United States

Department of

Agriculture

Marketing and

Regulatory 

Programs

Animal and 

Plant Health 

Inspection 

Service

Asian Longhorned Beetle

Field Trial

Environmental Assessment,

January 2000
Asian Longhorned Beetle 

Field Trial 

Environmental Assessment,

January 2000

Agency Contact:

Ron Milberg

Operations Officer

Plant Protection and Quarantine

Animal and Plant Health Inspection Service

U.S. Department of Agriculture

4700 River Road, Unit 134

Riverdale, MD 20737-1236

Telephone: 301-734-5255

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programs and activities on the basis of race, color, national origin, gender, 

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status. (Not all prohibited bases apply to all programs.) Persons with 

disabilities who require alternative means for communication of program 

information (Braille, large print, audiotape, etc.) should contact the USDA’s 

TARGET Center at 202-720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director of Civil Rights, 

Room 326-W, Whitten Building, 14th and Independence Avenue, SW, 

Washington, DC 20250-9410 or call 202-720-5964 (voice and TDD). USDA

is an equal opportunity provider and employer. 

Mention of companies or commercial products in this report does not 

imply recommendation or endorsement by the U.S. Department of Agriculture 

over others not mentioned. USDA neither guarantees nor warrants the 

standard of any product mentioned. Product names are mentioned solely 

to report factually on available data and to provide specific information.

This publication reports research involving pesticides. All uses of pesticides 

must be registered by appropriate State and/or Federal agencies before they 

can be recommended.

CAUTION: Pesticides can be injurious to humans, domestic animals, 

desirable plants, and fish or other wildlife—if they are not handled or applied 

properly. Use all pesticides selectively and carefully. Follow recommended 

practices for the disposal of surplus pesticides and pesticide containers.
Table of Contents

I. Need for Proposal .......................................... 1

A. Introduction .............................................. 1

B. Purpose and Need ........................................ 1

II. Alternatives ............................................... 3

A. No Field Trials ............................................ 3

B. Injection Application Field Trials .............................. 3

C. Injection Application and Bark Treatment Field Trials .............. 5

III. Environmental Consequences ............................... 7

A. Potential Impacts .......................................... 7

 1. No Field Trials ......................................... 7

 2. Injection Application Field Trials ............................ 8

 3. Injection Application and Bark Treatment Field Trials ........... 11

IV. Agencies, Organizations, and Individuals Consulted ........... 16
1

I. Need for Proposal

A. Introduction 

The U.S. Department of Agriculture (USDA), Animal and Plant Health

Inspection Service (APHIS), is proposing a program to run field tests for the

control of the Asian longhorned beetle, Anoplophora glabripennis

(Motschulsky). The program is necessary to develop methods suitable for

program operations to reduce the potential for damage from this major pest

of trees. The Asian longhorned beetle bores into and kills a variety of tree

species (including species of maple, elm, chestnut, birch, poplar, and willow). 

This nonnative pest has the potential to spread to other areas of the United

States and cause extensive losses to ornamental and commercial tree species. 

It has been detected at several locations in the Chicago and New York City

metropolitan areas, and ultimately may be found in other areas as well. 

Under APHIS' National Environmental Policy Act Implementing Procedures,

7 CFR Part 372, the proposed action is a class of action for which an

environmental assessment (EA) is normally prepared. This EA considers the

potential effects of the proposed action and its alternatives, including no

action.

North America has abundant forest resources. Most logs and lumber

imported into the United States have historically been limited to those from

the forests of Canada. Increased trade has resulted in more frequent and

greater quantities of logs and lumber (including solid wood packing materials)

entering the United States from other parts of the world. Various plant pests

such as the Asian longhorned beetle from China can occur on or in these

unfinished wood products. Protection of the forest resources of the United

States from damage by foreign pest species is part of the mission of the U. S.

Department of Agriculture, Animal and Plant Health Inspection Service

(APHIS) and exclusion of those pest species is the most effective method of

preventing the losses associated with new pest infestations. 

B. Purpose and Need

Increased trade and the resultant increased opportunities for invasion by alien

agricultural pests have placed the United States and its agricultural economies

at substantially increased risk in recent years. In particular, a 
2

number of infestations and interceptions of exotic forest wood boring insects

have been associated with solid wood packing material (SWPM) from the

People’s Republic of China. Outbreaks of the Asian longhorned beetle

(Anoplophora glabripennis), a destructive pest of maple and other

hardwoods, were first detected in New York in 1996, and in Chicago, Illinois

in 1998. In addition, four genera of wood borers (Anoplophora, Ceresium,

Hesperophanes, and Monochamus) have been intercepted in shipments

from China that were delivered to warehouses in 11 States. The effects of

those outbreaks and interceptions, and of control and regulatory measures to

deal with them have been costly from environmental and economic

perspectives. 

APHIS has responsibility for taking actions to exclude, eradicate and/or

control plant pests including Asian Longhorned beetle, under the Plant

Quarantine Act (7 U.S.C. 151-165, 167), the Organic Act of 1944 

(7 U.S.C. 147a), and the Federal Plant Pest Act (7 U.S.C. 150dd). APHIS

has been delegated the authority to administer these statutes and has

promulgated Quarantines and Regulations (7 CFR 319), which regulate the

importation of commodities and means of conveyance. 

The current exclusion and eradication program consists of various regulations

designed to require treatment of solid wood packing material from China and

eliminate the Asian longhorned beetle by removing infested trees detected in

the United States. This approach is currently effective at preventing new

infestations from wood products imported from China, but it has not

effectively contained the Asian longhorned beetle within new areas of

infestation. Removal and destruction of infested host trees is time-consuming

and expensive. Effective elimination of the beetle by removal of infested host

plants depends upon early and timely identification of infestations in trees and

cutting before the beetle can spread to nearby host plants. Small infestations

that are detected early may be eradicated easily, but the infestations in New

York and Illinois have spread further and become difficult to eliminate. 

Therefore, the program is seeking prophylactic methods to prevent infestation

of healthy trees from adult beetles in the vicinity of presently infested areas. 

The systemic nature of the insecticide applications being considered may also

eliminate beetle larvae from recent infestations of living trees. Field tests for

several treatments are underway in China, but the results have not yet been

tabulated. The intent of the proposed field trial is to develop cost-effective

treatment methods that control the beetle and that are suitable for eradication

programs in the United States. 
3

This environmental assessment has been prepared in compliance with the

National Environmental Policy Act of 1969 (42 U.S.C. 4321-4327 (NEPA))

and its implementing regulations. 

II. Alternatives

APHIS considered carefully three alternatives to respond to the need for

developing better methods to contain Asian longhorned beetle infestations: 

(1) no field trials; (2) injection application field trials (the proposed action);

and (3) injection application and bark treatment field trials. Each is described

briefly in this section and the potential impacts of each are considered in the

following section.

A. No Field Trials 

Under the no field trials alternative, APHIS would take no action of any kind

to develop suitable methods for control of Asian longhorned beetle. Some

research could be taken by other Federal or non-Federal entities; those

actions would not be under APHIS control or funded by APHIS. In the

absence of development of more effective measures to contain and control

Asian longhorned beetle, the continuing gradual spread of the beetle in the

vicinity of the New York and Illinois area infestation would be expected to

continue. This would result in continuing costs for detection and removal of

infested host trees. Although the anticipated spread to surrounding areas is

limited, the cumulative environmental and fiscal costs could be considerable

and would increase commensurate with the expansion of the area infested by

the Asian longhorned beetle.

B. Injection Application Field Trials (Proposed 

 Alternative)

Under this alternative, field trials would be conducted applying systemic

insecticide treatments against Asian longhorned beetles by various injection

methods. This would include testing by either soil injections or injections

directly into the lower plant trunk just above the roots of uninfested trees. 

Current regulations require any infested trees discovered by the program to

be marked and cut in a manner that eliminates all life stages of the beetle. The

intent of the injection treatments would be to facilitate transport of the active 
4

ingredient of the pesticide from the site of application (root zones) to active

tree growth areas where the beetles would be expected to feed and lay eggs. 

Uninfested trees adjacent to those infested by Asian longhorned beetles

would receive priority to test the field effectiveness. The desired period of

protection for the uninfested trees coincides with the period of beetle activity

and is primarily between June 15 and October 15. The limited testing of

possible insecticides with systemic activity against woodboring beetles

indicates that imidacloprid (Merit 75WP®) shows the most promise for

effective use in an operational program. The preliminary testing indicates

some activity of imidacloprid against adult beetles as they feed on small twigs

and possibly when the female beetles deposit their eggs. Some reports have

indicated that imidacloprid provided two years of control against target insect

pests. 

The soil injections of imidacloprid are made with a power soil injector at 

100 to 250 pounds per square inch (psi) pressure to a depth of 4 to 8 inches

in a circular pattern surrounding the tree trunk. Application rates for soil and

trunk injections are determined by the diameter of the trees at breast height

(DBH). A minimum of 2 quarts of formulation (1.89 g Merit 75WP®) are

required per inch of DBH. The treatment holes will generally be made in a

circle that is 3 feet from the trunk. A second circle may be treated at 6 feet

from the trunk as required for larger trees based upon the tree diameter at

breast height. The systemic uptake by the tree will require approximately 

2 months, depending upon the tree species, soil conditions, and the time of

year when the application is applied. Optimal timing of soil treatments are

during the Fall (September/October) or during the Spring (March/April)

when systemic transport of insecticide could occur throughout the tree. Soil

applications are less effective when drought conditions result in dry soil. 

These applications do require large amounts of water to ensure that the

mixture will be taken up by the tree. The advantage of soil injection is that the

placement occurs where exposure to people or nontarget wildlife is unlikely

and the applicator may proceed to treat the next tree without need to limit

access (unlike Mauget® trunk injections) to the area after application is made. 

Imidacloprid has moderate water solubility, but it has low soil mobility due to

adsorption to soil particles, so exposure to humans by these applications is

unlikely unless the soil under the trees is dug up. If pavement covers the soil

under trees in urban areas, soil injection treatments may not be an option and

the trunk injections described in the next paragraph may be selected. 
5

The trunk injections of imidacloprid are applied through four milliliter 

Mauget® trunk injectors. One injector is required for every 2 inches of DBH

of the tree. Holes are drilled at a 45 degree angle to the trunk for dispenser

placement in the root flares close to the soil (two to six inches above the soil

wood line). Dispensers are activated by hitting the top with a rubber mallet

or pressing with hands. The injection takes a few hours and the area must be

secured to prevent disturbance of injectors during this period. Maintaining

security is important both to ensure effective treatment and to prevent public

exposure to imidacloprid from contact with dispenser contents. Preliminary

tests indicate that this method may provide some control of newly developing

larvae as well as feeding adult beetles. The systemic movement of

imidacloprid from these injections in the tree occurs shortly after treatment to

3 weeks. This is much less than the two month period required for soil

injection, but the insecticidal properties may not last as long in the tree as with

soil injection. Unlike soil injections, no water or mixing tank are needed. 

This method is preferable in areas where soil under trees is paved and where

high water table or related problems prevent soil injection. Damage to trees

from drill holes could be a problem, but the primary concerns would relate to

pests other than insects (e.g., fungal pathogens). 

The precise placement of injection treatments and the security during

applications preclude many potentially adverse environmental effects. The

physical environment is minimally impacted because imidacloprid residues are

restricted to the tree or the treated soil. Neither persistence nor

bioaccumulation problems are expected from injection treatments. In the

unlikely event that a person did receive imidacloprid exposure from the

injection applications, their exposure would not be expected to result in any

adverse effects to human health as long as the individual did not have allergies

or other sensitivity to the formulation. There are some nontarget species that

occur in trees and soil under trees that could be affected by these treatments. 

In particular, invertebrates directly exposed to imidacloprid would be

expected to have high mortality, but the effects on local populations of these

species are anticipated to be temporary. Some local insectivores could have

to increase their foraging efforts. Other nontarget wildlife are not expected to

be affected.

C. Injection Application and Bark Treatment Field 

 Trials

Under this alternative, field trials would include the testing of the injection

techniques as described above. In addition, this alternative would also 
6

analyze the effectiveness of various bark treatments in control of Asian

longhorned beetle. Bark sprays are made to target the adult beetles as they

feed on the twigs and deposit eggs. These applications would need to be

made during or just prior to the adult flight period between June 15 and

October 15 to provide effective control. The efficacy results from these

treatments are readily observable, but the residual action depends upon

environmental conditions. More than one bark treatment could be required

during the long flight season of the Asian longhorned beetles. Complete

coverage of the bark is necessary for these treatments to be effective,

therefore, a hydraulic type sprayer with high pressure (400-800 psi) is

required for pesticide application. Adequate coverage of the bark may be

difficult for 60 to 80 foot trees. Unlike some injection treatments, these

applications to bark have not been shown to have systemic action against

larvae. Large amounts of water are used for this type of application and

limiting runoff is important. The potential bark treatment insecticides include

formulations of permethrin, chlorpyrifos, bifenthrin, and deltamethrin. 

The bark treatments have several environmental consequences to the physical

environment, human health, and nontarget species that would not be expected

for injection applications. Phytotoxicity to some plants could be an important

issue, particularly where bark applications must penetrate through the foliage. 

Air, soil and water quality could be affected by contamination from drift and

runoff from bark treatments. The full coverage increases the likelihood of

exposure to humans and other nontarget species with increased risk of

adverse effects from these treatments. Other than direct effects on

invertebrates, toxicity to birds from the full coverage treatment is likely,

particularly with chlorpyrifos. Unlike the injections that limited residues to

locations within the tree and below the soil surface, detectable residues from

bark treatments are likely to occur at locations where humans and animals

could be exposed. In addition to higher potential exposure from bark

treatments, the relative toxicity of the bark treatment insecticides is

comparable to or higher than that of imidacloprid. These potential adverse

effects from the bark treatments greatly exceed those from injection

applications. 
7

III. Environmental Consequences

A. Potential Impacts

There are potential impacts from each of the alternatives being considered. 

The pest risk from Asian longhorned beetle is an important consideration for

all alternatives. Potential program impacts arise from each of the chemical

treatments, but most of the treatment impacts are not expected to be

substantial. The potential affected areas are primarily urban parks and

residential areas. Exposure to humans and potential effects to human health

are primary considerations addressed for program actions in these locations. 

1. No Field 

 Trials

Environmental impacts that could result from APHIS’ implementation of the

no field trials alternative relate primarily to pest risk effects if current

eradication programs fail to contain and eliminate new infestations of Asian

longhorned beetle. The lack of available treatments for controlling this insect

pest restricts control measures to removal of infested trees and elimination of

potentially available host plants. The adverse effects from removal of

individual plants may be minimal, but the Asian longhorned beetle has many

host plants and the potential impacts from ongoing removal of infested

vegetation are considerable with expansion of the infested areas. The

potential establishment of Asian longhorned beetle would be associated with

damage to and loss of valuable ornamental and commercial trees, spread of

the beetle to other areas of the country with resultant damage to and loss of

trees, loss of associated forest products (e.g., maple syrup), and private or

uncoordinated use of pesticides to control the pest with associated adverse

impacts to the environment (the physical environment, human environment,

and nontarget species). The wide distribution of host plants suggests the

danger of spread across much of the country with increases in damage and

losses commensurate with the spread. The damage and losses could result in

reductions in private property value. Structural lumber could be internally

damaged, resulting in risk of structural failure, losses to property, and injuries

to humans. The damage and losses to commercial trees would lower the

value and production of timber and tree products such as maple syrup. The

changes in the composition and age structure of forests resulting from no

action could have long-term effects on the ecological relationships in the

forested areas. There could be losses in recreational revenue to some areas

from diminished amount of certain activities such as fall foliage visitations. 

There would be losses of valuable shade and ornamental trees in residential

areas. The potential for future quarantine restrictions on the export of logs 
8

and nursery stock increases if field trials do not provide more effective control

and eradication methods. The primary environmental consequences of this

alternative are increased risk of pest spread and elevated environmental risks

from uncoordinated application of pesticides to limit damage from the Asian

longhorned beetle. The potential adverse impacts from selection of this

alternative are considerably greater than those anticipated for the other

alternatives. 

2. Injection 

 Application 

 Field Trials

The environmental consequences of this alternative relate primarily to the

potential for decreased pest risk and to potential environmental effects from

treatment methods. Development of an effective prophylactic injection

application could be applied operationally to protect susceptible host plants

and assist in the efforts to contain and eradicate Asian longhorned beetle from

infested areas of Illinois and New York. This could eliminate concerns about

continuing expansion of the current eradication program. It could prevent the

damage to and loss of many valuable ornamental and commercial trees, loss

of associated forest products (e.g., maple syrup), and private or

uncoordinated use of pesticides to control the pest with associated adverse

impacts to the environment (the physical environment, human environment,

and nontarget species).

The development of effective injection applications would provide an

alternate means of protection for trees to the present program practice of

removing and destroying newly infested trees. The insecticide proposed for

field testing this technique is imidacloprid. Determination of the potential

environmental impacts from this alternative requires analysis of toxicity,

environmental fate, exposure, and associated risks from imidacloprid

injections. 

Toxicity

Imidacloprid is a systemic, chloronicotinyl insecticide. The mode of toxic

action is unique and involves direct binding to the acetylcholine receptors. 

This binding causes a nerve impulse to be sent, but acetylcholinesterase is

incapable of removing imidacloprid from the site. The receptor site becomes

overstimulated and is eventually blocked. The nicotinergic site of action is

more prevalent in insects than in higher organisms, so the toxicity is selectively

more toxic to insects. 

The acute toxicity to mammals is moderate. The acute oral median lethal

dose of imidacloprid to rats is 450 milligrams per kilogram (mg/kg) body 
9

weight. The acute dermal median lethal dose to rats of imidacloprid is greater

than 5,000 mg/kg. Imidacloprid is not irritating to eyes or skin and is not a

skin sensitizer. Signs and symptoms of intoxication include fatigue, twitching,

cramps, and muscle weakness including the muscles for breathing. 

Chronic toxicity from imidacloprid is low. The systemic No Observed Effect

Level (NOEL) for a 2-year feeding study of male rats was 5.7 mg/kg based

on increased thyroid lesions observed at the next higher dose, 17.1 mg/kg. 

The reproductive NOEL determined from a three generation reproduction

study of rats was 8 mg/kg based upon decreased pup body weight at 

20 mg/kg. Imidacloprid may be weakly mutagenic. Test results were

negative for mutagenicity in all but two of the 23 laboratory mutagenicity

assays conducted. The positive assays were for genotoxicity in Chinese

hamster ovary cells and changes in chromosomes in human lymphocytes. The

U.S Environmental Protection Agency (EPA) has classified imidacloprid in

“Group E” in regards to carcinogenic potential. This indicates that the

submitted studies provide evidence of noncarcinogenicity for humans. 

Toxicity to other wildlife varies considerably. Imidacloprid is moderately to

severely toxic to birds. It is severely toxic to bees, but it is not considered a

hazard to bees when used as a seed treatment. Imidacloprid is practically

nontoxic to fish and slightly toxic to daphnia. 

Environmental Fate and Exposure

Imidacloprid residues from injection applications are not expected to persist

in the environment. The vapor pressure of imidacloprid is low and little

volatilization to the atmosphere is expected. Imidacloprid is moderately

soluble in water and the half-life in water exceeds 31 days at pH 5, 7, and 9. 

Soil injection applications and trunk injections are not expected to result in

any transport of imidacloprid to groundwater or surface water. Imidacloprid

adsorbs to soil particles and has low mobility. The half-life in soil varies from

48 to 190 days depending upon the organic matter, ground cover, and plant

uptake. The systemic action of Imidacloprid from trunk injections would be

expected to carry the residues to other locations within the plant. 

Adherence to the pesticide label and standard operating procedures ensures

that exposures are minimal. The injections would not be expected to

routinely result in any exposure to humans except the program applicators. 

The required protective gear and safety precautions minimize applicator

exposure. The applicators ensure that the Mauget® injection dispensers are 
10

not disturbed during injection and the dispensers are removed from the drill

holes when the application is complete to prevent exposure to the public. 

The only route for potential exposure of the public to imidacloprid is from the

accidental scenario of a person digging in the treated soil following soil

injection applications. Much of the compound would have adsorbed to soil

particles and the actual exposure to imidacloprid would be minimal. The

injection applications avoid exposure to most species of wildlife. The only

species likely to be directly exposed by these injections are those nontarget

invertebrates present in the treated soil or in the wood of the treated tree. 

Some insectivores and scavengers could also be exposed to residues during

foraging activities in the soil below or in the bark of treated trees. The

exposures of these species to imidacloprid are expected to be light. 

Risk Assessment

The risk of adverse effects to environmental quality are minimal. The

imidacloprid from soil injections and trunk injections is not expected to

volatilize to the atmosphere, is not expected to be leached to groundwater,

and is not expected to be carried to surface water except from heavy

rainstorms. The soil and plant residues are expected to remain active for up to

2 years to protect the trees from infestation by Asian longhorned beetles. 

The risks to human health are minimal. The required protective gear and

safety precautions for applicators result in potential exposures much lower than

any that could result in adverse effects. The anticipated margins of safety from

the accidental exposure scenario where a person digs up the soil from the

treated area under a tree are less than for the applicators, but no adverse

effects are anticipated for those individuals either.

Mortality from exposure would be expected for some invertebrates. The

populations of insects directly exposed to imidacloprid would be expected to

decrease temporarily in the treatment area until the residues decrease and

recolonization occurs from surrounding areas. This recovery would be

expected to occur more rapidly in the soil because the compound would be

readily taken up by the tree roots and residues would not persist in the soil. 

The insects exposed to residues in the trees would require longer periods of

time for recolonization. Although the prey for some insectivores would

decrease in treated areas, the additional forage effort by these species is not

expected to be increased greatly. The low exposures to birds and insectivores

foraging in the soil and tree bark are not expected to result in any adverse

effects to those species. 
11

Other Issues

An effort was made by APHIS to determine what if any measures would be

required for compliance of the field trials with the Endangered Species Act of

1973. The potential for exposure and any adverse effects was analyzed for

those endangered and threatened species and their habitats within the

proposed program area for the field trials. Based upon the findings of that

analysis, it was determined that the proposed field trials would have no effect

on those species or their habitats. 

Consistent with Executive Order No. 12898, “Federal Actions to Address

Environmental Justice in Minority Populations and Low-Income Populations,”

APHIS considered the potential for disproportionately high and adverse

human health or environmental effects on any minority populations and lowincome populations. The environmental and human health effects from the

proposed field trials are minimal and are not expected to have

disproportionate adverse effects to any minority or low income populations. 

Consistent with Executive Order No. 13045, “Protection of Children From

Environmental Health Risks and Safety Risks,” APHIS considered the

potential for disproportionately high and adverse environmental health and

safety risks to children. The field trials include applications to trees and soil

below trees in urban parks and residential areas where children would be

expected to play and climb trees. The program applicators ensure that the

general public is not in or around areas being treated, so no exposure will

occur for Mauget® injection applications and the only possible exposure could

occur from a child playing in the treated soil under a tree. This accidental

exposure scenario was analyzed and it was determined that no adverse human

health effects would result to the child. Therefore, it was determined that no

disproportionate effects on children are anticipated as a consequence of

implementing the proposed field trials.

3. Injection 

 Application 

 and Bark 

 Treatment 

 Field Trials

The environmental consequences of this alternative related to the potential for

decreased pest risk and injection applications are the same as those described

for the injection application field trials alternative. The field trials using the bark

treatments, however, have considerably greater potential for adverse effects to

the physical environment, human health, and nontarget species. The

insecticides being considered for bark treatments include permethrin,

chlorpyrifos, bifenthrin, and deltamethrin. 
12

Effective bark treatments require application to all surfaces of bark on the tree. 

The logistics for complete bark treatment of tall trees (60 to 80 foot) are

challenging and would require ladders or tall cherry pickers to be close enough

for good treatment, even with the high-pressure hydraulic rig applicators used. 

These treatments could result in considerable drift, particularly on windy days. 

Runoff from these applications to nearby water is likely, particularly if a

rainstorm occurred shortly after treatment. Chemicals used in the bark

treatments are expected to undergo degradation (photolysis or chemical

breakdown) over time and could require more than one treatment to ensure

good control during the period of June 15 to October 15 when the adult

beetles are active. For example, deltamethrin residues on some treated plants

have been shown to decrease to below the detection limit within 10 days. The

high visibility of these treatment would be expected to draw the public’s

attention to the actions and increase the potential for direct exposures.

Toxicity

The bark treatment insecticides are of two chemical classes. Chlorpyrifos is

an organophosphate insecticide. Permethrin, bifenthrin, and deltamethrin are

synthetic pyrethroid insecticides. Although both classes affect the nervous

system, the mechanisms of intoxication differ. The mode of toxic action of

chlorpyrifos occurs primarily through acetylcholinesterase (AChE) inhibition. 

Inhibition of AChE results in an accumulation of acetylcholine at the nerve

synapse and continual transmission of nerve impulses. The mode of toxic

action of the synthetic pyrethroids occurs through effects on the sodium

channels that stimulate nerves to produce repetitive discharges. Muscle

contractions are sustained until a block of the contractions occurs. 

The insecticides all have moderate acute oral toxicity to mammals, but differ

considerably in other known toxicological effects. The acute oral median lethal

doses to rats range from 53.8 mg/kg for bifenthrin to 430 mg/kg for

permethrin. The systemic NOEL values range from 0.03 mg/kg/day for

chlorpyrifos to 5 mg/kg/day for permethrin. Reproductive and developmental

toxicity from these compounds occurs only at much higher exposures. None

of the insecticides are known to be skin sensitizers. Irritation to skin and eyes

of rabbits from exposure tests was undetectable to slight. Mutagenicity tests

have shown negative results (deltamethrin, permethrin) or both positive and

negative results (bifenthrin, chlorpyrifos). The carcinogenic potential of these

insecticides vary considerably. Information about oncogenicity studies was not

located for deltamethrin. EPA has classified chlorpyrifos as not carcinogenic. 

Permethrin is suspected of being a weak oncogen, but EPA has not 
13

determined carcinogenic potency for these borderline effects. Bifenthrin has

been classified by EPA as a class C (possible human) oncogen. The cancer

potency of bifenthrin was determined by EPA to be 5.4 x 10-1 (mg/kg/day)-1 in

human equivalents. 

The toxicity to nontarget wildlife depends upon the insecticide. All are

moderately toxic to mammals. Permethrin is very slightly toxic to birds. 

Bifenthrin and deltamethrin are slightly toxic to birds. Chlorpyrifos is

moderately to severely toxic to birds. All insecticides are severely toxic to

terrestrial invertebrates. All are very highly toxic to fish and aquatic

invertebrates.

Environmental Fate and Exposure

The environmental fate of these insecticides applied to the bark of trees will

depend upon the weather conditions. Chlorpyrifos is quite volatile and

detectable amounts could be detected in the air. There could be some

permethrin residues in air following bark treatments, but these should dissipate

readily. Bifenthrin and deltamethrin have lower vapor pressure and their

residues would not be expected to remain detectable in air after treatments are

completed. None of these compounds are very mobile in soil and adsorption

to soil organic matter would be expected. The half-life in soil varies from one

to two weeks for deltamethrin to as long as a year for chlorpyrifos. All of

these compounds readily adsorb to sediments in water, but residues may

persist for several weeks. These bark applications would not be expected to

contaminate water except possible drift or runoff from a heavy storm. These

compounds are not systemic and little if any translocation within the treated

plants is expected. Residues of these insecticides on the foliage and bark of

treated plants may persist throughout the growing season (permethrin) or

degrade within as little as 10 days (deltamethrin). 

The bark treatments require complete coverage to be effective against Asian

longhorned beetle. Penetration of the thick foliage to treat the bark of trees

with a hydraulic rig indicates that all parts of the trees above the roots will have

residues of the insecticide. The exposure from these applications would be

expected to be high to tree-dwelling invertebrates, woodland birds, and

squirrels. Drift and runoff to the soil below treated trees would expose some

soil and ground-dwelling organisms, but most of these exposures would be

more moderate. The human exposures would depend primarily upon contact

with the tree. Program pesticide applicators are required to wear protective

gear and follow specific safety precautions. These individuals would not be 
14

expected to have high exposures. An individual who decide to lean against a

treated tree or climb without protective clothing could receive a high exposure,

particularly if the treatment on the bark had not dried. 

Risk Assessment

The risk of adverse effects to environmental quality are greater for this

alternative than from the injection applications. The chlorpyrifos for some bark

treatments could volatilize with detectable residues in the atmosphere. 

Leaching to groundwater is highly unlikely, but drift and runoff could

contaminate surface waters, particularly in areas where many trees are treated

and heavy rainstorms occur shortly after treatments. Any need for additional

treatments within the season when the beetle are active makes the potential for

contamination more likely. The plant residues are expected to remain active

for several months to protect the trees from infestation by Asian longhorned

beetles. Residues in soil may remain for extended periods of time, particularly

with chlorpyrifos.

The potential risks to human health from these bark treatment applications are

considerably greater than from injection applications. The required protective

gear and safety precautions for applicators result in potential exposures much

lower than any that could result in adverse effects for all compounds except

chlorpyrifos. The risks to mixers and loaders of chlorpyrifos are negligible, but

exposures of hydraulic rig applicators exceed the regulatory reference value

for both routine and extreme exposure scenarios. Adherence to proper

protective gear and safety precautions by hydraulic rig applicators is important

if chlorpyrifos applications are to be considered. The anticipated effects to the

general public could be adverse for some individuals. Exposures to the

individual who leans against a treated tree or climbs without any protective

clothing could be expected to have some symptoms of intoxication. 

Chlorpyrifos exposures from scenarios for soil consumption, contaminated

runoff, and contaminated vegetation all exceed regulatory reference values, so

adverse effects to the public from chlorpyrifos applications would be likely. 

Use of the other bark treatment insecticides do not pose such high risks in

these scenarios.

Mortality from exposure would be expected for many tree-dwelling and soildwelling invertebrates. The populations of tree-dwelling insects directly

exposed to the bark treatments would probably decrease temporarily in the

treatment area until the residues decrease and recolonization occurs from

surrounding areas. This recovery would depend on the size of the area where 
15

trees were treated. Recovery would take longer if all trees in a large city park

were treated because the insect populations in the surrounding areas might not

include all species in the park trees. The quantitative risk assessment

determined that populations of honey bees would be adversely affected by all

of the bark treatments. 

The soil invertebrates exposed to runoff and drift would also have decreases in

population. Their populations would recover more readily than tree-dwelling

insects for some treatment chemicals (eg., deltamethrin), but recovery could be

slower for the insecticides that persist in soil such as chlorpyrifos. Effects on

nesting birds from bark treatments could be devastating, particularly with a

severely toxic insecticide to birds such as chlorpyrifos. The quantitative risk

assessment for chlorpyrifos applications predicted mortality for all nontarget

species analyzed except deer and dogs. Although squirrels and other treedwelling mammals are unlikely to receive a direct exposure, their exposures to

these moderately toxic insecticide residues could result in various sublethal

neurological effects that make them more susceptible to predation. Likewise,

any insectivores that forage on the treated trees or soil within the dripline could

have exposures that result in adverse effects on potential survival. 

The environmental consequences and risks to the physical environment, human

health, and nontarget species of this alternative are clearly greater than those

from the injection application field trials alternative. The logistics of treating all

bark surfaces on tall trees make this alternative difficult to achieve, particularly

for potential future operations in urban parks and along residential streets. The

bark treatments can only ensure suppression of the adult beetle population for

as long as residues persist and this may only provide protection for part of a

season before retreatment is needed. Based upon these limitations, the

injection application field trials alternative would be more reasonable to

consider for development as a program control measure against the Asian

longhorned beetle. 
16

IV. Agencies, Organizations, and 

 Individuals Consulted

This environmental analysis was prepared and reviewed by APHIS. The

addresses of participating APHIS units, cooperators, and consultants (as

applicable) follow.

Win H. McLane

Section Leader

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Plant Protection and Quarantine

Insecticide and Application Technology Section

Building 1398

Otis ANG Base, MA 02542

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Plant Protection and Quarantine

Program Support

4700 River Road, Unit 134

Riverdale, MD 20737-1236

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Policy and Program Development 

Environmental Analysis and Documentation

4700 River Road, Unit 149

Riverdale, MD 20737-1238