, the Lake Sweeper is attached at one

end to a dock or other fixed location and consists of a 24’ – 42’ metal pole that moves

forward and reverse in a 270-degree arc. A pump provides the force to move the floating

pole back and forth. Instead of rolling along the sediment, the Lake Sweeper floats along

the lake surface, with a series of lightweight rakes dragging behind it. According to the

manufacturer, these rakes can kill a variety of submerged aquatic plants within 3 to 5

days by gradually weakening the plants. The Lake Sweeper may be an economically

viable management option for small, high use locations. Purchase cost for a Lake

Sweeper is approximately $2,000. Installation is said to be simple and operating costs are

reported by the manufacturer to be very low (Kretsch 2003). Contact information for the

manufacturer (Lake Restoration, Inc.) is available in Appendix A. The potential for the

Lake Sweeper to increase rate of release of viable plant fragments has not been

independently evaluated.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 37 Diver-operated Suction Dredging

Diver dredging is a mechanical control technology for plant removal, in which

divers use pump systems to suction plants and roots from the sediment. The pumps are

mounted on barges or pontoon boats and the diver uses a long hose with a cutter head to

remove the plants. The plants are vacuumed through the hose to the support vessel where

plants are retained in a basket and sediment and water are discharged to the water body.

A silt curtain can be deployed to the treatment site to control turbidity (Washington State

Department of Ecology 2001).

The cost of diver dredging can vary depending on density of plants, type of

equipment used, and disposal requirements. Nevertheless, it is typically a costly control

option. State regulations on contract divers for dredging work are stringent and prevailing

wage rates are high. Two divers and a tender are needed. Costs can range from a

minimum of $1,100 per day to upwards of $2,000 per day with actual removal rates

varying from approximately 1⁄4 to one acre per day (Taylor 1998).

Considered a selective technique, driver dredging is particularly well suited for

low-level, early infestations of noxious weeds. It can also be used to assist in long-term

maintenance following herbicide treatments. Diver dredging is not recommended for

control of aquatic beneficial plants (WDFW 1997). It has shown success in controlling

noxious species, such as Eurasian watermilfoil. For example, suction dredging increased

the number of native plant species one year after dredging and reduced the biomass of

Eurasian watermilfoil in an oligotrophic lake (Boylen et al. 1996).

Sediment Removal

Sediment dredging has been used to remove nutrient rich sediment from irrigation

canals. Plant propagules can also be removed when large amounts of sediment are

dredged. Increased turbidity and suspended sediments can occur with this method. In a

field study, plant biomass had a patchy distribution in areas where sediment was dredged

compared to control sites (Sytsma and Parker 1999).

Shading and Piping

Shading may reduce plant/algal growth by limiting the amount of

photosynthetically available light. Shading can be established by shade fabrics, canal

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 38 bank vegetation, or piping (putting irrigation underground) for irrigation systems (Sytsma

and Parker 1999). Piping and shading can also reduce water loss due to evaporation.

High storm water runoff and extensive maintenance requirements can be problems

associated with these methods. Aquashade, a chemical product added to waters to reduce

light penetration, is another shading method; it is discussed in the “Non-Conventional

Chemicals” section of this review. Shading is also one of the mechanisms of control for

bottom barriers, described below.

Experimental studies have evaluated shading as a control method with varying

degrees of success. Field experiments in English drainage channels showed that low

shade (white geotextile material with 38% PAR reduction) and high shade (black

geotextile material with 92% PAR reduction) had no significant effect on curly pondweed

( Potamogeton crispus L.) biomass (Sabbatini and Murphey 1996). Filizadeh and

Murphey (2002) provided evidence that shading may be effectively combined into

integrated methods. In this study, shading combined with application of the herbicide,

diquat, significantly reduced biomass of Sago pondweed ( Potamogeton pectinatus L.).

The combination of cutting, shading and diquat had better control on plant biomass than

any of the methods tested individually (Filizadeh and Murphy 2002). Pondweeds are

distributed throughout California, including the Bay region and Central Valley

(DiTomaso and Healy 2003).

For irrigation delivery canals, replacement of the canal by piping is an effective,

long-term shading option. Pipes up to 36 inches in diameter can be readily installed in

existing canal beds, and are likely to be able to transport 15 to 20 cfs. Pipes also provide

for significant water conservation by eliminating seepage and evaporative losses.

However, pipes are very costly to install, and not always appropriate for control of storm

water flows (Sytsma and Parker 1999).

Bottom Barriers

Bottom barriers are semi-permanent materials that are laid over the top of the

plant beds. They are analogous to using landscape fabric to suppress the growth of weeds

in yards. By eliminating the sunlight from the area, bottom barriers interfere with

photosynthesis, causing covered plants to die.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 39 Although bottom barriers may kill and remove plants originally present, once the

barriers are removed, the nuisance species often rapidly recolonizes. This has frequently

been observed for Eurasian watermilfoil. In one study, Eurasian watermilfoil re-colonized

44% of grid squares within 30 days of benthic barrier removal (Boylen et al. 1996). In

Lake George, New York, and in a Wisconsin study, Eurasian watermilfoil rapidly recolonized sites after barriers were removed, indicating a continuing need for control after

removal (Eichler et al. 1995; Helsel et al. 1996).

Bottom barriers have had some success in lakes in Wisconsin, New York, and

Washington, but were not reported successful in Clear Lake, California. In Lake George,

New York, no plants remained after use of a PVC barrier (the Palco TM 

# barrier), but there

were plants under mesh screen (Aquascreen TM 

# ) barriers (Eichler et al. 1995). In

Wisconsin, Palco TM 

# liners completely eliminated all plants under the barrier (Helsel et al.

1996). In a 700-acre Seattle-area reservoir, bottom barriers were used to control a new

infestation of milfoil plants. In this system, the bottom barriers were part of a successful

eradication program that did not use herbicides (Zisette 2001).

In California waters, bottom barriers are being used in a variety of management

circumstances, including some integrated control and innovative methods. The Invasive

Spartina Project is conducting experimental evaluations of bottom barriers constructed of

biodegradable fiber cloth for control of new Spartina infestations. Use of these

biodegradable materials reduces the possibility that bottom barrier material will pollute

the ecosystem, because barriers can be difficult to retrieve (Erik Grijolva, pers. comm. ).

In offshore waters of the southern California coast, bottom barriers are currently part of

an integrated program to eradicate the noxious algae, Caulerpa taxifolia

. In this program,

plants are covered with vinyl containment tarps, and solid chlorine pucks are placed

under the barriers. This combination of chemical and non-chemical stressors has been

successful in eradicating this hardy species (Bill Paznokas, pers. comm. ). Bottom barrier

pilots in Clear Lake have been less successful. Bottom mats, installed at a Clear Lake

resort, had sediments and vegetation growing on top of them within a year, and the area

had to be mechanically harvested (Lake County Water Resource Division 1999).

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 40 Bottom barriers are more difficult to install in water bodies where currents or

strong tides occur. The installed fabric can loosen, float to the surface, and cause danger

to boat traffic or swimmers. Because of this, bottom barriers may be difficult to maintain

in tidally influenced areas of the Sacramento-San Joaquin River Delta, estuarine areas,

and coastal areas.

Bottom barriers will result in the loss of habitat for benthic organisms due to the

loss of the bottom vegetation. A physical and chemical evaluation of sediment conditions

under synthetic fabric barriers showed that invertebrate density declined up to 90%.

Benthic barriers apparently blocked sedimentation and caused an increase in NH 4 

# and a

decline in dissolved oxygen to near zero beneath the fabric. Community effects were

reported to be more severe in warm water. However, biotic conditions recovered quickly

after barriers had been removed (Ussery et al. 1997). Nevertheless, the impact would be

limited to the area where bottom barriers are applied, and would be unlikely to have

widespread impact on a large water body.

Bottom barrier material costs vary depending on the type of material used. Costs

can range from $0.1 – $0.6 per square foot; costs for professional installation are an

additional $0.25 - $.50 per square foot. Bottom barriers are generally not a cost effective

method to control infestations covering large surface areas. They are appropriate to

control growth in specific areas, such as adjacent to marinas and docks.

Bottom barriers and covers may be used for irrigation canals. Lining irrigation

canals with concrete or geotextile material can reduce the substrate available for plants to

root (Sytsma and Parker 1999). Sediment deposition may reduce the long-term

effectiveness of this procedure.

Manual Removal

Many programs involve manual removal of plants from the lake bottom.

Typically, care is taken to remove the entire root crown and to not create fragments. In

deeper waters, divers are often needed to reach the plants. Depending on visibility in the

water, sediment type, and restriction on plant fragmentation, manual eradication methods

may not be suitable for certain water bodies.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 41 Hand removal has several advantages and disadvantages over more sophisticated

methods of aquatic weed control. In shallow waters, or with floating plants, it requires

little skill or equipment to manually remove aquatic plants. Therefore, the method can be

employed by volunteers, untrained workers, or inmates, and large capital expenses are

not required. With proper training, the method can be employed to selectively remove

specific weeds, while limiting disturbance to desirable plants. The disadvantage to hand

removal is that it is slow and labor intensive, and is therefore not generally appropriate

for controlling large or dense infestations or eradicating plants with extremely rapid

growth. One example of a manual removal effort that failed was a multi-agency pilot

effort to control giant salvinia ( Salvinia molesta ) in the lower Colorado River. In this

project, several dozen volunteers from various agencies used nets to scoop out many tons

of salvinia. Because of the inability to remove all plant material, the great abundance of

remaining plant material, and the extremely rapid vegetative regrowth, the project was

considered a complete failure and was discontinued (Laura Crum, pers. comm. ). In

general, the method will prove most successful with early infestations or to maintain

control in limited areas.

A hand-pulling program has been established for hydrilla control in several

California water bodies. For example, in the Yuba canal, one CDFA Associate Biologist

has been spending approximately five full months per year conducting hand removal of

approximately 30,000-40,000 individual hydrilla plants. Plants were disposed of by

drying and placing in a closed container in the trash. In the Yuba canal, the hand removal

was conducted in combination with application of the copper herbicide KomeenTM to the

water column. This integrated pest control method was reasonably effective at reducing

hydrilla growth, resulting in a statistically significant reduction in tuber density over the

sampling years (Ross O’Connell, pers. comm. ).

A number of California agencies have expressed interest in conducting hand

removal programs but have reported a surprising degree of difficulty with permitting

issues. The CDBW intends to implement a hand-pulling program for water hyacinth in

the Delta to augment current chemical control efforts. In this program, plants would be

disposed of cost-effectively, by placing them along levee banks (USDA and CDBW

2003). This program has had difficulty obtaining the necessary permits for

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 42 implementation. It did receive approval from USFWS and NOAA-NMFS, but has been

hindered by difficulty obtaining NEPA and CEQA approval from the Regional Water

Quality Control Board. Approval has been hindered by the concern that hand removal

efforts may stir up the water body, creating a discharge of nutrients from the disturbed

plants. Additionally, it was determined that landowner approval must be obtained to

dispose of removed material on any levee banks (Cynthia Gause, pers. comm. ).

According to the 1994 Integrated Aquatic Vegetation Management Plan Manual,

hand-pulling expenses can run between $500 and $2,400 per day (Gibbons et al. 1994).

As with diver dredging, removal rates for hand pulling depend on plant density, visibility,

and sediment characteristics. Use of volunteer labor could considerably reduce costs.

Some volunteer manual removal programs are quite sophisticated. For example, to

control Eurasian watermilfoil in Lulu Lake, Wisconsin, volunteer divers with The Nature

Conservancy clip individual plants at the base, and volunteer canoers collect and remove

the resulting fragments (Hannah Spaul, pers. comm. ).

Water Level Manipulation

Aquatic weeds can sometimes be effectively controlled by dewatering water

bodies. This may involve pumping or releasing water via a dam or weir. Drawdown is

frequently used in wildlife refuges by federal or state wildlife agencies or local duck

clubs. For example, three months of drawdown can control emergent wetland vegetation

(cattails and bulrush) at the Kern National Wildlife Refuge in California (Dave Hardt,

pers. comm. ). It is also viable in some man-made reservoirs and irrigation canals.

Nevertheless, many water bodies lack the water level control structures needed to achieve

significant plant control (Washington State Department of Ecology 2001).

Water drawdown can have variable impacts on water quality and aquatic plant

survival. Water drawdown may increase phosphorus release from the sediment upon

rewetting (Klotz and Linn 2001). Alternatively, phosphorus loading may decrease by

increasing benthic oxygen levels, which favors sequestering of phosphorus in the

sediment (Coops and Hosper 2002). If there is sufficient water flushing, drawdown can

reduce water column nutrient concentrations and algae growth (Holdren et al. 2001).

However, drawdown can have varying impacts on different rooted plant species, with

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 43 some nuisance species not harmed by the manipulation. In fact, aquatic plant biomass can

even increase after drawdown (Wagner and Falter 2002). The impacts of drawdown to

flora and fauna are severe and this method should only be applied to water bodies where

short-term habitat impacts are acceptable to resource agencies.

In systems where water levels may be readily controlled, water level manipulation

may be used to control the timing of aquatic plant infestation growth. For example, in

irrigation drainage systems, it may be possible to add water prior to the irrigation season,

allow aquatic plants to grow, and then remove the water to kill the plants. This method

may reduce the capacity for plant growth during the irrigation season by reducing the

pool of available nutrients (Lars Anderson, pers. comm. ).

If a water level structure is in place, costs may be minimal (Washington State

Department of Ecology 2001). In some cases, natural fluctuations in water levels

resulting from drought can result in substantial die-off of invasive aquatic plants (Gene

Martin, pers. comm. ).

Channel Clearing or Excavation

In some cases, it may be cost-effective to remove plant and surface sediment

material from a water-body. This may be achieved by a mechanical excavator or by

flushing material downstream of a given site. It may also be achieved by chaining, in

which a chain is dragged along the channel bottom between two heavy-duty vehicles.

Removal of plants and sediments may also reduce future growth by reducing the

abundance of seeds and the pool of available nutrients.

These methods are more appropriate for storm water or irrigation canals, because

the water level may be relatively low, access to the entire water surface is relatively easy,

and the habitat value is not considered to be important. There is the potential for

increased turbidity downstream of the target site, and disposal of removed material may

be an issue. Often times, these methods are easier in systems having a hard-bottomed

substrate or a concrete base.

Excavation is a method commonly used throughout California for management of

irrigation canals and other small waterways. The Los Banos Wildlife Area (managed by

CDFG) uses it for control of water hyacinth and water primrose in some of their

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 44 irrigation canals (Bill Cook, pers. comm .). Mechanical excavation is also used on a

limited basis at the Merced and Solano Irrigation Districts. These districts use excavators

to remove sediment, overlying vegetation, and perennial below ground structures. They

prefer to use chemical control, finding it more cost-effective in most channels, but use

excavation in channels where there is a risk of chemical release into tightly regulated

natural waters. The Solano Irrigation District channel is concrete lined, making it

possible to remove most of the sediment, thereby limiting plant growth (Bob Acker, pers.

comm. ; Mark Vale, pers. comm. ).

The Richvale Irrigation District relies on mechanical excavation for aquatic plant

control in both main and lateral irrigation canals. They switched to mechanical methods

20 years ago, to avoid permitting issues, recreational concerns, and inadvertent fish kills

in the public recreation area downstream of the irrigation canals. A single excavator

operator can clear about one mile of ditch per day and the plant removal is reported to be

very effective. Regrowth with this method is slow; typically, a single site requires

excavation only once every one to three years. Spoils are stacked along the edge of the

canals, and either used to maintain the adjacent roads or transferred to the canal edge to

reduce erosion. The system is relatively easy to apply in this region, because the channel

bed is composed of hardpan (extremely compacted clay), but it is appropriate (and used)

for irrigation canals in other regions. Several other agencies subcontract with the

Richvale Irrigation District, to have their channels excavated, at the cost of $75/hour

(Troy Kellet, pers. comm. ).

Sediment excavation may also be used in lake restoration, though the expense of

the method is significant and success rate varies among water bodies. Sediment

excavation has been used in a New York lake to remove thick organic sediment and an

infestation of curly pondweed ( Potamogeton crispus L.) from the lakebed (Tobiessen et

al. 1992). Dredging the sediment bed with a Mudcat Model MC-10 hydraulic dredge

resulted in a sustained (ten year) decrease in biomass of pondweed at the dredged sites.

Dredging may reduce light availability to bottom dwelling plants by increasing the depth

of the water column. Sediment dredging was not successful at a highly eutrophic lake in

Sweden (Annadotter et al. 1999). Despite removal of 25% of the sediment area,

phosphorous was still being released to the water column.

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# 45 Exposure of Plants to Extreme Environmental Conditions (Heat, Steam, Flame, Cold, or Electricity)

In theory, aquatic plant survival and growth may be inhibited by subjecting the

plants to extreme environmental conditions. Steam applications, exposure to heated

water, flame, or freezing conditions could all kill vascular plants. In dewatered areas,

high voltage electricity could be used to kill plants. In practice, these methods have

received little study or evaluation for field application. The limited studies of these

methods do indicate promising results (reviewed in Sytsma and Parker 1999). For

example watermilfoil fragments exposed to heated water for ten minutes were severely

reduced. A New Zealand-based company (Waipuna; www.waipuna.com ) has developed a

commercially available system, which sprays heated water directly on plants and then

covers it with an organic foam surfactant, which traps the heat and kills the plants. The

method would be appropriate for vegetation control in riparian or dewatered areas; in

some management circumstances, it is comparable in cost and effectiveness to glyphosate

applications (Quarles 2001).

Gourd and Ferrell (2003a, b, c) evaluated use of propane flame treatment and

steam spraying using commercially available equipment for weed control. In their

studies, two early season applications with a butane flamer generally controlled perennial

weeds in irrigation canals and ditch banks. In contrast to flaming, steam spraying did not

achieve adequate control in the work of Gourd and Ferrell (2003a). Although flaming

appeared to be more effective than steaming, it could only be used in locations having

low wildfire risks, and where permitted by air pollution laws.

Another potential alternative control method is application of extremely cold

material to aquatic plants. Liquid nitrogen or liquid helium could be sprayed directly onto

exposed portions of floating or emergent plants. This method has never been attempted

(Jeffrey Stuart, pers. comm. ). In dewatered areas, plants could also be subjected to high

voltage electricity. The human health risks of both these methods would be considerable

(Lars Anderson, pers. comm. ).

Aeration, Oxygenation, and Water Circulation

In water bodies where excess growth of nuisance algae is a concern, water quality

can often be improved by physically mixing the water (circulation), or interspersing the

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 46 water with surface air (aeration) or pure oxygen (oxygenation). When applied correctly,

these methods can help maintain oxygen levels throughout the water body, and reduce

algae production (Holdren et al. 2001).

Aeration, oxygenation, and water circulation can all help maintain oxygen levels

in the hypolimnion, which ultimately reduces algae growth by reducing the rate of

nutrient recycling into the water. Thermal stratification can create a barrier to full mixing

of the water column, resulting in a hypolimnion that is anoxic. Nuisance phytoplankton

blooms can occur in the epilimnion of aquatic systems as long as there are ample

nutrients and light available. This is particularly a problem in aquatic systems that have

excess nutrients. Anoxia in the hypolimnion and the sediment-water interface can

enhance the release of phosphorus and nitrogen from the sediment into the water column.

Eventual mixing will bring these nutrients into the photic zone where they stimulate

primary production (Horne and Goldman 1994). When used effectively, aeration,

oxygenation, or water circulation control the release of nutrients from the lake bottom,

thereby reducing algal growth and consequent reliance on direct herbicide application.

Many municipal water districts and waste treatment operations in California

currently use aeration and circulation to reduce production of algae and foul taste and

odor producing compounds. For example, Marin Municipal Water District has several

aerators established in their reservoirs to maintain water circulation (Larry Grabow, pers.

comm.).

In aeration, water-air surface exchange is increased by mechanical means, which

can increase oxygen content of low-oxygen waters (Fast and Boyd 1992). In

oxygenation, pure oxygen is injected directly into the water. The advantages of

oxygenation to the hypolimnion (vs. aeration) are 1) maintenance of thermal stratification

and a cold-water environment for fish habitat 2) an increased solubility of oxygen in

water over air 3) an increased transfer efficiency and 4) avoidance of excess nitrogen in

the water column (Beutal and Horne 1999). Methods of oxygenation include side stream

pumping systems, deep oxygen injection systems, and submerged contact champer

systems. All three systems have been able to increase dissolved oxygen concentrations in

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 47 water, and some can reduce internal loading of nutrients from sediment to the water

column.

There are two primary types of aerators, ‘splashers’ that aerate by dispersing

water through air, and ‘bubblers’ that aerate by dispersing air through water (Fast and

Boyd 1992). These devices can be run electrically or by solar power. The Solar-Bee 

aerator uses solar energy to pump water from depth and disperse it over the surface.

Initial cost of the Solar-Bee  is higher than non-solar aerators, but the energy savings

over the long term may make Solar Bee systems cost-effective.

Some California agencies report using physical pumping or recirculation of water

as a method to control production of nuisance algae. The Tahoe Keys Property Owners

Association has established a series of water circulation pumps to control the algae

problem (Greg Tischler, pers. comm.). The manager of Alameda Lagoon has also

reported success with water aeration units, for breaking up algal mats (Tom Jordan, pers.

comm.). For very small water bodies, practitioners have even reported using a spray

pump and fire hose system to break up and sink algal mats (Tom McNabb, pers. comm.).

The method may interfere with algal growth via water disturbance and movement of the

algae to portions of the water column that inhibit development (e.g., areas with reduced

light availability). Recirculation may also be achieved by installation of water pumps or

fountains.

Studies of Aeration in Aquatic Systems

Hypolimnetic aeration may be useful in lakes that have internal loading of

nutrients from bottom sediments to the photic zone. A number of peer-reviewed research

studies suggest that hypolimnetic aeration may be an effective method of controlling

algal growth and related chemical parameters. Prepas and Burke (1997) studied

hypolimnetic oxygenation of a deep eutrophic lake in central Alberta over a six-year

period. The hypolimnetic oxygenation resulted in reduction of phosphorus release from

sediments, hypolimnetic reductions in ammonia, increased oxygen levels in the

hypolimnion and an increase in nitrate + nitrite in the hypolimnion. Concentrations of

total phosphorous, inorganic nitrogen, and chlorophyll-a all decreased in the epilimnion

during the summer months. Continual aeration was necessary to maintain these

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# 48 conditions. The cost of the project was $30,000 capital costs and $49,000/year for

aeration.

Cowell et al. (1987) studied full lake aeration in a small sinkhole lake in Florida.

The aeration completely eliminated thermal stratification in the warm months. Dissolved

oxygen of the bottom waters increased significantly and turbidity, pH, alkalinity, total

nitrogen, hydrogen sulfide, and iron decreased significantly. Although there were

decreases in many of the nutrients, and a decrease in blue-green algae, neither primary

production nor chlorophyll-a concentrations changed significantly. The authors

concluded that continued aeration over a few years may be necessary to reduce primary

production.

Aeration was not successful in removing total ammonia nitrogen from waters

under laboratory conditions (Chiayvareesajja and Boyd 1993). In aquaculture ponds,

aeration increased dissolved oxygen in bottom waters and reduced soluble reactive

phosphorus but increased total phosphorus due to re-suspension of phosphorous from the

sediment (Masuda and Boyd 1994).

In addition to altering nutrient flux from sediment to the water column, aeration

may also aid in fish growth and reproduction. In an aerated eutrophic Florida lake, total

catch/hour increased by 50% over a non-aerated period of the same lake (Leslie et al.

1986). The aeration system was able to completely turn over the 10.5-hectare lake every

7

– 11 days. Costs, including capital costs, were $436/month for the two-year aeration

period.

Nutrient Removal

In lakes or impoundments with a high degree of nutrient recycling from the

bottom sediments, it may be possible to remove nutrient-rich waters or sediment directly

from the bottom of the lake. This method is uncommon, and requires a good

understanding of the chemistry and nutrient budget of the lake. Removal of nutrient-rich

water appears to be working in Devil’s Lake, an important recreational lake in southern

Wisconsin (Richard Lathrop, pers. comm. ). Devil’s lake is characterized by water very

rich in phosphorus in the deepest portion of the lake, resulting from historic loads of

phosphorus. Natural resource managers with the Wisconsin Department of Natural

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# 49 Resources have set up a 20-inch diameter siphon pipe running from the deepest portion of

the lake out to an intermittent stream channel. To maintain the lake-level, water is

pumped from a nearby stream, low in nutrients. Because the water nutrient concentration

is highest at the lake bottom, the expectation is that withdrawal of this phosphorus rich

water should limit nutrient loading and resulting algal blooms over the next 15 years. The

project is also expected to reduce incidence of swimmer’s itch and mercury

concentrations in sport fish, as indirect results of the reduced lake productivity

(Wisconsin Department of Natural Resources 2001; Richard Lathrop, pers. comm. ).



# NON-CONVENTIONAL CHEMICAL CONTROLS

In addition to conventional herbicides and pesticides, there are other chemicals

that can be utilized to reduce primary production in aquatic systems. These are typically

used to control development of nuisance algal blooms. Nuisance algal blooms create

unpleasant conditions in recreational water bodies and can create taste and odor problems

in drinking water reservoirs. Although not well studied, alternative chemicals may also be

used for control of benthic algae and floating and submerged vascular plants. The US

EPA has so far only approved Aquashade for use in aquatic environments. The effects of

many other non-conventional control methods are not well tested, particularly for use in

the littoral zone and for control of rooted or free-floating vascular plants.

Research has been conducted to study the effects of certain chemicals on the

release of nutrients from anoxic sediments of eutrophic lakes. Eutrophic lakes can have

internal source loading of nutrients from sediment to the water column, especially when

the hypolimnion and porewater are anoxic. Primary production can be reduced by

reducing nutrient concentrations in the photic zone. Under anoxic conditions,

phosphorous, an important nutrient for algal/plant growth, is released from the sediment

to the water column. Certain chemicals can be added to eutrophic lakes that can bind

phosphorous and precipitate it out of the water column into the sediments where it stays

sequestered as long as oxic conditions continue (Horne and Goldman 1994). Jaynes and

Carpenter (1985) found that the roots of certain macrophyte species can release oxygen

directly into the sediment, thereby changing the redox potential to favor sequestering of

phosphorus in the sediment. However, the net flux of phosphorus into eutrophic systems

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# 50 must be determined as senescence of macrophytes may also be a source of internal

loading.

These chemical applications have generally received little attention in California

waters. Both rigorous scientific studies and field trials should be undertaken to evaluate

the effectiveness of these methods in California lakes and reservoirs. Currently, the

Marin Municipal Water District, funded by the Aquatic Pesticide Monitoring Program, is

evaluating the effectiveness of gypsum and alum for control of benthic algae in one of

their reservoirs.

Calcium-based Products

Calcium based products, including lime (Ca(OH) 2 

# ), limestone (CaCO 4 

# ), and

gypsum (CaSO 4 

# ) are frequently used for control of aquatic algae and submerged aquatic

plants. Several studies have documented reduced plant growth as a result of lime

application. Repeated treatments (over a seven year period) to hard water eutrophic lakes

in Canada reduced photic zone phosphorous and chlorophyll-a concentrations and

average macrophyte biomass was reduced (Prepas et al. 2001). Single applications of

lime gave short-term (< 1 year) control of phosphorous and long-term control (>1 year)

of submerged aquatic plants (Reedyk et al. 2001).

Positive results have been observed in studies using iron gypsum (Fe-CaSO 4 

# ).

Iron gypsum was effective in reducing hypolimnic total phosphorus (TP) by 90% and

increased water clarity (secchi depth reading) from 50 to 270 cm in a Finnish eutrophic

lake. One year after application, TP was reduced by an average of 62% for the entire

water column (Salonen et al. 2001). Iron gypsum also reduced methane production and

release, reduced release of phosphorous from anoxic sediment, and improved redox

conditions in laboratory experiments utilizing sediments from a eutrophic lake in Finland

(Varjo et al. 2003). The reduction of methane production is important because methane

released from sediments can transport nutrients into the photic zone. Iron is important in

adsorbing phosphorous in the sediment.

As compared to lime and iron-gypsum, limestone studies have had less positive

results. Studies of limestone application in aquaculture ponds have shown mixed results

in reduction of nutrients and algae production. In aquaculture ponds, limestone did not

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# 51 reduce TP or soluble reactive phosphorous (SRP) concentrations compared to controls

(Masuda and Boyd 1994). Application in catfish ponds did not reduce TP, chlorophyll-a

concentrations, or cyanobacterial abundance but oxygen production did decrease (Giri

and Boyd 2000). Limestone application was not effective in reducing phytoplankton

densities.

Aluminum based products

Alum (Al 2 

# (SO 4 

# ) 3 

# ) is a salt that can precipitate phosphate out of the water column

and sequester it in the sediment, thereby reducing phosphate availability to primary

producers (Horne and Goldman 1994). In a French soft water eutrophic lake, SRP

concentrations were reduced by alum, although alum was not added in sufficient amounts

(due to potential aluminum toxicity) to reduce total phosphorus (Van Hullebusch et al.

2002). Despite low SRP, a bloom of the noxious algae species ( Microcystis sp.)

appeared. In the lab utilizing sediments from shallow eutrophic Swedish lakes,

aluminum treated sediments released less phosphorous than untreated sediment. If

sediment conditions are anoxic the dosing of alum is dependent on the concentrations of

Fe-P (phosphate adsorbed to iron) as oxidation of Fe-P will release phosphate from the

sediments to the water column. (Rydin and Welch 1998). Alum reduced SRP and

turbidity in aquaculture ponds (Masuda and Boyd 1994), though repeated applications

were necessary.

A 13-year follow-up study on a Vermont lake showed that one application of

alum and sodium aluminate increased water quality. Summer photic zone total

phosphorus and chlorophyll-a had decreased by 68% and 61%, respectively, since preapplication measurements. Weight loss occurred in large yellow perch for the first three

years following application and the macroinvertebrate density decreased by 90% one year

after treatment. The macroinvertebrate density recovered in all areas with some densities

exceeding pre-treatment numbers (Smeltzer et al. 1999). Alum treatment was effective

for a range of 8-11 years in polymictic lakes and a range of 13-20 years in dimictic lakes

(Welch and Cooke 1999).

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# 52 Nitrate

Nitrate has also been utilized to reduce internal loading of phosphorous from

sediments to the water column. Sondergaard et al. (2000) injected low doses of nitrate

into the hypolimnion of a thermally stratified eutrophic lake. Hypolimnetic dissolved

organic phosphorous was reduced by 23 – 52% during the treatment years. Dissolved

nitrate was more effective than granulated nitrate.

Many of the above chemicals are successful in sequestering nutrients in the

sediment by precipitating nutrients out of the water column and sequestering them in the

sediment. How these chemicals may affect aquatic and benthic organisms still needs to

be addressed. For example, the iron in iron gypsum compounds can be harmful to

animals. In lab studies of effects on zooplankton, particulate iron caused mortality and

decreases in reproduction (Randall et al. 1999).

Aquashade

Aquashade is an EPA registered chemical that controls growth by filtering out

photosynthetically available radiation (PAR) in the range of blue-violet and red-orange.

Several contractors use Aquashade for control of algal growth in California waters. It is

commonly used in recreational lakes and ponds, when homeowners are interested in

reduced algae or aquatic plant growth. However, certain municipalities choose not to

apply it because local stakeholders think it creates an unnatural appearance in the water

body (Craig Crawford, Santa Clara County Department of Parks and Recreation, pers.

comm. ). In California, the Central Valley Regional Water Board has received a small

number of applications to use Aquashade and calcium products for nuisance vegetation

control. They did not instruct the applicants to seek an NPDES permit but are still

awaiting guidance from the State Water Board on this issue (Emily Alejandrino, pers.

comm. ).

The limited available experimental research suggests that Aquashade is an

effective method of controlling aquatic algae. Lab experiments have shown that

applications of Aquashade in varying concentrations reduce the transparency of the water

and increase the light extinction coefficient (K d 

# ) over control locations. Aquashade

absorbs light in the spectrum of 550 – 650 nm (Madsen et al. 1999). In the lab,

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# 53 application of Aquashade did not affect the oxygen uptake rates of the crayfish,

Orconectes propinquus (Spencer 1984), suggesting that it is not toxic to crayfish.

Additional research on how Aquashade affects plant/algal growth is necessary to see

under what circumstances this method is successful.

Salt (Sodium Chloride)

Aquatic plants generally have limited salinity regimes in which they can survive,

and exposure to saline conditions will kill hydrilla, Eurasian watermilfoil, and other

freshwater plant species (Twilley and Barko 1990). Exposure of water bodies or

dewatered areas to solid salts (sodium chloride) could potentially kill plant beds and

inhibit future growth. However, addition of salt in large quantities would likely kill native

plants and animals, along with introduced plants.

We have identified two case studies of salt addition attempts for control of aquatic

plants. The Mountain View Sanitary District, in California, added rock salt to mowed

cattails that had experienced a natural dewatering event. The practitioners hypothesized

that the combination of multiple stresses (recent mowing, drying, and salt addition)

would kill the plants. But their experiment was hampered by difficulties in

implementation, including insufficient penetration of treatment area, followed by

flooding, which ultimately resulted in insufficient salinity for toxicity (Dick Bogaert,

pers. comm. ). The other case study is Capital Lake, in Washington State. The Washington

Department of Ecology is currently considering controlling Eurasian watermilfoil in

Capital Lake by reintroducing salt water (historically, it was a salt water lake), but there

is concern that saltwater influx would damage the newly developing freshwater

ecosystem (Condon 2003). In summary, the addition of salt probably has limited

application for aquatic plant control.

NPDES Permitting Status of Non-Conventional Chemicals

Alternative chemicals such as gypsum, lime, alum, acetic acid and Aquashade

may be better received by the public than conventional target-specific pesticides. Also, in

many cases, they are relatively inexpensive to purchase. However, as with barley straw,

the permitting status of these chemicals is not clearly established. Calcium products, iron,

and alum all reduce primary production by sequestering nutrients, rather than direct

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# 54 mortality to aquatic plants. Because their mechanisms of action do not direct mortality to

plants or algae, they are not herbicides, per se. Aquashade, as well, functions by reducing

light penetration, and is not a direct herbicide. Acetic acid does act as a contact herbicide,

and has not been permitted as such, so it may not be appropriate for use by public

entities.

In California, the Central Valley Regional Water Board has received a small

number of applications to use Aquashade and calcium products for nuisance vegetation

control. They did not instruct the applicants to seek an NPDES permit but are still

awaiting guidance from the State Water Board on this issue (Emily Alejandrino

, pers.

comm. ).



# PREVENTIVE MEASURES

In addition to methods for removing nuisance plants, algae, or nutrients from

water bodies, there are a variety of proactive methods to keep the infestation or algal

bloom from occurring in the first place. Nutrient loading to water bodies can be curtailed

by watershed management strategies. Nuisance species introductions can be limited by a

variety of preventive measures. Extensive reviews have been developed elsewhere on the

range of options available for both watershed management (e.g., Holdren et al. 2001; Lee

and Jones-Lee 2002) and prevention of alien species invasion (e.g., Wittenberg and Cock

2001; Madsen 1997). A brief summary of available preventive measures follows.

Early Detection

The spread of invasive species can be controlled by patrolling water bodies,

detecting early infestations, and removing the invasives before they have a chance to

spread (Madsen 1997; Wittenberg and Cock 2001). Early detection can reduce the

environmental and economic costs associated with noxious weeds. For a given water

body, fewer resources are needed to remove early infestations than widespread

infestations. In many instances, the costs of early detection programs can be limited by

enlisting volunteers from environmental non-profits. In coordination with local

management agencies, The Nature Conservancy is setting up a volunteer early detection

program to control the spread of Eurasian watermilfoil in Adirondack State Park

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# 55 waterways in New York (The Nature Conservancy 2003; Hilary Oles, pers. comm. ).

States with active weed watcher programs include Minnesota, New Hampshire, and

Vermont (Madsen 1997).

Coordinated early detection programs have not been established to control

infestations in California fresh waters, though such programs would be appropriate for a

number of noxious weeds. California does have a border quarantine in effect for hydrilla

(described below). The Department of Fish and Game is conducting visual and sonar

inspections of high-risk areas for the marine invasive plant, Caulerpa taxifolia (Johnson

2001).

Quarantine and Regulation

In some cases, the federal or state government can pass legislation controlling the

spread or possession of nonindigenous species, including aquatic plants. The state of

California has established a quarantine policy that restricts the importation of noxious

species, including a number of aquatic invasive pests. State regulators are able to reject

the import of shipments infested with viable fragments or seeds from hydrilla, Eurasian

watermilfoil, water primrose, Salvinia species, and other aquatic and terrestrial weeds.

These restrictions occur at the roadside agricultural inspection stations at the borders with

other states. In the case of hydrilla, shipments of aquatic plants, such as vegetation in fish

shipments, are also prohibited in entry from areas with large hydrilla infestations, unless

accompanied by a certificate verifying that no hydrilla is present. Other species, including

water hyacinth and water lettuce are restricted only from transition to locations where

they are rare or currently being eradicated (CDFA 2003b), and the enforcement

mechanism for these restrictions is not clear.

In addition to quarantine, there are additional legal protections and enforcements

that can be undertaken to restrict invasion of aquatic pests. For example, the State of

Washington has a list of invasive aquatic plants that are banned from sale within the state.

The Oregon State Department of Agriculture enforces these bans by inspecting nurseries

and pet stores for the banned plants. Civil penalties can result from sale of these plants

(Hamel and Parsons, 2001).

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# 56 On the Internet, most invasive aquatic plants are readily available for purchase. A

recent search of the internet found that twelve highly invasive plants were found listed for

sale by wetland nurseries and water garden dealerships throughout the U.S. and

internationally. This finding indicates a clear need to improve development and

enforcement of laws needed to prevent further introduction of noxious weeds from

commercial sale (Kay and Hoyle 1991).

Education and Outreach

For many noxious weeds, educational information can be provided to water body

users, to help reduce the probability of unintentional introductions. This information

could be provided in the form of brochures, web sites, and posters. Additionally, signs

can be posted at water body boat launches, bait shops, or nurseries where aquatic plants

are sold, identifying nuisance species likely to be inadvertently introduced. The

expectation is that once people are educated about the problem plants and how they

spread, people will be less likely to put them in natural waters. To achieve this,

educational materials often discourage disposal of nuisance species in or near natural

waters, transfer of nuisance species between waterways (e.g., on boat hulls or trailers), or

intentional release of nuisance species into the wild.

Riparian Buffer Strips

Buffer strips alongside waterways can impede the inflow of effluents, thereby

reducing eutrophication. Planting native perennial species at the perimeter of water

bodies may aid in the absorption of nutrients. This may also help reduce soil erosion

(Lembi, 2003). In Gainesville, Florida, a non-profit organization (Adopt-A-River) works

closely with local wetland biologists and municipal employees to plant riparian buffer

strips on a city creek. To control costs, they populated the strips with native plants dug up

from storm water ditches from other locations (Fritzi Olson, pers. comm. ). In southern

Wisconsin, The Nature Conservancy has extensive planting programs for native prairie

and savannah grassland species. These programs are undertaken to achieve the duel

benefits of conserving native grass species and improving the water quality of nearby

lakes and rivers (Hannah Spaul, pers. comm. ). Riparian buffer strips are also used to

control storm water phosphorus loading from residential developments (e.g., Woodard

and Rock 1995). As with many watershed management techniques, the cost-effectiveness

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 57 of buffer strips for controlling bioavailable nutrient loading has not been systematically

evaluated for California waterways (Lee and Jones-Lee 2002).

Retention Pond or Wetland Construction

Establishing a settling or retention pond or a wetland at effluent sources can allow

nutrients to settle or be processed before they reach water bodies. Retention ponds can be

used in agricultural settings, as well as to reduce loading from urban storm water runoff

sources (Holdren et al. 2001; Lee and Jones-Lee 2002). A 30-hectare wetland was

constructed to filter out the effluent from a wastewater treatment plant in Sweden

(Annadotter et al. 1999). The effluent previously drained directly into very eutrophic

Lake Finjasjon. After the wetland become operative, the lake Secchi depth increased

from 0.9 to 1.5 meters, chlorophyll-a concentrations decreased and total phosphorous

decreased by 25%. The use of wetlands as filters has long been established.

Watershed Best Management Practices

There are many additional methods to reduce watershed loading of nutrients to

water bodies. People may implement Best Management Practices, activities or structures

to prevent pollution. In agricultural systems, fertilizer input rates can be tailored to the

specific soil types and crop yields of individual plots, thereby reducing the likelihood of

applying excess nutrients to the watershed. Soil erosion and corresponding P losses can

be further reduced by contour farming, strip cropping, or setting up permanent vegetative

cover. There are currently little data in California with which to compare the

effectiveness of these methods for reducing loading of bioavailable nutrients (Lee and

Jones-Lee 2002).

For water bodies surrounded by residential development, landowners can be

encouraged to properly construct and maintain septic systems, and limit shoreline

erosion, to reduce the risk of nutrient loading. In some cases, wastewater treatment

facilities can be improved to reduce point source nutrient loading, and significantly

improve overall water quality (Williams 2001). There are many resources available to

develop a wide array of additional Best Management Practices (Holdren et al. 2001).

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# 58 

# RELATIVE RELIANCE ON CONVENTIONAL PESTICIDES VS.

ALTERNATIVE METHODS

There was variation among different regions and practitioners in the extent of

conventional chemical versus alternative methods used. These differences result from

local, regional, and statewide differences in legal restrictions, varying experiences with

feasibility of alternative methods, and amount of resources available to specific

organizations.

Not surprisingly, alternative methods are practiced most extensively in locations

where conventional pesticides are banned, strongly opposed by the public, or extremely

difficult to permit. For example, in the Adirondack State Park in New York, conventional

pesticides are highly restricted, resulting in exclusive reliance on alternative methods.

Within the park, local lake management agencies attempt to control Eurasian watermilfoil

with hand harvesting, benthic barriers, grass carp, and suction harvesting, depending on

the degree of infestation (Hilary Oles, pers. comm. ). In less regulated areas of New York

State, many lake management associations apply for permits to apply fluridone or other

conventional chemical pesticides (Nancy Mueller, pers. comm .).

Vermont tends not to rely on chemical methods because of public perception, and

because one of the major concern lakes, Lake Champlaign, is on the border of VT, NY,

and Canada, making regulations for chemical use very complex and difficult to address.

The costs would be high to deal with the regulatory challenge of applying chemicals. The

predominant methods are mechanical harvesting and hand pulling, with lesser reliance on

diver operated suction dredging and chemical application (Ann Bove, pers. comm. ).

Recently, however, Vermont approved the use of whole-lake fluridone treatment for the

control of Eurasian watermilfoil in two Vermont lakes (Getsinger et al., 2002).

Sometimes, within states with heavy reliance on conventional chemicals,

localized infestations can be effectively managed using alternative methods. The

Ichetucknee River in Florida is a good example of a high profile area where public

interest has been harnessed to develop an effective hand-removal campaign. In this river,

a three-mile stretch of water lettuce infestation has been effectively controlled using

hand removal alone. Chemical pesticide applications were ruled out because the river is

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# 59 extensively used for recreational water sports and is also perceived as having high natural

value that needs to be protected. The local hand-removal program effectively capitalizes

on the high popularity and strong sense of stewardship for the river. Nine times per year,

the local management agency recruits a crew of between 15 and 90 volunteer laborers,

who manually harvest the water lettuce. Additionally, a permanent staff member

“nitpicks,” laboring every day to remove young water lettuce plants from among native

vegetation. This extensive coordination has resulted in successful control of a very hardy

invasive species. Meanwhile, at the statewide level, Florida management agencies rely

predominantly on conventional chemicals to control water hyacinth and other noxious

invasives (Fritzi Olson, pers. comm. ).

Despite examples of alternative successes, many regions and agencies rely

predominantly or exclusively on chemical pesticides, based on previous experience that

the chemical pesticides were more cost-effective. For example, in Delaware Bay, nonnative Phragmites are controlled by glyphosate application. After initial public

opposition to chemical application, research tests were undertaken to evaluate nonchemical methods, both separately, and in combination with chemical application. The

test results indicated that only chemical application was effective, resulting in exclusive

reliance on herbicide application for Phragmites control (Teal and Peterson 2003).

The majority of aquatic plant management activity in Florida entails application

of chemical pesticides. Numerous insect species have been introduced for biological

control with varying success, but mechanical control efforts are restricted to high use

areas (e.g., alongside bridges), and locations with high water flow velocity. After decades

of trial and error with biocontrol and mechanical control options, Florida practitioners

predominantly rely on chemicals, based on funding and institutional limitations, and the

experience that the chemical pesticides were more effective in most management

circumstances (Florida Department of Environmental Protection 2003).

Reliance on chemical pesticides can extend to non-profit conservation

organizations, such as The Nature Conservancy (TNC). The Ohio chapter of TNC spent

many years attempting to control invasive emergent species such as reed canary grass and

Phragmites using mechanical methods. A multi-year effort to interfere with vegetation

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# 60 growth by repeated cutting was unsuccessful. Eventually, TNC Ohio chapter came to the

realization that their objective of preserving biodiversity on their sites could only be

effectively achieved by judicious use of chemical herbicide applications. They did not

have the staff or financial resources to continue mechanical efforts. Currently, they

routinely use glyphosate, but attempt to minimize total chemical pollution by methods

such as manually sponging individual plants with chemical, and applying chemical to cut

stumps (Marleen Kromer, pers. comm. ).

Some states, such as Indiana, use companies partially owned by pesticide

corporations as plant management specialists, and also have very widespread use of

chemical control methods. ReMetrix, a company that works closely with the state of

Indiana, uses remote sensing and other GIS technologies to accurately quantify

biovolume and distribution of introduced plants. ReMetrix is partially owned by a major

chemical manufacturer.



# GENERAL PERMITTING REQUIREMENTS FOR NONCHEMICAL METHODS

Most mechanical methods require the completion of a 1600 permit application

from the Department of Fish and Game (DFG). The Department of Fish and Game will

issue a no-fee permit for harvesting projects. No project size limits apply. DFG will

restrict aquatic weed control during fish spawning season and approvals will be given for

that time on a case-by-case basis. The disposal of plant material may require additional

permits (Lake County Water Resource Division 2002).

Mechanical harvesting might require an endangered species permit from the U.S.

Fish and Wildlife Service or NOAA Fisheries for anadromous fish species or other listed

species. In addition, a waste disposal permit for disposing the plant material after

harvesting might have to be obtained from the Department of Public Works. A California

Environmental Quality Act (CEQA) document is also sometimes required for potential

environmental impacts.

Diver dredging projects may require a federal permit from the U.S. Army Corps

of Engineers. The necessity for the Corps of Engineers permit is site dependent

(Washington State Department of Ecology 2001).

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# 61 To stock grass carp in California waters, a planting permit must be obtained from

the Department of Fish and Game. Also, if inlets or outlets need to be screened, an

additional permit may be required.



# GENERAL DISCUSSION

We found considerable variation in the amount of research and application among

the alternative aquatic pest control methods. Some methods, such as grass carp,

mechanical harvesting, calcium and aluminum based products, and aeration have been

extensively studied for decades. For these methods, careful discussions with impartial

experts and current practitioners could significantly help managers determine whether

application would be appropriate in a given management scenario. Other methods, such

as terrestrial herbivores, acetic acid amendment, salt application, shading, and use of

native plants for competition, have been explored on a much more limited basis. For

these methods, careful documentation of effectiveness and environmental impacts could

really benefit future practitioners. Many methods have currently only been evaluated in

research experiments, and have not been refined, or in some cases permitted, for widescale management applications. In California, on the initiative of local Mosquito and

Vector Control Districts, a variety of fishes and one invertebrate species are currently

being evaluated as alternative mosquito predators. Nationwide, plant pathogens and

cyanobacteria control agents are current research topics, where more funding is needed

before they can be applied in the field. Peer reviewed research on commercially available

biocontrol agents suggests that, despite their popularity in the field, they are not effective

for aquatic algae control.

Like permitted chemical pesticides, alternative aquatic pest control methods,

when used improperly, can present environmental risks to aquatic ecosystems. In some

situations, mechanical methods such as harvesting and rotovation could actually increase

an aquatic plant infestation over the long-term, or cause the infestation to spread more

rapidly to new areas. Introduction of new plant or animal species for use in biocontrol can

have unintended consequences on an aquatic ecosystem. Caution is particularly

warranted with introduction of non-native biocontrol species, given the fact that unlike

chemical and mechanical pest control methods, introduced plants or animals could

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 62 reproduce and spread to new water bodies, causing permanent ecological changes in

widespread areas. The sterile grass carp program in California is a good example of a

program with regulatory mechanisms in place to reduce the likelihood of widespread

adverse impacts.

Preventive measures are sometimes overlooked as methods to control future

spread of aquatic infestations. Extensive resources and effort are spent to control nonnative aquatic weeds, with the potential for adverse environmental impacts. It would be

appropriate for decision-makers in California to consider whether sufficient

organizational effort is currently being targeted to preventive measures such as early

detection, quarantine, and regulation of aquatic plant transport.

For a successful and cost effective non-chemical weed control program, managers

should assess the environmental conditions, physical characteristics, and use of the water

body in detail. They should then make a decision regarding appropriate treatment

methods based on this evaluation. To avoid budgetary constraints in the long run, all

factors have to be taken into account, and the most effective and least disruptive control

method should be determined. Appendix C of this report provides a summary framework

for managers to decide whether some of the most commonly used plant control methods

may be appropriate for a particular management circumstance in California.

In many weed management situations a mix of techniques, possibly including

non-chemical and chemical methods, will be appropriate. Currently, research on

integrated approaches involving multiple methods is limited (Van Vierssen et al. 2001).

Novel application and evaluation of integrated approaches should hopefully control

nuisance aquatic species, while minimizing potential negative environmental effects.



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# Annual Conference (2003) of the Western Aquatic Plant Management Society, Sacramento, CA.

Lake County, Water Resource Division Website. 1999. 1999 Aquatic Weed Pilot Project. http://watershed.co.lake.ca.us/programs/aquaticplants/pilotproject.html

Lake County, Water Resource Division Website. 2002. Clear Lake Aquatic Weed Control Permit. Guide to the Clear Lake Aquatic Plant Management Program, 2002. http://watershed.co.lake.ca.us/programs/aquaticplants/aquaticweedpermit.html

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 70 Lake Minnetonka Conservation District. 2002. 2002 Eurasian Water Milfoil (EWM) Final Harvesting Report. Deephaven, MN, 55391. http://www.winternet.com/~lmcd/pdf/EWM%20Harvesting%20Report/EWM%20Final% 20Harvesting%20Season%20Report-%202002.pdf

Lee, G. F. and A. Jones-Lee. Review of management practices for controlling the water quality impacts of potential pollutants in irrigated agriculture storm water runoff and tail water discharges. California Water Institute Report TP 02-05 to California Water Resources Control Board/Central Valley Regional Water Quality Control Board. California State University Fresno. Fresno, CA. 128 pp. http://www.gfredlee.com/BMP_Rpt.pdf

Lembi, C.A. 1996. Assessment of 2,4-D Use in Aquatic Systems in the United States. Chapter 12 In Biologic and Economic Assessment of Benefits from Use of Phenoxy Herbicides in the United States. U.S. Department of Agriculture, NAPIAP Report No. 1-

PA-96. http://www.24d.org/Frontpg.pdf ; http://www.24d.org/chaptr12.pdf

Lembi, C.A. 2002. Aquatic Plant Management: Barley Straw for Algae Control. APM-1- W. Department of Botany and Plant Pathology, Purdue University. http://www.btny.purdue.edu/Pubs/APM/APM-1-W.pdf

Leslie, A.J., Nall, L.E., Jubinsky, G.P. and J.D. Schardt. Effects of grass carp on the aquatic vegetation in Lake Conway, Florida. In: Proceedings of the Grass Carp Symposium, 7-9 March 1994, Gainesville, Florida. US Army Engineer Waterways Experiment Station, Vicksburg, Mississippi. pp. 121-128. http://www.dep.state.fl.us/lands/invaspec/2ndlevpgs/pdfs%20for%20pubs/Conway94.pdf

Leslie, A.J., Nall, L.E., Jr. and D.C. Schmitz. 1986. The effects of aeration on the shoreline fishes of a eutrophic Florida lake. Florida Department of Natural Resources, Bureau of Aquatic Plant Research and Control. Tallahassee, Fl. http://www.dep.state.fl.us/lands/invaspec/2ndlevpgs/pdfs%20for%20pubs/brookr3.pdf

Lounibos, L.P., Nishimura, N. and L.B. DeWald. 1992. Predation of Mansonia (Diptera: Culicidae) by native mosquitofish in Southern Florida. Entomological Society of
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Madsen, J.D. 1990. Water chestnut ( Trapa natans L.) research in Watervliet reservoir – 1989 report. Prepared for the City of Watervliet, New York.

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# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 71 Madsen, J.D., Adams, M.S. and P. Ruffier. 1988. Harvest as a control for sago pondweed ( Potamogeton pectinatus L.) in Badfish Creek, Wisconsin: frequency, efficiency and its impact on the stream community oxygen metabolism. Journal of Aquatic Plant Management. 26: 20-25.

Madsen, J.D., Getsinger, K.D., Stewart, R.M., Skogerboe, J.G., Honnell, D.R. and C.S. Owens. 1999. Evaluation of transparency and light attenuation by Aquashade TM



# . Journal of Lake and Reservoir Management. 15(2): 142-147.

Madsen, J.D., Grodowitz, M.J., Stewart, R.M., Whitaker, S. and L. Jeffers. 1998. Computer tools developed for aquatic plant management. Journal of Aquatic Plant Management. 36: 78-82.

Madsen, J.D., Luu, K.T., and K.D. Getsinger. 1993. Allocation of Biomasss and carbohydrates in water hyacinth ( Eichhornia crassipes) : pond-scale verification. United States Army Corps of Engineers, Waterways Experiment Station.

Major, W.W. III, Grue, C.E., Grassley, J.M. and L.L. Conquest. 2003. Mechanical and chemical control of smooth cordgross in Willapa Bay, Washington. Journal of Aquatic Plant Management. 41: 6-12.

Maldonado, D.C. 2001. Aquatic weed control in Salt River Project canals. Abstract from
the 20 th 

# Annual Conference (2001) of the Western Aquatic Plant Management Society, Bozeman, Montana. http://www.wapms.org/abstracts/abstracts01.html

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# 72 Meinesz, A. 1999. Killer algae – the true tale of a biological invasion. University of Chicago Press. Chicago, IL. 360 pp.

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Abstract from the 19 th 

# Annual Conference (2000) of the Western Aquatic Plant Management Society, Bozeman, Montana. http://www.wapms.org/abstracts/abstracts00.html

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36.

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# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 73 http://www.nmfs.noaa.gov/prot_res/PR3/Permits/ESAPermit.html

Olson, M.H., Carpenter, S.R., Cunningham, P., Gafny, S., Herwig, B.R., Nibbelink, N.P., Pellett, T., Storlie, C. Trebitz, A.S. and K.A Wilson. 1988. Managing macrophytes to improve fish growth: a multi-lake experiment. Fisheries Management. 23(2): 6-12.

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# Annual Conference (2003) of the Western Aquatic Plant Management Society, Sacramento, California.

Parker, M.S. and M.D. Sytsma. 1998. Aquatic vegetation management in Southern Oregon irrigation canals. Phase II: Evaluation of techniques to prevent and reduce plant growth. Report for the Oregon Department of Agriculture and Talent Irrigation District. Southern Oregon University, Ashland OR. 28 pp.

Pauley, G.B., Thomas, G.L., Bonar, S.A., Frodge, J.D., Marino, D.A., Thiesfeld, S.L., Vecht, S., Bowers, K.L. and H. Sehgal. 1994. An overview of the use and efficacy of triploid grass carp Ctenopharyngodon idella as a biological control of aquatic macrophytes in Oregon and Washington state lakes. In: Proceedings of the Grass Carp Symposium, 7-9 March 1994, Gainesville, Florida. US Army Engineer Waterways Experiment Station, Vicksburg, Mississippi. pp. 46-54.

Phillips, G., Bramwell, A., Pitt, J., Stansfield, J. and M. Perow. 1999. Practical application of 25 years’ research into the management of shallow lakes. In D.M. Harper, B. Brierley, A.J.D. Ferguson and G. Phillips (eds), The Ecological Bases for Lake and Reservoir Management. Hydrobiologia. 395/396: 61-76.

Pine, R.T., Anderson, L.W.J. and S.S.O. Hung. 1990. Control of aquatic plants in static and flowing water by yearling triploid grass carp. Journal of Aquatic Plant Management.

28: 36-40.

Prepas, E.E., Babin, J., Murphy, T.P., Chambers, P.A., Sandland, G.J., Ghadouani, A. and M. Serediak. 2001. Long-term effects of successive Ca(OH) 2 

# and CaCO 3 

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Prepas, E.E. and J.M. Burke. 1997. Effects of hypolimnetic oxygenation on water quality in Amisk Lake, Alberta, a deep, eutrophic lake with high internal phosphorous loading rates. Canadian Journal of Fish and Aquatic Science. 54: 2111-2120.

Quarles, W. 2001. Improved hot water weed control system. IPM Practitioner. 23(1): 1-4.

Queiroz, J.F. and C.E. Boyd. 1998. Effects of a bacterial inoculum in channel catfish ponds. Journal of the World Aquaculture Society. 29: 67-73.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 74 Randall, S., Harper, D. and B. Brierley. 1999. Ecological and ecophysiological impacts of ferric dosing in reservoirs. In D.M. Harper, B. Brierley, A.J.D. Ferguson and G. Phillips (eds), The Ecological Bases for Lake and Reservoir Management. Hydrobiologia. 395/396: 355-364.

Reeder, R.H. 2003. International Mycoherbicide Programme for Eichhornia crassipes control in Africa (IMPECCA). Proceedings of the Fourth International Bioherbicide Workshop. Canberra, Australia.

Reedyk, S., Prepas, E. and P.A. Chambers. 2001. Effects of single Ca(OH) 2 

# doses on phosphorus concentration and macrophyte biomass of two boreal eutrophic lakes over 2 years. Freshwater Biology. 46: 1075-1087.

ReMetrix. 2001. Vegetation assessment and management plan for Big Bear Lake (San Bernadino County, California). Report prepared for Big Bear Municipal Water District. January 10, 2001. Remetrix, LLC. 18 pp. + Appendices.

Rydin, E. and E.B. Welch. 1998. Aluminum dose required to inactivate phosphate in
lake sediments. Water Resources. 32: 2969-2976.

Sabbatini, M.R. and K.J. Murphy. 1996. Response of Callitriche and Potamogeton to cutting, dredging and shade in English drainage channels. Journal of Aquatic Plant Management. 34: 8-12.

Salonen, V.P., Varjo, E. and P. Rantala. Gypsum treatment in managing the internal phosphorus load from sapropelic sediments:; experiments on Lake Laikkalammi, Finland.
Boreal Environment Research. 6: 119-129.

Santha, C.R., Martyn, R.D., Neill, W.H. and K. Strawn. 1994. Control of submersed weeds by grass carp in water lily production ponds. Journal of Aquatic Plant Management. 32: 29-33.

Schulthorpe, C.D. 1967. The Biology of Aquatic Vascular Plants. Edward Arnold, London, 610 pp.

Scheffer, M. 1999. Searching explanations of nature in the mirror world of math. Conservation Ecology 3(2): 11. http://www.consecol.org/vol3/iss2/art11

Scheffer, M., Hosper, S.H., Meijer, M.L. and B. Moss. 1993. Alternative equilibria in shallow lakes. Trends in Ecology and Evolution 8: 275-279.

Schon, W. 2003a. Guppies ( Poecilia reticulata ) and their use in California mosquito control. Unpublished report. Sacramento – Yolo Mosquito and Vector Control District. Elk Grove, CA. 5 pp.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 75 Schon, W. 2003b. The stickleback family (Gasterosteidae). Unpublished report. Sacramento – Yolo Mosquito and Vector Control District. Elk Grove, CA. 5 pp.

Shearer, J.F. 2002. The potential role of an endophytic fungus in the decline of stressed Eurasian water milfoil. Journal of Aquatic Plant Management. 40: 76-78.

Shearer, J.F. and L.S. Nelson. 2002. Integrated use of endothall and a fungal pathogen for management of the submersed aquatic macrophyte Hydrilla verticillata. Weed Technology. 16: 224-230.

Sheldon, S.P. and R.P. Creed, Jr. 2003. The effect of a native biological control agent for Eurasian water milfoil on six North American watermilfoils. Aquatic Botany. 76:

259-265.

Sheldon, S.P. and L.M. O’Bryan. 1996. The effects of harvesting Eurasian water milfoil on the aquatic weevil Euhrychiopsis lecontei

. Journal of Aquatic Plant Management. 34:

76-77.

Sigee, D.C., Glenn, R., Andrews, M.J., Bellinger, E.G., Butler, R.D., Epton, H.A.S. and R.D. Hendry. 1999. Biological control of cyanobacteria: principles and possibilities. In D.M. Harper, B. Brierley, A.J.D. Ferguson and G. Phillips (eds), The Ecological Bases for Lake and Reservoir Management. Hydrobiologia. 395/396: 161-172.

Smeltzer, E., Kirn, R.A. and S. Fiske. 1999. Long-term water quality and biological effects of alum treatment of Lake Morey, Vermont. Journal of Lake and Reservoir Management. 15(3): 173-184.

Sondergaard, M., Jeppesen, E. and J.P. Jensen. 2000. Hypolimnetic nitrate treatment to reduce internal phosphorus loading in a stratified lake. Lake and Reservoir Management. 16(3): 195-204.

Spencer, D.F. 1984. Oxygen consumption by the crayfish Orconectes propinquus (Girard) exposed to aquashade. Bulletin of Environmental Contamination and Toxicology. 33: 373-378.

Spencer, D.F. and G.G. Ksander. 1995a. Differential effects of the microbial metabolite, acetic acid, on sprouting of aquatic plant propagules. Aquatic Botany 52: 107-119.

Spencer, D.F. and G.G. Ksander. 1995b. Influence of acetic acid on regrowth of dioecious hydrilla from root crowns. Journal of Aquatic Plant Management 33: 1995.

Spencer, D.F. and G.G. Ksander. 1997. Dilute acetic acid exposure enhances electrolyte leakage by Hydilla verticillata and Potamogeton pectinatus tubers. Journal of Aquatic Plant Management 35: 25-30.

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# 76 Spencer, D.F. and G.G. Ksander. 1999. Influence of dilute acetic acid treatments on survival of monoecious hydrilla tubers in the Oregon House Canal, California. Journal of Aquatic Plant Management 37: 67-71.

Spencer, D.F., Ksander, G.G. and S.R. Bissell. 1992. Growth of monoecious hydrilla on different soils amended with peat or barley straw. Journal of Aquatic Plant Management

30: 9-15.

Stewart, R.M. and W.A. Boyd. 1999. The grass carp stocking rate model (AMUR/STOCK). TN APCRP MI-03. APCRP Technical Notes Collection. U.S. Army Engineer Research and Development Center, Vicksburg, MS. http://www.wes.army.mil/el/aqua

Su, T. 2003a. Pupfish (Cyprinodontiformes: Cyprinodontidae) and their potential use for mosquito control. Unpublished report. Coachella Valley Mosquito and Vector Control District. Indio, CA. 6 pp.

Su, T. 2003b. Tadpole shrimp (Notostraca: Triopsidae), a potential biological control agent against immature mosquitoes. Unpublished report. Coachella Valley Mosquito and Vector Control District. Indio, CA. 10 pp.

Systma, M. D. and Parker, M. 1999. Aquatic Vegetation in Irrigation Canals: A Guide to Integrated Management. Report for Oregon Department of Agriculture and U.S. EPA. Center For Lakes and Reservoirs, Portland State University, Portland, OR. http://www.clr.pdx.edu/publications.html

Taylor, S. and G. Gately. 1998. Lake Leland Integrated Aquatic Plant Management Plan. Jefferson County Conservation District.

Teal, J.M and S.B. Peterson. 2003. The interaction between science and policy in control
of Phragmites in oligohaline marshes of Delaware Bay. Abstract from the 17 th 

# Biennial Conference of the Estuarine Research Federation, Seattle, Washington.

Terlizzi, D.E., Ferrier, D.M., Armbrester, E.A. and K.A. Anlauf. 2002. Inhibition of dinoflagellate growth by extracts of barley straw. Journal of Applied Phycology, 12:275-

280.

The Nature Conservancy. 2003. Adirondack Park Invasive Plant Action Plan for the Adirondack Park Invasive Plant Program. Prepared by The Nature Conservancy, New York State (NYS) Adirondack Park Agency, NYS Department of Environmental Conservation, and NYS Department of Transportation. June, 2003. 27 pp.

Tobiessen, P., Swart, J. and S. Benjamin. 1992. Dredging to control curly-leaved pondweed: a decade later. Journal of Aquatic Plant Management. 30: 71-72.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 77 Unmuth, J.M.L., Sloey, D.J. and R.A. Lillie. 1998. An evaluation of close cut mechanical harvesting of Eurasian water milfoil. Journal of Aquatic Plant Management.

36: 93-100.

U.S. Army Corps of Engineers. 2001. Aquatic Plant Information System. Version 2. Aquatic Plant Control Research Program. U.S. Army Corps of Engineers. http://www.wes.army.mil/el/aqua/apis/apishelp.htm

U.S. Army Corps of Engineers. 2002. Mechanical Control of Exotic Aquatic Plants. Aquatic Plant Control Operations Support Center (APCOSC), Jacksonville, FL 32232.

USDA (United States Department of Agriculture) and CDBW (California Department of Boating and Waterways). 2003. Water hyacinth control program proposed winter season non-chemical control methods. Draft Proposal.

U.S. Fish and Wildlife Service. Endangered Species Regional Permit Offices. http://forms.fws.gov/esrtnaddr.html

Ussery, T.A., Eakin, H.L., Payne, B.S., Miller, A.C. and J.W. Barko. 1997. Effects of Benthic Barriers on Aquatic Habitat Conditions and Macroinvertebrate Communities. Journal of Aquatic Plant Management. 35: 69-73.

Van Hullebusch, E., Deluchat, V., Chazal, P.M. and M. Baudu. 2002. Environmental impact of two successive chemical treatments in a small shallow eutrophied lake: Part I.
case of aluminum sulfate. Environmental Pollution. 120: 617-626.

Van Nes, E. H., van den Berg, M. S., Clayton, J. S., Coops, H., Scheffer, M. and E. van Ierland. A simple model for evaluating the costs and benefits of aquatic macrophytes. Hydrobiologia. 415: 335-339.

Van Vierssen, W., Van Hofwegen, P.J.M. and J.E. Vermaat. 2001. The age of water scarcity: in search of a new paradigm in aquatic weed control. Journal of Aquatic Plant Management. 39: 3-7.

Varjo, E., Liikanen, A., Salonen, V.P. and P.J. Martikainen. 2003. A new gypsum-based technique to reduce methane and phosphorus release from sediments of eutrophied lakes: (Gypsum treatment to reduce internal loading). Water Research. 37: 1-10.

Wagner, T. and C.M. Falter. 2002. Response of an aquatic macrophyte community to fluctuating water levels in an oligortrophic lake. Lake and Reservoir Management. 18(1): 52-65.

WDFW (Washington State Department of Fish and Wildlife). 1997. Aquatic Plants and
Fish. Publication Number APF 11-97.

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# 78 Washington State Department of Ecology. 2001. Final Supplemental Environmental Impact Statement for Freshwater Aquatic Plant Management. Publication Number 00-10-

040.

Watson, A.K. 2003. Where did it go wrong? Why is the concept of bioherbicide suffering from limited success? Proceedings of the Fourth International Bioherbicide Workshop. Canberra, Australia.

Webb, M.A., Elder, H.S., and Howells, R.G. 1994. Grass carp reproduction in the Lower Trinity River, Texas. In: Proceedings of the Grass Carp Symposium, 7-9 March 1994, Gainesville, Florida. US Army Engineer Waterways Experiment Station, Vicksburg, Mississippi. pp. 29-32.

Welch, E.B. and G.D. Cooke. 1999. Effectiveness and Longevity of Phosphorus Inactivation with Alum. Journal of Lake and Reservoir Management. 15(1): 5-27.

Williams, V.P. 2001. Effects of point-source removal on lake water quality: a case history of Lake Tohopekaliga, Florida. Journal of Lake and Reservoir Management. 17(4): 315-329.

Wisconsin Department of Natural Resources. 2001. Restoration of Devil’s Lake by bottom water withdrawal. Environmental Analysis and Decision on the Need for an Environmental Impact Statement (EIS). Prepared by Richard Lathrop, WDNR, Madison, Wisconsin. 10 pp.

Wittenberg, R. and M.J.W. Cock (eds.). 2001. Invasive alien species: a toolkit of best prevention and management practices. CAB International. Wallingford, Oxon, UK. 228

pp. http://www.cabi-bioscience.ch/wwwgisp/

Woodard, S.E. and C.A. Rock. 1995. Control of residential storm water by natural buffer strips. Lake and Reservoir Management. 11(1): 37-45.

Zisette, R. 2001. Eurasian water milfoil control and exotic species prevention in Seattle’s Lake Youngs Reservoir. Herrera Environmental Consultants, 2200 Sixth Avenue, Suite 601, Seattle, WA 98121.

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# 79 

# APPENDIX A: CONTRACTORS/ RETAILERS THAT SPECIALIZE

IN NON-CHEMICAL CONTROL METHODS

This listing includes contractors who regularly perform some of the aquatic pest

control methods described in the literature reviews. All California-based contractors we

are aware of have been listed.

Contractors who conduct Non-Pesticide Control Methods

American Civil Constructors
3701 Mallard Dr. Benicia, CA 94510
Contact: Dan Palmer

707-746-8028 x28 http://www.acconstructors.com/index.html

Specialties include: mechanical harvesting; mechanical excavation

Aquatic Environments Inc.

P.O. Box 1406. Alamo, CA 94507 Contact: George Forni

925 314-0831 email: gforni@covad.net www.aquaticenvironmentsinc.com/

Specialties include: mechanical harvesting, cutting, and rotovation; mechanical excavation; shading; biocontrol (bacteria); aeration; habitat restoration

Clean Lakes, Inc.

P.O. Box 3186
Martinez CA 94553
Contact: Tom McNabb

925 - 957 1905

1-877-FIX-LAKE

Fax: 925 957-1906 email: info@cleanlake.com
www.cleanlake.com

Specialties include: mechanical harvesting and cutting; shading; biocontrol (bacteria);
aeration

Environmental Water Works

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 80 Contact: Steve Walters

714 801-8546 email: stevenwalters@msn.com

Specialties include: mechanical cutting and harvesting on small ponds, biocontrol

PMC Production 10173 Croydon Way, Suite 3 Sacramento, CA 95827

916 638-8990
fax: 916 638-8991 email: info@pmcproduction.com http://pmcproduction.com/

Specialties include: mechanical harvesting and cutting

Southwest Aquatics

P.O. Box 13212 Palm Desert, CA 92225 Contact: Paul Beaty

760 568-5499

Fax: 760 568-4019 email: SWAquatics@aol.com

Specialties include: small pond management; grass carp

United Storm Water, Inc. 14000 E. Valley Blvd., Suite B City of Industry, CA 91746-2801
Contact: Paul Corn

1-877-71-STORM

Fax: 626-961-3166 email: pcorn@unitedstormwater.com

Specialties include: mechanical excavation and dredging

Companies that Manufacture and Sell Aquatic Plant Harvesters or Other NonChemical Devices

Aquamarine 1444 S. West Avenue, Waukesha Wisconsin 53186, USA Tel: (262)547-0211 Fax: (262)547-0718 E-Mail: weedharvesters@aol.com http://www.aquamarine.ca/

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 81 Aquarius Systems

PO Box 215 North Prairie, Wisconsin 53153-0215 262-392-2162 (phone) 800-328-6555 (toll free) 262-392-2984 (fax) email: info@aquarius-systems.com http://www.aquarius-systems.com/

Lake Restoration, Inc.
12425 Ironwood Circle Rogers, Minnesota 55374 Phone: (763) 428-9777 Toll free: (877) 428-8898 Fax: (763) 428-1543 E-mail: lrmail@lakerestoration.com http://www.lakerestoration.com/

Miller Aquatic Technologies LLC 358 S Main Street, No 86 Orange, California 92868

1-714-667-5053 email: info@milleraquatics.com http://www.milleraquatics.com/

PMC Production 10173 Croydon Way, Suite 3 Sacramento, CA 95827

916 638-8990
fax: 916 638-8991 email: info@pmcproduction.com http://pmcproduction.com/

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 82 

# APPENDIX B: PRACTITIONERS INTERVIEWED FOR REVIEW

California Practitioners

Bob Acker Merced Irrigation District

P.O. Box 2288 Merced, CA 95344-0288 (209) 722-5761 rack@mercedid.org

Earl Andress USDA-APHIS-PPQ-PPPC 4151 Hwy 86 Bldg 10 Brawley, CA 92227
Phone 760-344-7857

FAX 760-351-0532 e-mail: eandress@quix.net

Steve Andrews University of California Berkeley 301 Campbell Hall Berkeley, CA 94720-2922 (510) 381-1321 sandrews@uclink.berkeley.edu

Dr. Richard Bailey
Lake Merritt Institute
568 Bellevue Avenue Oakland, CA 94610 (925) 314-0531 lmi@netwiz.net

Walt Barret Golf Course Vegetation Manager Green Hills Country Club Millbrae, CA (650) 588-4616

Dr. Paul Beaty Southwest Aquatics P.O. Box 13212 · Palm Desert, CA 92255 (760) 568-5499 swaquatics@aol.com

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 83 Larry Bezark California Department of Food and Agriculture (916) 654-0768 Lbezark@cdfa.ca.gov

Dick Bogaert Mt. View Sanitary District dbogaert@mvsd.org

Steve Brueggeman California Department of Fish and Game Mendota Wildlife Refuge (559) 655-4645

Mark Bryant Garberville Sanitary District

P.O. Box 211 Garberville, CA 95542 (707) 923-9566 scs@redwaymail.net

Jason Churchhill Lahontan RWQCB (530) 542-5571

Don Conley California Department of Boating and Waterways 2000 Evergreen Street Suite 100 Sacramento, CA 95815-3888 (916) 240-8722

Bill Cook
Los Banos Wildlife Area 18110 W. Henry Miller Rd. Los Banos, CA 93635-9508 (209) 826-0463

Laura Crum California Department of Fish and Game South Coast Region (Region 5) 4665 Lampson Ave., Suite C Los Alamitos, CA 90720 (562)493-6897 (Office) lcrum@dfg.ca.gov

Nate Dechoritz

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 84 California Department of Food and Agriculture Ndechore@cdfa.ca.gov 1220 N Street, Rm A-357 Sacramento, CA 94271

Ron Derma Bard Irrigation District

PO Box 776 Bard, CA 92222 (760) 572-0704

George Forni Aquatic Environments, Inc. gforni@covad.net (925) 314-0831

Tony Gallegos Lake County Water Resources Division
255 North Forbes Street Lakeport, CA 95453 Telephone: (707) 263-2341 Fax: (707) 263-7748 tonyg@co.lake.ca.us

Cynthia Gause California Department of Boating and Waterways 2000 Evergreen Street Suite 100 Sacramento, CA 95815-3888" (916) 263-1819 CGause@dbw.ca.gov

Larry Grabow Marin Municipal Water District
220 Nellen Ave. Corte Madera, Ca. 94925 (415) 945-1551 lgrabow@marinwater.org

Erik Grijolva, Peggy Olofson, Katy Zaremba Coastal Conservancy Invasive Spartina Project (510) 681-5371 ISPOlofson@aol.com, kzaremba@scc.ca.gov

Dan Hamon

USDA-APHIS (916) 857-6260

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 85 Dave Hardt

USFWS Kern NWR Kern National Wildlife Refuge Complex

P.O. Box 670 Delano, CA 93216-0670 (661) 725-2767 dave_hardt@r1.fws.gov

Jim Husting Golf Course Vegetation Manager Woodbridge, CA (209) 368-9040 jchust@softcom.net

Jeff Janik California Department of Water Resources jjanik@water.ca.gov

Tom Jordan Harbor Bay Homeowner's Association (510) 865-3363

Troy Kellet Richvale Irrigation District Manager

P.O. Box 147
Richvale CA 95974 (530) 882-4243

Dr. Robert Leavitt California Department of Food and Agriculture 1220 N Street, Sacramento, CA 95814 (916) 654-0768 rleavitt@cdfa.ca.gov

Chuck Locher
Turlock Water District
333 E. Canal Dr. Turlock, California 95380 (209) 883-8300

Dr. Karl Malamud-Roam Environmental Projects Manager Contra Costa Mosquito and Vector Control District
155 Mason Circle Concord, CA 94520

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 86 (925) 685-9301 x107

Florence Maly California Department of Food and Agriculture

1220 N Street Sacramento, California 95814

Gene Martin Big Bear Municipal Water District

P.O. Box 2863
40524 Lakeview Dr. (909) 866-5796 gmartin@bbmwd.org

Tom McNabb Clean Lakes, Inc.

P.O. Box 3186 Martinez, CA 94553 (925) 957 1905 info@cleanlake.com

Mike Mizumoto Imperial Irrigation District (760) 339-0565 mrmizumoto@iid.com

Marty Muschinske California Department of Fish and Game (619) 468-3064 mmuschin@dfg2.ca.gov

Dave Najera Aquatic Environments, Inc. (510) 406-0784 davenajera@hotmail.com

Ross O'Connell California Department of Food and Agriculture 1220 N Street, Sacramento, California, U.S.A. 95814 (916) 654-0768 roconnel@cdfa.ca.gov

Dave Omoto
Contra Costa Water District
1331 Concord Ave. Concord, CA 94524

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 87 925-688-8023 domoto@ccwater.com

Pat Panus
Contra Costa Water District
1331 Concord Avenue. P.O. Box H2O Concord, CA 94524 (925) 688-8090

Jeff Pasek Water District of San Diego City of San Diego Water Production Div., Water Quality Lab
5530 Kiowa Drive La Mesa, CA 91942

619-668-3240 jpasek@sandiego.gov

Bill Paznokas CDFG S. Coast Region (858) 467-4218

Jane Sooby Organic Farming Research Foundation

P.O. Box 440 Santa Cruz, CA 95061

831-426-6606 jane@ofrf.org

Dr. David Spencer USDA Agricultural Research Station (530) 752-1096 dfspencer@ucdavis.edu

Jeff Stuart National Oceanic & Atmospheric Administration
National Marine Fisheries Service
Protected Resources Division 650 Capitol Mall, Suite 8-300 Sacramento, CA 95814-4706 (916) 930-3607 j.stuart@noaa.gov

Brian Sullivan Golf Course Vegetation Manager Bel Air Country Club

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 88 Thousand Oaks, CA (310) 440-2428

Dr. Bill Taylor Metropolitan Water District of Southern California

700 Moreno Avenue La Verne, CA 91750 (909) 392-5149 wtaylor@mwdh2o.com

Greg Tischler Tahoe Keys Property Owners Association
356 Ala Wai Blvd. South Lake Tahoe, CA 96150 (530) 542-6444

Mark Vale Solano Irrigation District (707) 448-6847 ext. 40

Mark Wander Santa Clara Valley Water District 5750 Almaden Expressway San Jose, CA 95118-3686 mwander@valleywater.org

Bob Weber
Reclamation District 999 (916) 775-2144 recdist999@sprintmail.com

Frank Zarate California Department of Food and Agriculture (559) 445-5031

Out of State Practitioners

Jonathan Bates Willopa National Wildlife Refuge

360-484-3482 Washington

Dr. John Barko Waterways Experiment Station, USACE

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# 89 Vicksburg, Mississippi (601) 634-3654

Ann Bove

Vermont DEC Vermont Department of Environmental Conservation Water Quality Division
103 South Main Street Building 10 North Waterbury, Vermont 05671-0408 (802) 241-3782 annbo@dec.anr.state.vt.us

Dr. Raghavan Charudattan Professor, Plant Pathology Department

PO Box 110680 University of Florida Gainesville, FL 32611-0680 TEL: 352-392-3631, ext: 354

FAX: 352-392-6532 EMAIL: rc@ifas.ufl.edu

Wayne Corban St. John’s River Water Management

386-329-4276 wcorban@sjrwmd.com
Florida

Dr. Al Cofrancesco Waterways Experiment Station, USACE Vicksburg, Mississippi cofrana@wes.army.mil

Dr. Lee DeHaan
The Land Institute
2440 E. Water Wells Road Salina, Kansas 67401

785-823-5376 theland@landinstitute.org

Dr. Bill Haller Institute for Food and Agricultural Sciences University of Florida

352-392-9615 wth@mail.ifas.ufl.edu

Kathy Hamel

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# 90 Aquatic Plant Specialist Washington Department of Ecology

360-407-6562

Daniel Helsel Wisconsin Department of Natural Resources Water Program Supervisor Black-Buffalo-Trempealeau River Basins 910 Hwy 54, Black River Falls, WI 54615

715-284-1431 Daniel.Helsel@dnr.state.wi.us

Bret Henninger Resource Quality Department

513-728-3551 ext. 265 www.greatparks.org
Ohio

Martin Hilovsky
President EnviroScience, Inc.
3781 Darrow Road Stow, Ohio 44224 (800) 940-4025
www.enviroscienceinc.com

Jill Hoffmannn Aquatic Biologist Lake and River Enhancement Program
IDNR - Division of Soil Conservation Indianapolis, Indiana (317) 233-5468

Vanessa Howard
Center for Lakes and Reservoirs Portland State University Portland, Oregon (503) 725-9076 vhoward@pdx.edu

Marleen Kromer Director of Interagency Program Development The Nature Conservancy – Ohio Chapter
6375 Riverside Drive Dublin, Ohio 43017

614-717-2770

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# 91 mkromer@tnc.org

Dr. Richard C. Lathrop Aquatic Community Ecologist Wisconsin Department of Natural Resources c/o UW Center for Limnology Madison, WI 53706 Telephone (608)-261-7593; fax (608)-265-2340 email: rlathrop@facstaff.wisc.edu

Judy Ludlow Bureau of Invasive Plant Management

850-245-2816
Florida

Dr. John Madsen Mississippi State Georesources Institute ERC, Rm 225

Box 9652 Mississippi State University, MS 39762 (662) 325-2428

Terry McNabb AquaTechnex

P.O. Box 118 Centralia, WA 98531 (360) 330-0152 Fax: (360) 330-0174

Nancy J. Mueller
New York State Federation of Lake Associations fola@nysfola.org

Hilary Oles Adirondack Park Invasive Plant Program c/o Adirondack Nature Conservancy

P.O. Box 65 Keene Valley, New York 12943

518-576-2082 x 131 holes@tnc.org

Fritzi Olson Adopt a River

PO Box 357098 Gainesville, Florida 32635

352-264-6827

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# 92 aar@currentproblems.org

Sheilpa Patel Florida Orange Port President of Dredging and Marine Consultants spatel@dmces.com (386) 304-6505

David Penny Masters Dredging, Inc.

Kansas (913) 583-3335

Dr. Judy Shearer Waterways Experiment Station, USACE Vicksburg, Mississippi shearej@wes.army.mil (601) 634-2516

Hannah Spaul The Nature Conservancy – Wisconsin Field Office
Madison Field Office
633 West Main Street Madison, WI 53703 (608) 251-8140 wisconsin@tnc.org

Dr. Mark Sytsma Portland State University Portland, Oregon www.clr.pdx.edu (503) 725-3833

Dean Wong
New York State Federation of Lake Associations (518) 587-8100 ext.219

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# 93 

# APPENDIX C: FEASIBILITY SCREENING FOR DIFFERENT

WEED CONTROL METHODS

This Appendix develops practical recommendations, based on best available

science, for what control methods may be appropriate in different plant management

scenarios. The focus of the Appendix is on alternative methods used to control aquatic

weeds. The end-users of this information will include the California State Water Quality

Control Board, special interest groups, and the various state, local, and private agencies

that control aquatic plants. This Appendix is not an evaluation of all potential aquatic pest

control methods presented in the main body of the report. Rather, it provides a general

starting point for practitioners having little experience with aquatic plant control methods,

to decide if some of the most commonly used methods are appropriate for their

management circumstances. This information may also be a useful reference in permit

preparation, as it summarizes the recommendations of local experts regarding what

methods may or may not be appropriate in various management scenarios.

This Appendix presents tables indicating what non-chemical control methods may

work for plant management scenarios that are common in California. Once a manager has

identified a water body type and plant problem to control, they may use these tables to

quickly determine potential control methods. The tables provide information on

feasibility of the methods, expected control costs, and permitting requirements. These

tables were developed based on the recommendations of the aquatic plant scientists and

managers from the Non-Chemical Alternatives Environmental Economic Workgroup,

interviews with field practitioners in the state, and reviews of the scientific and

management literature on these plant control methods.

Table 1 depicts an initial screening of plant control methods, to determine which

ones are likely to be feasible for a given water body and plant type (the methods are

described in much greater detail in the main body of the report). Numbered cells indicate

significant limitations that may make a particular method unfeasible in a particular

management scenario. Table 2 presents narrative information about the limitations of the

particular methods. As with Table 1, this information is organized according to water

body type and plant type. Additionally, environmental hazards associated with the

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# 94 methods are presented, as well as other potential limitations. Both tables should be

considered in creating an initial listing of potential methods.

Table 3 indicates the permitting requirements of the different control methods.

Permits that may be required include Section 404 permits, Section 401 permits, 1600

permits, and NPDES permits

. Several other types of permits are only required for one

type of method, as presented in the table. Several permitting requirements may be

addressed by filing a Joint Aquatic Resource Permit Application (JARPA).

The Army Corps of Engineers (USACE) requires a Section 404 permit if large

volumes of soil, sediment, or vegetation are discharged into “waters of the United

States”. Waters of the United States are defined as any water body connected to U.S.

navigable waters. Whether the discharge is of sufficient scale to require a permit is

somewhat subjective, but permits are typically required for operations that discharge

more than 750 cubic yards of material. The California Regional Water Quality Control

Boards (RWQCB) administers Section 401 permits, which are required for certain

activities that affect water quality (these are also referred to as CEQA permits). For

practices possibly requiring Section 401 permits, an inquiry should be made with the

RWQCB office. California Department of Fish and Game require “ 1600 Lake and

Streambed Alteration Permits ” for practices that may damage benthic habitat. NPDES

permits are required for all chemical control methods that result in discharge of

chemicals into “waters of the United States”.

Additionally, many control methods may require that a Biological Assessment be

submitted to USFWS and/or NMFS, who will then prepare a formal Biological Opinion

.

A formal review by these agencies will be required if there is the possibility that federally

endangered or threatened species will be harmed or killed, or their habitat degraded, by

the control methods. This pertains to locations where USFWS or NOAA/NMFS has

identified habitat for listed species. The USFWS/NMFS reviews can take upwards of a

year or more, particularly for projects that are not conducted in collaboration with a

federal organization.

Table 4 presents general cost information on the implementation of the methods.

This table can be usable to generate some “back of the envelope” cost calculations for the

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 95 methods. Managers wanting guidance on how to perform a more detailed cost

effectiveness analysis for their particular management scenario should consult the report

prepared by Mann (2003).

With many aquatic weed species, the risk of further spreading of the infestation

should also be considered in control method selection. This is particularly important for

species that readily spread by fragmentation. Although it is difficult to exactly quantify

the risk that a particular control method will cause new infestations to develop, Table 5

qualitatively compares the relative risk among control methods and plant species. It

should be noted that the risk of control methods spreading infestations within or among

water bodies is an area where future scientific research is needed.

Several aspects of the water body are important in determining whether further

spread is a concern. Spreading poses a much greater risk in water bodies with outlets

flowing into other water bodies. Also, great caution should be exercised in controlling

new infestations or infestations that have not taken over the entire water body. For

example, CDFA’s hydrilla eradication program on Clear Lake does not permit methods

that spread fragments in areas adjacent to hydrilla infestations (CDFA 2003a). In

contrast, closed systems that are completely taken over by an infestation do not pose a

significant risk for further spread. In these systems, method selection may be more driven

by other factors, such as the method that is likely to provide immediate relief from the

infestation.

For methods listed as high risk in Table 5, specific management practices may be

conducted to mitigate the risk of infestation spreading. For example, booms, curtains,

nets, or other structures may be set up in the water bodies to keep fragments from

spreading.

There is a trade-off in presenting these tables; by condensing a wide variety of

management recommendations into a short space, many subtleties are overlooked. Please

refer to the main body of the report to address these subtleties. Tables 1 and 2 should be

viewed only as practical screening devices for identifying methods that may be effective

for a given management problem. Table 3 should be used as an indicator of what

agencies should be contacted to evaluate whether their permits will be required.AquaticPesticideMonitoringProgramReviewofAlternativeAquaticPestControlMethodsForCaliforniaWaters96Table1.Look-uptableforfeasibilityofaquaticplantmanagementpracticesbywaterbodyandplanttype.WaterBodyTypeCommonWeedSpeciesPlantType

Practice Delta Small Lake Large Reservoir Irrigation Canal Stormwater Canal Wildlife Refuge Estuarine Wetland Eurasian watermilfoil Hydrilla Water hyacinth Pondweed Egeria densa Spartina Cattail/Tule General Emergent General Floating General SubmergedHarvesting54,55Cutting54,55Excavation112ManualRemoval*BottomBarriers*66662Rotovation54,5252WaterDrawdown16555332SterileGrassCarp4,83,843,8773,6,73,6,72,3,6,7Insect377777ChemicalControls6Cellscontainingfootnotesmaynotbefeasiblebecauseofreasonslistedbelow.*Methodworksbestonsmallinfestations1–Likelytobeverycostlyandlogisticallydifficult2–Unlikelytobeeffective3–Feasibilityunknown;nevertriedinCAwaters4–IllegalorpossiblyillegalinCA5–Mayenhancespeciesorspreadinfestation6–Rapidwaterfloworestuaryconditionsmayinterfere7–Notapreferredfooditem8–Fishescapeormortalitylikely9–EffectivebiologicalcontrolagentnotavailableAquaticPesticideMonitoringProgramReviewofAlternativeAquaticPestControlMethodsForCaliforniaWaters97Table2.ListofAquaticPlantManagementPracticesAndLimitationsPracticeDescriptionRestrictionsbyTypeofWaterBodyRestrictionsbyTypeofPlantEnvironmentalRestrictionsOtherLimitationsNoPracticeNointentionalactionstoreduceaquaticplantsPlantimpactsontheecosystemandtheenvironmentmaybeunacceptableHarvestingCut,harvestanddisposalPotentialforfragmentreleaseisworseinflowingwaterMayspreadinfestationformilfoil,hydrilla,egeria,orotherspeciesthatspreadbyfragmentationWillremoveaquaticanimals(e.g.,juvenilefish),particularlyindensevegetationMusthaveacceptabledisposallocationCuttingCutaquaticweedsPotentialforfragmentreleaseisworseinflowingwaterLikelytospreadinfestationformilfoil,hydrilla,egeria,orotherspeciesthatspreadbyfragmentationMayaddexcessnutrientstowatercolumnandcausedissolvedoxygenreductionCollectionmayincludeweedrakes,nets.Environmentalimpactsmaydictatewhethercollectionisneeded.ExcavationRemovesedimentsandoverlyingplants.Methodsincluderotovation,chaining,suctiondredging,backhoewithrakeGenerallyrequireeasyshorelineaccessforcosteffectiveness;preferableindewateredsystemsTurbidityandcontaminantflux.MayspreadinfestationdownstreamMayrequirewastedisposal.WastescontainingsedimentsveryexpensivetodisposeManualRemovalIndividuals"weed"bottoms,mayrequirediversWorksbestforsmallinfestationsorsmallareasBottomBarriersSemi-permanentmaterialslaidoverplantbedsDifficulttomaintaininflowingortidallyinfluencedwatersNotusuallyeffectiveforfloatingoremergentplantsCouldaffectbenthichabitatOftenusedneardocksandmarinas.BarriermaterialmustbegaspermeableAquaticPesticideMonitoringProgramReviewofAlternativeAquaticPestControlMethodsForCaliforniaWaters98Table2.Continued.ListofAquaticPlantManagementPracticesandLimitationsPracticeDescriptionRestrictionsbyTypeofWaterBodyRestrictionsbyTypeofPlantEnvironmentalRestrictionsOtherRotovationSubmergedaquaticrototillingWatermustbeatleast6”-8”deep,butnottoodeepWillnotworkforfloatingplantsMaycontributetoturbidityandcontaminantfluxWaterLevelDrawdownDewatersystemtokillplantsMusthavewatercontrolstructuresSomespeciesenhancedbydrawdownMustbesufficientlylongtimetokillplants.GreatercontrolachievedinfreezingclimatesSterileGrassCarpStockjuvenilecarpEurasianwatermilfoil,parrotfeather,andwaterhyacinthnotpreferredfoodsCanswitchlakefrommacrophytedominatedtoalgaedominated.NotpermittedinwatersthatoutflowtoothernaturalwatersThereisriskthatallplantswillbecompletelyeliminated.MustdetermineappropriatestockingdensityInsectIntroduceinsectsthatspecializeinconsumingtargetplantsPopulationestablishmentmoredifficultinflowingwatersCurrentlyavailableinCAforpurpleloosestrifeandwaterhyacinth.InsectshavesubstantiallycontrolledalligatorweedincoastalstatesfromVirginiatoTexas.PathogensorpredatorsinsystemmayreducebiologicalcontrolagentpopulationGenerallylong-termefforts;resultsmaytake5-10years.AquaticPesticideMonitoringProgramReviewofAlternativeAquaticPestControlMethodsForCaliforniaWaters99Table3.PermittingRequirementsForAquaticPlantManagementPractices(notdefinitive)PracticePermitsThatMayBeRequiredGeneralUSFWSorNMFSformalBiologicalOpinionmayberequiredHarvestingRWQCBSection401CuttingRWQCBSection401SedimentExcavationCDFG1600;RWQCBSection401;USACESection404HandpullCertificationrequiredifSCUBAused.BottomBarriersCDFG1600RotovationCDFG1600;USACESection404;RWQCBSection401WaterLevelDrawdownRWQCBSection401;CDFGPermittokillfish,ifdrawdownwillcausemortalityinnaturalwatersSterileGrassCarpRWQCBSection401;CDFGStockingPermit;MethodonlypermittedwhennotcontiguouswithotherCaliforniawatersorinFEMAdefined100yearfloodplain;notpermittedinwaterbodiescontainingendangeredspecies.InsectChemicalControlNPDESpermits;RWQCBSection401;applicatormustbelicensedbyDPRAquaticPesticideMonitoringProgramReviewofAlternativeAquaticPestControlMethodsForCaliforniaWaters100Table4.EstimatedCostsforVariousAquaticPlantControlMethods.Non-ChemicalControlCostEstimatesperAcreinU.S.DollarsNumberofTreatmentsperGrowingSeasonReferencesGrassCarp45-1251WashingtonStateDepartmentofEcology2001MechanicalHarvesting500-9002–6(2–3forsubmersed,3–6forfloatingplants)WashingtonStateDepartmentofEcology2001Rotovation1,200–1,7001-2TaylorandGately1998DiverDredging1,100–2,0001-2TaylorandGately1998BottomBarriers14,000–26,2000.5TaylorandGately1998MechanicalCutting100–11,00010-12WashingtonStateDepartmentofEcology2001WeedRollers2,00010-30WashingtonStateDepartmentofEcology2001ManualPulling500–2,4001Gibbonsetal.1994Note:Arangeofdifferentenvironmentalconditionsanddifferentcontractagreementsapplyforalloftheabovemethods.

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# 101 Table 5. Relative Risk That Aquatic Plant Management Practices Will Cause an Infestation to Spread to New Locations.

H = high risk of infestation spreading; M = medium risk; L = relatively low risk. N/A = Method not appropriate for that species for other reasons.

PracticeEurasianwatermilfoilParrotfeatherHydrillaEgeriadensaSalviniamolestaWaterhyacinthCattail/TuleSpartinaPondweed



# Mechanical Cutting* H H H H H M M H H Mechanical Harvesting* H H H H H M M M M

Rotovation * H H H H N/A N/A H H H

Sediment Excavation M M M M N/A N/A L1 L1 L1 Grass Carp** 

# L L L L N/A L N/A N/A L
Hand Pulling L L L L L L L1 L2 L

Bottom Barrier L L L L N/A N/A L L L

Insects N/A N/A N/A N/A L L N/A N/A N/A

Chemical Treatment L L L L L L L L L *Specific management practices may reduce potential of spreading (e.g., booms, curtains) **Grass carp is an introduced species that may not be used when spread between water bodies is likely. L1Assumes complete removal of cut/harvested material. L2 Only seedling, or very young Spartina is feasible to remove by hand.

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# 102 

# APPENDIX D: PEER REVIEW

The following peer review of this report was provided by Dr. John Madsen, Faculty Member, Mississippi State University. Dr. Madson is the author of many aquatic plant management publications, including ”Advantages and disadvantages of aquatic plant management techniques,” LakeLine 20(1): 22-34. Available at http://www.aquatics.org/pubs/madsen2.htm

. This document has been revised in April, 2004, in response to the comments of this peer review.

Review of Report:

“Review of Alternative Aquatic Pest Control Methods for California Waters”

Written by San Francisco Estuary Institute

Reviewed by John Madsen, 2 March 2004

General Comments:

1. The review of alternative management techniques was complete in both breadth and depth, without being encyclopedic. I think the discussion of each technique was objective and balanced. I have made numerous specific points below, but I think that these points are, on the whole, minor.

My main comment is a caution in terms of how this review is used. For managing invasive aquatic plants we need all the tools at our disposal, without unnecessarily restricting our selection. To eliminate one set of tools, herbicides, from our arsenal would be as foolhardy as to use this tool in a completely indiscriminate manner. The exact balance between chemical and nonchemical methods is one determined by the species managed, the ecological system, and other factors. The main problem is the invasive plant species, not the management. Invasive species are the second leading cause of species extinction and reduction of species diversity, as well as having other negative impacts on ecosystems.

In particular, herbicides are the single best tool for managing intermediate to large dense infestations. While significant progress can be made with a number of difference techniques on small infestations, the use of alternative techniques becomes progressively more difficult as the infestations grow in size.

Eliminating herbicides from management planning may only serve to unnecessarily increase the cost of managing invasive plants, or allow infestations to grow in size unchecked to the point where available tools or resources are not capable of managing the population. Often, these are resources that might be better placed in mitigating nontarget impacts of management.

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# 103 If we sit back and reconsider how we are managing invasive species, without continuing our management activity, the invasive species will not observe our moratorium. They will continue to grow, developing a larger problem once we decide to address the issue once

more.

2. I sensed a general willingness to introduce exotic animals (insects, snails, etc.) to control exotic plants, in lieu of using synthetic pesticides. I think that, while it is a value judgment whether the risk of new exotic infestations is more significant than the risk from synthetic pesticides in the environment, the potential for these exotic biocontrol agents to then become a problem has not been addressed. Aquatic pesticides, to be labeled for use in the US, must have no evidence of biomagnification, must break down and dissipate in the environment, and have a short half- life. A biocontrol agent, to be effective, must biomagnify (e.g., reproduce), ha ve a long and increasing half- life, and

not dissipate in the environment but in fact persist. As an ecologist, this concerns me. John Magnuson aptly put it in 1976, that managing exotics with exotics is playing with
fire.

Specific Comments:

1. Literature review, pg. 5. You did not specifically cite the Aquatic Plant Information Retrieval Service (APIRS) at the University of Florida. They are a particularly good source of information on gray literature regarding aquatic plant management, at http://plants.ifas.ufl.edu/search80/NetAns2/

.

2. Practitioner Survey, page 5. I commend you for interviewing practitioners – they are an important source of information that is often overlooked.

3. Fish Biomanipulation, Page 10. Fish biomanipulation only works on planktonic algae, and has generally been most successful in small lakes when combined with nutrient input control. In addition, most lakes have only had successful water quality improvement (e.g., reduction in algal growth) for a few years after manipulation. Fish manipulation usually results in an increase in the growth of submersed plants. Fish biomanipulation works best in shallow lakes when top predator fish are increased AND omnivorous, benthivorous fish (e.g., carp) are controlled.

4. Insect biocontrol, pg. 12. It is highly debatable how effective insect biocontrol has been for waterhyacinth in Florida. Florida State DEP officials put so little stock in its effectiveness that they have continued their management program of maintenance management with herbicides on small populations of waterhyacinth. While some researchers contend that biocontrol on waterhyacinth reduces plant height and flowering, they concede it does little to prevent the expansion of the mat.

The hydrilla flies have shown even less propensity to control hydrilla in the field, though sporadic declines of hydrilla have been noted in the presence of the hydrilla flies. This contrasts with the hugely successful use of the alligatorweed flea beetle to control alligatorweed, which rapidly reduced the aquatic infestations of this pest throughout

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# 104 much of its range (though not its terrestrial or wetland growth). Other biocontrol projects with purple loosestrife and melaleuca have likewise shown demonstrable results. All of the projects above are examples of the classical approach to biocontrol, in which insects that feed on the target plant are found in the overseas native habitat and, after a long series of studies, released into the wild in the US. Eurasian watermilfoil biocontrol is completely different. The naturalized milfoil weevil was found to feed on Eurasian watermilfoil, but also feeds on the native northern watermilfoil, but with less damage. By serendipity, the milfoil weevil can cause declines of Eurasian watermilfoil under laboratory, experimental field, and natural field conditions. However, there is no guarantee that these high populations of weevils are sustainable. Simply put, there is no theoretical basis for believing that release of the milfoil weevil alone with suppress Eurasian watermilfoil populations, and no operational plan for their use has been implemented. The only way to make the weevils work predictably is to perform augmentive releases from reared populations, a prospect that is prohibitively expensive.

5. Organic Material Amendment, page 17. While some organic additions may reduce algal growth and some rooted plants, they may actually increase the growth of waterhyacinth and other free-floating plants, which prefer acidic water for nutrient uptake.

6. Acetic Acid, page 18. Acetic acid is effective on waterhyacinth, but has not been approved for use in aquatic environments by the US EPA as a pesticide, and is unlikely to receive this approval. Likewise, application of acetic acid to aquatic vegetation will increase acidity of surface waters and impact aquatic life. While it may be effective for floating vegetation, I predict that the impact on aquatic life will be far more than
conventional herbicides.

7. Plant Competition, page 19. I have done a number of plant competition or native plant revegetation experiments. Invariably, the nuisance plant must first be controlled, and then the native plant added. Native plant revegetation is less a control technique itself than a remediation to prolong the effectiveness of control – and even at that, it does not always
work as intended.

8. Mechanical Harvesting, page 22. The main problem with mechanical harvesting is that it is relatively slow; a single harvester may only be able to cut 1 to 4 acres per day. Mechanical harvesting of large infestations is therefore problematic, requiring a large
number of harvesters.

The ability of harvesting to remove nutrients from lakes has been dramatically overstated. Carpenter’s calculations, while correct, assume that one harvests all of the plants in the littoral zone – an unlikely scenario. The amount of nutrients removed by a typical management program is usually far less than internal loading rates, much less external inputs to the lake.

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 105 9. Mechanical Cutting, page 24. One overlooked aspect of cutting is that it is demonstrably faster than harvesting, thus allowing the same area to be treated by fewer machines than harvesting.

10. Rotovation, page 26. Rotovation creates a lot of turbidity, resuspends nutrients from the sediment, and produces large numbers of fragments that may spread target species, even if a harvester is attempting to collect fragments.

11. Weed Rollers, page 27. The State of Minnesota (DNR) requires permitting of weed rollers and limits their size and location to reduce impacts on littoral habitats. They are particularly concerned about the use of weed rollers on sediments high in organic matter.

12. Manual Removal, page 31. Manual removal seems to work best when occasional scattered plants are the target, rather than dense growths of plants. Particularly with submersed plants, once the first plant is pulled, visibility drops to almost nothing and companion plants are difficult to locate and remove.

13. Non-conventional Chemical Controls, page 38. One overlooked problem with nonconventional chemical controls is that US EPA has approved none of these chemicals for use in aquatic environments as pesticides, with the exception of Aquashade. The effects of many of these chemical treatments on aquatic life are virtually unknown. While many of these chemicals are widely used on pelagic algal growth, with generally predictable results, their use in the littoral zone for control of rooted or free- floating vascular plants are largely experimental or untested.

14. Relative Reliance, page 44. While I agree that some natural resource and regulatory agencies are attempting to manage invasive aquatic plants, notably Eurasian watermilfoil, using alternative methods exclusively, in Lake George they are losing that battle. Alternative methods work best if the infestation is managed as soon as possible, and on populations before they reach dense beds of greater than 1 acre. Once dense beds are formed, it is difficult if not impossible to control them with available appropriate alternative techniques.

Vermont recently approved the use of fluridone to control Eurasian watermilfoil, with considerable success. The number of applications and pressure to follow this up with additional treatments in other lakes was significant.

15. Preventive Measures, page 47. I heartily concur that any aquatic plant management program should include an element of prevention – both to prevent the spread of the target plant to other waters, and to prevent the introduction of new invaders to the waters being managed.

16. Mix of techniques, page 47. I would concur that any aquatic plant management program should have a mix of manage ment techniques, including both chemical and nonchemical techniques. Preferably, nonchemical techniques would predominate when target invasive plant populations would reach small numbers and density. Likewise, any

# Aquatic Pesticide Monitoring Program Review of Alternative Aquatic Pest Control Methods For California Waters



# 106 management effort focusing on reducing the growth of planktonic algae must include reducing the source of nutrients in the watershed. With nuisance rooted and floating plants the problem, however, is not the management technique itself, but all-too-often is the results of an introduction of no nnative aquatic vascular plants.

17. Page 49. Recheck the citation for Caffrey et al. 1996. I suspect that this is an article authored by either Boylen or Eichler, in a volume edited by Caffrey et al.

18. Page 55. Madsen 1997 was cited in the text, but is not listed in the literature cited
section.

19. Appendix 3, Table 2, page 82, No practice. The “no management option” overlooks the impact of the nonnative aquatic plant invader on the ecosystem and environment that, in some cases, can be significant.

20. Appendix 3, Table 2, Page 83, Insect. Insects may be available for waterhyacinth in California, but they won’t make much difference to the problem growth of waterhyacinth in the Delta. You could add insects have substantially controlled alligatorweed.

21. Appendix 3, Table 4, Page 85, Mechanical Cutting. I think 10-14 cuts per year are pretty excessive for mechanical cutting of submersed plants and, even, emergent plants. I don’t see why cutting would be an order of magnitude higher than harvesting, which is essentially the same thing except that the cut material is collected. This might need
clarification.

22. Appendix 3, Table 4, Page 85, Mechanical harvesting. I think 1-2 cuts per year is on the low side for submersed plants (in California), and well below what would be needed for emergent and floating plants – a better estimate would be 2 to 6 (2 to 3 for submersed,

3 to 6 for floating plants).

Completeness of Report:

The report on alternative pest control methods for California waters produced by the San Francisco Estuary Institute is thorough in both breadth (options discussed) and depth, without being unnecessarily verbose or encyclopedic. The most likely and applicable alternative technologies are discussed, a significant proportion of the scientific literature (both peer-reviewed and agency reports) is reviewed, and a relatively balanced view presented.