United States

Department of

Agriculture

Marketing and

Regulatory

Programs

Animal and

Plant Health

Inspection

Service

Rangeland Grasshopper 

and Mormon Cricket 

Suppression Program 1

Final Environmental Impact 

Statement—2002
Grasshopper Environmental Impact Statement iii

Grasshopper 

Environmental Impact 

Contents 1

 iii

Preface v

Executive Summary 1

I. Purpose of and Need for the Proposed Action 15

II. Background 21

III. Alternatives 31

IV. The Affected Environment 37

V. Environmental Consequences 43

VI. Other Environmental Considerations 85

VII. References for Chapters I through VI 91

Appendix A. Background Information on Grasshopper Programs 101

Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides 117

Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides 189

Appendix D. References for Appendices A, B, and C 207

Appendix E.Federal Register Notices Associated With This Document 

235

Appendix F. Summary of Public Comments on the Draft Environmental 

Impact Statement 237

Appendix G. Preparers and Reviewers 257

Appendix H. Distribution List 259

Appendix I. Acronyms and Glossary 269
Contents

iv Grasshopper Environmental Impact Statement
Preface

Grasshopper Environmental Impact Statement v

Preface

Several changes to assist readers have been made from the draft to 

this Final Rangeland Grasshopper and Mormon Cricket Suppression 

Program Environmental Impact Statement (EIS). This document has 

two sections as follows: 

◆ The first section consists of chapters 1 through 6, and the 

references cited in those chapters are listed in chapter 7. 

◆ The second section contains the appendices. Appendix A 

provides additional background information, appendix B is an 

environmental risk assessment, and appendix C is the 

environmental fate and transport modeling. The references cited 

in those appendices are listed in appendix D. Appendix F has 

been added and contains the public comments received by the 

Animal and Plant Health Inspection Service (APHIS) on the draft 

EIS as well as APHIS’ responses to those comments. 
Preface

vi Grasshopper Environmental Impact Statement

FIGURE 1-1: Grasshopper Control - circa 1930s—Spreading bait by hand (Photo Credit USDA-APHIS)
Executive Summary

Grasshopper Environmental Impact Statement 1

Executive Summary

This final programmatic environmental impact statement (EIS) 

describes actions available to the United States Department of 

Agriculture (USDA), Animal and Plant Health Inspection Service 

(APHIS) to suppress grasshopper and Mormon cricket populations 

that have reached a level of economic infestation on rangeland in the 

17 Western States.1 This EIS examines the environmental effects of 

two suppression alternatives that use insecticides and a no action 

alternative.

Rangeland is a complex ecosystem, and grasshoppers are a natural 

part of rangeland ecosystems. (The term “grasshoppers” in this 

document refers to both grasshoppers and Mormon crickets unless 

differentiation is needed.) Rangeland is also an important agricultural 

resource that is used mainly for livestock production. In some years, 

grasshoppers become serious pests when populations reach high 

densities. These outbreaks can destroy rangeland forage and 

devastate rangeland habitats.

There are rangeland management actions that are intended to prevent 

or drastically reduce grasshopper outbreaks. While APHIS can 

provide technical assistance and expertise regarding grasshopper 

management actions, the responsibility for implementing land 

management practices lies with Federal, State, and private land 

managers. Therefore, management practices are not available for 

APHIS to implement and are not analyzed in this EIS.

Grasshopper populations may build up to levels of economic 

infestation despite even the best land management and other efforts to 

prevent outbreaks. At such a time, a rapid and effective response may 

be requested and needed to reduce the destruction of rangeland 

vegetation, or in some cases, to also prevent grasshopper migration to 

cropland adjacent to rangeland. This EIS analyzes the alternatives 

available to APHIS when a Federal land management agency or State 

agriculture department (on behalf of a State, a local government, or a 

private group or individual) requests APHIS to suppress economically 

damaging grasshopper populations. APHIS is authorized under the 

Plant Protection Act (PPA) (7 United States Code (U.S.C.) § 7701 et 

seq.) to protect rangeland from economic infestations of grasshoppers. 

Purpose of and Need for the Proposed Action

This environmental impact statement (EIS) is prepared in accordance 

with the requirements under the National Environmental Policy Act of 

1969 (NEPA) (42 U.S.C. § 4321 et seq.) and the NEPA procedural 

requirements promulgated by the Council on Environmental Quality, 

1 Arizona, California, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, 

Oklahoma, Oregon, South Dakota, Texas, Utah, Washington, and Wyoming.
Executive Summary

2 Grasshopper Environmental Impact Statement

USDA, and APHIS. This document considers the potential for 

environmental impacts from APHIS grasshopper suppression 

programs in all or part of 17 Western States. 

Rather than a specific proposed action, this EIS analyzes 

environmental impacts associated with programmatic actions related 

to grasshopper suppression. These environmental impacts are based 

on new information and technological advances that have occurred 

since the completion of the Rangeland Grasshopper Cooperative 

Management Program, Final Environmental Impact Statement—1987. 

This programmatic document contains information that can be used 

by APHIS and Federal land management agencies when preparing the 

NEPA documentation for their proposed actions. The methods for 

using this information in such documents include adoption, 

combining, incorporation by reference, and tiering (see chapter 1).

Alternatives Available to APHIS to Protect Rangeland From 

Grasshopper Outbreaks

APHIS conducts surveys for grasshopper populations on rangeland in 

the Western United States, provides technical assistance on 

grasshopper management to land owners/managers, and 

cooperatively suppresses grasshoppers when direct intervention is 

requested and deemed necessary.

The need for rapid and effective suppression of grasshoppers when an 

outbreak occurs limits the options available to APHIS. The application 

of an insecticide within all or part of the outbreak area is the response 

available to APHIS to rapidly suppress or reduce (but not eradicate) 

grasshopper populations and effectively protect rangeland. The 

following alternatives are available to APHIS and analyzed in this EIS.

Alternative 1: No Action 

Under Alternative 1, APHIS would not fund or participate in any 

program to suppress grasshopper infestations. Some Federal land 

management agencies, State agriculture departments, local 

governments, or private groups or individuals would likely conduct 

their own suppression programs against grasshoppers. 

Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage

Alternative 2 is generally the approach that APHIS has used for many 

years. The insecticide APHIS would consider under this alternative 

includes carbaryl, diflubenzuron, and malathion. Carbaryl and 

malathion are insecticides that have traditionally been used by APHIS. 

The insect growth regulator, diflubenzuron, is also included in this 
Executive Summary

Grasshopper Environmental Impact Statement 3

alternative. Applications would cover all treatable sites within the 

infested area (total or blanket coverage) per label directions. The 

application rate analyzed under this alternative are as follows: 

◆ 16 fluid ounces (0.50 pound active ingredient (lb a.i.)) of carbaryl 

spray per acre, 

◆ 10 pounds (0.50 lb a.i.) of 5 percent carbaryl bait per acre,

◆ 1.0 fluid ounce (0.016 lb a.i.) of diflubenzuron per acre, or

◆ 8 fluid ounces (0.62 lb a.i.) of malathion per acre.

Alternative 3: Reduced Agent Area Treatments (RAATs)

Alternative 3 is a recently developed grasshopper suppression method 

in which the rate of insecticide is reduced from conventional levels, 

and treated swaths are alternated with swaths that are not directly 

treated. The RAATs strategy relies on the effects of an insecticide to 

suppress grasshoppers within treated swaths while conserving 

grasshopper predators and parasites in swaths not directly treated. 

Either the insecticide carbaryl, diflubenzuron, or malathion would be 

considered under this alternative at the following application rate:

◆ 8 fluid ounces (0.25 lb a.i.) of carbaryl spray per acre, 

◆ 10 pounds (0.20 lb a.i.) of 2 percent carbaryl bait per acre,

◆ 0.75 fluid ounce (0.012 lb a.i.) of diflubenzuron per acre, or

◆ 4 fluid ounces (0.31 lb a.i.) of malathion per acre.

The area not directly treated (untreated) under the RAATs approach is 

not standardized. In the past, the area infested with grasshoppers 

that remains untreated has ranged from 20 to 67 percent. This EIS 

analyzed the reduced pesticide application rates associated with the 

RAATs approach, but assumed pesticide coverage on 100 percent of 

the area because there is no way to predict in this EIS how much area 

will actually be left untreated. 

Rather than suppress grasshopper populations to the greatest extent 

possible, the goal of this alternative is to suppress grasshopper 

populations to a desired level. 

Environmental Consequences

Alternative 1: No Action

Under Alternative 1, APHIS would not fund or participate in any 

program to suppress grasshoppers infestations. Despite 

implementing the best land management practices, Federal land 

management agencies, State agriculture departments, local 

governments, or private groups or individuals may not effectively 
Executive Summary

4 Grasshopper Environmental Impact Statement

combat outbreaks in a coordinated effort. In these situations, 

grasshopper outbreaks could develop and spread unimpeded. 

Unsuppressed outbreaks can destroy rangeland forage, devastate 

rangeland habitats, threaten crops, and become a public nuisance.

Another potential scenario, if APHIS does not participate in any 

grasshopper suppression programs, is that some Federal land 

management agencies, State agriculture departments, local 

governments, or private groups or individuals may attempt to conduct 

widespread grasshopper programs. Without the technical assistance 

and program coordination that APHIS can provide to grasshopper 

programs, it is possible that a large amount of insecticides, including 

those APHIS considers too environmentally harsh but labeled for 

rangeland use, could be applied, reapplied, and perhaps misapplied in 

an effort to suppress or even locally eradicate grasshopper 

populations.

Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage 

Under Alternative 2, APHIS would participate in grasshopper 

programs with the option of using one of the insecticides carbaryl, 

diflubenzuron, or malathion, depending upon the various factors 

related to the grasshopper outbreak and the site-specific 

characteristics. The use of an insecticide would occur at the 

conventional rates. With only rare exceptions, APHIS would apply a 

single treatment in an outbreak year that would blanket affected 

rangeland areas in an attempt to suppress grasshopper outbreak 

populations by a range of 35 to 98 percent, depending upon the 

insecticide used. 

Treatments made during grasshopper outbreaks, when densities can 

be 60 or more per square meter, still leave a number of grasshoppers 

that may be higher than the number of grasshoppers found in a 

normal year. Detailed information about the consequences of 

insecticide applications under this alternative can be found in chapter 

5, Environmental Consequences, and in appendix B. 

Carbaryl: Carbaryl is of moderate acute oral toxicity to humans. The 

mode of toxic action of carbaryl occurs through inhibition of 

acetylcholinesterase (AChE) function in the nervous system. This 

inhibition is reversible over time if exposure to carbaryl ceases. EPA 

has classified carbaryl as a “possible human carcinogen.” However, it 

is not considered to pose any mutagenic or genotoxic risk. 

Potential exposures to the general public from conventional 

application rates are infrequent and of low magnitude. These low 

exposures to the public pose no risk of direct toxicity, carcinogenicity, 
Executive Summary

Grasshopper Environmental Impact Statement 5

neurotoxicity, genotoxicity, reproductive toxicity, or developmental 

toxicity. The potential for adverse effects to workers are negligible if 

proper safety procedures are followed, including wearing the required 

protective clothing. Carbaryl has been used routinely in other 

programs with no reports of adverse health effects. Therefore, routine 

safety precautions are expected to provide adequate worker health 

protection. 

Carbaryl is of moderate acute oral toxicity to mammals. Carbaryl 

applied at Alternative 2 rates is unlikely to be directly toxic to upland 

birds, mammals, or reptiles. Field studies have shown that carbaryl 

applied as either ultra-low-volume (ULV) spray or bait at Alternative 2 

rates posed little risk to killdeer, vesper sparrows, or golden eagles in 

the treatment areas. AChE inhibition at 40 to 60 percent can affect 

coordination, behavior, and foraging ability in vertebrates. Multi-year 

studies conducted at several grasshopper treatment areas have shown 

AChE inhibition at levels of no more that 40 percent with most at less 

than 20 percent. Carbaryl is not subject to significant 

bioaccumulation due to its low water solubility and low octanol-water 

partition coefficient.

Carbaryl will most likely affect nontarget insects that are exposed to 

ULV carbaryl spray or that consume carbaryl bait within the 

grasshopper treatment area. Field studies have shown that affected 

insect populations can recover rapidly and generally have suffered no 

long-term effects, including some insects that are particularily 

sensitive to carbaryl, such as bees. The use of carbaryl in bait form 

generally has considerable environmental advantages over liquid 

insecticide applications: bait is easier than liquid spray applications 

to direct toward the target area, bait is more specific to grasshoppers, 

and bait affects fewer nontarget organisms than sprays. 

Should carbaryl enter water, there is the potential to effect the aquatic 

invertebrate assemblage, especially amphipods. Field studies with 

carbaryl concluded that there was no biologically significant effect on 

aquatic resources, although invertebrate downstream drift increased 

for a short period after treatment due to toxic effects. Carbaryl is 

moderately toxic to most fish.

Diflubenzuron: The acute oral toxicity of diflubenzuron formulations to 

humans ranges from very slight to slight. The most sensitive indicator 

of exposure and effects of diflubenzuron in humans is the formation of 

methemoglobin in blood. 

Potential exposures to the general public from Alternative 2 rates are 

infrequent and of low magnitude. These low exposures to the public 

pose no risk of methemoglobinemia, direct toxicity, neurotoxicity, 
Executive Summary

6 Grasshopper Environmental Impact Statement

genotoxicity, reproductive toxicity, or developmental toxicity. Potential 

worker exposures are higher than the general public but are not 

expected to pose any risk of adverse health effects. 

Because diflubenzuron is a chitin inhibitor that disrupts insects from 

forming their exoskeleton, organisms without a chitinous exoskeleton, 

such as mammals, fish, and plants are largely unaffected by 

diflubenzuron. In addition, adult insects, including wild and cultivated 

bees, would be mostly unaffected by diflubenzuron applications. 

Among birds, nestling growth rates, behavior data, and survival of wild 

American kestrels in diflubenzuron treated areas showed no 

significant differences among kestrels in treated areas and untreated 

areas. The acute oral toxicity of diflubenzuron to mammals ranges 

from very slight to slight. Little, if any, bioaccumulation of 

diflubenzuron would be expected. 

Diflubenzuron is most likely to affect immature terrestrial insects and 

early life stages of aquatic invertebrates. While this would reduce the 

prey base within the treatment area for organisms that feed on 

insects, adult insects, including grasshoppers, would remain available 

as prey items. Many of the aquatic organisms most susceptible to 

diflubenzuron are marine organisms that would not be exposed to 

rangeland treatments. Freshwater invertebrate populations would be 

reduced if exposed to diflubenzuron, but these decreases would be 

expected to be temporary given the rapid regeneration time of many 

aquatic invertebrates.

Malathion: Malathion is of slight acute oral toxicity to humans. The 

mode of toxic action of malathion occurs through inhibition of AChE 

function in the nervous system. Unlike carbaryl, AChE inhibition 

from malathion is not readily reversible over time if exposure ceases. 

However, strong inhibition of AChE from malathion occurs only when 

chemical oxidation results in formation of the metabolite malaoxon. 

Human metabolism of malathion favors hydroxylation and seldom 

produces much malaoxon. 

Potential exposures to the general public from conventional 

application rates are infrequent and of low magnitude. These low 

exposures to the public pose no risk of direct toxicity, neurotoxicity, 

genotoxicity, reproductive toxicity, or developmental toxicity. Potential 

worker exposures are higher, but still have little potential for adverse 

health effects except under accidental scenarios. Malathion has been 

used routinely in other programs with no reports of adverse health 

effects. Therefore, routine safety precautions are expected to continue 

to provide adequate protection of worker health.
Executive Summary

Grasshopper Environmental Impact Statement 7

EPA has recently reviewed the potential for carcinogenic effects from 

malathion. EPA’s classification describes malathion as having 

“suggestive evidence of carcinogenicity, but not sufficient to assess 

human carcinogenic potential.” This indicates that any carcinogenic 

potential of malathion cannot be quantified based upon EPA’s weight 

of evidence determination in this classification. The low exposures to 

malathion from program applications would not be expected to pose 

carcinogenic risks to workers or the general public. 

Malathion is of slight acute oral toxicity to mammals. There is little 

possibility of toxicity-induced mortality of upland birds, mammals, or 

reptiles, and no direct toxic effects have been observed in field studies. 

Malathion is not directly toxic to vertebrates at the concentrations 

used for grasshopper suppression, but it may be possible that 

sublethal effects to nervous system functions caused by AChE 

inhibition may lead directly to decreased survival. AChE inhibition at 

40 to 60 percent affects coordination, behavior, and foraging ability in 

vertebrates. Multi-year studies at several grasshopper treatment 

areas have shown AChE inhibition at levels of no more than 40 

percent with most at less than 20 percent. Field studies of birds 

within malathion treatment areas showed that, in general, the total 

number of birds and bird reproduction were not different from 

untreated areas. Malathion does not bioaccumulate.

Malathion will most likely affect nontarget insects within a treatment 

area. Large reductions in some insect populations would be expected 

after a malathion treatment under Alternative 2. While the number of 

insects would be diminished, there would be some insects remaining. 

The remaining insects would be available prey items for insectivorous 

organisms, and those insects with short generation times may soon 

increase.

Malathion is highly toxic to some fish and aquatic invertebrates; 

however, malathion concentrations in water, as a result of 

grasshopper treatments, are expected to be low presenting a low risk 

to aquatic organisms, especially those organisms with short 

generation times.

Alternative 3: Reduced Agent Area Treatments (RAATs)

Under Alternative 3, either the insecticide carbaryl, diflubenzuron, or 

malathion would be used at a reduced rate and over reduced areas of 

coverage. Rarely would APHIS apply more than a single treatment to 

an area per year. The maximum insecticide application rate under the 

RAATs strategy is reduced 50 percent from the conventional rates for 

carbaryl and malathion and 25 percent from the Alternative 2 rate for 

diflubenzuron. Although this strategy involves leaving variable 

amounts of land not directly treated, the risk assessment for this 
Executive Summary

8 Grasshopper Environmental Impact Statement

document (appendix B) assumed 100 percent area coverage because 

not all possible scenarios could be analyzed. However, when utilized 

in grasshopper suppression, the amount of untreated area in RAATs 

often ranges from 20 to 67 percent of the total infested area but can be 

adjusted to meet site-specific needs. 

Applying the RAATs strategy during grasshopper outbreaks, when 

densities can be 60 or more per square meter, still leave a density of 

grasshoppers that may be higher than the density of grasshoppers 

found in a normal year. Grasshopper mortality using a RAATs 

strategy has been shown to range from 75 to 95 percent. Detailed 

information about the consequences of insecticide applications under 

this alternative can be found in chapter 5, Environmental 

Consequences, and appendix B. 

Carbaryl: Potential exposures to the general public and workers from 

RAATs application rates are lower than those from conventional 

application rates, and adverse effects decrease commensurately with 

decreased magnitude of exposure. These low exposures to the public 

pose no risk of direct toxicity, carcinogenicity, neurotoxicity, 

genotoxicity, reproductive toxicity, or developmental toxicity. The 

potential for adverse effects to workers is negligible if proper safety 

procedures are followed, including wearing the required protective 

clothing. Routine safety precautions are expected to provide adequate 

protection of worker health at the lower application rates under 

RAATs. 

Carbaryl will most likely affect nontarget insects that are exposed to 

liquid carbaryl or that consume carbaryl bait. While carbaryl applied 

at a RAATs rate will reduce susceptible insect populations, the 

decrease will be less than under Alternative 2 rates. Carbaryl ULV 

applications applied in alternate swaths have been shown to affect 

terrestrial arthropods less than malathion applied in a similar fashion. 

Direct toxicity of carbaryl to birds, mammals, and reptiles is unlikely 

in swaths treated with carbaryl under a RAATs approach. Carbaryl 

bait also has minimal potential for direct effects on birds and 

mammals. Field studies indicated that bee populations did not 

decline after carbaryl bait treatments, and American kestrels were 

unaffected by bait applications made at a RAATs rate. Using 

alternating swaths will furthermore reduce adverse effects because 

organisms that are in untreated swaths will be mostly unexposed to 

carbaryl.
Executive Summary

Grasshopper Environmental Impact Statement 9

Carbaryl applied at a RAATs rate has the potential to affect 

invertebrates in aquatic ecosystems. However, these affects would be 

less than effects expected under Alternative 2. Fish are not likely to be 

affected at any concentrations that could be expected under 

Alternative 3.

Diflubenzuron: Potential exposures and adverse effects to the general 

public and workers from RAATs application rates are commensurately 

less than conventional application rates. These low exposures to the 

public pose no risk of methemoglobinemia, direct toxicity, 

neurotoxicity, genotoxicity, reproductive toxicity, or developmental 

toxicity. Potential worker exposures pose negligible risk of adverse 

health effects. 

Because diflubenzuron is a chitin inhibitor that disrupts insects from 

forming their exoskeleton, organisms without a chitinous exoskeleton, 

such as mammals, fish, and plants are largely unaffected by 

diflubenzuron. Diflubenzuron exposure at Alternative 3 rates are not 

hazardous to terrestrial mammals, birds, and other vertebrates. 

Insects in untreated swaths would have little to no exposure, and 

adult insects in the treated swaths are not susceptible to 

diflubenzuron’s mode of action. The indirect effects to insectivores 

would be negligible as not all insects in the treatment area will be 

affected by diflubenzuron. 

Diflubenzuron is most likely to affect immature terrestrial insects and, 

if it enters water, will affect early life stages of aquatic invertebrates. 

While diflubenzuron would reduce insects within the treatment area, 

insects in untreated swaths would have little to no exposure. Many of 

the aquatic organisms most susceptible to diflubenzuron are marine 

organisms that would not be exposed to rangeland treatments. 

Freshwater invertebrate populations would be reduced if exposed to 

diflubenzuron, but these decreases may be temporary given the rapid 

regeneration time of many aquatic invertebrates.

Malathion: Potential exposures to the general public and workers from 

RAATs application rates are of a commensurately lower magnitude 

than conventional rates. These low exposures to the public pose no 

risk of direct toxicity, neurotoxicity, genotoxicity, reproductive toxicity, 

or developmental toxicity. 

Potential risks to workers are negligible if proper safety procedures are 

adhered to, including the use of required protective clothing. 

Malathion has been used routinely in other programs with no reports 

of adverse health effects. The low exposures to malathion from 

program applications are not expected to pose any carcinogenic risks 

to workers or the general public. 
Executive Summary

10 Grasshopper Environmental Impact Statement

Malathion applied at a RAATs rate will cause mortalities to susceptible 

insects. Organisms in untreated areas will be mostly unaffected. 

Field applications of malathion at a RAATs rate and applied in 

alternate swaths resulted in less reduction in nontarget organisms 

than would occur in blanket treatments. Birds in RAATs areas were 

not substantially affected. Should malathion applied at RAATs rates 

enter water, it is most likely to affect aquatic invertebrates. However, 

these effects would soon be compensated for by the surviving 

organisms given the rapid generation time of most aquatic 

invertebrates and the rapid degradation of malathion in most water 

bodies.

Species of Concern:This EIS has examined the effects of grasshopper 

suppression programs on three specific species, or groups of species, 

that are of concern in the Western United States. These species or 

groups were selected as examples of species that are found on 

rangeland habitats.

Sage grouse, which is a species of concern to land management 

agencies, has been in a state of decline throughout most of its entire 

range. Sage grouse can be present in grasshopper suppression areas, 

and grasshoppers can be a food item for sage grouse chicks. There is 

little likelihood that the insecticide APHIS would use to suppress 

grasshoppers would be directly or indirectly toxic to sage grouse. 

Treatments would typically not reduce the number of grasshoppers 

below levels that are present in nonoutbreak years. If grasshoppers 

were in short supply, sage grouse chicks may consume other insects. 

Grasshopper suppression would also conserve rangeland vegetation 

that may be used by sage grouse.

There are numerous biological control agents used to control invasive 

plants on Western rangeland. For example, species of flea beetles are 

used to control leafy spurge that threatens many rangeland habitats. 

Some of these same rangeland habitats may be locations where the 

grasshopper program is conducted, thus these biological control 

agents would likely be exposed to the insecticide used for grasshopper 

control. Field studies on the effects of grasshopper suppression 

programs on flea beetles demonstrated that after an initial decline in 

flea beetle populations immediately following after a grasshopper 

treatment, flea beetle populations recovered to pretreatment levels 

after 1 year.

Populations of threatened or endangered species in grasshopper 

suppression areas would be at a greater risk, because of the small 

number of individuals. Studies on two federally listed endangered fish 

species concluded that carbaryl and malathion posed no greater 

hazard to those endangered species than to species not listed as 

endangered. A programmatic consultation on the threatened and 
Executive Summary

Grasshopper Environmental Impact Statement 11

endangered species and their habitats that occur in the 17 Western 

States is presently underway. Protective measures will be developed 

that, when implemented, will ensure that threatened and endangered 

species and their habitats will not be adversely affected.

Cumulative Impacts: As this is a programmatic environmental 

document, the cumulative impacts of the program on the environment 

would best be considered when a site-specific environmental 

document is prepared for a particular grasshopper program. 

Grasshopper programs could occur on rangelands in any of the 17 

Western States. The location, magnitude, and characteristics of a 

treatment area where APHIS is requested to carry out an insecticide 

program would need to be defined in order to determine the past, 

present, and foreseeable future actions that have or will occur in the 

program area. 

Socioeconomic Impacts: This EIS considers the qualitative social and 

economic linkages regarding action taken or not taken against 

grasshopper outbreaks. Livestock owners, crop growers, and the 

general public (consumers of agricultural products) are among the 

social groups that, in various ways, would be economically adversely 

impacted under the No Action alternative. These socioeconomic 

impacts could result from the extensive damage to rangelands and 

associated resources from grasshopper outbreaks and the availability 

of funding by private individuals and government agencies to carry out 

efforts against outbreaks.

Under Alternative 2, socioeconomic impacts would be realized from 

the use of insecticides at conventional rates and complete area 

coverage. The socioeconomic impacts under this alternative would 

result from the timing and success of the treatments, the potential for 

adverse or beneficial environmental impacts, and the cost of the 

treatments.

Under Alternative 3, the socioeconomic impacts would be realized 

from the use of insecticides at reduced rates and reduced area 

coverage. The socioeconomic impacts would result from the timing 

and success of treatment methods used, the potential for adverse or 

beneficial environmental impacts from the reduced use of insecticides 

and area treated, and the decreased cost and greater economic 

benefits from using insecticide at reduced rates and area coverage.

Other Environmental Considerations: This EIS also addresses 

concerns about program actions on the following environmental 

considerations: environmental justice, the protection of children, 

cultural resources and events, endangered species, and monitoring.
Executive Summary

12 Grasshopper Environmental Impact Statement

In accordance with Executive Order (E.O.) 12898, APHIS will consider 

the potential for disproportionately high and adverse human health or 

environmental effects on minority populations and low-income 

populations for any of its actions related to grasshopper suppression 

programs. The appropriate environmental documentation for a 

site-specific program will include environmental justice 

considerations.

APHIS has also developed agency guidance for its programs to follow 

to ensure the protection of children as required by E.O. 13045. 

Information about the exposure risks to children from carbaryl, 

diflubenzuron, and malathion used for grasshopper suppression is 

discussed in appendix B of this EIS. The risk assessment concluded 

that the likelihood of children being exposed to insecticides used for 

grasshopper suppression is very slight and that no disproportionate 

adverse effects to children are anticipated over the negligible effects to 

the general population. 

The potential for impacts that could occur from grasshopper 

suppression activities to cultural and historical sites and artifacts, as 

well as cultural events, will be considered in site-specific 

environmental documents. In addition, APHIS will confer with land 

managers and tribal authorities to protect cultural resources and 

events.

In order to comply with the Endangered Species Act of 1973, APHIS is 

preparing a biological assessment that will be used in a programmatic 

consultation with the Fish and Wildlife Service and the National 

Marine Fisheries Service. The consultation process will address the 

impacts of grasshopper suppression on federally listed (and proposed) 

species and their habitats that occur in all or part of the 17 Western 

States. Through this process protection measures will be developed 

that, when implemented, will ensure that grasshopper suppression 

activities will not adversely affect those species or their habitats.

Monitoring could involve an evaluation of the efficacy of the 

grasshopper treatments, the safety of program personnel, and 

environmental monitoring to assure that insecticides are applied in 

accordance with the labels and sensitive sites and species are 

protected. If environmental monitoring is conducted, a monitoring 

plan will describe the types of samples to be collected. Additional 

information regarding the effects of grasshopper suppression 

programs on the environment can be found in the Grasshopper 

Integrated Pest Management Program User Handbook that is available 

at: www.sidney.ars.usda.gov/grasshopper/index.htm.
Executive Summary

Grasshopper Environmental Impact Statement 13

TABLE 1-1: Road warning sign (Photo Credit - USDA-APHIS)
Executive Summary

14 Grasshopper Environmental Impact Statement
I. Purpose of and Need for the Proposed Action

Grasshopper Environmental Impact Statement 15

I. Purpose of and Need for the Proposed Action

Grasshoppers and Mormon crickets are part of rangeland ecosystems, 

serving as a food source for wildlife and playing an important role in 

nutrient cycling. (The term “grasshopper” used in this environmental 

impact statement (EIS) refers to both grasshoppers and Mormon 

crickets, unless differentiation is necessary.) Many grasshoppers are 

strong fliers, often moving from rangeland to cropland and other 

vegetation where they can cause severe damage (Pfadt, 1994). Mormon 

crickets, although flightless, are also capable of moving long distances 

in large groups. (For more information about the biology of 

grasshoppers, see chapter 2, section D.)

Grasshoppers have a potential for sudden and explosive population 

increases, resulting in outbreaks. Such outbreaks produce high 

densities of grasshoppers and intense competition for the available 

food supply, which may cause damage to rangeland and nearby crops. 

Loss of wildlife habitats also may result from outbreaks. (For more 

information about damage caused by grasshoppers, see chapter 2, 

section E.) To date, there are no simple ecological explanations to 

predict grasshopper outbreaks (Belovsky et al., 1996). 

Despite the best land management efforts to prevent outbreaks, 

grasshopper populations may build to levels of economic infestation 

where direct intervention may be the most viable option to suppress 

grasshopper populations. Not all grasshopper species are damaging; 

therefore, action to protect rangeland resources is not always required 

when grasshopper populations increase. When a rapid and effective 

response to a developing grasshopper outbreak is required, a Federal 

land management agency or a State agriculture department (on behalf 

of a State, a local government, or a private group or individual) may 

request assistance from the Animal and Plant Health Inspection 

Service (APHIS) to suppress rangeland grasshopper populations. 

APHIS has the authority, according to the Plant Protection Act (PPA) (7 

United States Code (U.S.C.) § 7701 et seq.) and subject to the available 

funds, to treat Federal, State, or private lands that have economic 

infestations of grasshoppers. (See footnote 2 in this chapter for a 

definition of economic infestation.)

The U.S. Department of Agriculture (USDA), APHIS, has prepared this 

EIS, Rangeland Grasshopper and Mormon Cricket Suppression 

Program, Final Environmental Impact Statement, to comply with the 

National Environmental Policy Act of 1969 (NEPA), as amended (42 

U.S.C. § 4321et seq.), the Council on Environmental Quality (CEQ) 

Regulations for Implementing the Procedural Provisions of NEPA (40 

Code of Federal Regulations (CFR) §§ 1500–1508), the USDA NEPA 

regulations (7 CFR Part 1b), and the APHIS NEPA regulations (7 CFR 

Part 372).1 This EIS analyzes the potential for impacts on the human 
I. Purpose of and Need for the Proposed Action

16 Grasshopper Environmental Impact Statement

environment from APHIS’ use of any of three insecticides analyzed in 

this EIS to protect rangeland from economically damaging 

grasshopper infestations. 

The CEQ NEPA implementing regulations state that an EIS shall 

“briefly specify the underlying purpose and need to which the agency 

is responding in proposing the alternatives including the proposed 

action” (40 CFR § 1502.13). This EIS does not respond to a new action 

or proposal but looks at new information and technological advances 

to a broad program for treating grasshopper infestations when 

site-specific action is required.

New information and technological advances in the use of insecticides 

for grasshopper infestations have occurred since the preparation of 

the Rangeland Grasshopper Cooperative Management Program, Final 

Environmental Impact Statement—1987 (1987 EIS) (see appendix A 

for information about grasshopper programs and the 1987 EIS). There 

is a need to generally consider the potential for environmental impacts 

from the program and proposed changes to the program. The CEQ 

NEPA implementing regulations (40 CFR § 1502.4(c)) state “When 

preparing statements on broad actions. . . , agencies may find it useful 

to evaluate the proposal(s) in . . . the following way: . . . (3) By stage or 

technological development including federal or federally assisted 

research, development or demonstration programs for new 

technologies which, if applied, could significantly affect the quality of 

the human environment. Statements shall be prepared on programs 

and shall be available before the program has reached a stage of 

investment or commitment to implementation likely to determine 

subsequent development or restrict later alternatives.” The analysis of 

the treatments for grasshopper infestations needs to be updated based 

on new information and technological advances on the insecticides 

used and proposed for use and the methods by which the insecticides 

can be applied. 

According to the authority delegated under section 417 of the PPA (7 

U.S.C. § 7717), APHIS may be requested to work in conjunction with a 

Federal land management agency or a State agriculture department 

(on behalf of a State, a local government, or a private group or 

individual) to treat areas that are infested with grasshoppers when 

they reach a level of economic infestation.1 In satisfying this mandate, 

APHIS may be asked to carry out actions using insecticides to reduce 

grasshopper populations. The analysis of the potential for 

1 This document is also intended to satisfy the order of the United States District Court for the District of Idaho, dated 

January 9, 2001, dismissing a case (Civ. No. 00-337-E-BLW) pursuant to the Stipulation of the parties calling, in part, 

for APHIS to “issue a revised and updated Environmental Impact Statement for the Rangeland Grasshopper Cooperative Management Program.” See Rule 41(a) STIPULATION TO DISMISS, the ORDER OF DISMISSAL, as well as the 

documented history of the proceeding, at http://www.id.uscourts.gov/wconnect/

wc.dll?usdc_racer~get_case_jb~4:0-cv-337~~ALL+DOCUMENTS~~PUID+NOBILL.
I. Purpose of and Need for the Proposed Action

Grasshopper Environmental Impact Statement 17

environmental impacts of APHIS’ suppression programs includes a 

new insecticide and technological advances for the purpose of 

responding to grasshopper outbreaks.

This programmatic EIS closely follows the recommended standard 

format for this type of environmental document, as provided by CEQ 

NEPA implementing regulations 40 CFR §§ 1500–1508. This EIS 

discusses the (1) purpose of and need for the action, (2) alternatives 

considered, (3) affected environment, and (4) potential for 

environmental impacts from the alternatives. This EIS also includes 

other required sections, such as references used; a list of preparers; a 

list of agencies, organizations, and persons to whom copies of the EIS 

was sent; and an index. In adhering to CEQ’s guidelines, an attempt 

has been made to keep the required sections concise (not 

encyclopedic) and written so that both the decision makers and the 

public can readily understand this EIS (40 CFR § 1502.10).

Readers who may have questions that are relevant to rangeland 

grasshopper programs but that are outside the scope of this EIS 

should refer to appendix A. Appendix A includes supplemental 

information to this EIS, such as an historical overview of grasshopper 

programs in the United States, information about cooperator roles in 

grasshopper programs, a discussion about the difference in 

grasshopper management and suppression programs, and alternative 

approaches to grasshopper management that are outside the scope of 

this EIS. Readers who may want more technical information about the 

use of insecticides to suppress rangeland grasshoppers should refer to 

appendix B. Appendix B contains the detailed and technical risk 

assessment that supports chapter 5, Environmental Consequences. 

Additionally, appendix C has been added to this EIS. Appendix C is 

the environmental fate and transport modeling conducted on the three 

insecticides APHIS may use during a grasshopper program. 

This EIS includes analysis of those activities that APHIS is authorized 

to conduct, which includes the conduct of surveys and the use of 

insecticides for the suppression of grasshoppers. APHIS conducts 

1 The “level of economic infestation” is a measurement of the economic losses caused by a particular 

population level of grasshoppers or Mormon crickets to the infested rangeland. This value is determined 

on a case-by-case basis with knowledge of many factors including, but not limited to, the following: economic use of available forage or crops; grasshopper species, age, and density present; rangeland productivity and composition; accessibility and cost of alternative forage; and weather patterns. In decision 

making, the level of economic infestation is balanced against the cost of treating to determine an “economic threshold” below which there would not be an overall economic benefit for the treatment. 

Short-term economic benefits accrue during the years of treatments, but additional long-term benefit may 

accrue and be considered in deciding the total value gained by a treatment. Additional losses to rangeland 

habitat and cultural and personal values (e.g., esthetics and cultural resources), although they may also 

be a part of decision making, are not part of the economic values in determining the necessity for treatment.
I. Purpose of and Need for the Proposed Action

18 Grasshopper Environmental Impact Statement

these activities at the request of a Federal land management agency or 

a State agriculture department (on behalf of a State, a local 

government, or a private group or individual). 

The NEPA implementing regulations address the issue of how other 

agencies may use this programmatic document. The most obvious way 

in which another Federal agency may use this document is through 

the technique known as “incorporate by reference.” “Agencies shall 

incorporate material into an environmental impact statement by 

reference when the effect will be to cut down on bulk without impeding 

agency and public review of the action. The incorporated material shall 

be cited in the statement and its content briefly described. . . .” (40 

CFR § 1502.21). There is also a technique known as “adoption,” under 

which “An agency may adopt a Federal draft or final environmental 

impact statement or portion thereof provided that the statement or 

portion thereof meets the standards for an adequate statement under 

these regulations.” (40 CFR § 1506.3). A Federal agency may also 

“combine” documents. In 40 CFR § 1506.4 it states that “Any 

environmental document in compliance with NEPA may be combined 

with any other agency document to reduce duplication and 

paperwork.” 

A last method is tiering (40 CFR §1502.20). “Agencies are encouraged 

to tier their environmental impact statements to eliminate repetitive 

discussions of the same issues and to focus on the actual issues ripe 

for decision at each level of environmental review (40 CFR § 1508.28). 

Whenever a broad environmental impact statement has been prepared 

(such as a programmatic or policy statement) and a subsequent 

statement or environmental assessment is then prepared on an action 

included within the entire program or policy (such as a site specific 

action) the subsequent statement or environmental assessment need 

only summarize the issues discussed in the broader statement and 

incorporate discussions from the broader statement by reference and 

shall concentrate on the issues specific to the subsequent action. The 

subsequent document shall state where the earlier document is 

available (40 CFR § 1508.28).” 

This document is not restricted to the actions of a single agency; 

rather, it deals with a program, treating it by stage of technological 

development (40 CFR § 1502.4(c)(3)), in which other Federal agencies, 

States, or private citizens may cooperate, as needed, in more localized 

operations. 

This EIS supercedes the Rangeland Grasshopper Cooperative 

Management Program, Final Environmental Impact Statement—1987. 

The following table summarizes the similarities and differences 

between alternatives in the 1987 EIS and this EIS.
I. Purpose of and Need for the Proposed Action

Grasshopper Environmental Impact Statement 19

TABLE 1-1. Alternatives Analyzed in the 1987 and 2002 Grasshopper Environmental Impact 

Statements

1987 EIS

Alternative 1 - No Action

Alternative 2 - Chemical Controls

◆ ULV1

 Sprays

❖ Acephate: 0.094 lb a.i./acre2

❖ Carbaryl: 0.50 lb a.i./acre

❖ Malathion: 0.58 lb a.i./acre

◆ Bait

❖ Carbaryl:0.50 lb a.i./acre

Alternative 3 - Integrated Pest Management (IPM)

◆ ULV Sprays

❖ Acephate: 0.094 lb a.i./acre

❖ Carbaryl: 0.50 lb a.i./acre

❖ Malathion: 0.58 lb a.i./acre

◆ Bait 

❖ Carbaryl: 0.50 lb a.i./acre

◆ Biological Control Agents

◆ Combined Chemical/Biological Control Bait

◆ Other IPM strategies including: range management, database development and predictive modeling, environmental 

evaluation

2002 EIS

Alternative 1 - No Action

Alternative 2 - Insecticide Applications at Conventional Rates and Complete Area Coverage

◆ ULV Sprays 

❖ Carbaryl: 0.50 lb a.i./acre

❖ Diflubenzuron: 0.016 lb a.i./acre

❖ Malathion: 0.62 lb a.i./acre

◆ Bait

❖ Carbaryl: 0.50 lb a.i./acre

Alternative 3 - Reduced Agent Area Treatments (RAATs)

◆ ULV sprays applied onto 33 to 50% of treatment area, for example, application to 100-foot swaths alternating with 

100- to 200-foot untreated swaths 

❖ Carbaryl: 0.25 lb a.i./acre maximum

❖ Diflubenzuron: 0.012 lb a.i./acre maximum

❖ Malathion: 0.31 lb a.i./acre maximum

◆ Bait applied onto 33 to 50% of treatment area, for example, application to 100-foot swaths alternating with 100- to 

200-foot untreated swaths

❖ Carbaryl: 0.20 lb a.i./acre

1 Ultra-low-volume

2 Pound of active ingredient per acre
I. Purpose of and Need for the Proposed Action

20 Grasshopper Environmental Impact Statement
II. Background

Grasshopper Environmental Impact Statement 21

II. Background

A. Scope and Focus of This Environmental Impact Statement

On August 14, 2000, the Animal and Plant Health Inspection Service 

(APHIS) published in the Federal Register (FR) (65 FR 49533) a notice 

of its intent (appendix E) to prepare an environmental impact 

statement (EIS) relative to the agency’s activities to suppress 

rangeland grasshoppers and Mormon crickets (the term 

“grasshoppers” used in this document refers to both grasshoppers and 

Mormon crickets, unless differentiation is needed). This EIS is written 

to comply with the National Environmental Policy Act (NEPA) (42 

United States Code (U.S.C.) § 4321 et seq. and the Council on 

Environmental Quality’s NEPA implementing regulations (40 Code of 

Federal Regulations (CFR) §§ 1500–1508). It is designed to—

 1. examine the environmental effects of alternatives available to 

APHIS for the suppression of rangeland grasshoppers,

 2. inform the public about the environmental effects of APHIS’ 

rangeland grasshopper suppression activities, 

 3. be used for planning and decisionmaking, andp

 4. provide a document to which APHIS can tier site-specific 

analyses and environmental documents on grasshopper 

suppression activities. The information contained in the EIS can 

be used by Federal land management agencies when preparing 

their environmental documents. Federal land management 

agencies can adopt (§ 1506.3), combine (§ 1506.4), incorporate 

by reference (§ 1502.21), or tier (§ 1502.20) their activities to the 

data in this EIS.

Since the preparation of the Rangeland Grasshopper Cooperative 

Management Program, Final Environmental Impact Statement—1987, 

(1987 EIS) (USDA, APHIS, 1987b), new information and technological 

advances in insecticide treatments for grasshopper infestations have 

occurred. This EIS is a programmatic analysis that focuses 

specifically on insecticide treatments, current and proposed, for 

rangeland grasshopper programs. A rangeland grasshopper program 

could occur in any of the following 17 Western States: Arizona, 

California, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New 

Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Texas, 

Utah, Washington, and Wyoming. 
II. Background

22 Grasshopper Environmental Impact Statement

New Information 

and 

Technological 

Advances 

a. The Grasshopper Integrated Pest Management Program—The 

Grasshopper Integrated Pest Management (GHIPM) Program was 

established as a result of the 1987 EIS to study the feasibility of using 

integrated pest management (IPM) for managing grasshoppers. IPM 

includes biological control, chemical control, rangeland management, 

environmental monitoring and evaluation, modeling and population 

dynamics, and decision support tools. The results of the study have 

been provided to managers of public and private rangeland and are 

available at: www.sidney.ars.usda.gov/grasshopper/index.htm. The 

major objectives of the program were to (1) manage grasshopper 

populations in study areas, (2) compare the effectiveness of an IPM 

program for rangeland grasshoppers with the effectiveness of a 

standard chemical control program on a regional scale, (3) determine 

the effectiveness of early sampling in detecting incipient grasshopper 

infestations, (4) quantify short- and long-term responses of 

grasshopper populations to treatments, and (5) develop and evaluate 

new grasshopper suppression techniques that have minimum effects 

on nontarget species (Quinn et al., 2000). 

This program managed grasshopper populations with several available 

IPM techniques, described by the preferred alternative grasshopper 

management tactics outlined in the 1987 EIS. These techniques 

included (1) providing more detailed surveys of grasshopper 

populations so that small areas of infestations could be defined, (2) 

treating small areas of infestations (“hot spots”) rather than the larger 

areas of infestation traditionally treated, and (3) using control 

methods other than the conventional large-scale aerial applications of 

insecticidal sprays.

The program included data gathering during the first year, testing of 

range improvement techniques during a 5-year period after the data 

gathering, database development and predictive modeling, 

environmental evaluation, and economic research. The program was 

designed to provide data that would be used for improving APHIS’ 

ability to determine environmental effects of its use of insecticides and 

to refine its program operations accordingly. 

b. Acephate, Carbaryl, and Malathion—Since APHIS’ 1987 analysis of 

the potential for environmental impacts from the insecticides used for 

rangeland grasshopper control (USDA, APHIS, 1987b), updated 

information about the potential impacts from carbaryl and malathion 

on human health and nontarget species has become available. 

Specifically, information about the carcinogenicity, revised data on the 

reference doses of carbaryl and malathion, synergism of the program 

insecticides with other insecticides, and new information about 

carriers and inert ingredients used with the insecticides are analyzed 

in this EIS. The summary of the updated analysis on these 

insecticides can be found in chapter 5, Environmental Consequences, 
II. Background

Grasshopper Environmental Impact Statement 23

and an in-depth analysis of these insecticides can be found in 

appendix B. After the 1987 EIS was written, the registration of 

acephate for use on rangeland was not renewed; therefore, it can no 

longer be considered for use in rangeland grasshopper programs. 

d. Use of Diflubenzuron—Information about the potential use of the 

insecticide diflubenzuron for grasshopper infestations has become 

available. Diflubenzuron is an insect growth regulator that affects the 

formation of chitin which is essential for the development of insect 

exoskeletons. Although the mode of action for diflubenzuron is 

different than the mode of action for both carbaryl and malathion, the 

term “insecticide” used in this document refers to carbaryl, 

diflubenzuron, and malathion. 

Diflubenzuron primarily affects the immature stages of insects that 

need chitin to form cuticles or shells and, therefore, could be used 

during early growth stages of grasshoppers. The potential for APHIS’ 

use of diflubenzuron in grasshopper programs warrants analysis of its 

environmental impacts. The summary of the analysis on this 

insecticide can be found in chapter 5, Environmental Consequences, 

and an in-depth analysis of this insecticide can be found in appendix 

B.

e. Alternative Treatment Strategy—An alternative treatment strategy, 

referred to in this EIS as Reduced Agent Area Treatments (RAATs), for 

grasshopper suppression has been researched and developed. This 

strategy allows application of a treatment at a reduced rate and in 

alternating land swaths (thus using less insecticide). Therefore, this 

strategy results in conservation of nontarget biological resources, 

including predators and parasites of grasshoppers, in the areas not 

directly treated. In addition, this approach reduces the likelihood that 

insects will develop resistance to pesticides. This EIS analyzes RAATs 

as a new alternative for APHIS activities involving insecticide 

treatments in grasshopper programs. See chapter 3, Alternatives, for 

more information about this treatment strategy. 

2. Inform the 

Public

This EIS will provide the interested public with a programmatic 

analysis of the potential for environmental impacts from alternatives 

available to APHIS to suppress rangeland grasshopper infestations. 

3. Aid in 

Planning and 

Decision making

This EIS provides analyses of potential environmental impacts of 

alternatives based on new information and technological advances 

since 1987 and will serve as an aid to the program manager 

responsible for making a decision on a proposed action at the 

site-specific level. 
II. Background

24 Grasshopper Environmental Impact Statement

4. Provide a 

Basis for 

Site-specific 

Analysis

This EIS provides an overview of insecticides and approaches available 

to APHIS for grasshopper suppression and the potential for 

environmental impacts from their uses. This EIS can be used as a 

basis for tiering site-specific environmental analyses when APHIS is 

requested to suppress grasshopper outbreaks. In addition, Federal 

land management agencies can use this information when preparing 

their environmental documents. They can adopt, combine, incorporate 

by reference, or tier their activities to the data in this EIS.

B. APHIS’ Authority in Grasshopper Programs

APHIS has authority under the Plant Protection Act (PPA) (7 U.S.C. § 

7701) to take actions to control and minimize the economic, ecological, 

and human health impacts that harmful plant pests can cause. APHIS 

protects U.S. agriculture and forests and other natural resources from 

devastation that could occur from harmful pest species. 

Section 417 of the PPA (7 U.S.C. § 7717) authorizes efforts to minimize 

the economic impacts of grasshoppers. Section 417(a) states that 

subject to the availability of funds, the Secretary “shall carry out a 

program to control grasshoppers and Mormon crickets on all Federal 

lands to protect rangeland.” 

Section 417(c)(1) states that “Subject to the availability of funds 

pursuant to this section, on request of the administering agency or the 

agriculture department of an affected State, the Secretary, to protect 

rangeland, shall immediately treat Federal, State, or private lands that 

are infested with grasshoppers or Mormon crickets at levels of 

economic infestation, unless the Secretary determines that delaying 

treatment will not cause greater economic damage to adjacent owners 

of rangeland.” Section 417(c)(2) states, “OTHER PROGRAMS.—In 

carrying out this section, APHIS shall work in conjunction with other 

Federal, State, and private prevention, control, or suppression efforts 

to protect rangeland.” 

C. APHIS’ Role in Grasshopper Programs

APHIS conducts surveys for grasshopper populations on rangeland in 

the Western United States, provides technical assistance on 

grasshopper management to land owners/managers, and 

cooperatively suppresses grasshoppers when direct intervention is 

necessary. APHIS would only treat grasshoppers when requested and 

needed. In some cases APHIS rangeland treatments protect not only 

the rangeland, but reduce the likelihood that the grasshoppers will 

move from the rangeland onto crops and other lands that border 

rangeland. 

APHIS’ role in direct intervention of grasshopper infestations is to use 

insecticide treatments to reduce grasshopper populations to a level 

below that which constitutes an economic infestation. APHIS’ 

treatment alternatives analyzed in this EIS (see chapter 3, 
II. Background

Grasshopper Environmental Impact Statement 25

Alternatives) generally are carried out in conjunction with and 

complement Federal, State, and private efforts to prevent, control, or 

suppress grasshopper outbreaks. When a harmful grasshopper 

infestation reaches a level of economic infestation, direct intervention 

may be the most viable option to protect rangeland. 

APHIS surveys grasshopper populations. Survey information is used 

by APHIS and land managers/owners to assess whether treatments 

may be warranted. Treatments must be requested from a Federal land 

management agency or a State agriculture department (on behalf of a 

State, a local government, or a private group or individual) that has 

jurisdiction over the land before APHIS could begin to consider a 

treatment. Upon request, APHIS would then make a site visit to 

determine whether APHIS action is warranted by assessing various 

factors relevant to the infestation. These factors include, but are not 

limited to, the pest species, synchronous timing of the biological 

stages of the pest species, timing of treatment, cost benefits of 

conducting the action, and ecological considerations. Grasshopper 

surveys, conducted at certain times of the year, may show the 

potential for large grasshopper populations. Based on survey results, 

State and Federal officials may initiate early coordination of local 

programs and request APHIS assistance in a timely and effective 

cooperative effort. Appendix A contains more detailed information 

regarding grasshopper programs.

D. General Description and Biology of Target Organisms

Grasshoppers and crickets are closely related insects—both belong to 

the order Orthoptera. Mormon crickets are a flightless species of 

long-horned grasshopper. Grasshoppers occur throughout the North 

American continent and around the world; however, Mormon crickets 

are mostly found in the Great Basin and other areas of the Western 

United States. Nearly 400 species of grasshoppers are known to 

inhabit 17 Western States. Of these, approximately 20 or more 

species commonly cause damage to rangeland, grasses, and 

surrounding crops. Most of the economically damaging species are 

rather small or intermediate in size. Although as many as 15 to 45 

grasshopper species may be found in an area, only a few cause 

economic damage. However, when all the species are combined they 

can each provide a portion of the overall economic damage. It is very 

important to note that each species alone may not cause much 

damage but when combined can cause extensive damage.

Grasshoppers are relatively large insects with quite distinct 

appearances. Long-horned grasshoppers make up the family 

Tettigoniidae. 

Short-horned grasshoppers, also known as true grasshoppers, are 

named for their relatively short antennae and make up the family 

Acrididae. The Mormon cricket, also a member of the Tettigoniidae 
II. Background

26 Grasshopper Environmental Impact Statement

family, is classified as Anabrus simplex. Mormon crickets (actually 

wingless, long-horned grasshoppers) are included in this EIS because 

they have periodically caused extensive damage to lands in the 

Western United States (Pfadt, 1994).

1. Grasshoppers 

and Mormon 

Crickets

Grasshopper species vary in densities and dominance depending on 

the soil, vegetation, topography, and use of a habitat. They are 

generally grouped into grass feeders, forb feeders, or mixed feeders. 

Some species of grasshoppers will eat almost any vegetation, while 

other species are more selective (Pfadt, 1994). Grasshopper habitats 

may change because of the differential effects of weather, parasites, 

disease, or insecticidal treatments. It is thought that increases in the 

abundance of food and habitat or decreases in natural enemies are 

just as likely to trigger population explosions. Food sources and 

preferences may change during outbreaks.

Most grasshoppers are highly mobile with jumping hind legs and 

strong wings. They have short, relatively thick antennae, which are 

rarely longer than half of the body. The female’s ovipositor is short, 

often barely visible. Most grasshopper species are strong fliers as 

adults, although a few have only wing pads and do not fly. Some 

species have brightly colored wings; however, these species are usually 

not economically damaging. Some species of grasshoppers can be 

considered beneficial, feeding on other invertebrates or plant forms 

that are not consumed by other users of the rangeland. Grasshoppers 

range in length from less than 1 inch to 3 inches. 

2. Life Cycles The Mormon cricket is flightless but highly mobile. From the time it is 

half grown, the cricket is capable of migrating great distances in a 

single day. Mormon crickets have long, thin antennae, usually longer 

than the body. Like all members of the order Orthoptera, the 

grasshopper life cycle includes three stages of development: the egg, 

the nymph, and the adult. Each species appears to possess a unique 

set of ecological and physiological adaptations that allow it to grow, 

survive, and reproduce in its environment. The habitat plays an 

important role in providing nutritive food plants, adequate living 

space, satisfactory soil conditions for the eggs, and favorable biotic 

relationships for all the life stages. Generally, only one generation a 

year is produced except in the northern regions where eggs may 

occasionally require as many as 2 years to fully develop, depending 

upon species and climatic conditions. In warmer areas, such as in 

Kansas, Melanoplus sanguinipes may produce a smaller, second 

generation each year. 

In a normal life cycle (see figure 2–1), eggs are laid late in the summer 

and fall and enter a stage of inactive development known as diapause. 

The embryos remain physiologically active as transfer of nutrient 

materials from the yolk into the embryonic fat body and tissue 

continues. Cold temperatures slow or end this process, and the 
II. Background

Grasshopper Environmental Impact Statement 27

embryos enter into a dormant stage. In spring, when temperatures 

warm above threshold levels, the egg embryos continue their 

development.

The egg-laying habits of grasshoppers differ and, having mated with a 

male of her species, the female digs a small hole in the soil with her 

ovipositor and deposits the first group of eggs. Once egg laying begins, 

the female continues to mate and deposit eggs regularly for the rest of 

her life. The number of eggs laid may range from 3 pods per week to 1 

pod every 1 to 2 weeks, and each pod may contain as many as 15 to 

100 eggs. Grasshopper egg pods vary not only in the number of eggs 

they contain but also in their size, shape, structure, and where they 

are laid. Incubation of eggs may begin immediately after being 

deposited in the soil, depending upon climatic temperatures. 

Newly-hatched grasshoppers are capable of standing upright and 

being able to hop away from danger immediately after shedding their 

embryonic membrane. The young grasshoppers are active and begin 

feeding on green and nutritious host plants. A young grasshopper 

must shed (molt) its soft exoskeleton to grow and mature to an adult 

stage. The exoskeleton is composed of protein and polysaccharide 

called chitin. As the grasshoppers grow and develop they molt at 

intervals, changing their structures and form. Depending on species 

and sex, grasshoppers molt four to six times during their nymphal or 

immature life, and depending on weather conditions, the various 

molts may require 30 to 40 days to complete. Mormon crickets vary 

from grasshoppers in that they pass through seven nymphal instars 

and may take 60 to 90 days to complete their molting. The insect stage 

between molts is referred to as an instar. When the last instar molts, 

the exoskeleton hardens and the insect becomes an adult and is ready 

to mate and reproduce (Pfadt, 1994). 

E. Damage Caused by Grasshoppers 

Some grasshoppers cut grass stems and blades, eating only a part. 

Some eat closer to the ground than livestock and feed primarily on the 

growing part of grasses. Other species may cut off seed stalks, thus 

eliminating seed production and making soil erosion more likely to 

occur in denuded areas. Such changes may lead to soil degradation, 

the interruption of nutrient cycles, and the loss of important plant 

species or seed production that can lead to irreversible changes that 

reduce the amount and diversity of rangeland habitats. Soil damage 

causes erosion and also disrupts nutrient cycling, water infiltration, 

seed germination, and other ecological processes that are important 

components of rangeland ecosystems. Grasshoppers waste 

approximately six times as much foliage as they consume. 

Grasshoppers that invade cropland often develop on adjacent 

rangeland. In contrast to cropland, the value of forage produced on 

rangeland is of less value (Pfadt, 1994). 
II. Background

28 Grasshopper Environmental Impact Statement

FIGURE 1-1: The life cycle of the bigheaded grasshopper, Aulocara elliotti (Thomas). during summer in bare 

spots of grassland, the female deposits, at intervals, batches of eggs. As soon as the eggs 

are laid, they begin embryonic development and reach an advanced stage in which they 

enter diapause and pass the winter. In spring the eggs complete embryonic development and 

hatch. The young grasshopper sheds a serosal skin, the exoskeleton hardens, and the 

nymph begins to feed and grow. After molting five times and developing through five instars 

in 30 to 40 days, it becomes an adult grasshopper with functional wings. The adult female 

matures groups of six to eight eggs at a time and deposits them in the soil at intervals of 3 

to 4 days for the duration of her short life. (This figure is reproduced from the introduction to 

“Field Guide to Common Western Grasshoppers”, by Robert E. Pfadt, 1994, and is reprinted 

with permission.)
II. Background

Grasshopper Environmental Impact Statement 29

FIGURE 1-2: Surveying grasshoppers using the sweep-net technique. 

(Photo credit USDA-APHIS)
II. Background

30 Grasshopper Environmental Impact Statement
III. Alternatives

Grasshopper Environmental Impact Statement 31

III. Alternatives

The purpose of this environmental impact statement (EIS) is to 

analyze, in a programmatic manner, the environmental impacts 

anticipated from grasshopper and Mormon cricket suppression 

activities undertaken by the Animal and Plant Health Inspection 

Service (APHIS). (The term “grasshopper” used in this document 

refers to both grasshoppers and Mormon crickets, unless 

differentiation is needed.) The approach APHIS uses to suppress 

grasshoppers is only one of many approaches that are a part of 

grasshopper management. APHIS is fully aware that many other 

strategies can be taken to manage grasshopper populations—many of 

those strategies were investigated through the APHIS-funded 

integrated pest management (IPM) program, and the information has 

been transferred to land managers (see appendix A). However, 

implementing these strategies is not within the purview of APHIS. 

Rather, these strategies are best implemented and normally studied in 

the context of rangeland management programs by the respective land 

managers of Federal, State, and local governments and private groups 

and individual landowners who have stewardship over the lands.

The need for immediate treatments limits the options that are 

available to APHIS. The best grasshopper management strategies are 

preventative in nature and are long-term efforts that are designed to 

head off, rather than combat, outbreaks. They do not achieve the 

rapid reduction of grasshopper populations that is needed when 

devastating outbreaks occur. The response that most rapidly and 

effectively reduces grasshopper populations is the application of 

insecticides. This response, the application of insecticides within all 

or part of an outbreak area, is the response available to APHIS that 

rapidly suppresses (but does not eradicate) grasshopper outbreaks 

and effectively protects rangeland habitats and adjacent crops.

The following alternatives describe the options available to APHIS in 

fulfilling its mandate to carry out control programs for grasshopper 

infestations to protect rangeland. A No Action alternative is also 

included.

A. Alternative 1: No Action

Under this alternative, APHIS would not fund or participate in any 

program to suppress grasshopper infestations. Some Federal land 

management agencies, State agriculture departments, local 

governments, or private groups or individuals would likely conduct 

their own grasshopper treatments, but APHIS would not be involved 

with any suppression activities.
III. Alternatives

32 Grasshopper Environmental Impact Statement

B. Alternative 2: Insecticide Applications at Conventional Rates 

and Complete Area Coverage

Under this alternative, the application of insecticides, typically at the 

rates described in the Rangeland Grasshopper Cooperative Control 

Management Program, Final Environmental Impact Statement—1987 

(1987 EIS) and covering all treatable sites within the infested area 

(total or blanket coverage), has historically been the most common 

approach used to reduce grasshopper populations.

The insecticides APHIS considers using under this alternative are 

carbaryl, diflubenzuron, and malathion. Carbaryl and malathion are 

insecticides that have traditionally been used by APHIS. 

Diflubenzuron, an insect growth regulator, is also included in this 

alternative. Although diflubenzuron’s mode of action is very different 

than the mode of action for carbaryl and malathion, the term 

“insecticide” used in this document refers to carbaryl, diflubenzuron, 

and/or malathion. 

Carbaryl, diflubenzuron, and malathion are all currently registered for 

use and labeled by the U.S. Environmental Protection Agency (EPA) for 

rangeland grasshopper treatments. All applications of these 

insecticides by APHIS personnel will be conducted in strict adherence 

to the label directions. The insecticides could be applied aerially or by 

ground equipment. The application rates analyzed in this alternative 

are 16 fluid ounces (0.50 pound active ingredient) of carbaryl spray 

per acre, 10 pounds (0.50 pound active ingredient) of 5 percent 

carbaryl bait per acre, 1.0 fluid ounce (0.016 pound active ingredient) 

of diflubenzuron per acre, and 8 fluid ounces (0.62 pound active 

ingredient) of malathion per acre.

The traditional goal of grasshopper treatments, especially prior to the 

Grasshopper IPM Program, was often to suppress grasshoppers to the 

greatest possible extent (Foster, 1996). Recent studies by Foster et al.

(2000) have shown that the insecticides to be used as part of the 

suppression programs at conventional rates reduce grasshopper 

populations at 14 days after treatment by the following percentages: 

carbaryl spray at 96 to 97 percent reduction; carbaryl bait 35 to 85 

percent reduction; diflubenzuron at 98 percent reduction; and 

malathion at 89 to 94 percent reduction.

Because this is a programmatic document, issues associated with a 

specific site will need to be addressed in site-specific documents for a 

given treatment area, or in other documents prepared in accordance 

with other Federal, State, or local laws.
III. Alternatives

Grasshopper Environmental Impact Statement 33

C. Alternative 3: Reduced Agent Area Treatments (RAATs)

This alternative is a recently developed approach to grasshopper 

suppression that uses insecticides at low rates with a reduction in the 

area treated. The Reduced Agent Area Treatments (RAATs) strategy 

relies on the effects of an insecticide to suppress grasshoppers within 

treated swaths and the conservation of grasshopper predators and 

parasites in swaths not directly treated (untreated). 

For more than 20 years, various studies by APHIS have suggested that 

reduced rates of insecticides could provide acceptable levels of 

grasshopper suppression (Foster et al., 1979, 1989; Reuter et al.,

1993; Reuter and Foster, 1996), although none of these findings were 

implemented in the field. The concept of reducing the area of coverage 

while also applying less insecticide per treated acre was developed in 

1995, with the first field tests of RAATs in Wyoming (Lockwood and 

Schell, 1997). The potential economic advantages of this method were 

proposed by Larsen and Foster (1996) and empirically demonstrated 

by Lockwood and Schell (1997). Widespread efforts to communicate 

the advantages of RAATs across the Western States were undertaken 

in 1998 and have continued on an annual basis. The viability of this 

method at operational scales was initially demonstrated by Lockwood 

et al. (2000) and subsequently confirmed by Foster et al. (2000). The 

first government agencies to adopt RAATs in their grasshopper 

suppression programs were the Platte and Goshen County Weed and 

Pest Districts in Wyoming, who also funded research at the University 

of Wyoming to support the initial studies in 1995. This method has 

now been used by government agencies and private landowners in 

eight Western States. 

The insecticides APHIS considers using under this alternative are 

carbaryl, diflubenzuron, and malathion. All these insecticides are 

currently registered for use and labeled by EPA for rangeland control 

of grasshoppers, have been demonstrated to be effective, and would be 

used by APHIS personnel in strict adherence to the label. The RAATs 

rates analyzed in this document are 8 fluid ounces (0.25 pound active 

ingredient) of carbaryl spray per acre; 10 pounds (0.20 pound active 

ingredient) of 2 percent carbaryl bait per acre; 0.75 fluid ounce (0.012 

pound active ingredient) of diflubenzuron per acre; and 4 fluid ounces 

(0.31 pound active ingredient) of malathion per acre. It has been 

demonstrated that an acceptable level of grasshopper control can be 

achieved by reducing application rates to typically one-half the rates 

used in conventional control programs (Lockwood et al., 2000) and 

applying the insecticides to only a portion of the land. Because the 

entire range of application rates under the RAATs approach is not 

known, the analyses of this alternative will only consider the above 

application rates, which are the maximum rates used under this 

alternative. (See chapter 5, Environmental Consequences, and 

appendix B.)
III. Alternatives

34 Grasshopper Environmental Impact Statement

An important part of the RAATs alternative is the amount of area that 

is not directly treated (untreated). The concept of leaving intermittent 

swaths untreated is designed to both reduce cost and conserve 

nontarget, biological resources, including predators and parasites of 

grasshoppers, that are in the untreated areas. There is no 

standardized percentage of area that is left untreated. The proportion 

of land treated in a RAATs approach is a complex function of the rate 

of grasshopper movement, which is a function of developmental stage, 

population density, and weather (Narisu et al., 1999, 2000), as well as 

the properties of the insecticide (insecticides with longer residuals 

allow wider spacings between treated swaths). Foster et al. (2000) left 

20 to 50 percent of their study plots untreated, while Lockwood et al.

(2000) left 20 to 67 percent of their treatment areas untreated. 

Because there is no standardized area that is untreated for biological 

conservation purposes, this document will assume complete, 100 

percent coverage at the rates under the RAATs alternative in order to 

assess environmental impacts. This will be a substantial 

overestimation of the amount of insecticide applied in every RAATs 

strategy, and the analyses in this document will represent the 

worst-case scenario for this alternative. (See chapter 5, 

Environmental Consequences, and appendix B.) 

The goal of grasshopper suppression under the RAATs alternative is to 

economically and environmentally suppress grasshopper populations 

to a desired level rather than to reduce those populations to the 

greatest possible extent. The efficacy of a RAATs strategy in reducing 

grasshoppers is, therefore, less than conventional treatments. The 

efficacy of insecticide treatments under the RAATs alternative also is 

variable. Foster et al. (2000) reported that grasshopper mortality using 

RAATs was reduced 2 to 15 percent from conventional treatments, 

depending on the insecticide, while Lockwood et al. (2000) reported 0 

to 26 percent difference in mortality between conventional and RAATs 

areas. 

Not every conceivable combination of reduced rates and partial spray 

coverages are analyzed under this alternative. The absolute rates and 

areas covered will be described in site-specific documents, such as 

environmental assessments, when there is a need for action to be 

taken against grasshoppers. Setting the desired level of suppression 

in advance and conducting programs to meet that predetermined goal 

may be practical when using a RAATs approach (Larsen, personal 

communication, 2001). Indeed, the flexibility in application rates and 

treatment area will allow for decisions to be made on a case-by-case 

basis based on the economic and environmental considerations and 

the level of grasshopper mortality desired for a specific location.
III. Alternatives

Grasshopper Environmental Impact Statement 35

FIGURE 1-1: Diagram of a Reduced Agent Area Treatment showing treated swaths 

alternating with untreated swaths. In this example, the amount of 

the area that is reduced by 50%.
III. Alternatives

36 Grasshopper Environmental Impact Statement

FIGURE 1-2: Diagram of a Reduced Agent Area Treatment showing treated swaths of 

100 ft. alternation with untreated swaths of 25 ft. In this example, 

the amount of the area that is treated is reduced by 20%.
IV. The Affected Environment

Grasshopper Environmental Impact Statement 37

IV. The Affected Environment

The environment potentially affected by the Animal and Plant Health 

Inspection Service (APHIS) grasshopper and Mormon cricket 

suppression program is the rangeland of the 17 Western States as 

follows: Arizona, California, Colorado, Idaho, Kansas, Montana, 

Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, 

South Dakota, Texas, Utah, Washington, and Wyoming. (The term 

“grasshoppers” used in this document refers to both grasshoppers and 

Mormon crickets, unless differentiation is needed.) These vast 

rangeland areas are a valuable natural resource providing grazing for 

domestic livestock, food and habitat for a variety of plant and wildlife 

species, and recreational resources for the public.

A substantial threat to the animal and plant productivity of these 

rangeland areas is the proliferation of grasshopper populations. 

Grasshoppers have been a serious pest in the Western States since 

early settlement. Conditions favoring the hatching and survival of 

large numbers of grasshoppers can cause outbreak populations. The 

resulting damage to vegetation may be so severe that all grasses and 

forbs are destroyed, and plant growth is retarded for several years. 

The consequences are reduced grazing for livestock; loss of food and 

habitat for plants and wildlife, including endangered and threatened 

species; and soil erosion, possibly resulting in decreased water quality.

Programs to suppress economically damaging grasshopper 

infestations could occur on any of the rangeland within the 17 

Western States. APHIS sometimes cooperates in grasshopper 

suppression programs when requested by a Federal land management 

agency or a State agriculture department (on behalf of a State, a local 

government, or a private group or individual). APHIS’ involvement in 

grasshopper programs could include conducting surveys, providing 

technical advice, and applying insecticides. 

This environmental impact statement (EIS) is a programmatic 

document for APHIS’ grasshopper suppression programs that 

potentially could occur on rangeland within seven general regions as 

identified by Bailey (1980) (see figure 4–1). When there is a need to 

suppress damaging grasshopper populations, a site-specific 

environmental document identifying the area of a proposed treatment 

program will be prepared. This document will include the specific 

characteristics of the rangeland areas and will contain an analysis of 

the potential effects of the program on the environment of the 

treatment area.
IV. The Affected Environment

38 Grasshopper Environmental Impact Statement

The analysis of site-specific characteristics of a program may include 

the following considerations: 

◆ Potential effects of the program on human health

❖ workers and 

❖ the general public (see chapter 5, Environmental 

Consequences);

◆ Potential effects on nontarget species 

❖ terrestrial vertebrates and invertebrates, including bees,

❖ aquatic organisms, 

❖ plants, and 

❖ endangered and threatened plants and wildlife (see chapter 5, 

Environmental Consequences);

◆ Socioeconomic issues, such as the effects on 

❖ livestock owners, 

❖ crop growers, 

❖ beekeepers, and 

❖ recreationists, and (see chapter 5, Environmental 

Consequences);

◆ Special considerations for certain populations, such as 

❖ minorities and low-income populations and

❖ children (see chapter 6, Other Environmental 

Considerations).

The impacts of APHIS suppression programs will differ from one 

rangeland area to another because of differences in physical 

characteristics or certain biological elements. Bailey (1980) has 

identified seven ecoregions within the 17 Western States, as shown in 

figure 4–1.
IV. The Affected Environment

Grasshopper Environmental Impact Statement 39

The Tall-grass Prairie region is a contiguous grassland that lies 

between the deciduous forests of the east and the short-grass prairie 

of the west, on the flat-to-rolling-hill land of the central lowland. 

Elevation gradually increases from about 500 feet above sea level in 

the east to about 1,500 feet in the west. The northern boundaries 

extend into Canada, and the southern boundaries extend through 

southeastern Texas. 

The climate varies widely in this region. The length of the frost-free 

season varies from less than 120 days in the north to almost 300 days 

in the south. Annual precipitation ranges from 15 inches in the north 

to 30 inches in the south. In general, more precipitation occurs in the 

warmer months of the year. Drought periods are less frequent and 

less severe near the eastern forest than in more westerly areas. 

Annual average temperatures range from 40 °F in the north to 55 °F in 

the central portion to 70 °F in the south. 

FIGURE 1-1: The Seven ecoregions of the Western United states. (Source: Baile, R.G. 1980)
IV. The Affected Environment

40 Grasshopper Environmental Impact Statement

The Short-grass Prairie region lies in a broad belt that slopes 

gradually eastward from an altitude of 6,000 to 8,000 feet in the 

Wyoming Basin within the eastern Rocky Mountains to 1,500 feet in 

the Central States where it gives way to the tall-grass prairie. The 

mixed-grass prairie is included in the eastern portion of the analysis 

region and represents a transition zone between the tall-grass and 

short-grass prairies.

This region is characterized by rolling plains and table lands of 

moderate relief. It includes the areas known as the Great Plains and 

Wyoming Basin. The most striking feature of the region is the 

phenomenal flatness of the interstream areas, which make up a great 

expansive flood plain or alluvial slope.

The climate is semiarid and the total supply of moisture is low. 

Precipitation ranges from 10 inches in the north to more than 25 

inches in the south. Evaporation usually exceeds precipitation. 

Winters are cold and dry; summers are warm to hot. The frost-free 

season ranges from fewer than 100 days in the north to more than 200 

days in parts of Texas. Average annual temperatures range from 40 to 

60 °F.

The Plateau region includes two separate (noncontiguous) 

geographical areas: the Colorado Plateau in Arizona, New Mexico, and 

Utah, and the Mexican Highlands located between the American 

Desert on the west and the Chihauhuan Desert on the east. The 

topography covers high, grassy mountains of the Mexican plains as 

well as the table lands and mountains of the Colorado Plateau. Local 

relief is from 500 feet to more than 3,000 feet in some of the deeper 

canyons that dissect these table lands, and volcanic mountains rise 

1,000 to 3,000 feet above the plateau surfaces. Stream valleys are 

narrow and widely spaced.

The high elevations of this region produce moderate mean 

temperatures. However, summer days are hot and extremely cold 

weather occurs in winter. The annual average temperatures range 

from 40 to 55 °F in the plateau region and from 55 to 70 °F on the 

Mexican plains. Normal rainfall occurs in winter; summer rains occur 

as occasional, sudden thunderstorms. Average annual precipitation 

ranges from 10 to 20 inches on the Colorado Plateau. The Mexican 

Highlands are semiarid and have less rainfall.

The Desert region includes the Chihuahuan Desert in southern New 

Mexico and western Texas and the American Desert in California, 

Arizona, Nevada, and Utah. The topography is characterized by 

extensive plains from which isolated mountains and buttes rise 

abruptly. Elevations range from 280 feet below sea level to 11,000 feet 

above sea level in some mountain ranges. The only permanent water 
IV. The Affected Environment

Grasshopper Environmental Impact Statement 41

bodies are a few large rivers that include the Colorado, Rio Grande, 

and Pecos Rivers. Washes, dry most of the year, fill with water 

following a rain.

Summers are long and high temperatures prevail. Though winters are 

moderate, the region is subject to occasional frosts and freezing 

temperatures. Average annual temperatures range from 50 to 75 °F. 

Summer rains occur as torrential storms; in winter, the rains are more 

gentle and widespread. In the Colorado and Mojave Deserts of 

southeastern California, there are virtually no summer rains. Average 

annual precipitation ranges from 2 to 20 inches. The evaporation rate 

in summer is very high.

The Great Basin region occupies the area between the Rocky 

Mountains on the east and the Sierra Nevada Range on the west, its 

elevation varying from mountainous regions to low elevations along 

the Snake River plain. This includes areas in Nevada, Utah, southern 

Idaho, Washington, and Oregon. Much of this intermountain area has 

numerous separate interior basins, and only a small portion of it 

drains to the sea. Except for the Snake River and its tributaries in the 

Snake River plain, streams in this region are generally intermittent. 

Many mountains rise steeply from the semiarid, sagebrush-covered 

plains.

Summers are hot; winters are fairly moderate. The average annual 

temperature is 40 to 55 °F. Spring comes early except at the higher 

elevations. Total annual precipitation averages only 5 to 20 inches; 

almost no rain falls during the summer months except in the 

mountains.

The California Grassland region lies within the Central Valley of 

California, a flat alluvial plain between the Sierra Nevada and the 

coast ranges. Elevations range from sea level to 500 feet. This area 

has broad, nearly level valleys bordered by sloping alluvial fans, 

slightly dissected terraces, and the lower foothills of the surrounding 

uplands. Large undrained basins are in the south.

The precipitation of this region is characterized by winter rainfall. 

Except near the coast, summers are hot and the winters mild. Annual 

rainfall ranges from 6 inches in the upper San Joaquin Valley to nearly 

30 inches along the coast. Potential evaporation during the warmest 

months is often much greater than the precipitation. Annual 

temperatures average 60 to 67 °F in much of the area. Northern 

temperatures fall as low as 55 °F.

The Mountain region encompasses the wide variety of mountainous 

areas in the Western United States. The Pacific and Sierra Forests 

and California chaparral extend down the west coast while the Rocky 

Mountains, Columbian Forest, and Upper Gila Mountains dissect the 
IV. The Affected Environment

42 Grasshopper Environmental Impact Statement

central region. The mountain environments are characterized by high, 

steep, rugged slopes. Many areas are glaciated; others are volcanic. 

Plateaus of dissected, horizontally layered rocks are found in the 

Rocky Mountains and Upper Gila Mountains.

The climates vary considerably with altitude. Temperature decreases 

and precipitation increases with rising elevations. Winter produces 

the most precipitation and much of it falls in the mountains as snow. 

Average rainfall ranges from 10 inches in the semiarid Rockies to 150 

inches in the humid Pacific Northwest.

Overall, temperatures are moderate, although severe winters are 

characteristic of the northernmost regions. Average temperatures 

range from 35 to 55 °F in most areas. The southern coastal region is 

somewhat warmer. 

The parameters examined in a site-specific document will include 

human populations—particularly the populations potentially at risk in 

the APHIS grasshopper suppression program (workers and the general 

public), soils, vegetation (both native and introduced plants and 

agricultural crops), terrestrial wildlife (including endangered and 

threatened terrestrial wildlife species), water resources and aquatic life 

(including endangered and threatened aquatic species), and land uses 

and cultural resources.
V. Environmental Consequences

Grasshopper Environmental Impact Statement 43

V. Environmental Consequences

This chapter summarizes the potential effects that the Animal and 

Plant Health Inspection Service’s (APHIS) grasshopper and Mormon 

cricket program treatments could have on the human environment. 

Unless specifically stated otherwise in this chapter, the word 

“grasshopper” refers to both grasshoppers and Mormon crickets. 

These effects are described in detail in appendix B, Environmental 

Risk Assessment for Rangeland Grasshopper Suppression 

Programs—Insecticides, which is a more thorough risk assessment of 

program treatments on the environment. This chapter concentrates 

on the potential ecological impacts described during the APHIS 

Grasshopper Integrated Pest Management (GHIPM) Program (USDA, 

APHIS, 1996) and the human health information analyzed in Appendix 

B. This information from the GHIPM Program is considered pertinent 

because most of the studies were conducted during actual APHIS 

grasshopper suppression programs or under field conditions that 

closely followed the APHIS procedures used for grasshopper 

suppression. 

The available toxicity data from research on given pesticides is limited 

to a finite number of wildlife species. The determination of risk to a 

given species from potential program action is made by selection of 

toxicity data for that species or the most closely related surrogate 

species. The review of the quality of data from available research may 

influence the decision, made by a diverse team of scientists, to select a 

given study or specific data for a given surrogate species over other 

available data. The surrogate data were selected to best represent the 

species risk based upon the consensus of the team. This approach 

may not always portray the most sensitive outcome, but it is designed 

to provide the decisionmaker with a realistic description of impacts of 

potential program alternatives. This information allows the risk 

manager to make an informed decision about differences in potential 

impacts among available alternatives to the program. The literature 

citations in this chapter supplement the literature citations in 

appendix B.

A. Environmental Consequences of Alternative 1: No Action

Under Alternative 1, No Action, APHIS would not fund or participate in 

any program to suppress grasshoppers. Even with the 

implementation of the best land management practices, if APHIS does 

not participate in any grasshopper suppression programs, Federal 

land management agencies, State agriculture departments, local 

governments, or private groups or individuals may not effectively 

combat outbreaks in a coordinated effort. In these situations, 

grasshopper outbreaks would develop and spread unimpeded. 
V. Environmental Consequences

44 Grasshopper Environmental Impact Statement

Grasshoppers in unsuppressed outbreaks would consume 

agricultural and nonagricultural plants. The damage caused by 

grasshopper outbreaks could also pose a risk to rare, threatened, or 

endangered plants that often have a low number of individuals and 

limited distribution. Habitat loss for birds and other wildlife and 

rangeland susceptibility to invasion by nonnative plants are among 

the consequences that would likely occur should existing vegetation be 

removed by grasshoppers. 

Loss of plant cover due to grasshopper consumption will occur. Plant 

cover may protect the soil from the drying effects of the sun, and plant 

root systems hold the soil in place that may otherwise be eroded or 

lost to erosion. 

Another potential scenario, if APHIS does not participate in any 

grasshopper suppression programs, is that some Federal land 

management agencies, State agriculture departments, local 

governments, or private groups or individuals may attempt to conduct 

widespread grasshopper programs. Without the technical assistance 

and program coordination that APHIS can provide to grasshopper 

programs, it is possible that a large amount of insecticides, including 

those APHIS considers too environmentally harsh but labeled for 

rangeland use, could be applied, reapplied, and perhaps misapplied in 

an effort to suppress or even locally eradicate grasshopper 

populations. It is not possible to accurately predict the environmental 

consequences of the no action alternative because the type and 

amount of insecticides that could be used in this scenario are 

unknown.

B. Background Information on Alternative 2 and Alternative 3

The objective of a grasshopper suppression program is to reduce 

grasshopper populations below an economically damaging level. The 

suppression methods APHIS uses rely on either one of three 

insecticides: carbaryl, diflubenzuron, and malathion. These 

insecticides can be applied according to two separate strategies 

presented as Alternatives 2 and 3. Alternative 2 is the conventional 

strategy that uses insecticide rates described in the Rangeland 

Grasshopper Cooperative Management Program, Final Environmental 

Impact Statement—1987 (1987 EIS) (USDA, APHIS, 1987b) and 

applies those insecticides in a complete coverage of the treatment 

area. Alternative 3, Reduced Agent Area Treatments (RAATs), is a 

recently developed approach to grasshopper suppression that 

significantly lowers the amount of insecticide used by reducing both 

(1) the insecticide application rate and (2) the amount of area treated 

with insecticide. 

Because diflubenzuron is an insecticide that was not included in the 

1987 EIS, some sections in this chapter contain proportionately more 

information on the use and effect of diflubenzuron than is presented 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 45

for either carbaryl or malathion. This does not indicate that APHIS 

has a preference for one insecticide over another. The decision on 

which pesticide to use for grasshopper suppression treatments 

depends on a variety of factors which are described in greater detail in 

the following sections.

1. Insecticides 

Used by APHIS 

A number of insecticides are labeled by the U.S. Environmental 

Protection Agency (EPA) for use against grasshoppers on rangeland 

but are not considered by APHIS for use. APHIS chooses and approves 

insecticides based on (1) effective performance against grasshoppers 

on rangeland and (2) minimal or negligible impact on the environment 

and nontarget species (Foster and Reuter, 1996). 

Carbaryl, diflubenzuron, and malathion are the insecticides APHIS 

would use in the rangeland grasshopper program based on several 

factors, including efficacy, cost, and environmental concerns. These 

three insecticides are all labeled by EPA for rangeland use. Although 

diflubenzuron’s mode of action is very different than the mode of 

action for carbaryl and malathion, the term “insecticide” used in this 

document usually refers to carbaryl, diflubenzuron, and/or 

malathion. 

When direct intervention is requested by land managers, APHIS’ role 

in the suppression of grasshoppers is achieved through insecticide 

application. Generally APHIS would apply either carbaryl, 

diflubenzuron, or malathion one time to a treatment site. There may, 

however, be situations where it is appropriate to use one insecticide or 

formulation in one part of a treatment area and a different insecticide 

or formulation in another part of that same treatment area with all 

applications conducted according to the label directions. For example, 

ultra-low-volume malathion may be used over the majority of a 

treatment area, but areas of special consideration may be treated with 

carbaryl bait. Should these situations occur, no area would be treated 

with more than one insecticide, nor would insecticides be mixed or 

combined.

a. Carbaryl—Carbaryl is a carbamate, broad spectrum, insecticide 

that has many commercial uses for insect control on fruits, vegetables, 

ornamental plants, field crops, and forage crops. The mode of action 

for carbaryl occurs primarily through acetylcholinesterase (AChE) 

inhibition which affects transmission of the nerve impulses across the 

nerve synapse. This inhibition is reversible over time if exposure to 

carbaryl ceases. Carbaryl is active both as a contact and a stomach 

poison, although ingestion results in a greater level of mortality.

Carbaryl is of moderate acute oral toxicity to humans. EPA has 

classified carbaryl as a “possible human carcinogen” based on an 

increased incidence of vascular tumors in a chronic study of male 
V. Environmental Consequences

46 Grasshopper Environmental Impact Statement

mice exposed at 46 mg/kg/day (1000 parts per million (ppm)) (EPA, 

1993). However, carbaryl is not considered to pose any mutagenic or 

genotoxic risk based upon the weight of evidence.

Carbaryl is of moderate acute oral toxicity to mammals. It is slightly 

toxic to birds, slightly toxic to reptiles and amphibians, severely toxic 

to most terrestrial invertebrates, and of low phytotoxicity to most 

plants. Carbaryl is moderately toxic to fish and very highly toxic to 

aquatic invertebrates.

Carbaryl can be used effectively both early and late in the season to 

treat grasshoppers over a broad range of climatic conditions. Carbaryl 

is short-lived in rangeland ecosystems, but carbaryl is more persistent 

than malathion. The half-life of carbaryl in soil ranges from 7 to 28 

days. Carbaryl is not expected to have detectable runoff or any 

leaching to groundwater; its half-life in freshwater ranges from 1 to 6 

days. Insecticidal properties of carbaryl persist on exposed green 

plant surfaces from 3 to 10 days and perhaps longer. The main 

carbaryl metabolites and degradation products are considerably less 

toxic than carbaryl, the parent compound. The effects of carbaryl 

used for grasshopper suppression are described in greater detail in the 

following sections for Alternatives 2 and 3. 

b. Diflubenzuron—Diflubenzuron is an insect growth regulator that is 

used against a number of crop and forest insect pests. The mode of 

action for diflubenzuron is very different than the mode of action for 

carbaryl or malathion. 

Carbaryl and malathion are active against a broad spectrum of insects 

in both the adult and immature stages. When applied in liquid form, 

carbaryl and malathion are less selective and have a greater impact on 

nontarget insects in treatment areas. However, the growth-regulating 

insecticide, diflubenzuron, has a narrower spectrum of activity. 

Diflubenzuron causes mortality to immature insects by inhibiting 

chitin formation, which is a different mode of action than carbaryl or 

malathion. At very low doses, diflubenzuron selectively inhibits the 

ability of immature insects to synthesize chitin at the time of molting 

which prevents insects from forming their exoskeleton, or outer shell, 

causing death due to cuticle rupture or starvation. Diflubenzuron is 

primarily a stomach poison to immature insects. Because 

diflubenzuron is effective against immature insects, diflubenzuron can 

most effectively be used early in the treatment season. In many cases, 

the “window of opportunity” for applying diflubenzuron may be earlier 

than for carbaryl or malathion. 

The acute oral toxicity of diflubenzuron to humans ranges from very 

slight to slight. The most sensitive indicator of exposure and effects of 

diflubenzuron in humans is the formation of methemoglobin. 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 47

Diflubenzuron’s acute oral toxicity to mammals ranges from very 

slight to slight. Higher organisms that contain chitin or 

polysaccharides similar to chitin (such as birds and mammals) seem 

unaffected (Eisler, 2000). The toxicity of diflubenzuron is much 

greater to immature invertebrates whose required chitin production is 

inhibited by this insecticide. Diflubenzuron is highly toxic to larval 

stages of insects but is not toxic to adult insects that have already 

formed their exoskeleton. In addition to grasshoppers, other 

terrestrial insects such as beetle larvae, lepidopteran larvae, and 

chewing herbivorous insect larvae are susceptible to diflubenzuron. 

Larval stages of aquatic arthropods, especially crustaceans, are 

sensitive to the effects of diflubenzuron, although fish are not. 

Diflubenzuron has low mobility and leachability in soils, and has a 

half-life in soils of 7 to 19 days. Degradation is most rapid when soil 

bacteria are abundant and when small-particle formulations are 

applied, as would be done for grasshopper suppression. 

Diflubenzuron usually persists in water for only a few days. High 

organic and sediment loadings along with elevated pH and 

temperature are the conditions whereby diflubenzuron most rapidly 

degrades. When applied to terrestrial plants, diflubenzuron tends to 

remain adsorbed with little or no absorption or translocation from 

plant surfaces. Metabolites of diflubenzuron are rapidly degraded, 

and it is unlikely that there would be sufficient exposure to these 

products to cause adverse toxicological effects. The effects of 

diflubenzuron used for grasshopper suppression are described in 

greater detail in the following sections for Alternatives 2 and 3. 

c. Malathion—Malathion is an organophosphate, broad spectrum 

insecticide that has been widely used for many years in commercial 

agriculture, public health, and in homes and gardens. The mode of 

action for malathion is similar to carbaryl in that malathion primarily 

acts as an AChE inhibitor. Malathion acts as both a contact 

insecticide and a stomach poison, although ingestion results in a 

greater percentage of mortality. Malathion is recommended for use 

against grasshoppers during warm and dry conditions (Foster and 

Onsager, 1996a), and the quick action of malathion will result in 

mortality before grasshoppers mature and lay eggs. Because 

malathion is fast acting and has less persistence than carbaryl, it is 

preferred in situations where older-stage grasshoppers are present 

and limiting the egg-laying capacity of grasshoppers is a primary 

concern. 

Malathion is of slight acute oral toxicity to humans. The mode of toxic 

action of malathion occurs through inhibition of AChE function in the 

nervous system. Unlike carbaryl, this reaction that results in 

inhibition from malathion is not readily reversible over time if 

exposure ceases. However, strong inhibition of AChE from malathion 
V. Environmental Consequences

48 Grasshopper Environmental Impact Statement

occurs only when chemical oxidation occurs to form the metabolite 

malaoxon. Human metabolism of malathion favors hydroxylation and 

seldom produces much malaoxon. 

EPA has recently reviewed the potential for carcinogenic effects from 

malathion. EPA’s classification describes malathion as having 

“suggestive evidence of carcinogenicity, but not sufficient to assess 

human carcinogenic potential.” This indicates that any carcinogenic 

potential of malathion cannot be quantified based upon EPA’s weight 

of evidence determination in this classification (EPA, 2000). 

Malathion is of very slight to moderately acute oral toxicity to 

mammals. It is slightly to moderately toxic to birds. While malathion 

is not directly toxic to vertebrates at the concentrations used for 

grasshopper suppression, it may be possible that sublethal effects to 

nervous system functions caused by AChE inhibition may lead 

indirectly to decreased survival. Malathion is moderately to severely 

toxic to terrestrial invertebrates and of low phytotoxicity to most 

plants. Malathion is slightly to very highly toxic to fish, highly toxic to 

aquatic stages of reptiles and amphibians, and moderately to very 

highly toxic to aquatic invertebrates. Appendix B contains more 

information on the effects of malathion to aquatic organisms. 

Malathion is short-lived in virtually all components of the 

environment. The half-life in soil and on foliage ranges from 1 to 6 

days. Malathion does not penetrate much below the soil surface and 

is unlikely to leach into groundwater; its half-life in freshwater ranges 

from 6 to 18 days. Increased toxicity associated with malathion may 

be brought about through oxidation to malaoxon and isomerization to 

isomalathion. Neither chemical is persistent and should not present a 

problem to humans as long as proper storage and handling 

procedures are followed. The effects of malathion used for 

grasshopper suppression are described in greater detail in the 

following sections for Alternatives 2 and 3.

APHIS 

Insecticide 

Application 

Techniques

An insecticide used for grasshopper suppression can be applied in 

either of two different forms: liquid ultra-low-volume (ULV) sprays or 

solid-based baits. Depending upon the area requiring treatment, both 

forms have advantages and disadvantages. Habitat diversity, 

topographical features, meteorological conditions, economic concerns, 

and environmental considerations all have important roles in choosing 

the best form of treatment (Foster and Onsager, 1996a). Both ULV 

sprays and baits can be distributed by aerial or ground applications. 

Aerial applications are typical for treatments over large areas. Some 

grasshopper outbreak locations are economically or logistically 

accessible only by aircraft, while other locations may be best treated 

by ground applicators. Ground applications are most likely to be 

made when treating localized grasshopper outbreaks or for 

treatments where the most precise placement of insecticide is desired. 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 49

An important aspect of protecting humans from the effects of an 

insecticide used for grasshopper suppression is that APHIS will not 

conduct any suppression program unless requested to do so by the 

responsible land management agency. Those agencies have their own 

procedures for protecting humans that APHIS will abide by. APHIS 

also conducts stakeholder meetings involving the wide range of land 

managers, land owners, and the public before any suppression 

programs are conducted; and where health and safety issues can be 

addressed at these meetings. In addition, APHIS complies with all 

product label requirements for human health and safety including the 

Worker Protection Standard (40 Code of Federal Regulations (CFR) § 

170). 

Baits—Baits have been used for grasshopper control since the late 

1800s (Foster, 1996). The most common form of bait used today is 

wheat bran, similar to the product found in grocery stores for human 

consumption, that has been impregnated with carbaryl. A small 

amount of additives also may be mixed with bait to extend the 

product shelf life or assist in applying the product evenly. Other bait 

formulations include rolled whole grain and pelleted products that are 

impregnated with an insecticide. Commercial bait products 

containing carbaryl are currently marketed but are no longer 

registered for use on rangeland. The carbaryl bait used for 

grasshopper suppression is prepared by mixing the appropriate 

amount of SEVIN® XLR PLUS carbaryl insecticide with a cereal grain 

substrate as recommended on the current Section 3 label.

In general, baits have considerable environmental advantages over 

liquid insecticide applications. Compared to sprays, baits are easier to 

direct toward the target area than sprays, are much more specific 

toward grasshoppers, and affect fewer nontarget organisms than 

sprays (Foster, 1996). For example, bees (both cultivated and wild) are 

likely to be susceptible to some liquid insecticidal sprays (Tepedino, 

1996) while baits appear to be safe for bees and other insect 

pollinators (McEwen et al., 1996a).

However, grasshopper species vary considerably in their inclination to 

feed on wheat bran and other bait formulations and in their 

susceptibility to carbaryl-treated bait (Onsager et al., 1996). Bait 

applications, in general, yield less grasshopper mortalities than liquid 

sprays. Baits are usually more expensive per unit area than aerially 

applied treatments.

b. Ultra-low-volume (ULV) Applications—ULV applications are defined 

as any application of 0.5 gallon, or less, per acre. Liquid sprays, 

especially when applied at ULV rates, have several desirable 

characteristics when considering grasshopper suppression. For 

example, ULV applications typically produce a quicker, higher, and 
V. Environmental Consequences

50 Grasshopper Environmental Impact Statement

more predictable grasshopper mortality rate than bait applications 

(Fuller et al., 1996). Generally, contract costs are substantially lower 

for applying sprays than baits (Foster and Onsager, 1996b). 

When applying ULV treatments, it is vital to control spray distribution 

to avoid drift or the off-target movement of material (Sanderson and 

Huddleston, 1996). Drift can become a critical factor in protecting 

environmentally sensitive areas. Drift is also unsatisfactory from a 

program standpoint because drift results in less insecticide landing in 

the treatment area, which reduces program efficiency and economy. 

Various carriers and adjuvants are used to enhance ULV insecticide 

applications. These are primarily natural and synthetic oils. One 

adjuvant that may be used with insecticides considered for use by 

APHIS is canola oil, a vegetable oil commonly found in grocery stores. 

Canola oil may be a grasshopper attractant and feeding stimulant that 

increases the effectiveness of the insecticide; however, canola oil may 

become rancid if stored for extended periods of time and become 

unsuitable for use. In general, vegetable oils drift more than 

petroleum-based oils. The amount of oil used will be at the labeled 

rate. The label for diflubenzuron currently allows for, but does not 

mandate, the use of emulsified vegetable or paraffinic crop oil. The 

maximum rate that oil would be applied for grasshopper suppression 

is 10 ounces of oil per acre. The risk of toxic effects from oil at this 

rate is extremely low. Unless a concentrated spill should occur, the 

amount of oil applied to a given area is unlikely to be in high enough 

concentrations to affect nontarget organisms.

3.Insecticide 

Application 

Rates

All APHIS grasshopper treatments using carbaryl, diflubenzuron, and 

malathion would be conducted in strict adherence with the 

EPA-approved label directions. The insecticide application rates used 

by APHIS will, in many cases, be substantially less than the rates that 

can be used by private landowners conducting their own grasshopper 

programs. For example, the rates for malathion in Alternative 2, the 

conventional rates used by APHIS, are 33 percent lower than the 

maximum allowable rate (table 5–1). In Alternative 2, carbaryl and 

malathion will be applied at the conventional rate analyzed in the 

1987 EIS (USDA, APHIS, 1987b). The application rates for Alternative 

3, RAATs will all be reduced from the Alternative 2 rates by 50 to 60 

percent for carbaryl and malathion and 25 percent for diflubenzuron 

(table 5–1). 

Table 5–1.Insecticide Label Rates for Rangeland Grasshopper 

Suppression
V. Environmental Consequences

Grasshopper Environmental Impact Statement 51

APHIS typically applies either carbaryl, diflubenzuron, or malathion 

one time to a treatment site. Retreatments seldom occur for both 

scientific and economic reasons. The goal of a treatment is to reduce 

grasshopper populations to below those levels that cause economic 

damage. A single treatment is intended to sufficiently reduce 

grasshopper populations, and there should be no need for another 

treatment. In addition, while a single treatment must be 

cost-effective, there are very few situations where multiple treatments 

would be cost-effective. An exception could be that migrating Mormon 

crickets may sometimes require a second treatment. 

C. Environmental Consequences of Alternative 2: Insecticide 

Applications at Conventional Rates and Complete Area Coverage

Under this alternative, an insecticide application, typically at the rates 

described in the 1987 EIS (USDA, APHIS, 1987b) and covering all 

treatable sites permitted by the label and within the infested area 

(total or blanket coverage), has historically been the most common 

approach used in grasshopper programs. 

The insecticide APHIS would use under this alternative includes 

carbaryl, diflubenzuron, or malathion. Carbaryl and malathion are 

insecticides that APHIS has traditionally used. Diflubenzuron, an 

insect growth regulator, is also included in this alternative. Although 

diflubenzuron’s mode of action is very different than the mode of 

action for carbaryl and malathion, the term “insecticide” used in this 

document refers to carbaryl, diflubenzuron, and/or malathion. 

Carbaryl, diflubenzuron, and malathion all currently are registered for 

use and labeled by EPA for rangeland grasshopper treatments and 

have been demonstrated to be effective. Applications of these 

insecticides could be done aerially or by ground equipment, and 

APHIS personnel would conduct the treatments in strict adherence to 

the label directions. The application rates analyzed in this document 

are 16 fluid ounces (0.50 pound active ingredient) of carbaryl spray 

per acre, 10 pounds (0.50 pound active ingredient) of 5 percent 

TABLE 1-1: Insecticide Label Rates for Rangeland Grasshopper

Rates for Various Uses

Carbaryl Spray 

(lb a.i./acre)1

1 lb a.i./acre = pound of active ingredient per acre

Carbaryl Bait

(lb a.i./acre)1

Diflubenzuron

(lb a.i./acre)1

Malathion

(lb a.i./acre)1

Maximum label rate for 

grasshopper

1.0 0.50 0.016 0.91

Alternative 2 

(conventional APHIS 

rate)

0.50 0.50 0.016 0.62

Alternative 3 

(RAATs rate)

0.25 .20 0.012 .31
V. Environmental Consequences

52 Grasshopper Environmental Impact Statement

carbaryl bait per acre, 1.0 fluid ounce (0.016 pound active ingredient) 

of diflubenzuron per acre, and 8 fluid ounces (0.62 pound active 

ingredient) of malathion per acre. 

The goal of grasshopper treatments, especially prior to the GHIPM 

Program, was often to suppress grasshoppers to the greatest possible 

extent (Foster, 1996). Recent studies by Foster et al. (2000) have 

shown that following the use of insecticides at conventional rates (and 

the labeled rate for diflubenzuron) grasshopper populations are 

reduced at 14 days after treatment by the following percentages: 

carbaryl spray at 96 to 97 percent reduction, carbaryl bait at 35 to 85 

percent reduction, diflubenzuron at 

98 percent reduction, and malathion at 89 to 94 percent reduction. During 

grasshopper outbreaks when grasshopper densities can be 60 or more per square meter 

(Norelius and Lockwood, 1999), grasshopper treatments that have a 90 to 95 percent 

mortality still leave a number of grasshoppers (3 to 6) that is generally greater than the 

average number found on rangeland, such as in Wyoming, in a normal year (Schell 

and Lockwood, 1997). 

1. Carbaryl Direct and Indirect Toxicity—Carbaryl is an AChE inhibitor. For 

vertebrates, such as birds, AChE is essential for normal nervous 

system functions. A moderately severe AChE inhibition of 40 to 60 

percent affects coordination, behavior, and foraging ability. Such 

inhibition can lead to death from weather, predators, or other stresses 

of survival in the wild. The effects of lower AChE levels are still open 

to question regarding biological significance. In samples collected over 

a period of several years from multiple grasshopper treatment areas, 

not a single bird or mammal was found to have more than a 40 

percent AChE inhibition, and only a few individuals over the course of 

the entire study had an AChE inhibition as high as 20 percent 

(McEwen et al., 1996a). Fish exposed to carbaryl showed no inhibition 

of AChE (Beyers et al., 1994). At the carbaryl ULV application rate in 

Alternative 2, there is very little possibility of toxicity-caused mortality 

of upland birds, mammals, or reptiles, and none has been observed 

(McEwen et al., 1996a). Carbaryl is not subject to significant 

bioaccumulation due to its low water solubility and low octanol-water 

partition coefficient (Dobroski et al., 1985). 

Human Health—EPA has classified carbaryl as a “possible human 

carcinogen” based on an increased incidence of vascular tumors in a 

chronic study of male mice exposed at 46 milligrams/kilograms/day 

(mg/kg/day) (1000 ppm) (EPA, 1993). Carbaryl, however, is not 

considered to pose any mutagenic or genotoxic risk based upon the 

weight of evidence. 

Potential exposures to the general public from conventional 

application rates are infrequent and of low magnitude. These low 

exposures to the public pose no risk of direct toxicity, carcinogenicity, 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 53

neurotoxicity, genotoxicity, reproductive toxicity, or developmental 

toxicity. Potential worker exposures are higher and have the potential 

for adverse effects if proper safety procedures, including required 

protective gear, are not used. Carbaryl has been used routinely in 

other programs with no reports of adverse health effects. Therefore, 

routine safety precautions are anticipated to continue to provide 

adequate protection of worker health. 

Immunotoxic effects from carbaryl exposure are generally expected at 

concentrations much higher than those from grasshopper 

applications, but individuals with allergic or hypersensitive reactions 

to the insecticide or other chemicals in the formulated product could 

be affected. These individuals are advised to avoid treatment areas at 

the time of application until the insecticide has time to dry on the 

treated vegetation. 

c. Terrestrial Invertebrates—Applications of broad spectrum 

insecticidal sprays can cause large reductions in populations of both 

target arthropods (grasshoppers) and nontarget arthropods 

immediately after treatment. Insects that are active during treatments 

or that feed on moribund grasshoppers have the greatest potential for 

exposure to insecticides. Insects of this type include ground beetles, 

darkling beetles, blister beetles, spiders (especially wolf spiders), field 

crickets, foraging bees, and ants.

Catangui et al. (1996) assessed the impact of grasshopper suppression 

programs that used ULV carbaryl at Alternative 2 rates on nontarget 

arthropods in South Dakota. There were no substantial reductions in 

the numbers of ants, spiders, predatory beetles, or scavenger beetles 

from 7 to 76 days after treatment. Even after 1 year, no substantial 

reductions in soil surface-associated arthropods were detected. That 

study also found that flying nontarget arthropods such as pollinator 

bees, predators, and parasites showed no substantial reductions 

either immediately after carbaryl treatments or 1 year later. Swain 

(1986) conducted a field study on the effects of grasshopper 

treatments on nontarget arthropods and reported that malathion was 

initially more detrimental than either ULV carbaryl or carbaryl bait, 

but there was no indication of long-term effects on the arthropod 

complex. 

Carbaryl bait applications affect only species that consume the baits 

directly or prey that have consumed the baits (Quinn, 1996). These 

species include darkling beetles, ground beetles, field crickets, and 

ants. Bait applied at Alternative 2 rates for grasshopper suppression 

did not cause any long-term effects on those species (Quinn, 1996). 

There are many reasons for this lack of long-term effects, including 

resiliency of populations. 
V. Environmental Consequences

54 Grasshopper Environmental Impact Statement

d. Terrestrial Vertebrates—No toxic signs of bird mortality were 

observed during studies on killdeer populations in North Dakota when 

carbaryl ULV sprays were applied at Alternative 2 rates (McEwen et 

al., 1996a). Killdeer foraging effectiveness increased in the carbaryl 

treatment area, probably in response to the presence of dead and 

moribund grasshoppers. The quantitative risk assessment in 

appendix B established that the estimated carbaryl dose that 

rangeland birds would accumulate, by both direct exposure and 

indirectly through diet, in grasshopper treatment areas is well below a 

toxic dose. 

However, in some areas the reduced number of invertebrates 

necessary for bird survival and development may result in birds 

having less available food. In these cases, birds either will have less 

than optimal diets or will travel to untreated areas for suitable prey 

items causing a greater foraging effort and a possible increased 

susceptibility to predation. 

Golden eagles are a protected species and also are designated as a 

“species of concern” by wildlife conservation and land management 

agencies. This bird also has special significance for some Native 

American tribes. Golden eagles nest in remote rangeland areas and 

can be found on areas requiring grasshopper suppression treatments. 

A study of carbaryl sprayed directly over golden eagle nests at the 

Alternative 2 rate found that there was little risk to nesting golden 

eagles (McEwen et al., 1996b). 

The effects of carbaryl bait applied at Alternative 2 rates on vesper 

sparrow nestling growth and survival were investigated in North 

Dakota (McEwen et al., 1996a). Vesper sparrow survival, growth, and 

fledgling rates were not affected by the bait treatments around the 

nesting areas, and there was no difference in any of the productivity 

parameters between vesper sparrow nests on treated and untreated 

sites (Adams et al., 1994). 

Live trapping studies of small rodent populations (primarily deer mice) 

in areas treated with carbaryl showed no posttreatment decreases in 

number of animals (McEwen et al.,1996a). 

By contrast, Martin et al. (2000) reported the effects of the carbamate 

insecticide, carbofuran, on two species of upland birds. Although 

grasshopper populations were reduced by more than 90 percent, the 

rate of prey delivery, nestling weight and size, and total arthropod 

biomass delivered to nestlings in the treated areas were no different 

than in the untreated areas. The number of grasshoppers in nestling 

diets was significantly decreased, although the total number of food 

items was similar in both treated and untreated areas. 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 55

e. Aquatic Organisms—Beyers and McEwen (1996) intensively 

studied six freshwater ponds exposed to carbaryl. The only evidence 

of direct mortality was to pond-dwelling amphipods, and that was 

observed in only one of the six ponds. Amphipods are known to be 

extremely sensitive to carbaryl. All other aquatic invertebrates and 

other taxa in the six ponds appeared to be unaffected by the exposure 

to carbaryl. 

Studies by Beyers et al. (1995) were conducted in the Little Missouri 

River during a drought year when insecticide exposure to aquatic 

organisms was high because the insecticides were less diluted by the 

river water. Of the many effects on aquatic organisms measured, the 

only negative impact detected was an increase in invertebrate drift 

during the first 3 hours of carbaryl application. Sampling later that 

same day showed that the increase in invertebrate drift was transient 

and undetectable after 3 hours. The overall conclusion was that the 

grasshopper suppression program had no biologically significant effect 

on aquatic resources. 

Toxicity tests conducted on two fish, the Colorado squawfish, renamed 

the Colorado pikeminnow, and bonytail chub, using carbaryl and 

malathion exposures that simulated field conditions after a 

grasshopper treatment indicated in their laboratory experiments that 

carbaryl was several times more toxic than malathion to those fish 

(Beyers and Sikoski, 1994). 

2. Diflubenzuron Under Alternative 2, diflubenzuron would be applied at the rate of 1.0 

fluid ounce (0.016 pound active ingredient) per acre, using ULV sprays 

that provide complete coverage within the treatment area. A 

grasshopper mortality rate of up to 98 percent after 2 weeks could 

occur, although mortalities may be less. In addition to grasshoppers, 

diflubenzuron also would have the greatest effect on other immature 

terrestrial insects and early life stages of aquatic invertebrates. 

a. Direct and Indirect Toxicity—Because of its mode of action and low 

toxicity, diflubenzuron would not be toxic to or directly affect humans, 

terrestrial wildlife, plants, or fish at the application rate in Alternative 

2. The highest potential for exposure to diflubenzuron would be to 

insectivorous (organisms that consume insects) vertebrates such as 

birds, rodents, and reptiles that may be exposed to diflubenzuron 

treatments and then consume considerable quantities of 

grasshoppers, other rangeland invertebrates, and/or plants that 

contain diflubenzuron. Yet, the quantitative risk assessment in 

appendix B has demonstrated that vertebrates have a negligible risk of 

adverse toxicological effects from full coverage treatments using 

diflubenzuron. The assessment of 12 representative species 

demonstrated that diflubenzuron accumulation at Alternative 2 rates 

is many orders of magnitude below a lethal dose. 
V. Environmental Consequences

56 Grasshopper Environmental Impact Statement

McEwen et al. (1996b) exposed wild American kestrels in north-central 

Colorado to diflubenzuron rates that were 50 percent greater than the 

estimated rates that kestrels would be exposed to under Alternative 2. 

No statistically significant differences were detected in nestling growth 

rates, behavior data, or survival among treated and untreated 

kestrels. Fledgling survival for the kestrels treated with diflubenzuron 

was lowered for 1 year, but in the subsequent year no statistically 

substantial differences were observed between treated and control 

fledglings. Little, if any, bioconcentration or bioaccumulation would 

be expected for any animals (Booth, 1978). The rapid metabolism and 

lack of bioconcentration indicate that only acute toxic effects would be 

expected for diflubenzuron exposures (Opdycke et al., 1982). 

In addition to direct toxicity, there is a concern that wildlife and other 

species that feed upon grasshoppers and other insects would be 

indirectly affected because there would be fewer insects left in a 

treatment area for insectivores to consume. Because diflubenzuron is 

most effective against immature insects, adult insects in the treatment 

area would be largely unaffected and still available to insectivorous 

species for consumption. 

b. Human Health—Potential exposures to the general public from 

conventional application rates are infrequent and of low magnitude. 

These low exposures to the public pose no risk of methemoglobinemia, 

direct toxicity, neurotoxicity, genotoxicity, reproductive toxicity, or 

developmental toxicity. Potential worker exposures are higher but are 

not expected to pose any risk of adverse health effects.

Immunotoxic effects from exposure to diflubenzuron or formulation 

ingredients, if treatment-related, only could occur at concentrations 

much higher than those from grasshopper applications, but 

individuals with allergic or hypersensitive reactions to the insecticide 

or formulation ingredients could be affected. These individuals are 

advised to avoid treatment areas at the time of application until the 

insecticide has time to dry on the treated vegetation. 

c. Terrestrial Invertebrates—Diflubenzuron applied at the rate and 

coverage in Alternative 2 has a minimal impact on many insects 

common to rangeland ecosystems and is mostly limited to larval 

insects that are exposed to the spray or ingest diflubenzuron. Adult 

insects and spiders would not be affected. Predatory invertebrates 

that consume grasshoppers affected by diflubenzuron are not affected 

by the toxicant (Lockwood et al., 2001). In addition, any reductions in 

nontarget insects are of short duration, typically measured in days. 

This is most likely a result of nontarget insects not being in early life 

(larval) stages during the exact time diflubenzuron is applied or 

exhibiting a behavior (such as being nocturnal or burrowing) and, 

therefore, not exposed to this insecticide.
V. Environmental Consequences

Grasshopper Environmental Impact Statement 57

Catangui et al. (1996) assessed the impact of grasshopper suppression 

programs that used diflubenzuron at Alternative 2 rates on nontarget 

arthropods in South Dakota. In general, there were no significant 

reductions in the numbers of ants, spiders, predatory beetles, or 

scavenger beetles from 7 to 76 days after treatment. Even after 1 year, 

no substantial reductions in soil surface-associated arthropods were 

detected. That study also found that flying nontarget arthropods such 

as pollinator bees, predators, and parasites were not substantially 

reduced either immediately after diflubenzuron treatments or 1 year 

later. 

Bees, such as honey bees and leafcutter bees, are insects of special 

concern because they pollinate crops. In the Western United States 

more than 2,500 species of native bees are found that may be 

specialized pollinators for many noncultivated flowering plants, 

including threatened and endangered species (Tepedino, 1996). 

However, diflubenzuron has been shown to adversely affect honey bees 

only at dietary concentrations much higher and for time periods much 

longer than the concentrations and exposure periods than in 

grasshopper treatment areas. Diflubenzuron application rates as high 

as 0.3125 lb a.i./acre (Schroeder, et al., 1980) and 0.357 lb a.i./acre 

(Emmett and Archer, 1980) resulted in no effects on adult bee 

mortality and brood production. Therefore, diflubenzuron can be 

applied at the rates and coverage in Alternative 2 without 

substantially affecting adult honey bees. 

d. Terrestrial Vertebrates—Chitin or chitin-like substances are not as 

important to terrestrial mammals, birds, and other vertebrates as 

chitin is to insects; therefore, the chitin-inhibiting properties of 

diflubenzuron will have little to no direct toxic impact on vertebrates. 

However, indirect effects may occur after diflubenzuron applications 

under the conditions of Alternative 2, such as reductions in the food 

base for insectivorous wildlife species, especially birds. As stated 

above, diflubenzuron is practically nontoxic to birds, including those 

birds that ingest moribund grasshoppers resulting from diflubenzuron 

applications, as described in Alternative 2. 

While immature grasshoppers and other immature insects can be 

reduced up to 98 percent in areas covered with diflubenzuron, some 

grasshoppers and other insects remain in the treatment area. 

Although the density of grasshoppers and other insects may be low, it 

is most likely sufficient to sustain birds and other insectivores until 

insect populations recover. Those rangeland birds that feed primarily 

on grasshoppers may switch to other diet items. However, in some 

areas the reduced number of invertebrates necessary for bird survival 

and development may result in birds having less available food. In 

these cases, birds will either have less than optimal diets or travel to 

untreated areas for suitable prey items, causing a greater foraging 
V. Environmental Consequences

58 Grasshopper Environmental Impact Statement

effort and a possible increased susceptibility to predation. It also 

should be noted that suppressing grasshopper populations conserves 

rangeland vegetation that often is important habitat to rangeland 

wildlife. Habitat loss is frequently the most important factor leading to 

the decline of a species, and reducing grasshopper densities can be an 

aid in reducing habitat loss.

e. Aquatic Organisms—Although diflubenzuron has relatively few 

effects on most nontarget terrestrial organisms, the same is not the 

case for aquatic organisms, especially freshwater crustaceans and 

immature aquatic insects. Arthropods, including crabs, crayfish, 

lobsters, shrimp, daphnids, mayflies, stoneflies, barnacles, copepods, 

and horseshoe crabs, that are in developing stages can be adversely 

affected by diflubenzuron (Eisler, 2000). Many aquatic invertebrates 

have short life cycles and produce offspring several times a year. 

Aquatic vertebrates, such as fish, are not directly susceptible to 

diflubenzuron. Reductions in the invertebrate food base would likely 

be readily compensated by other food items. 

Diflubenzuron used for grasshopper suppression in Alternative 2 is 

unlikely to cause long-term damage to aquatic ecosystems in the 

Western United States. Many of the organisms most susceptible to 

diflubenzuron, such as marine invertebrates, do not occur in 

rangeland ecosystems. While some aquatic invertebrate populations 

could temporarily decrease if exposed to diflubenzuron, this decrease 

would not likely be permanent because aquatic invertebrates 

regenerate rapidly, and the populations would have the potential to 

recover quickly. 

3. Malathion a. Direct and Indirect Toxicity—Malathion is an AChE inhibitor. For 

vertebrates such as mammals and birds, AChE is essential for normal 

nervous system functions. A moderately severe AChE inhibition of 40 

to 60 percent affects coordination, behavior, foraging ability, and can 

lead to death from weather, predators, or other stresses of survival in 

the wild. The effects of lower AChE levels are still open to question 

regarding biological significance. In samples collected over several 

years from multiple grasshopper treatment areas, not a single bird or 

mammal was found to have more than a 40 percent AChE inhibition, 

and only a few individuals over the course of the entire study had an 

AChE inhibition as high as 20 percent (McEwen et al, 1996a). At the 

malathion ULV application rate in Alternative 2, there is very little 

possibility of toxicity-caused mortality of upland birds, mammals, or 

reptiles, and none has been observed (McEwen et al., 1996b). 

Bioconcentration factors for fish range from 7.36 in lake trout to 34.4 

in willow shiners. The concentration in fish tissues decreases readily 

and consistently with decreasing concentrations of malathion in water. 

No concerns about bioaccumulation are anticipated for grasshopper 

suppression programs (HSDB, 1990; Tsuda et al., 1989). 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 59

b. Human Health—Potential exposures to the general public from 

conventional application rates are infrequent and of low magnitude. 

These low exposures to the public pose no risk of direct toxicity, 

neurotoxicity, genotoxicity, reproductive toxicity, or developmental 

toxicity. Potential worker exposures are higher, but still have no 

potential for adverse health effects except under accidental scenarios. 

The risks to workers under accidental scenarios are minimized if 

proper safety procedures, including required protective gear, are used. 

Malathion has been used routinely in other programs with no reports 

of adverse health effects. Therefore, routine safety precautions are 

anticipated to continue to provide adequate protection of worker 

health. 

EPA has recently reviewed the potential for carcinogenic effects from 

malathion. Their classification describes malathion as having 

“suggestive evidence of carcinogenicity, but not sufficient to assess 

human carcinogenic potential.” This indicates that any carcinogenic 

potential of malathion cannot be quantified based upon the weight of 

EPA’s evidence determination in this classification (EPA, 2000). The 

low exposures to malathion from program applications would not be 

expected to pose any carcinogenic risks to workers or the general 

public. 

Immunotoxic effects from malathion exposure may be expected at 

concentrations much higher than those from grasshopper 

applications, but individuals with allergic or hypersensitive reactions 

to the insecticide or formulation ingredients could be affected. 

c. Terrestrial Invertebrates—Applications of broad spectrum 

insecticidal sprays can cause large reductions in populations of both 

target arthropods (grasshoppers) and nontarget arthropods 

immediately after treatment. Insects that are active during treatments 

or that feed on moribund grasshoppers have the greatest potential for 

exposure to insecticides. Insects of this type include ground beetles, 

darkling beetles, blister beetles, spiders (especially wolf spiders), field 

crickets, foraging bees, and ants. 

A field study (Quinn, 1996) on the effects of malathion applied at 

Alternative 2 rates to suppress grasshoppers summarized that there is 

little evidence that grasshopper control treatments cause any 

long-term effects on nontarget arthropods. Swain (1986) conducted a 

field study on the effects of grasshopper treatments on nontarget 

arthropods and reported that malathion was initially more detrimental 

than either ULV carbaryl or carbaryl bait, but there was no indication 

of long-term effects on the arthropod complex. 
V. Environmental Consequences

60 Grasshopper Environmental Impact Statement

d. Terrestrial Vertebrates—A 3-year field study of indirect effects of 

malathion applied at Alternative 2 rates on nesting birds was 

conducted in Idaho (McEwen et al., 1996b). In the malathion 

treatment area, total invertebrate availability for foraging birds was 

significantly reduced. However, nesting birds switched their diets to 

the remaining insects and reproduced as successfully as birds on 

untreated comparison plots, as also reported by Howe et al. (1996) and 

(2000).

McEwen et al. (1996a) reported about the general response of total 

bird populations to grasshopper treatments. The total number of 

birds of all species within a treatment area did not change after 

treatments with the exception of the western meadowlark, a highly 

insectivorous species. 

Presumably the decrease in western meadowlark was due to reduced 

food availability because there was no evidence of toxic signs in the 

meadowlarks that remained in the treatment area, no dead birds were 

found, and the birds temporarily moved to untreated areas where food 

was more available. 

An alternative explanation not supported by Howe et al. (1996) is that 

meadowlarks could possibly have moved to untreated areas and died, 

or birds may have died on the treated plots but were scavenged, or 

moribund birds were predated upon before observations occurred. 

Howe et al. (1996) determined the effects of malathion applied at 

Alternative 2 rates for grasshopper suppression on reproduction of 

passerine birds in shrubsteppe habitat in southern Idaho. Malathion 

had no observable direct effects on Brewer’s sparrow and sage 

thrasher. There was a significant reduction in food items, but nestling 

growth and survival were not severely affected and the indirect effects 

on those birds were only marginal. 

In some areas, the reduced numbers of invertebrates necessary for 

bird survival and development may result in birds having less 

available food. In these cases, birds will either have less than optimal 

diets or travel to untreated areas for suitable prey items causing a 

greater foraging effort and a possible increased susceptibility to 

predation. 

Small mammals, such as rodents, are not affected to the extent birds 

are affected from an insecticide application. Most small mammals are 

nocturnal and are often in underground burrows during and 

immediately after a treatment. This provides more time for the 

insecticide to dissipate before small mammals are exposed. Deer mice 

collected from an area treated with malathion had lower residues than 

did birds from the same sites (McEwen et al., 1996a). Live trapping 

studies of small rodent populations (primarily deer mice) in areas 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 61

treated with malathion showed no posttreatment decreases (McEwen 

et al., 1996a). The risk assessment in appendix B indicates that of the 

12 species assessed, the species that are at greatest risk from 

malathion applied at Alternative 2 rates are bobwhite quail, American 

kestrel, and Woodhouse’s toad. 

e. Aquatic Organisms—Acute toxicity of malathion varies widely from 

slightly toxic to some species of fish to very highly toxic to other 

species. A direct exposure to malathion in water is toxic to many 

aquatic invertebrates and may kill sensitive fish species (Beyers and 

McEwen, 1996). Appendix B contains more information on the effects 

of malathion to aquatic organisms. Toxicity tests conducted on two 

fish, the Colorado pikeminnow and bonytail chub, using carbaryl and 

malathion exposures that simulated field conditions after a 

grasshopper treatment indicated in their laboratory experiments that 

carbaryl had severalfold higher mortality than malathion to those fish 

(Beyers and Sikoski, 1994). 

D. Environmental Consequences of Alternative 3: Reduced Agent 

Area Treatments (RAATs)

The RAATs strategy has two components: insect suppression and 

conservation biological control. First, treatments made under RAATs 

rely on grasshopper suppression using insecticides. Grasshoppers in 

the treated area are directly exposed to insecticides and suffer 

mortality. Grasshoppers in the areas not directly treated (untreated) 

may also be exposed to insecticides if drift occurs from the treated 

areas or if individuals move from the untreated area into the treated 

area and thus become exposed to the insecticide. Second, RAATs 

strategy relies on conservation biological control. This means that 

naturally occurring predators and parasites of grasshoppers are 

retained in the untreated areas. These predators and parasites remain 

after treatments and are available to suppress grasshoppers in both 

the treated and untreated areas. 

The insecticide APHIS would use under this alternative would be 

either carbaryl, diflubenzuron, or malathion. Carbaryl, diflubenzuron, 

and malathion are all currently registered for use and labeled by EPA 

for rangeland grasshopper treatments and have been demonstrated to 

be effective. Applications of these insecticides could be conducted 

aerially or by ground equipment, and APHIS personnel would conduct 

the treatments in strict adherence to the label directions. The 

application rates analyzed in this document are 8 fluid ounces (0.25 

pound active ingredient) of carbaryl spray per acre, 10 pounds (0.20 

pound active ingredient) of 

2 percent carbaryl bait per acre, 0.75 fluid ounce (0.012 pound active 

ingredient) of diflubenzuron per acre, and 4 fluid ounces (0.31 pound 

active ingredient) of malathion per acre.
V. Environmental Consequences

62 Grasshopper Environmental Impact Statement

The goal of grasshopper suppression under the RAATs alternative is to 

economically and environmentally suppress grasshopper populations 

to a desired level rather than to reduce those populations to the 

greatest possible extent. The efficacy of the RAATs alternative in 

reducing grasshoppers is therefore less than conventional treatments. 

The RAATs efficacy is also variable. Foster et al. (2000) reported that 

grasshopper treatment mortality using RAATs was reduced 2 to 15 

percent from conventional treatments while Lockwood et al. (2000) 

reported 0 to 26 percent difference in mortality between the 

conventional and RAATs alternatives. During grasshopper outbreaks 

when grasshopper densities can be 60 or more per square meter 

(Norelius and Lockwood, 1999), grasshopper treatments that have a 

90 to 95 percent mortality still leave a number of grasshoppers (3 to 6) 

that is generally greater than the average number found on rangeland, 

such as in Wyoming, in a normal year (Schell and Lockwood, 1997). 

The risk assessment (appendix B) used reduced application rates, but assumed 100 

percent coverage because there is no way of knowing how much area will be left 

untreated. In certain circumstances, untreated areas may receive an unintended, small 

amount of insecticide from adjacent treated areas, so complete coverage was used for 

our analyses. Therefore, the actual effects associated with grasshopper suppression 

programs, according to RAATs, are likely to be less severe than described in the risk 

assessment. The untreated areas in RAATs may also be viewed as protected areas that 

play a vital role in protecting nontarget species (Winks et al., 1996). 

1. Carbaryl a. Human Health—EPA has classified carbaryl as a “possible human 

carcinogen” based on an increased incidence of vascular tumors in a 

chronic study of male mice exposed at 46 mg/kg/day (1000 ppm) 

(EPA, 1993). Carbaryl, however, is not considered to pose any 

mutagenic or genotoxic risk based upon the weight of evidence. 

Potential exposures to the general public from RAATs application rates 

are lower than those from conventional application rates, and adverse 

effects decrease commensurately with decreased magnitude of 

exposure. These low exposures to the public pose no risk of direct 

toxicity, carcinogenicity, neurotoxicity, genotoxicity, reproductive 

toxicity, or developmental toxicity. Potential worker exposures are 

higher and have the potential for adverse effects if proper protective 

gear is used. Carbaryl has been used routinely in other programs with 

no reports of adverse effects. Therefore, routine safety precautions are 

anticipated to provide adequate protection of worker health at the 

lower application rates under RAATs. 

Immunotoxic effects from carbaryl exposure are generally expected at 

concentrations much higher than those from grasshopper 

applications, but individuals with allergic or hypersensitive reactions 

to the insecticide or formulation ingredients could be affected. These 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 63

individuals are advised to avoid treatment areas at the time of 

application until the insecticide has time to dry on the treated 

vegetation.

b. Terrestrial Invertebrates and Vertebrates—A decrease in 

susceptible invertebrate populations is evident when carbaryl is 

applied at rates under the RAATs alternative. The immediate effect of 

a treatment results in a more limited predator avoidance by 

susceptible insects and easier foraging for insectivorous species that 

are within the treatment areas or that may migrate into the treated 

area from untreated areas. The decreases in populations of 

susceptible insects following carbaryl applications are expected to be 

minimal with rapid colonization of the treated areas from surrounding 

untreated areas. Using alternating swaths and reducing rates even 

lower as part of a RAATs strategy will further limit the adverse effects 

to nontarget insect populations, thereby minimizing any potential 

adverse effects on foraging insectivorous vertebrates.

A carbaryl bait study applied at Alternative 3 rates for grasshopper 

suppression in North Dakota (George et al., 1992) indicated that low 

rate carbaryl bait applications have minimal potential for direct toxic 

effects on birds and mammals, but may have limited indirect effects 

on species that depend on arthropod groups for food or seed dispersal. 

Also, that study found that Halictid bees, which are the primary 

pollinators of some native plants, did not decline after the bait 

treatments.

AChE inhibition at 40 to 60 percent affects coordination, behavior, 

and foraging ability in vertebrates. This could lead to death from 

weather, predators, or other stresses of survival in the wild. Studies 

over several years for multiple grasshopper treatment areas have 

shown AChE inhibition at levels of no more than 40 percent with most 

at less than 20 percent (McEwen et al., 1996a). After a RAATs 

application, live grasshoppers often remain at a higher density than 

grasshopper populations present in nonoutbreak years and, thus, 

they are available as prey to insectivores. 

McEwen et al. (1996b) studied the effects of carbaryl bait applied at 

Alternative 3 rates to American kestrel nests. No adverse effect was 

noted on the treated nests, and all kestrel nestlings fledged normally. 

Field applications of carbaryl spray at Alternative 3 rates and applied 

in alternate swaths resulted in less reduction to nontarget organisms 

than did blanket applications. Under a RAATs strategy, carbaryl 

affects arthropods less than malathion (Lockwood et al., 2000). The 

effect of carbaryl on bird populations in RAATs areas was similar to 

the effect of malathion RAATs, although malathion perhaps had a 

greater suppressive effect on populations (Norelius and Lockwood, 
V. Environmental Consequences

64 Grasshopper Environmental Impact Statement

1999). Carbaryl is not subject to significant bioaccumulation due to 

its low water solubility and low octanol-water partitian coefficient 

(Dobroski et al., 1985).

c. Aquatic Organisms—Carbaryl has the potential to affect 

invertebrates in aquatic ecosystems but is unlikely to affect 

vertebrates such as fish at any concentrations that could be expected 

under Alternative 3. Although invertebrate populations may be 

reduced, these changes would not be permanent. Over a few months 

it is likely that most, if not all, invertebrate populations have a chance 

to recover to pretreatment levels.

Diflubenzuron Under Alternative 3, the maximum rate that diflubenzuron would be 

applied is 0.75 fluid ounce (0.012 pound active ingredient) per acre 

using ULV sprays. In addition, the area treated is currently 50 

percent of the total suppression area, but this amount is not 

standardized and may decrease substantially. Other RAATs 

applications cover only 33 percent of the suppression area, and it may 

be possible to achieve acceptable grasshopper reduction by treating an 

even smaller area. Because not every possible combination of reduced 

rates and reduced areas could be analyzed, this section is based on 

only the maximum RAATs rate of 0.75 fluid ounce and 100 percent 

coverage. Although this is not a realistic RAATs scenario, this rate/

area combination represents the maximum insecticide burden and 

subsequent environmental effects that could be realized under 

Alternative 3. Grasshopper mortality of 75 to 95 percent after 2 weeks 

would be expected to occur. 

a. Human Health—Potential exposures and adverse effects to the 

general public from RAATs application rates are commensurately less 

than conventional application rates. These low exposures to the 

public pose no risk of methemoglobinemia, direct toxicity, 

neurotoxicity, genotoxicity, carcinogenicity, reproductive toxicity, or 

developmental toxicity. Potential worker exposures are higher, but are 

not expected to pose any risk of adverse health effects. 

Immunotoxic effects from exposure to diflubenzuron or formulation 

ingredients, if treatment-related, could only occur at concentrations 

much higher than those from grasshopper applications, but 

individuals with allergic or hypersensitive reactions to the insecticide 

or formulation ingredients could be affected. These individuals are 

advised to avoid treatment areas at the time of application until the 

insecticide has time to dry on the treated vegetation. 

b. Direct and Indirect Toxicity—Because of its mode of action and low 

toxicity, diflubenzuron would not be toxic to or directly affect humans, 

terrestrial wildlife, plants, and fish at the application rate under 

Alternative 3. The lower application rate under Alternative 3 results in 

commensurately lower overall exposures. Although the highest 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 65

potential for exposure to diflubenzuron would be to insectivorous 

(organisms that consume insects) vertebrates such as birds, rodents, 

and reptiles that consume considerable quantities of grasshoppers 

and other rangeland invertebrates that contain diflubenzuron after a 

treatment, the overall risk to insectivores would be less than the 

negligible risk posed in Alternative 2. The quantitative risk 

assessment in Appendix B has demonstrated that vertebrates have a 

very negligible risk of adverse toxicological effects from full coverage 

treatments using diflubenzuron. None of the 12 representative species 

assessed in Appendix B would accumulate an amount of 

diflubenzuron that even begins to approach a lethal dose under 

Alternative 3. 

In addition to direct toxicity, there is a concern that nontarget species 

that feed upon grasshoppers and other insects would be indirectly 

affected because there would be fewer insects left in a treatment area 

to consume. Because diflubenzuron is most effective against 

immature insects, adult insects in the treatment area would be largely 

unaffected and still available to insectivorous species. 

c. Terrestrial Invertebrates—Diflubenzuron applied at Alternative 3 

rates will have a minimal impact on many insects common to 

rangeland ecosystems. Not all insects in the area treated will be 

affected because adult insects are unaffected by diflubenzuron. In 

addition, immature insects in the untreated areas will have little 

exposure to diflubenzuron and can move into the treated area and 

become adults after diflubenzuron has degraded. 

Although protected in brood chambers, larval honey bees, leafcutter 

bees, and native rangeland bees in the treatment area will be 

indirectly exposed to even the reduced rates of diflubenzuron in 

Alternative 3. Adult bees are not likely to be affected because contact 

with diflubenzuron does not directly affect adult insects, and the 

dietary uptake of small amounts of diflubenzuron in the treatment 

area is brief. Diflubenzuron application rates as high as 0.3125 lb 

a.i./acre (Schroeder et al., 1980) and 0.357 lb a.i./acre (Emmett and 

Archer, 1980) resulted in no effects on adult bee mortality and brood 

production. Bees in the untreated areas would not be affected even if 

they later enter the treated area. 

d. Terrestrial Vertebrates—Chitin or chitin-like substances are not as 

important to terrestrial mammals, birds, and other vertebrates as 

chitin is to insects; therefore, the chitin-inhibiting properties of 

diflubenzuron will have little to no direct toxic impact on vertebrates. 

However, indirect effects may occur after diflubenzuron applications 

under RAATs, such as reductions in the food base for insectivorous 

wildlife species, especially birds. As stated above, diflubenzuron is 

practically nontoxic to birds, including those birds that ingest 
V. Environmental Consequences

66 Grasshopper Environmental Impact Statement

moribund grasshoppers resulting from diflubenzuron applications 

described in Alternative 3. Little, if any, bioconcentration or 

bioaccumulation would be expected for any animals (Booth, 1978). 

The rapid metabolism and lack of bioconcentration indicate that only 

acute toxic effects would be expected for diflubenzuron exposures 

(Opdycke et al., 1982).

Grasshopper densities are reduced less in RAATs than in conventional 

treatments. Therefore, grasshoppers remain not only in the treatment 

area but the untreated area as well. In many cases, the level of 

grasshoppers after RAATs is as large, if not larger, than grasshopper 

populations in nonoutbreak years. For example, grasshopper 

densities during outbreaks can be greater than 50 per square yard. 

Reducing those populations by 90 percent would leave 5 grasshoppers 

per square yard in the treated area. This density may be more 

grasshoppers than in normal years. Norelius and Lockwood (1999) 

reported that grasshopper densities remaining after a grasshopper 

treatment were above the average found on Wyoming rangeland. The 

remaining grasshoppers can sustain birds and other insectivores until 

insect populations recover. 

Rangeland birds also may temporarily switch to diet items other than 

grasshoppers. In years when grasshopper levels are naturally low, 

rangeland birds are forced to find alternative food items. It should 

also be noted that suppressing grasshopper populations conserves 

rangeland vegetation that often is important habitat to rangeland 

wildlife. Habitat loss is frequently the most important factor leading to 

the decline of a species. 

Reducing grasshopper densities can be an aid in reducing habitat 

loss. While perennial plants may remain defoliated for only one 

growing season, Pfadt (1994) attributed high grasshopper densities to 

the defoliation and death of 11 species of native shrubs as well as 

forbs and grasses. 

e. Aquatic Organisms—Diflubenzuron used for grasshopper 

suppression under Alternative 3 is unlikely to cause long-term 

damage to aquatic ecosystems in the Western United States. Although 

diflubenzuron can adversely affect aquatic crustaceans, insects, and 

other arthropods, the rapid regeneration time for these organisms 

ensures rapid recolonization. Diflubenzuron is not toxic to fish. Fish 

that feed on arthropods whose populations may be reduced by 

diflubenzuron may increase their feeding on other diet items until the 

more preferred invertebrate populations recover. 

Malathion a. Human Health—EPA has recently reviewed the potential for 

carcinogenic effects from malathion. EPA’s classification describes 

malathion as having “suggestive evidence of carcinogenicity, but not 

sufficient to assess human carcinogenic potential.” This indicates 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 67

that any carcinogenic potential of malathion cannot be quantified 

based upon EPA’s weight of evidence determination in this 

classification (EPA, 2000). 

Potential exposures to the general public from RAATs application rates 

are of a commensurately lower magnitude than conventional rates. 

These low exposures to the public pose no risk of direct toxicity, 

neurotoxicity, genotoxicity, reproductive toxicity, or developmental 

toxicity. Potential worker exposures are higher than for the general 

public, but still have no potential for adverse health effects except 

under accidental scenarios. The risks to workers under accidental 

scenarios are minimized if proper protective gear is used. Malathion 

has been used routinely in other programs with no reports of adverse 

health effects. Therefore, routine safety precautions are anticipated to 

continue to provide adequate protection of worker health. The low 

exposures to malathion from program applications would not be 

expected to pose any carcinogenic risks to workers or the general 

public. 

Immunotoxic effects from malathion exposure are generally expected 

at concentrations much higher than those from grasshopper 

applications, but individuals with allergic or hypersensitive reactions 

to the insecticide or formulated ingredients could be affected. These 

individuals are advised to avoid treatment areas at the time of 

application until the insecticide has time to dry on the treated 

vegetation. 

b. Terrestrial Invertebrates and Vertebrates—The toxic effects of 

malathion from RAATs application rates cause decreases in 

susceptible invertebrate populations. The immediate effect of a 

treatment results in prey insects having a more limited predator 

avoidance. After treatments, foraging may be easier for insectivorous 

species, both within the suppression areas or those that migrate into 

the treated area from untreated areas. The decreases in populations 

of susceptible insects following malathion applied at Alternative 3 

rates are expected to be minimal with rapid colonization of the treated 

areas from surrounding untreated areas. Using alternating swaths 

and reducing rates even lower as part of a RAATs strategy will further 

limit the adverse effects to nontarget insect populations, minimizing 

any potential adverse effects on foraging insectivorous vertebrates. 

AChE inhibition at 40 to 60 percent affects coordination, behavior, 

and foraging ability in vertebrates. This could lead to death from 

weather, predators, or other stresses of survival in the wild. Studies 

over several years for multiple grasshopper treatment areas have 

shown AChE inhibition at levels of no more than 40 percent with most 

inhibition at less than 20 percent (McEwen et al., 1996a). After a 

conventional treatment, live grasshoppers often remain at a higher 
V. Environmental Consequences

68 Grasshopper Environmental Impact Statement

density than grasshopper populations present in nonoutbreak years, 

and thus they are available as prey to insectivores. Bioconcentration 

factors for fish range from 7.36 in lake trout to 34.4 in willow shiners. 

The concentration in fish tissues decreases readily and consistently 

with decreasing concentration of malathion in water. No concerns 

about bioaccumulation are anticipated for grasshopper suppression 

programs (HSDB, 1990; Tsuda et al., 1989). 

Field applications of malathion at Alternative 3 rates and applied in 

alternate swaths resulted in less reduction in nontarget organisms 

than would occur with blanket applications. However, arthropods in 

malathion RAATs areas were affected more than those in the carbaryl 

RAATs areas (Lockwood et al., 2000). The effect of malathion on bird 

populations in RAATs areas was similar to the effect of carbaryl RAATs 

areas, although malathion perhaps had a greater suppressive effect on 

populations (Norelius and Lockwood, 1999). It should be noted that 

although adult birds can migrate into untreated areas, this activity 

could possibly result in decreased foraging success and increased 

predation on chicks. 

c. Aquatic Organisms—Aquatic field studies on the effects of 

malathion applied at Alternative 3 rates have not been conducted by 

APHIS. However, based on the risk assessment in appendix B, 

malathion applied for grasshopper suppression is most likely to affect 

aquatic invertebrates, especially amphipods and cladocerans. These 

effects would soon be compensated for by the survivors, given the 

rapid generation time of most aquatic invertebrates and the rapid 

degradation of malathion in water. Organisms that normally feed on 

aquatic invertebrates would likely switch temporarily to an alternate 

food source. If no alternate food source is available, the rapid 

generation time of invertebrates means that the affected population 

would quickly recover to pre-exposure levels, or in flowing waters, 

upstream drift would result in recolonization before the predator 

populations would be permanently affected. Therefore, malathion 

applied at Alternative 3 rates would not likely cause long-term effects 

on the aquatic ecosystem. 

E. Species of Concern

This section will describe the effects of grasshopper treatments on 

three species of concern in the Western United States. These species 

are provided as three examples of the many species of concern found 

on rangeland habitats. Species of concern, including federally listed 

endangered and threatened species, will also be addressed during 

consultation with the Fish and Wildlife Service and/or the National 

Marine Fisheries Service as well as in site-specific documents, such as 

environmental assessments, that will be prepared in conjunction with 

grasshopper program activities.
V. Environmental Consequences

Grasshopper Environmental Impact Statement 69

Sage Grouse Grasshoppers and sage grouse are a natural part of rangeland 

ecosystems in the Western United States. Sage grouse is the largest 

grouse in North America and is known for the stunning mating ritual 

of the males that has been considered one of the continent’s great 

wildlife spectacles (Weidensaul, 2001). Sage grouse, a species of 

concern to land management agencies, have been in a state of decline 

throughout most of their entire range. Currently, the Washington 

State population of the sage grouse is a candidate for listing under the 

Endangered Species Act (ESA), with habitat loss as a major factor in 

their decline. 

The organophosphorous insecticides, dimethoate and 

methamidophos, applied to crops can adversely affect sage grouse 

(Blus et al., 1989). A carbamate insecticide, carbofuran, can also 

effect wildlife (Forsyth and Westcott, 1994). APHIS neither uses those 

insecticides nor applies those insecticides to crops as part of the 

grasshopper program. Although malathion is also an 

organophosphorus insecticide and carbaryl is a carbamate insecticide, 

malathion and carbaryl are much less toxic to birds than are 

dimethoate, methamidophos, or carbofuran. The risk assessment in 

appendix B analyzed sage grouse as an indicator species. The risk 

assessment concluded that malathion and carbaryl used for 

grasshopper treatments under Alternative 2 would not directly affect 

sage grouse, and Alternative 3, when 50 to 75 percent less malathion 

and carbaryl would be applied, would have even less of a potential to 

affect sage grouse. 

Sagebrush leaves and buds comprise the vast majority (up to 99 

percent) of sage grouse diet in the winter. Even in summer, sage 

grouse live in close association with sagebrush, but succulent forbs 

and other plants predominate the diet. In the spring, however, sage 

grouse chicks consume a wide variety of foods, including insects that 

are necessary for their growth and survival (Johnson and Boyce, 1990; 

Drut et al., 1994). 

Grasshoppers can be diet items for sage grouse chicks. During 

grasshopper outbreaks when grasshopper densities can be 60 or more 

per square meter (Norelius and Lockwood, 1999), grasshopper 

treatments that have a 90 to 95 percent mortality still leave a density 

of grasshoppers (3 to 6) that is generally greater than the average 

density found on rangeland, such as in Wyoming, in a normal year 

(Schell and Lockwood, 1997). Even though grasshoppers may be less 

available to sage grouse, behavioral changes, such as switching to 

other diet items or increased foraging time, may help compensate for 

the lack of grasshoppers (Howe et al., 2000). 

Although most grasshoppers do not directly damage sagebrush, Pfadt 

(1994) described that grasshopper nymph densities of 100 to 3,000 

per square yard resulted in the defoliation and death of 11 species of 
V. Environmental Consequences

70 Grasshopper Environmental Impact Statement

native shrubs, as well as forbs and grasses. Furthermore, the 

grasshopper damage disrupted the natural biodiversity of the plant 

community and opened the land to soil erosion and invasion by 

noxious weeds. Despite attempts to reduce these outbreaks, one 

outbreak in Nevada that began in 1938 lasted until 1951 (Pfadt, 

1994). 

Forbs and other rangeland vegetation are also important sage grouse 

diet items, especially for juveniles. It is likely that in outbreak 

conditions grasshoppers cause a widespread destruction of forbs. In 

those situations when grasshopper densities exceed the ability of 

predators to control population size (including immature sage grouse), 

the remaining grasshoppers represent a competitive threat to the food 

base of juvenile sage grouse. 

A temporary reduction in the available food for immature sage grouse 

is only one of a multitude of threats facing sage grouse. Fire is a 

threat to physically destroy sagebrush. Rangeland fires can be a 

natural event, a land management tool, a result of human 

carelessness, or even an attempt to control grasshoppers. Regardless 

of the cause, fire directly removes sagebrush habitat for sage grouse 

until the sagebrush has revegetated. Other causes of habitat loss 

include livestock grazing, human development (e.g., building roads, 

housing, and power lines), and anything that serves to fragment or 

degrade sagebrush habitat. Permanent habitat losses are a greater 

threat to sage grouse than are grasshopper treatments. Reducing 

grasshopper numbers in a given area should also increase the number 

of other plants that sage grouse consume in the spring and summer. 

In conclusion, grasshopper suppression programs reduce 

grasshoppers and at least some other insects in the treatment area. 

Sage grouse, both adults and chicks, are likely to be present in some 

areas when grasshopper treatments are made, and grasshoppers can 

be a food item for sage grouse chicks. There is little likelihood that the 

insecticides APHIS would use to suppress grasshoppers would be toxic 

to sage grouse, either by direct exposure to the insecticides or 

indirectly through immature sage grouse eating moribund 

grasshoppers. Because grasshopper numbers are so high in outbreak 

years, treatments would not likely reduce the number of grasshoppers 

below levels present in normal years. Should grasshoppers be 

unavailable in small, localized areas, sage grouse chicks may consume 

other insects, which sage grouse chicks probably do in years when 

grasshopper numbers are unusually low. By suppressing 

grasshoppers, rangeland vegetation is available for use by other 

species, including sage grouse, and rangeland areas are less 

susceptible to invasive plants that may be undesirable for sage grouse 

habitat. Habitat degradation and removal by fire, grazing, and human 

development presents longer lasting and more serious threats to sage 

grouse survival than temporary insect reductions.
V. Environmental Consequences

Grasshopper Environmental Impact Statement 71

2.Biological 

Control Agents 

There are numerous biological control agents being used for the 

control of invasive weeds. The potential effect of the use of insecticides 

is of concern, and this will be addressed when site-specific 

environmental documentation is prepared. One study has been 

conducted to determine the effects of program insecticides on flea 

beetles, Aphthona nigrisutus and A. lacertosa. They are used to 

control leafy spurge, an invasive weed that is spreading on rangeland 

and other ecosystems in Western States. Because leafy spurge 

infestations can occur on rangeland where damaging grasshopper 

populations may require treatment, Aphthona beetles could be 

exposed to insecticides. 

Foster et al. (2001) determined the effect of grasshopper suppression 

programs on flea beetles addressing issues such as how much flea 

beetle mortality grasshopper program insecticides cause and how long 

it takes for flea beetles to return to pretreatment levels. In laboratory 

tests diflubenzuron produced no substantial flea beetle mortality; 

malathion spray produced moderate (25 to 41 percent) mortality; and 

carbaryl spray produced an 86 to 96 percent mortality. Field 

evaluations showed that diflubenzuron resulted in 18 percent 

mortality at 1-week posttreatment and a full recovery to pretreatment 

levels 2 weeks after treatment. Carbaryl bait resulted in a 17 percent 

mortality, carbaryl spray resulted in a 60 to 82 percent mortality, and 

malathion resulted in a 21 to 44 percent mortality. In these field 

evaluations at 1 year after treatment, adult Aphthona populations in 

23 of 24 plots had surpassed pretreatment levels. 

3.Threatened 

and Endangered 

Species

A concern when considering the environmental effects of insecticides 

used for grasshopper suppression is that threatened or endangered 

species may be particularly susceptible either directly or indirectly to 

the effects of those insecticides. Populations of endangered and 

threatened species would be at greater risk, because of the small 

number of individuals, than nonlisted species should the endangered 

or threatened species have an acute sensitivity to program 

insecticides. In some cases, the removal of only a few individuals 

could drastically impact the potential for endangered species to 

survive, whereas other species are better able to compensate when a 

small portion of the population is affected. Endangered and 

threatened species are being examined in a programmatic section 7 

consultation in accordance with the ESA (see chapter 6.D.). 

In order to assess the impacts of grasshopper suppression programs 

on endangered aquatic organisms, studies were conducted on two 

federally listed endangered species: the Colorado pikeminnow and the 

bonytail chub. Each of these species was exposed to carbaryl and 

malathion at concentrations that could incidentally be in water within 

grasshopper treatment areas. These fish were chosen because of 

experimental availability and the historic occurrence of these species 

within the Colorado River Basin, which covers a large portion of the 
V. Environmental Consequences

72 Grasshopper Environmental Impact Statement

affected environment. In addition, the timing of grasshopper 

suppression programs coincides with the early life stages of these fish. 

These life stages may be particularly vulnerable to insecticide 

exposure and are found in shallow, nearshore habitats where 

insecticides typically do not become as dilute as in mainstream areas.

Beyers and Sikoski (1994) reported that Colorado pikeminnow and 

bonytail chub were relatively tolerant of carbaryl and malathion. 

These endangered fish are roughly as sensitive to insecticides as are 

fathead minnows (Beyers and McEwen, 1996), a fish commonly found 

throughout North America. In addition to direct toxicity, the effects of 

carbaryl and malathion on AChE levels in Colorado pikeminnow were 

measured by Beyers and Sikoski (1994). These studies point out that 

carbaryl and malathion used for grasshopper suppression pose no 

greater hazard to endangered or threatened species than to species 

not listed as endangered or threatened. Indirect effects, such as a 

reduction in the number of invertebrate food items, would also affect 

endangered as well as species not endangered. 

F. Cumulative Impacts

Cumulative impact, as defined by the Council on Environmental 

Quality’s National Environmental Protection Act implementing 

regulations (40 CFR § 1508.7) “is the impact on the environment 

which results from the incremental impact of the action when added 

to other past, present, and reasonably foreseeable future actions 

regardless of what agency (Federal or non-Federal) or person 

undertakes such other actions. Cumulative impacts can result from 

individually minor but collectively significant actions taking place over 

a period of time.” 

This EIS is a programmatic environmental document for APHIS’ 

grasshopper suppression programs that involve the application of 

insecticides. It is the effects of the use of insecticides that will be 

added to the past, present, and future actions that have or will occur 

in the action area when considering cumulative impacts. Grasshopper 

program treatments could occur on rangeland in any of the 17 

Western States. The cumulative impact of the application of 

pesticides, as well as other actions, in these same areas will be 

considered on a site-specific basis when a treatment program is 

proposed for a grasshopper infestation. Application of pesticides could 

be carried out by Federal land management agencies, State 

departments of agriculture, local governments, or private groups or 

individuals. The location and magnitude of a treatment area in which 

APHIS is involved need to be defined in order to determine the 

cumulative impacts. 

APHIS cooperates in a grasshopper program at the request of Federal 

land management agencies or State agriculture departments. Once 

APHIS determines that an area requires treatment, the specifics of 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 73

that treatment area will be known. At this time that cumulative 

impacts will be examined in the environmental document that is 

prepared. 

G. Socioeconomic Impactsbah

This section discusses the potential qualitative social and economic 

impacts that could result from the alternatives analyzed in this EIS: 

 1. No Action

 2. Insecticide Applications at Conventional Rates and Complete 

Area Coverage, and 

 3. Reduced Agent Area Treatments (RAATs) in response to a 

grasshopper infestation. 

Under Alternative 1, APHIS would not participate in any grasshopper 

suppression programs. The socioeconomic impacts of APHIS not 

taking any action could result from (1) the extent of damage to 

rangeland and associated resources from grasshopper infestations 

and (2) the availability of funding by private individuals or other 

government agencies (Federal, State, and local) to carry out efforts 

against outbreaks. 

Under Alternative 2, APHIS would apply an insecticide treatment at 

the recommended conventional rate to an entire block of land, 

completely blanketing an area to minimize grasshopper damage. The 

socioeconomic impacts of APHIS using insecticide under this 

alternative would result from (1) the timing and success of chemical 

methods used, (2) the potential for adverse or beneficial environmental 

impacts from this alternative to reduce grasshopper populations, (3) 

the costs of the insecticides and their application, and (4) the resulting 

economic benefits of using insecticides at conventional rates to treat 

an entire infestation area. 

Under Alternative 3, APHIS would apply an insecticide treatment at a 

reduced (less than full) rate and in alternating swaths to an infested 

area to alleviate grasshopper damage. The socioeconomic impacts of 

APHIS’ use of an insecticide at a reduced rate and reduced area 

coverage would result from (1) the timing and success of the treatment 

method used, (2) the potential for adverse or beneficial environmental 

impacts from the reduced rate and reduced area coverage, and (3) the 

decreased cost and greater economic benefits from using an 

insecticide at the reduced rate and on less land area. Foster et al.

(2000) conducted a 3-year study of grasshopper control carrying out 

treatments at conventional rates and treatments at reduced rates 

(RAATs approach) using the insecticides carbaryl, diflubenzuron, and 

malathion. The findings of the study generally concluded that the 

RAATs strategies “can substantially reduce the amount of pesticide 

applied per treated acre, the amount of infested area requiring 
V. Environmental Consequences

74 Grasshopper Environmental Impact Statement

treatment and the overall cost of control actions while demonstrating 

higher economic returns than conventional treatments. RAATs 

techniques offer a great potential for managing grasshoppers at an 

affordable cost while minimally impacting the environment . . . .” 

(Foster et al., 2000).

1.Livestock 

Owners

Livestock owners are one of the major social groups that could be 

economically impacted by grasshopper infestations. Although 

livestock owners can request APHIS to conduct a grasshopper 

suppression program through their State department of agriculture, 

the owners would not make that request unless they were confident 

the program was cost-effective and economically justified. The chief 

commercial use of U.S. rangeland is livestock grazing to produce food, 

fiber, and draft animals (National Research Council (NRC), 1994). 

Livestock (such as cattle) are raised primarily for meat; however, other 

products derived from livestock include hides, tallow, insulin, and 

wool. 

a. Alternative 1: No Action—Under the No Action alternative, forage 

for grazing livestock could be destroyed by a grasshopper infestation. 

Under this scenario, individual livestock owners may have to lease 

rangeland in another area and relocate their livestock, find other 

means to feed them (such as purchasing hay or grain), or sell their 

livestock early. Individual livestock owners could incur economic 

losses from personal attempts to control grasshopper damage, leasing 

alternate grazing rangeland and relocating livestock, or purchasing 

alternate sources of feed (such as hay) for livestock. However, many 

outbreaks occur during droughts when other land leases are 

unavailable and alternate feed is more expensive. Local communities 

where losses occur would incur an adverse economical impact under 

this alternative.

b.Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage—Livestock owners comprise the largest 

social group likely to economically benefit from insecticide treatments 

used to suppress grasshopper infestations. Range and nonrange 

grazing are crucial in domestic livestock production. Insecticides used 

at the conventional control rate and to completely cover an infested 

area would prevent destruction of most forage for livestock on 

rangeland and, thus, would be beneficial for the livestock. This 

treatment method also could economically benefit livestock owners 

who depend on ample forage for their livestock. However, grasshopper 

suppression costs for ranchers are estimated to have increased by 

approximately 30 to 50 percent since the last major outbreak in 1987 

(Foster, pers. comm., 2001, and Helbig and Winks, pers. comm., 

2001), while the price of cattle is virtually unchanged due to inflation 

and decreases in Federal subsidies (Lockwood et al., 1999). 

Large-scale coverage (conventional rates of insecticides used over large 

land areas) is more costly than it was more than a decade ago. The 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 75

cost effectiveness of conducting the conventional approach for 

grasshopper outbreaks would have to be considered on a case-by-case 

basis in determining the overall economic benefits to livestock owners. 

c. Alternative 3: Reduced Agent Area Treatments (RAATs)—

Insecticides used at reduced rates and reduced area coverage would 

suppress grasshopper populations and prevent destruction of most 

forage for livestock. This alternative would most likely economically 

benefit livestock owners who depend on ample forage for their 

livestock. The economics of the RAATs strategy has been studied by 

both Foster et al., 2000, and Lockwood and Schell, 1997. In 

summarizing both studies (which used various rates of insecticide 

below the conventional rates for suppression of rangeland 

grasshoppers and treated less area), the results concluded that 

treatment costs, under this alternative, when compared to the costs 

for conventional treatments for rangeland grasshopper infestations, 

were reduced as follows: 38 to 62 percent with malathion, 

57 to 66 percent with carbaryl, and 56 percent with diflubenzuron. It 

is apparent from these studies that the RAATs alternative has 

potential to result in a viable means for suppressing grasshopper 

infestations below an economic infestation level, could result in 

sustainable rangeland production, and would reduce economic losses 

to livestock owners. 

2. Crop Growers Crop growers include another social group that could be economically 

impacted if rangeland grasshopper infestations occurred near crops. 

Crops are grown both for human and livestock consumption. Some 

grasshopper species feed on and destroy crops. If rangeland is dry or 

vegetation is depleted by grasshoppers, they could move to crops 

growing near rangeland. 

a. Alternative 1: No Action—Under the No Action alternative, crops 

could be destroyed by grasshoppers if no cooperative control efforts 

were implemented. Individual growers could incur financial losses 

from their efforts in attempting to control a grasshopper infestation, 

their outlay in cultivating the crops, and the loss of crops that they 

would not be able to harvest and sell. The loss of crops would have an 

adverse economic effect on local communities. 

b. Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage—The use of insecticides under this 

alternative would suppress a rangeland grasshopper outbreak to some 

level below an economic infestation, thus providing a level of 

protection to nearby crops unaffected by an outbreak. Crop growers 

near rangeland could economically benefit from this alternative in that 

fewer grasshoppers would remain to move from rangeland to their 

crops, thus resulting in reduced crop loss. 
V. Environmental Consequences

76 Grasshopper Environmental Impact Statement

c. Alternative 3: Reduced Agent Area Treatments (RAATs)—

Insecticide used at reduced rate and coverage would suppress a 

rangeland grasshopper infestation, thus possibly preventing 

grasshoppers from moving to nearby crops and, consequently, 

providing crops with some level of protection from an outbreak. Crop 

growers could economically benefit from this alternative in that a 

suppressed grasshopper population on rangeland would most likely 

result in reduced grasshopper movement to crops and reduced crop 

damage. 

3. General 

Public 

Consumer segments of the general public rely on products (such as 

meat and crops) and byproducts (such as insulin or tallow) from 

agricultural resources produced on or near rangeland. Consumers 

could be economically affected by grasshopper infestations. 

a. Alternative 1: No Action—In the case of the No Action alternative, 

some consumer segments of the general public, on a local or regional 

basis, could incur loss of a sufficient supply of products (e.g., meat 

and crops) that were not produced because of grasshopper 

infestations that impact the sources of the products and their 

byproducts. Demand, which could be placed on other markets for 

these products and byproducts, could cause increased prices of those 

items. If livestock owners or crop growers incur the costs for 

suppressing grasshopper outbreaks, these costs could be passed on to 

the consumer through higher commodity prices. Consumers of 

livestock, crops, or byproducts of these commodities could face higher 

prices. Consumers in the local communities where grasshopper 

infestations deplete vegetation would incur adverse economic impacts. 

b.Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage—Individuals of the general public in regional 

and local areas could economically benefit from insecticides used 

against grasshopper infestations at the conventional rate and 

coverage. The use of insecticides at the full rate and for complete area 

coverage would reduce grasshopper populations, thereby conserving 

forage for livestock and possibly preventing grasshoppers from moving 

to nearby crops that otherwise would be destroyed by them. This 

alternative would economically benefit consumers of meat, crops, or 

byproducts of these commodities because markets for these 

commodities most likely would be minimally affected in that they 

would not face major decreases in commodities and the costs 

associated with these commodities most likely would be minimally 

affected. 

c. Alternative 3: Reduced Agent Area Treatments (RAATs)—

Individuals of the general public in regional and local areas could 

economically benefit from insecticides used against grasshopper 

infestations at a reduced rate and reduced area coverage. 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 77

Grasshopper populations on rangeland would be reduced, thus 

conserving resources for livestock and possibly conserving nearby 

crops that otherwise could be destroyed by grasshoppers. This 

alternative could economically benefit consumers of livestock, crops, 

and byproducts because markets and costs for these commodities 

would be minimally affected. 

4.Beekeepers Ample and healthy bee populations are economically important to 

various crop growers and commodity producers. Some beekeepers 

cultivate bee colonies for the purpose of providing pollination services 

to crop growers. Producers of various crops and commodities rely on 

bees for pollination, resulting in increased production. For example, 

alfalfa seed producers use several bee species in farming practices to 

increase the yield of alfalfa seeds. Honey producers rely on bees and 

their hives for honey production. Without the appropriate bee 

populations in crop and commodity production areas, a decline in 

pollination would occur, most likely decreasing some crop and 

commodity production. 

a. Alternative 1: No Action—Under the No Action alternative, 

individuals who rely on bees for their livelihood, such as pollination 

services, honey producers, and alfalfa seed producers, could incur 

economic losses. Grasshopper destruction leading to loss of 

vegetation that bees frequent for food and that they pollinate could 

adversely impact beekeepers. In addition, the loss of honey bees as a 

result of precautions not implemented to protect beehives from 

uncoordinated use of insecticides to protect nearby crops and other 

agricultural resources from grasshoppers (non-APHIS use of 

insecticides) also could impact individuals who rely on bees. Some bee 

species are susceptible to some insecticides and can be protected 

through moving or protecting cultivated beehive colonies. Individual 

beekeepers, alfalfa seed producers, or honey producers could be 

economically impacted under this alternative. 

b. Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage—Beekeepers and others who rely on bees for 

their livelihood could be economically affected more by the use of 

carbaryl and malathion than by the use of diflubenzuron under this 

alternative. In areas where bees are required for honey production or 

alfalfa cultivation, the use of liquid formulations of carbaryl and 

malathion for grasshopper suppression potentially could impact bee 

populations, thus impacting individuals who rely on bees for their 

livelihood. Both carbaryl and malathion are highly toxic to honey bees 

(Johansen and Mayer, 1990, and Johansen et al., 1983). 

Diflubenzuron is relatively nontoxic to honey bees (Robinson and 

Johansen, 1978), especially adults, and thus would not have the 

potential for adverse impacts that the other two insecticides have. 
V. Environmental Consequences

78 Grasshopper Environmental Impact Statement

APHIS will work to protect bees. This will protect both the livelihood of 

individuals who rely on bees and native bees that may be in a 

treatment area. Examples of measures that can be implemented to 

protect bees are notifying beekeepers in advance of any spray 

programs so that hives can be moved or protected, conducting spray 

treatments at a time of day when the fewest number of bees would be 

away from the hive, choosing an insecticide that has a relatively low 

potential to affect bees, using a bait formulation (when available) 

instead of a liquid formulation, and strict adherence to label 

restrictions. Any protective measures that may be implemented to 

reduce the potential effects of grasshopper suppression activities on 

bees would best be described in a site-specific environmental 

document. However, the full coverage application of liquid malathion 

or carbaryl at conventional rates could temporarily expose some bee 

populations, especially native bees, and subsequently have some 

economic impact on producers who depend on bee species for 

production purposes. 

c. Alternative 3: Reduced Agent Area Treatments (RAATs)—

Beekeepers and others who rely on bees for their livelihood could be 

economically affected by insecticides used under the reduced rate and 

coverage alternative. The use of spray formulations of carbaryl and 

malathion, even at reduced rates for grasshopper infestations, 

potentially could impact bee populations that these groups depend 

upon. However, the use of insecticides at reduced rate and over 

reduced area of coverage would conserve more wild bees than the use 

of insecticides at the conventional rate and coverage. As stated in the 

paragraph above, measures implemented to reduce the effects of 

grasshopper suppression activities on bees would be best described in 

a site-specific environmental document. Although the reduced rate 

and reduced area coverage could impact bee populations resulting in 

some economic impact on producers, the adverse economic impact will 

be less than that of the economic impact from the conventional rate 

and coverage. 

5.Recreationists Public lands, including Federal and State forests, parks, wilderness, 

and recreational areas are used for a variety of recreational activities, 

including camping, fishing, and hiking. Some public land may be 

leased to ranchers for livestock grazing use; however, the 

socioeconomic impacts to livestock owners is addressed earlier in this 

section. If infestations occurred near public lands, grasshoppers 

could impact these lands by feeding on grasses and other vegetation in 

these areas. 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 79

Western rangeland is increasingly used as recreational resources by 

millions of visitors each year (NRC, 1994). People use rangeland for a 

variety of recreational activities, including vacations, horseback riding, 

hiking, picnicking, fishing, hunting, skiing, snowmobiling, and driving 

off-road vehicles. 

a. Alternative 1: No Action—Depending upon the available funding 

and actions of other government agencies to manage grasshoppers, 

vegetation on public lands on or near rangeland could be adversely 

impacted by grasshopper damage if insecticide is needed but not 

applied before an infestation reaches an economically damaging level. 

If grasshoppers deplete vegetation on rangeland or public use lands, 

soil erosion could result and lead to reduction in water quality. This 

could cause temporary decreases in use of some areas, thereby 

impacting some recreationists who may then travel to alternate public 

land locations to carry out their activities. Alternatively, viewing large 

swarms of grasshoppers may be a source of attraction to some 

members of the public. 

Under this alternative, temporary reduction in or displacement of 

wildlife species could occur if grasshopper infestations devastate 

forage and habitat used by game wildlife and other wildlife. Reduction 

in wildlife habitat and forage could diminish plant and animal 

diversity, thus resulting in a decrease in wildlife-associated recreation. 

Less recreational opportunities could result in some economic loss to 

those who sell licenses, permits, or sporting goods and equipment to 

recreationists who use public lands for activities, such as hunting, 

fishing, or bird watching. If lands are denuded from grasshopper 

infestations, this also could lead to soil erosion and result in 

sedimentation problems in water, thus adversely affecting game fish. 

When considering an economic value on consumptive recreational 

activities, such as hunting or fishing or nonconsumptive recreation, 

such as bird watching or photography, less recreation means an 

economic loss (Skold and Kitts, 1996). A loss could be realized for 

several years until native vegetation and wildlife are able to 

reestablish, provided they are not displaced.

b. Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage—Recreational users of rangeland or public 

lands on or near rangeland most likely would not be affected by the 

use of insecticides at the conventional rate and complete area coverage 

for grasshopper infestations. Insecticide treatments are short-lived 

and most likely would impact land uses temporarily. In fact, 

recreationists would most likely benefit from efforts that will help to 

protect the natural ecosystems and their resources from grasshopper 

devastation. 
V. Environmental Consequences

80 Grasshopper Environmental Impact Statement

Any protective measures that may be implemented to reduce potential 

effects of grasshopper suppression activities on recreationists would 

best be described in a site-specific environmental document. The use 

of insecticide treatments at conventional rates would most likely 

reduce loss of natural resources on public land and associated 

economic losses. 

Suppression of economically damaging grasshopper populations using 

insecticide at the conventional rate and area coverage could help to 

maintain forage and habitat for wildlife, thus maintaining wildlife 

populations on lands for recreational purposes. While insecticide use 

potentially could impact wildlife species, approved treatment options 

are the result of careful evaluation and selection to determine 

materials and methods that minimize the threat to the environment 

(Skold and Kitts, 1996). The environmental monitoring component of 

past grasshopper control programs (including insecticides used at 

conventional rates and coverage) has not found adverse effects on 

wildlife resulting from grasshopper suppression programs (Skold and 

Kitts, 1996). If grasshopper treatments do not result in wildlife 

depletion, economic losses from reductions in wildlife-associated 

recreation most likely would not occur (Skold and Kitts, 1996). 

Treatments are short-lived and most likely would result in brief 

closure of areas for recreational purposes and minimal loss of 

activities to recreationists and minimal economic losses to those who 

profit from recreation-related sales.

c. Alternative 3: Reduced Agent Area Treatments (RAATs)—The use 

of insecticide treatments, even at a reduced rate and area coverage, 

would most likely prevent loss of natural resources on public land and 

associated economic losses. Insecticide treatments are short-lived and 

most likely would impact recreational uses briefly. Using less 

insecticide and treating less land area would be economically 

advantageous to public land management agencies. Reduced use of 

insecticide and area coverage results in lower treatment cost than the 

conventional treatment. 

The RAATs alternative most likely would have minimal socioeconomic 

impact on recreationists who use grasshopper-affected lands for 

activities such as hunting, fishing, or bird watching or those who sell 

licenses, permits, or sporting goods to recreationists. While 

grasshopper infestations can destroy rangeland grasses and other 

vegetation that wildlife species rely on for forage or habitat, the use of 

insecticide treatments, even at a reduced rate, would most likely 

minimize economic damage from grasshoppers to rangeland used for 

recreation. While insecticides would impact grasshoppers in infested 

areas, insecticide use according to labels, and at reduced rates and 

reduced coverage (consistent with scientific and conservation 

principles) most likely would have minimal, if any, impacts on wildlife 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 81

populations for recreational purposes. Treatments are short-lived and 

most likely would result in brief closure of areas for recreational 

purposes and minimal loss of activities to recreationists and minimal 

economic losses to those who profit from recreation-related sales. 

6.Esthetics of 

the Natural 

Environment

Grasshoppers are a food source for some wildlife species and serve as 

an important role in rangeland nutrient cycling; however, grasshopper 

infestations can severely affect natural resources that give rangeland 

its esthetic characteristics. According to Skold and Kitts (1996), 

rangeland is increasingly recognized as important for its 

environmental and recreational amenities. Rangeland not only 

produces tangible products such as forage, wildlife habitat, water, 

minerals, energy, plant and animal gene pools, recreational 

opportunities, and some wood products, but also produces intangible 

products (non-use values), including natural beauty, open space, and 

the mere existence as a natural ecosystem, that are the result of use 

(NRC, 1994). Others emphasize biological diversity and the associated 

potential array of products and services as a distinct intangible 

product (West, 1993, cited in Skold and Kitts, 1996). Further, 

rangeland covers vast areas, often contiguously, and thereby 

possesses the scale necessary for biological diversity of communities, 

ecosystems, and landscapes (West, 1993, cited in Skold and Kitts, 

1996). 

a. Alternative 1: No Action—Under the No Action alternative, the use 

of affected rangeland for esthetics and biological resources could be 

lost for several years until native vegetation and wildlife are able to 

reestablish. Loss of native vegetation disturbs natural environments 

and then provides the opportunity for invasive plant species to 

outcompete native vegetation. Post-fire revegetation would also be 

jeopardized. Humans who enjoy these lands for their beauty and 

wildlife species that use the ecosystems of these lands could be 

adversely affected by grasshopper destruction. Lost economic benefits 

(e.g., photography, vacation uses, enjoyment of the natural scenery 

including wildlife) of enjoying or using these lands for their intangible 

products could be incurred from uncontrolled grasshopper outbreaks. 

b. Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage—Under this alternative, the impact on the 

use of affected rangeland for esthetics and biological resources could 

be minor. Treatment activities involving the use of insecticides at 

conventional rates and complete area coverage are temporary and 

would most likely impact the use and enjoyment of affected areas for 

short periods of time. Some loss of economic benefits (e.g., from 

photography, hiking, and vacation uses) from not being able to enjoy 

or use these lands for a short duration could occur. Most likely, the 

long-term benefits of treating these lands for grasshopper infestations 

outweigh any temporary economic losses. 
V. Environmental Consequences

82 Grasshopper Environmental Impact Statement

c. Alternative 3: Reduced Agent Area Treatments (RAATs)—Under 

this alternative, the socioeconomic impact of grasshopper infested 

areas, such as rangeland, for esthetics and biological resources could 

be minor. Treatment activities are temporary and would impact the 

use and enjoyment of affected areas for a short duration. Minimal loss 

of economic benefits from not being able to enjoy or use these lands 

(e.g., from photography, hiking, and vacation uses) could occur for a 

short duration. Most likely, the long-term economic benefits of using 

this alternative for grasshopper infestations on these lands outweigh 

the short-term economic losses. In addition, reduced insecticide use 

and reduced area coverage under the RAATs alternative would 

minimally affect the esthetics and biological resources that comprise 

the natural environment of rangeland.

7. Artificial 

Surfaces

Some chemicals, including insecticides, can affect artificial surfaces. 

Malathion could be used as a treatment for grasshopper infestations 

and is known to damage some paint surfaces (Mabry, 1981, and 

Mangum, 1981). Artificial surfaces, such as vehicles and signs, 

painted with metallic acrylic lacquers and baked enamel could be 

affected by the use of malathion for grasshopper infestations. Some 

owners of vehicles or signs could be economically impacted from the 

cosmetic damage malathion could cause. However, certain measures 

can be taken to avoid damage from malathion on painted surfaces. In 

areas where this is a concern, malathion surface damage will be 

addressed in a site-specific environmental document. 

a. Alternative 1: No Action—Under the No Action alternative, the 

extent of insecticide use by others (e.g., State or local agencies or 

private groups or individuals) is unknown; however, some efforts using 

insecticides to suppress infestations most likely would occur. 

Therefore, it is possible that some artificial surfaces could be affected 

by non-APHIS use of malathion and that vehicle owners and others 

who own items covered with certain paints could be economically 

impacted by this alternative. It also has been anecdotally reported 

that grasshoppers have eaten paint on houses; under this reported 

scenario, if APHIS takes no action, it is possible that uncontrolled 

grasshopper infestations could cause economic damage to some 

painted surfaces. 

b. Alternative 2: Insecticide Applications at Conventional Rates and 

Complete Area Coverage—Under this alternative, some vehicle and 

sign owners could be economically impacted by the use of malathion 

for grasshopper infestations. If a vehicle or sign, painted with metallic 

acrylic lacquer or baked enamel paints, is in or downwind of a 

treatment site, there is potential for damage to its paint finish from the 

use of malathion. Damage of this kind is likely to be negligible 

compared to normal wear on a paint finish from windborne dust and 
V. Environmental Consequences

Grasshopper Environmental Impact Statement 83

road debris from road travel in rangeland areas. The economic impact 

to vehicle and sign owners from malathion used under this alternative 

most likely would be negligible. 

It may be necessary to take measures that reduce the potential for 

malathion to come in contact with certain artificial surfaces. These 

measures include ensuring that vehicles are not in areas of rangeland 

treatments, covering susceptible surfaces that are in areas of 

rangeland treatments, and even choosing a different formulation of 

program insecticide that will not harm these surfaces. Any protective 

measures that may be implemented to reduce the potential effects of 

grasshopper suppression activities on certain artificial surfaces would 

best be described in a site-specific environmental document in areas 

where this is a concern. 

c. Alternative 3: Reduced Agent Area Treatments (RAATs)—Under 

the RAATs alternative, the paint on some vehicles and signs could be 

cosmetically damaged by the use of malathion for grasshopper 

infestations the same as they could under the conventional treatment 

alternative. Damage of this kind is likely to be negligible compared to 

normal wear on a paint finish from windborne dust and road debris 

from road travel in rangeland areas. With the reduced use of 

insecticide and area coverage from this alternative, the potential for 

economic damage to artificial surfaces is decreased. As stated above, 

for insecticide application at conventional rates and complete 

coverage, it may be necessary to take measures that reduce the 

potential for malathion to contact certain artificial surfaces. Any 

protective measures that may be implemented to reduce the potential 

effects of grasshopper suppression activities on certain artificial 

surfaces would best be described in a site-specific environmental 

document in areas where this is a concern. 
V. Environmental Consequences

84 Grasshopper Environmental Impact Statement
VI. Other Environmental Considerations

Grasshopper Environmental Impact Statement 85

VI. Other Environmental Considerations

A. Environmental Justice

Executive Order (E.O.) 12898, Federal Actions To Address 

Environmental Justice in Minority Populations and Low-Income 

Populations, was signed by President Clinton on February 11, 1994 

(59 Federal Register (FR) 7269). This E.O. requires each Federal 

agency to make achieving environmental justice part of its mission by 

identifying and addressing, as appropriate, disproportionately high 

and adverse human health or environmental effects of its programs, 

policies, and activities on minority populations and low-income 

populations. Consistent with this E.O., the Animal and Plant Health 

Inspection Service (APHIS) will consider the potential for 

disproportionately high and adverse human health or environmental 

effects on minority populations and low-income populations for any of 

its actions related to grasshopper and Mormon cricket suppression 

programs. (The term “grasshoppers” used in this document refers to 

both grasshoppers and Mormon crickets, unless differentiation is 

needed.) 

When planning a site-specific action related to grasshopper 

infestations, APHIS will consider the potential for disproportionately 

high and adverse human health or environmental impacts of its 

actions on minority populations and low-income populations in the 

environmental document for the proposed action. In doing so, APHIS 

program managers will work closely with representatives of these 

populations in the locale of planned actions. 

In developing site-specific environmental documents, there are nine 

opportunities in the National Environmental Policy Act (NEPA) process 

where environmental justice issues can be integrated, as identified 

and described in detail in the U.S. Department of Agriculture’s (USDA) 

Departmental Regulation 5600-2, Environmental Justice (USDA, 

1997). A few of these opportunities are explained here. The first 

opportunity would be when the agency defines the action, purpose, 

need, and area of potential effect. The action proposed by the agency 

should be clearly defined so that interested parties understand what is 

being proposed. The agency should identify the purpose of the action 

and provide justification as to why the action is needed. The area of 

potential concern should be defined (i.e., physical boundary of area 

reasonably expected to be affected by the action) so that the agency 

can include all of the minority and low-income populations within this 

area in all of its outreach efforts. The second opportunity is during 

scoping. Once the potentially affected parties are identified, it is 

important to communicate with and understand the concerns of these 

groups. Notification should be accomplished by such means as 
VI. Other Environmental Considerations

86 Grasshopper Environmental Impact Statement

publishing notices in local newspapers and broadcasts on local radio 

and television stations. This information may need to be translated 

into the language of minority populations. 

Two other opportunities where consideration of minorities and 

low-income populations can be considered include the analysis of the 

effects of the alternatives and the development of mitigation to 

minimize adverse effects. The analysis of impacts should include 

potential impacts to subsistence consumption and human health as 

well as the related economic and social effects of the alternatives. 

When developing mitigation, the concerns and suggestions of 

minorities and low-income populations should be carefully 

considered. Once mitigation measures have been developed, there 

should be followup to ensure they are implemented and are effective.

In past grasshopper programs, the U.S. Department of the Interior’s 

(DOI) Bureau of Land Management (BLM) or Bureau of Indian Affairs 

(BIA) have notified the appropriate APHIS State Plant Health Director 

when any new or potentially threatening grasshopper infestation is 

discovered on BLM lands or tribal lands held in trust and 

administered by BIA. APHIS has cooperated with BIA when 

grasshopper programs occur on Native American tribal lands. In 

future grasshopper programs involving Native American populations, 

APHIS program managers will work with BIA and contacts established 

under the APHIS Native American Working Group to communicate 

information to tribal organizations and representatives when 

programs have the potential to impact the environment of their 

communities, lands, or cultural resources. 

B. Protection of Children

The increased scientific knowledge about the environmental health 

risks and safety risks associated with hazardous substance exposures 

to children and recognition of these issues in Congress and Federal 

agencies brought about legislation and other requirements to protect 

the health and safety of children. On April 21, 1997, President 

Clinton signed E.O. 13045, Protection of Children From 

Environmental Health Risks and Safety Risks (62 FR 19885). This 

E.O. requires each Federal agency, consistent with its mission, to 

identify and assess environmental health risks and safety risks that 

may disproportionately affect children and to ensure that its policies, 

programs, activities, and standards address disproportionate risks to 

children that result from environmental health risks or safety risks. 

APHIS has developed agency guidance for its programs to follow to 

ensure the protection of children (USDA, APHIS, 1999). 

The human health risk assessment for this environmental impact 

statement (EIS) analyzed the effects of exposure to children from 

carbaryl, diflubenzuron, and malathion. Information about the 

exposure risks to children from these insecticides is discussed in 
VI. Other Environmental Considerations

Grasshopper Environmental Impact Statement 87

appendix B of this EIS. Based on review of the insecticides and their 

use in the grasshopper programs, the risk assessment concluded that 

the likelihood of children being exposed to insecticides is very slight 

and that no disproportionate adverse effects to children are 

anticipated over the negligible effects to the general population. 

Treatments used for grasshopper programs are primarily conducted 

on open rangelands where children would not be expected to be 

present during treatment or enter should there be any restricted entry 

period after treatment. In the preparation of the site-specific 

environmental documents, an evaluation of the risk of the program 

exposing children to an insecticide will be conducted. If protection 

measures are determined to be necessary, they will be implemented. 

C. Cultural Resources and Events

The potential for impacts that could occur from program-related 

activities to cultural and historical sites and artifacts, such as 

petroglyphs and monuments, and cultural events, such as Native 

American sun dances, will be considered in site-specific environmental 

documents, as needed. An example of a concern about a potential 

program impact to cultural artifacts occurred in 1995. BLM in 

Wyoming expressed concern about the possibility that a malathion 

formulation containing oil might have an adverse effect on 

carbon-dating techniques used for pictographs and petroglyphs. In 

that particular situation, site-specific protective measures were 

implemented to mitigate any possible impacts from drift of the 

insecticide near the petroglyphs. 

A program treatment is of short duration and generally would occur 

once in a program area during the treatment season. Treatments 

typically do not occur at cultural sites, and drift from a program 

treatment at such locations is not expected to adversely affect natural 

surfaces, such as rock formations and carvings. However, to ensure 

that historical and cultural sites, monuments or buildings, or artifacts 

of special concern are not adversely affected by program treatments, 

APHIS will confer with BLM or other appropriate land management 

agencies at the local level to protect these areas. APHIS also will 

confer with the appropriate tribal authority and, as needed, with the 

BIA office at a local level to ensure that the timing and location of a 

planned program treatment does not coincide or conflict with cultural 

events or observances, such as sun dances, on tribal lands. 

D. Endangered Species Act 

Policies and procedures for protecting endangered and threatened 

species of wildlife and plants were established by the Endangered 

Species Act (ESA) of 1973, as amended (16 United States Code (U.S.C.) 

§ 1531 et seq.). The ESA is designed to ensure the protection of 

endangered and threatened species and the habitats upon which they 

depend for survival. Regulations implementing the provisions of the 

ESA have been issued.
VI. Other Environmental Considerations

88 Grasshopper Environmental Impact Statement

In accordance with section 7 of the ESA, consultation is to be 

conducted for any action authorized, funded, or carried out by a 

Federal agency that may affect listed endangered or threatened 

species or their habitats. APHIS includes proposed species in their 

consultations. Consultations are conducted with Fish and Wildlife 

Service (FWS), DOI, for terrestrial species and most aquatic species 

and with the National Marine Fisheries Service (NMFS), U.S. 

Department of Commerce, for marine and anadromous species.

The document APHIS prepares to determine the potential impacts of 

an action on endangered and threatened species and their habitats is 

a biological assessment (BA). A BA for the grasshopper program 

(USDA, APHIS, 1987a) was completed in conjunction with the 

Rangeland Grasshopper Cooperative Management Program, Final 

Environmental Impact Statement—1987 (USDA, APHIS, 1987b). 

APHIS is now preparing the BA that will be used to conduct a new 

programmatic consultation with FWS and/or NMFS for APHIS’ 

grasshopper suppression programs that may affect listed or proposed 

endangered or threatened species or their habitats. The BA will 

evaluate the potential direct and indirect effects of the use of the three 

insecticides on the endangered and threatened species and their 

habitats that occur in the 17 Western States. Through the 

consultation process, protection measures will be developed that, 

when implemented, will ensure the grasshopper program will not 

adversely affect endangered or threatened species or their habitats.

E. Monitoring

Monitoring involves the evaluation of various aspects of the 

grasshopper suppression programs. There are three aspects of the 

programs that may be monitored. The first is the efficacy of the 

treatment. APHIS will determine how effective the applications of an 

insecticide has been in suppressing the grasshopper population within 

a treatment area. 

The second area included in monitoring is safety. This includes 

ensuring the safety of the program personnel through medical 

monitoring conducted specifically to determine risks of a hazardous 

material. Part of such a program could be checking to make sure the 

proper use of protective equipment is being used, such as long-sleeved 

or long-legged clothing and respirators, and the implementation of 

cholinesterase testing to prevent overexposure. (See APHIS Safety and 

Health Manual (USDA, APHIS, 1998) available online at: 

www.aphis.usda.gov/mb/aseu/shes/shes-manual.html.)

The third area of monitoring is environmental monitoring (APHIS 

Directive 5640.1) (USDA, APHIS, 2002). This includes such things as 

checking to make sure the insecticides are applied in accordance with 

the labels and sensitive sites and organisms are protected. Should 
VI. Other Environmental Considerations

Grasshopper Environmental Impact Statement 89

environmental monitoring be conducted, a monitoring plan will 

describe the where, when, what, and how many samples should be 

collected. The types of samples collected might include flowing or 

stationary water, soil, sediment, fish, insects, and vegetation, as well 

as measuring airborne drift using dye cards. Precision monitoring 

could be utilized to limit pesticide use to areas where pests actually 

exist or are reasonably expected and where economically and 

technically feasible. Samples will be analyzed for insecticide residues, 

and monitoring reports will be written should monitoring be 

conducted.

Sensitive sites include habitats of endangered and threatened species, 

wildlife refuges or preserves, surface water, or other sites of concern to 

the public. As a result of the consultation conducted in compliance 

with the ESA, environmental monitoring may be required to ensure 

adverse impacts to endangered and threatened species or their 

habitats do not occur. Under NEPA, monitoring would be conducted 

to ensure compliance with mitigation adopted as part of the decision 

to conduct a treatment program. 

The Grasshopper Integrated Pest Management (IPM) Program has 

conducted studies on the effects of insecticide treatments on 

nontarget organisms. This information can be found in the IPM 

Manual (USDA, APHIS, 1996) which is also available online at: 

www.sidney.ars.usda.gov/grasshopper/index.htm. 
VI. Other Environmental Considerations

90 Grasshopper Environmental Impact Statement
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Grasshopper Environmental Impact Statement 91

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Grasshopper Environmental Impact Statement 97

Reuter, K.C. and Foster, R.N., 1996. Success with reduced rates of 

carbaryl, malathion, and acephate sprays. In U.S. Department of 

Agriculture, Animal and Plant Health Inspection Service, 1996. 

Grasshopper Integrated Pest Management User Handbook, Tech. 

Bul. No. 1809. Sec. II.5. Washington, DC.

Reuter, K.C., Foster, R.N., Jech, L.E., Walgenbach, D.D., Walgenbach, 

D.R., and Roland, T.J, 1993. Field evaluation of a reduced rate of 

carbaryl spray on rangeland grasshoppers (Orthoptera: Acrididae). 

Journal of the Kansas Entomology Society 66(2):231–236.

Robinson, W.S., and Johansen, C.A., 1978. Effects of control 

chemicals for Douglas-fir Tussock moth Orgyia pseodotsugata

(McDonnough) on forest pollination (Lepidoptera: Lymantriidae). 

Melanderia 30:10–56.

Sanderson, R., and Huddleston, E., 1996. Factors affecting 

application and chemical deposition. In U.S. Department of 

Agriculture, Animal and Plant Health Inspection Service, 1996. 

Grasshopper Integrated Pest Management User Handbook, Tech. 

Bul. No. 1809. Sec. II.7. Washington, DC.

Schell, S., and Lockwood, J., 1997. Spatial characteristics of 

rangeland grasshopper population dynamics in Wyoming: 

implications for pest management. Environmental Entomology 

26:1056–1065.

Schroeder, W.J., Sutton, R.A., and Beavers, L.B., 1980. Diaprepes 

abbreviatus: Fate of diflubenzuron and effect on nontarget pest 

and beneficial species after application to citrus for weevil control. 

J. Econ. Entomol. 73:637–638.

Skold, M.D., and Kitts, A.W., 1996. Rangeland environmental 

amenities and grasshopper management programs. In U.S. 

Department of Agriculture, Animal and Plant Health Inspection 

Service, 1996. Grasshopper Integrated Pest Management User 

Handbook, Tech. Bul. No. 1809. Sec. VII.12. Washington, DC.

Swain, J.L., 1986. Effect of chemical grasshopper controls on 

non-target arthropods of rangeland in Chaves County, New Mexico. 

New Mexico State University, Masters Thesis, Las Cruces, New 

Mexico. December 20, 1996.

Tepedino, V.J., 1996. The reproductive biology of rare rangeland 

plants and their vulnerability to insecticides. In U.S. Department 

of Agriculture, Animal and Plant Health Inspection Service, 1996. 

Grasshopper Integrated Pest Management User Handbook, Tech. 

Bul. No. 1809. Sec. III.5. Washington, DC.
VII. References for Chapters I through VI

98 Grasshopper Environmental Impact Statement

Tsuda, T., Aoki, S., Kojima, M., and Harada, H., 1989. 

Bioconcentration and excretion of diazinon, IBP, malathion, and 

fenitrothion by willow shiner. Toxicology and Environmental 

Chemistry 24:185–190.

USDA—See U.S. Department of Agriculture.

U.S. Department of Agriculture, 1997. Departmental Regulation 

5600-2, Environmental Justice. December 15, 1997. U.S. 

Department of Agriculture, Washington, DC. 

USDA, APHIS—See U.S. Department of Agriculture, Animal and Plant 

Health Inspection Service.

U.S. Department of Agriculture, Animal and Plant Health Inspection 

Service, 1987a. Biological Assessment—Rangeland Grasshopper 

Cooperative Management Program.

U.S. Department of Agriculture, Animal and Plant Health Inspection 

Service, 1987b. Rangeland Grasshopper Cooperative Management 

Program, Final Environmental Impact Statement—1987. U.S. 

Department of Agriculture, Animal and Plant Health Inspection 

Service. Washington, DC. 221 pp.

U.S. Department of Agriculture, Animal and Plant Health Inspection 

Service, 1996. Grasshopper Integrated Pest Management User 

Handbook, Tech. Bul. No. 1809. U.S. Department of Agriculture, 

Animal and Plant Health Inspection Service, Washington, DC.

U.S. Department of Agriculture, Animal and Plant Health Inspection 

Service, 1998. Safety and health manual. Safety, Health, and 

Environmental Staff, Riverdale, MD. February 28, 1998. [online] 

available: http://www.aphis.usda.gov/mb/aseu/shes/

shes-manual.html.

U.S. Department of Agriculture, Animal and Plant Health Inspection 

Service, 1999. APHIS Directive 5600.3, Evaluating APHIS 

programs and activities for ensuring protection of children from 

environmental health risks and safety risks. September 3, 1999. 

U.S. Department of Agriculture, Animal and Plant Health 

Inspection Service, Riverdale, MD. [online] available: http://

www.aphis.usda.gov/library/directives.

U.S. Department of Agriculture, Animal and Plant Health Inspection 

Service, 2002. APHIS Directive 5640.1, Environmental monitoring 

for APHIS pest and disease control and eradication programs. 

April 19, 2002. U.S. Department of Agriculture, Animal and Plant 

Health Inspection Service, Riverdale, MD. 
VII. References for Chapters I through VI

Grasshopper Environmental Impact Statement 99

U.S. Environmental Protection Agency, 1993. Carcinogenicity peer 

review of carbaryl, 1–napthyl n–methylcarbamate. MRID 

421889—01, 02. Memorandum from Ray Landolt, Toxicological 

Branch II, October 7, 1993, 35 pp.

U.S. Environmental Protection Agency, 2000. Cancer Assessment 

Document #2. Evaluation of the carcinogenic potential of 

malathion. Report of the 12 April 2000 meeting and its 29 

attachments. April 28, 2000. U.S. Environmental Protection 

Agency, Washington, DC. 

Weidensaul, S., 2001. Sage grouse. Smithsonian Magazine. June 

2001.

West, N.E., 1993. Biodiversity of rangelands. Journal of Range 

Management 46:2-13. In Skold, M.D., and Kitts, A.W., 1996. 

Rangeland environmental amenities and grasshopper management 

programs. In U.S. Department of Agriculture, Animal and Plant 

Health Inspection Service, 1996. Grasshopper Integrated Pest 

Management User Handbook, Tech. Bul. No. 1809, Sec. VII..12. 

Washington, DC.

Winks, L.K., McEwen, L.C., Foster, R.N., Sampson, M.W., Green, M., 

and Tepedino, V.J., 1996. Buffer zones: their purpose and 

significance in grasshopper control programs. In U.S. Department 

of Agriculture, Animal and Plant Health Inspection Service, 1996. 

Grasshopper Integrated Pest Management User Handbook, Tech. 

Bul. No. 1809. Sec. III.8. Washington, DC.
VII. References for Chapters I through VI

100 Grasshopper Environmental Impact Statement
Appendix A. Background Information on Grasshopper Programs

Grasshopper Environmental Impact Statement 101

Appendix A. Background Information on Grasshopper Programs

A. Summary of Grasshopper Programs

U.S. Department of Agriculture (USDA) became involved in 

grasshopper and Mormon cricket control on Federal rangeland in the 

1930s. (The term “grasshoppers” used in this document refers to both 

grasshoppers and Mormon crickets, unless differentiation is needed.) 

During that decade, grasshopper infestations covered millions of acres 

in 17 Western States. Unsuccessful efforts to control grasshopper 

outbreaks on a local basis proved that grasshoppers needed to be 

dealt with on a broader basis. In 1934, Congress charged USDA with 

controlling grasshopper infestations on Federal rangeland. Thereafter, 

USDA was the lead agency in cooperative efforts among Federal 

agencies, State agriculture agencies, and private ranchers to control 

grasshopper outbreaks. USDA’s legal authorities to cooperate in those 

outbreaks came from the Incipient and Emergency Control of Pests 

Act (1937), the Organic Act of the Department of Agriculture (1944), 

the Cooperation With State Agencies in the Administration and 

Enforcement of Certain Laws Act (1962), and the Food Security Act 

(1985). Most recently, APHIS derives its authority from the Plant 

Protection Act (PPA).

Efforts against rangeland grasshoppers have evolved over the decades. 

During the first half of the 20th century, control efforts mostly relied 

on poison baits. Grasshopper control was mainly conducted to protect 

crops, but rangeland was treated to save forage and prevent 

grasshopper movement to nearby cropland. Insecticide sprays 

sometimes were used but caused concern because they poisoned 

vegetation, thereby endangering livestock (Parker, 1952). 

1940s–1950s In the late 1940s and early 1950s, several major developments 

changed grasshopper control. Baits, made from chlorinated 

hydrocarbon insecticides that acted quickly and had longer residual 

effects, became available. The formulation of these dry baits made 

large-scale aerial application much easier. At the same time, sprays of 

the same compounds were developed and were more effective and less 

expensive than the bait formulations. Organized large-scale control 

programs were started for rangeland grasshoppers. 

Change in Focus. Prior to 1950, direct financial aid from the 

government had been available for treatment of cropland and 

rangeland. In 1950, a State/Federal task force studying grasshopper 

control recommended that the Federal government drop its 

involvement with grasshopper control on cropland. The task force 

reasoned that then-newly developed, relatively inexpensive, effective 

chemicals—as well as improved application equipment—made it 

possible for growers to control grasshoppers on higher value cropland 

than on their own, or with only periodic State assistance. In 1952, 
Appendix A. Background Information on Grasshopper Programs

102 Grasshopper Environmental Impact Statement

State agriculture departments and USDA, through a memorandum of 

understanding, agreed that cooperative grasshopper control programs 

would be reserved for rangeland. The federally sponsored cooperative 

grasshopper control program became focused on rangeland, both 

private and public. 

1960s–1970s In the early 1960s, the use of ultra-low-volume (ULV) applications 

(defined as less than 0.5 gallon per acre) of insecticides was refined 

specifically for grasshopper control in the United States. By 1964, the 

use of a new organophosphate insecticide, malathion ULV spray, 

became favored for cooperative rangeland grasshopper control 

programs. 

Problems were realized with the chlorinated hydrocarbon compounds. 

Their residual features began to accumulate in the food chain, posing 

a threat to nontarget organisms. In 1962, the use of these compounds 

was discontinued in cooperative rangeland grasshopper control 

programs. A formulation of carbaryl became available for use in the 

cooperative programs in 1962 and was used annually on rangeland 

through 1967. During that time, control of grasshoppers using 

carbaryl was not as high or as consistent as with the chlorinated 

hydrocarbons previously used. There also were compatibility problems 

between the spray formulations and aerial spraying systems. 

The carbaryl formulation was greatly improved by 1972 and replaced 

the earlier carbaryl formulation used in the cooperative rangeland 

grasshopper control programs.

1980s and 

Beyond

By the early 1980s, after several years of research, acephate became 

available for use in cooperative rangeland grasshopper control 

programs. By that time, the recommended insecticides for 

grasshopper control were acephate, carbaryl, and malathion. 

(Acephate is no longer registered for use on rangeland.)

Until the mid-1980s, the Animal and Plant Health Inspection Service 

(APHIS) played a lead role in monitoring and controlling destructive 

grasshopper populations and, thus, managed large-scale cooperative 

control programs for rangeland grasshoppers. In 1985, heavy 

grasshopper infestations covered 55 million acres of western 

rangeland, of which APHIS treated 14 million acres with insecticides. 

These insecticide treatments were applied aerially to blocks of 10,000 

or more acres per treatment (see figure A–1 for acreage treated 

annually). Although the insecticides used for grasshopper infestations 

were chosen for their minimal or negligible impact on the 

environment, the magnitude of the treatments raised concern about 

the potential effects of insecticides on the environment. 
Appendix A. Background Information on Grasshopper Programs

Grasshopper Environmental Impact Statement 103

The cost and concerns associated with large-scale applications of 

insecticides after the major outbreak in the mid-1980s elevated the 

need for developing new and improved ways to manage grasshoppers. 

From that need, Congress authorized APHIS to undertake a program 

for the prevention, suppression, control, or eradication of grasshopper 

outbreaks. APHIS’ goal was to further develop a grasshopper 

management program to reduce grasshopper outbreaks to 

noneconomic levels. Thus, the idea for the use of an integrated pest 

management (IPM) approach developed into the Grasshopper 

Integrated Pest Management (GHIPM) Program.

In 1987, APHIS completed the Rangeland Grasshopper Cooperative 

Management Program, Final Environmental Impact Statement—1987 

(1987 EIS) in response to the development of an IPM approach for 

grasshopper control efforts. APHIS’ role in the preparation of the EIS 

was as a lead agency working with three cooperating Federal agencies 

to prepare and coordinate an environmental analysis of IPM methods 

for grasshopper control. The 1987 EIS analyzed the potential for 

environmental impacts from several alternatives that included (1) no 

action, (2) chemical controls using acephate, carbaryl, both liquid and 

bait, or malathion in ULV aerial application, and (3) an IPM 

alternative. APHIS proposed the development of IPM techniques to 

keep rangeland grasshoppers below economically damaging levels as 

an alternative to standard grasshopper control programs (USDA, 

APHIS, 1987). 

As stated in the 1987 EIS, the IPM alternative included flexibility in 

choosing among the then-available insecticide controls (acephate, 

carbaryl, and malathion) and biological control (Nosema locustae, a 

disease-causing microorganism to a wide range of grasshoppers), and 

potential future components of an IPM approach that would be tested 

to determine their effectiveness against grasshopper infestations. The 

components discussed in the EIS included inflight encapsulation as 

an alternative delivery method for chemical spray; Nosema (after 

testing at various rates and application times); carbaryl bait; carbaryl/

Nosema bait mixture; fungal pathogens of grasshoppers and locusts; 

pathogenic viruses; and cultural/mechanical control methods, such 

as various techniques of range management (livestock grazing 

practices and prescribed burning of grasshopper-infested areas) and 

the physical destruction of grasshopper eggs. 

The IPM approach coordinated the use of pest and environmental 

information along with available pest control methods, including 

combinations of cultural, biological, and chemical methods. The 

approach was designed to prevent unacceptable levels of pest damage 

by the most economical means and with the least possible hazard to 

people, property, and the environment. The approach was developed 

to complement initiatives of other agencies, such as range 

management, water quality, and food safety. The cultural/mechanical 
Appendix A. Background Information on Grasshopper Programs

104 Grasshopper Environmental Impact Statement

component (rangeland management) of the IPM approach involved the 

cooperative efforts of the U.S. Department of the Interior’s (DOI) 

Bureau of Land Management (BLM), USDA’s Forest Service (FS), the 

Idaho and North Dakota Agricultural Experiment Stations, and 

livestock producers. The 1987 EIS led to the implementation of an 

IPM program for grasshopper management, which extended over a 

7-year period. An overview of the program and conclusions resulting 

from the program are provided in section B of this appendix.

Funding and Statutory Changes . During the mid-1980s, APHIS played 

a lead role in monitoring and controlling grasshopper populations. In 

1986, responding to extremely high and destructive grasshopper 

outbreaks, Congress appropriated $18 million for grasshopper control. 

Congress also created no-year funding for grasshopper programs by 

stipulating that approximately $16 million shall remain available until 

expended. This funding mechanism provided APHIS with immediate 

access to resources for controlling economically damaging 

grasshopper populations. 

From Fiscal Year (FY) 1987 until FY 1992, Congress appropriated $5 

million annually for no-year grasshopper reserve funds. In FY 1990, 

APHIS received $6.8 million to cooperate with States and individuals 

to control grasshoppers on lands designated under the Conservation 

Reserve Program (CRP) and other lands. As high-level damaging 

grasshopper populations failed to materialize or were kept under 

control, the no-year grasshopper reserve fund exceeded $16.5 million 

in 1993. 

Beginning in FY 1994, Congressional appropriations for grasshopper 

programs ceased. The lack of funding has affected long-term 

management for grasshopper outbreaks; treatments for grasshopper 

outbreaks since 1994 have utilized mostly the chemical component of 

IPM. The Office of Management and Budget (OMB) directed APHIS to 

fund all grasshopper-related activities, surveys, and control from the 

accumulated no-year reserve. To conserve no-year funds starting in 

FY 1995, APHIS conducted only crop protection programs, designed to 

protect high value crops by treating strips of Federal rangeland that 

border the crops. Crop protection programs provide short-term, 

immediate control of grasshoppers and do not include long-term 

rangeland management. The crop protection programs are conducted 

using a small contingency fund, which must cover other APHIS 

emergencies. Following the OMB funding directive, APHIS exhausted 

all grasshopper program resources during FY 1999. In FY 2000, 

lacking appropriated funding for grasshopper outbreaks, APHIS 

managed grasshopper outbreaks using contingency funds, as directed 

by Congress. However, the grasshopper populations were not as high 
Appendix A. Background Information on Grasshopper Programs

Grasshopper Environmental Impact Statement 105

as projected because of weather conditions, and most of the 

grasshopper control funds were returned to the no-year APHIS 

contingency fund.

USDA’s authority to participate in grasshopper programs now comes 

from the PPA (7 United States Code (U.S.C.) § 7701 et seq.) under 

section 417 (7 U.S.C. § 7717). This act specifies that APHIS “shall 

work in conjunction with other Federal, State, and private prevention, 

control, or suppression efforts to protect rangeland.” The act also 

states that APHIS, “to protect rangeland, shall immediately treat 

Federal, State, or private lands that are infested with grasshoppers or 

Mormon crickets at levels of economic infestation, unless the 

Secretary [USDA] determines that delaying treatment will not cause 

greater economic damage to adjacent owners of rangeland.” APHIS’ 

cost sharing role in grasshopper programs is also reestablished in the 

act. 

Methods for controlling economically damaging grasshopper 

infestations have evolved over the years and most likely will continue 

to do so. Improvements in IPM methods for grasshopper control 

resulting from research and development will lead to the application of 

more economical methods with less potential for environmental 

impacts in responding to grasshopper outbreaks, or perhaps 

ultimately could lead to the prevention of outbreaks. 

B. The Grasshopper Integrated Pest Management Program

The GHIPM Program was initiated in 1987 as a 5-year experimental 

demonstration project. The project’s major objectives were (1) the 

management of grasshopper population densities at two 

demonstration areas, (2) the evaluation of management techniques, 

and (3) the development of new rangeland grasshopper management 

strategies. To achieve those objectives, the program was divided into 

Field Operations and Field Support Agreements. Field Operations was 

responsible for the overall program management and the management 

of grasshopper population densities at two demonstration areas. Field 

Support Agreements provided evaluation and research for the most 

effective management of rangeland grasshoppers. The approximate 

location of the demonstration areas coincided with the DOI BLM 

Shoshone District in Idaho and the Little Missouri National 

Grasslands of North Dakota. However, during the program years, 

most of the grasshopper densities occurred in North Dakota, resulting 

in most of the research being conducted there. 

In furthering the program’s overall objectives, additional objectives of 

the project research in the North Dakota location included (1) 

comparing the effectiveness of an IPM program for rangeland 

grasshoppers with the effectiveness of a standard chemical control 

program on a regional scale, (2) determining the effectiveness of early 

sampling in detecting incipient grasshopper infestations, (3) 
Appendix A. Background Information on Grasshopper Programs

106 Grasshopper Environmental Impact Statement

quantifying short- and long-term responses of grasshopper 

populations to treatments, and (4) developing and evaluating new 

grasshopper suppression techniques that have minimal effects on 

nontarget species (Quinn et al., 2000). 

During this program, several available IPM techniques were used to 

manage grasshopper populations, as described by the preferred 

alternative grasshopper management tactics outlined in the 1987 EIS. 

These techniques included (1) providing more detailed surveys of 

grasshopper populations so that small areas of infestations could be 

defined; (2) treating small areas of infestations (“hot spots”) rather 

than the minimum 10,000 acres of infestation required under 

standard grasshopper control programs; and (3) using control 

methods other than the conventional large-scale aerial applications of 

insecticidal sprays.

The program included data gathering during the first year, testing of 

range improvement techniques during a 5-year period after the data 

gathering, database development and predictive modeling, 

environmental evaluation, and economic research. The program was 

designed to provide data that would be used for improving APHIS’ 

ability to determine environmental effects of its program. 

The following information summarizes the studies on the treatment 

components of the GHIPM program from Quinn et al., 2000: 

Nosema-bran Bait Treatments. A 3-year study of the effect of 

Nosema-bran bait on grasshopper populations suggested that the 

microbial insecticide has little, if any, effect on grasshoppers either 

immediately after treatment or in subsequent years.

Carbaryl and Malathion Spray Treatments. Aerial and ground 

applications of carbaryl and malathion sprays were the most 

efficacious treatments. Immediate reductions in the total number of 

grasshoppers at nine blocks treated with these insecticides ranged 

from 84 to 99 percent. 

Carbaryl-bran Bait Studies. Twenty-two evaluation sites were assessed 

for three aerial application and six ground application experiments to 

determine the effects of carbaryl-bran bait on grasshoppers. Total 

populations of grasshoppers were reduced by an average of 44.5 

percent at the evaluation sites in the treated areas as compared to a 

decline of only 3.3 percent at 18 untreated control sites. Ground and 

aerial applications of the bait had similar short-term effects on total 

grasshopper populations.
Appendix A. Background Information on Grasshopper Programs

Grasshopper Environmental Impact Statement 107

Hot-spot Treatments. The treatment of small areas of grasshopper 

infestation, or hot spots, with either ground applications of malathion 

sprays or carbaryl-bran baits was effective in suppressing grasshopper 

populations. Two applications of carbaryl-bran bait were needed to 

control grasshoppers in some cases, particularly when densities were 

very high.

Suppression of Grasshoppers After Treatment. Eighteen field 

experiments compared grasshopper populations in treated sites and 

untreated control sites (excluding the Nosema-bran bait experiment) 1 

year after treatment. Overall, populations at treatment evaluation 

sites declined by an average of 53.2 percent 1 year after treatment. In 

contrast, grasshopper densities at untreated control sites increased by 

an average of 33.6 percent 1 year after treatment. The data suggest 

that, in general, treatments were effective in suppressing second-year 

populations of grasshoppers.

Overall Conclusions of the GHIPM Program. The results from the 

GHIPM Program indicate that incorporating the following more 

intensive management methods into IPM programs will greatly reduce 

both the cost of grasshopper control treatments and the amount of 

insecticide applied to rangeland: (1) increased sampling to delineate 

more exactly the area of grasshopper infestation, (2) carefully timed 

treatment applications, and (3) the use of hot-spot treatments with 

ground applications of either insecticidal sprays or baits (Quinn et al., 

2000). 

C. Cooperator Roles in Grasshopper Programs

Federal and State land management agencies, State agriculture 

departments, and private groups or individuals may carry out 

activities, many of which were identified in the GHIPM Program. Some 

of these activities are grazing management practices, cultural and 

mechanical methods, and prescribed burning of rangeland areas. 

These techniques have been tried with varying success in rangeland 

management and some have been associated with the prevention, 

control, or suppression of harmful grasshopper populations on 

rangeland. A primary goal of grasshopper IPM is to prevent the 

buildup of populations to damaging levels; however, some periodic 

outbreaks will occur, and some will require immediate intervention in 

the form of fast-acting insecticide control (Foster, 1996). 

1. Federal 

Agencies

Rangeland makes up about 770 million acres in the United States, 

from the wet grasslands of Florida to the desert floor of California 

(National Research Council (NRC), 1994). Federal agencies own and 

manage about 43 percent of rangeland in the United States (NRC, 

1994). The DOI’s BLM and Bureau of Indian Affairs (BIA) and USDA’s 

FS manage most of the Federal lands where grasshopper programs 

have been implemented. BLM manages about 170 million acres, BIA 
Appendix A. Background Information on Grasshopper Programs

108 Grasshopper Environmental Impact Statement

manages about 56 million acres (Helbig, pers. comm., 2001), and FS 

manages about 40 million acres of rangeland. These agencies develop 

land management plans that include livestock grazing allotment. 

APHIS could be requested by any of these Federal agencies to assist 

with actions to prevent, control, or suppress grasshopper populations. 

When APHIS cooperates with a Federal agency in these efforts, a 

division of work is established. Generally, the land management 

agency (either BLM, BIA, or FS) would prepare an environmental 

analysis for treatments planned on rangeland under their jurisdiction 

(USDA, APHIS, 1987). 

The PPA (§ 417(d)(1)) authorizes APHIS to pay 100 percent of the cost 

of grasshopper control on Federal lands to protect rangeland.

2. State and 

Local Agencies

Less than 7 percent of rangeland is owned by State and local 

government agencies. State agencies, such as agriculture 

departments, as well as local governments, could initiate efforts 

against grasshopper infestations on lands they manage. If a State 

requests APHIS, through the State agriculture department, to take 

action against a grasshopper infestation, APHIS would undertake the 

appropriate environmental process for the action. 

In earlier years when funding was available for large-scale programs, 

an agreement between APHIS and the involved State agency 

established the division of work and funding. The PPA (§ 417(d)(2)) 

allows for 50 percent cost-sharing of cooperative actions to control 

rangeland grasshoppers when State lands are involved. 

3. Private Land 

Owners

More than half of U.S. rangeland is privately owned (NRC, 1994), and 

these landowners could initiate efforts against grasshopper 

infestations. They also can request, through the State agriculture 

department, APHIS’ assistance to control grasshopper infestations. 

The land owner and APHIS could cooperate in actions on private 

lands, and APHIS would undertake the appropriate environmental 

process for such actions. 

The PPA (§ 417(d)(3)) authorizes APHIS to pay 33.3 percent of the cost 

of rangeland grasshopper control on private lands.

D. What is Grasshopper Management and How is it Different 

From Grasshopper Suppression?

Grasshopper management involves a wide variety of actions of which 

the ultimate goal is to prevent or drastically reduce the adverse 

impacts of grasshopper outbreaks on rangeland ecosystems and 

agricultural production. Grasshopper management is primarily the 

responsibility of rangeland managers whether they are managing 

Federal, State, tribal, or private lands. It is the land managers who 

are best able to make decisions and set priorities for actions that will 
Appendix A. Background Information on Grasshopper Programs

Grasshopper Environmental Impact Statement 109

affect the land they steward. APHIS assists in making grasshopper 

management decisions by providing survey information and technical 

assistance to the land managers.

Some grasshopper management actions are long-term while other 

management decisions are implemented in the short-term. Long-term 

grasshopper management focuses on measures that predict and 

hopefully prevent devastating outbreaks. Should those long-term 

measures fail, or should natural forces prevail over human actions, 

grasshopper outbreaks can develop. It is at this point when 

short-term measures can be taken to mitigate the effects while 

sustaining, to the extent possible, those processes that allow 

long-term management. Short-term grasshopper management 

actions most often are designed to rapidly reduce the number of 

grasshoppers within the outbreak area.

A comprehensive grasshopper management program would have 

several components, including predictive forecasting and population 

monitoring (survey); informed decisionmaking; and an array of 

mechanical, biological, and chemical strategies to prevent outbreaks 

or minimize the damage should outbreaks occur and grasshopper 

populations threaten rangeland ecosystems and agricultural 

production.

Despite recent progress by researchers, such as Joern (2000), the 

ability does not yet exist to accurately predict when and where 

grasshopper populations will increase to the point that rangeland and 

cropland resources are at risk (Onsager, 1996). Among the factors 

that contribute to grasshopper population fluctuations are 

temperature, precipitation, vegetation, soil qualities, natural enemies, 

as well as many other parameters—some of which remain to be 

discovered. The role of temperature in grasshopper egg development 

was investigated by Fisher et al. (1996b). Weather was considered to 

be a primary factor controlling fluctuations in southern Idaho 

(Fielding and Brusven, 1996b). The relationships between vegetation 

and grasshoppers have been described by Lockwood and Lockwood 

(1991), Joern et al. (1996), Joern (1996c and d), and Fielding and 

Brusven (1996a). However, as more information becomes known, the 

task of forecasting outbreaks becomes more complex (Joern, 1996a; 

Belovsky et al., 1996b; Lockwood and Lockwood, 1997).

Land managers may adopt management techniques that, over time, 

are designed to prevent or lessen the severity of grasshopper 

outbreaks. The most researched grasshopper management methods 

involve cultural control and biological control. Each of these methods 

is considered to be a long-term, preventative approach. The potential 

to manipulate grasshopper habitat through cultural methods, such as 

grazing, was discussed by Manske (1996) and Belovsky et al. (1996a). 
Appendix A. Background Information on Grasshopper Programs

110 Grasshopper Environmental Impact Statement

Recently, Onsager (2000) reported that grasshopper outbreaks in the 

northern Great Plains can be suppressed through grazing 

management.

The most traditional approaches to grasshopper control have involved 

physically destroying grasshoppers and grasshopper eggs. For 

centuries on the African Continent, locust control has been attempted 

by techniques such as physical harvesting, trampling, or trapping and 

burying migrating bands in trenches. These techniques have been 

tried (Lockwood and DeBrey, 1990) on western rangeland but are very 

labor intensive and unlikely to have any large-scale impact (Panos 

Institute, 1993). Prescribed burning to physically destroy 

grasshoppers and remove the vegetation that is their food source is 

unlikely to be practical on a large scale (USDA, APHIS 1987).

The most reliable way to assess rangeland grasshopper populations is 

to gather information on species composition, density, and 

developmental stage by conducting field sampling and surveys. A 

general description of grasshopper survey methods can be found in 

Berry et al. (1996). It is important to know which grasshopper species 

are present in any given area because there are about 400 

grasshopper species in the Western United States (Pfadt, 1994). A 

typical rangeland area, over the course of 1 year, has 15 to 40 species 

(Foster, 1996), but not all grasshopper species cause economic 

concern. Dysart (1996) ranked grasshopper pest-status and reported 

that there are about 2 dozen western grasshoppers that can be 

considered pests to agricultural production. 

The total number of grasshoppers in an area is less important than 

determining the number of pest species per unit area when deciding 

whether or not control measures are necessary. Information on the 

stage of development is used to formulate when control measures can 

be most effectively implemented, because some insecticides are only 

effective against early life stages of grasshoppers. It is known that 

grasshopper species have widely varying hatching times (Cushing et 

al., 1996) and that the same species of grasshopper develops at 

different times in different geographic locations (Fisher et al., 1996a).

To better understand grasshopper population dynamics, land 

managers and technical advisors can apply the survey information to 

data management tools such as maps. Examples of grasshopper 

maps include a State distribution atlas (Lockwood et al., 1993) and 

general maps showing grasshopper distribution and density 

throughout the 17 Western States. (See http://www.aphis.usda.gov/

ppq/maps/finalhazard01.jpg for the 2002 Rangeland Grasshopper 

Hazard Map.) Use of recent technological advances, such as the 

Global Positioning System (GPS) and geographic information systems 

(GIS), will increase map accuracy and usefulness (Kemp et al., 1996). 
Appendix A. Background Information on Grasshopper Programs

Grasshopper Environmental Impact Statement 111

Biological and economic models have been developed to estimate 

grasshopper population dynamics, forage losses, and changes in cattle 

feeding regime. These models indicate that grasshoppers cause 

damage which reduces the weight gain of animals and, because of the 

reduced overall health of the herd, production (including calving rates) 

is adversely affected. Grasshopper damage also may change livestock 

management practices forcing producers to feed hay, sell early, reduce 

stocking rates, or relocate their herds. Damage caused by 

grasshoppers goes beyond actual consumption of forage (Pfadt, 1994). 

Past experience and survey information have shown that certain 

rangeland grasshopper species occasionally experience an outbreak 

and become pests that consume crops and rangeland forage. While 

most species increase only slightly, some pest grasshopper 

populations can increase dramatically (Joern and Gaines, 1996).

Biological control is often viewed as a way to reduce pesticide use and 

has long been considered to be an important component of an IPM 

approach to control grasshoppers. The development of native 

biological control agents (predators, parasites, and diseases) was a 

major focus of the Grasshopper IPM Program. Despite advances in the 

knowledge on the biological control of grasshoppers reported in the 

Grasshopper IPM User Handbook (USDA, APHIS, 1996a), no reliable 

biological control agents have been developed and registered for use by 

the Environmental Protection Agency. Onsager and Olfert (2000) have 

reported that there appears to be little potential for augmentation of 

natural grasshopper parasites or predators, yet those authors also 

state that there appears to be a great potential for conserving natural 

enemies. 

When land managers are faced with increasing populations of pest 

grasshopper species, several actions can be taken to reduce, or even 

eliminate, the damage those populations can cause to rangeland 

ecosystems. In order to optimize these actions, these strategies must 

be employed over long time periods. Other actions are more 

immediate in their effect on grasshoppers. Should all other 

management techniques fail, insecticides remain the most effective 

and immediate grasshopper reduction method. 

An IPM approach to grasshopper management using intensive surveys 

and “hot-spot” treatments has been successfully demonstrated in 

North Dakota by Quinn et al. (2000). In order to sustain the limited 

success of many nonchemical grasshopper control strategies, it would 

be necessary to apply these management techniques in a uniform 

fashion. As Joern (1996b) states: 
Appendix A. Background Information on Grasshopper Programs

112 Grasshopper Environmental Impact Statement

FIGURE 1-1: Background Information on Grasshopper Programs
Appendix A. Background Information on Grasshopper Programs

Grasshopper Environmental Impact Statement 113

"Understanding how grasshopper populations are regulated and 

how regulation differs between regions of the western rangeland 

is essential for the development of new control strategies that 

involve reduced insecticide use, biocontrol agents, and grazing 

and habitat manipulation.”

APHIS is fully aware of IPM strategies—many of which were 

investigated through the APHIS-funded IPM Program. However, 

implementing these strategies is not within the purview of APHIS. 

Rather, these strategies are best implemented and normally studied in 

the context of rangeland management programs by the respective land 

managers of Federal, State, private lands. APHIS lacks land 

management authority.

E. Alternative Approaches to Grasshopper Management

This section describes alternative approaches that have been 

considered by some to be effective ways to address grasshopper 

outbreaks and the damage those outbreaks cause. APHIS has not 

considered these as alternatives to its program. 

1. Grasshopper Eradication. This approach would dedicate all efforts 

toward a planned eradication of grasshopper populations. All efforts 

would focus on implementing technical assistance, direct control, and 

methods development to completely eliminate target grasshopper 

populations in areas where damage has occurred or could occur. 

Under an eradication approach, all applicable control methods would 

be utilized.

Eradication is an unsound and impractical consideration both 

ecologically (Belovsky, 1996) and economically. Grasshoppers play an 

important role in rangeland ecosystems, as Belovsky et al. (1996b) and 

Belovsky (2000) have indicated. Eradication programs would have 

major consequences on nontarget species as well. Eradication would 

require vast Federal, State, and local government funding, as well as 

large amounts of private funds. Such funding is not likely to occur for 

grasshopper eradication.

2. Use of Insecticides Not Registered by EPA for Rangeland Use.

Some insecticides are used outside of the United States to control 

grasshoppers and locusts. For example, fipronil has been widely used 

in Africa and Europe for locust control, and dimethoate and 

deltamethrin are used in Canada and other countries to control 

grasshoppers and locusts (Onsager and Olfert, 2000). However, none 

of those insecticides are currently registered for rangeland use by EPA. 

Acephate is an insecticide that was analyzed in the 1987 EIS (USDA, 

APHIS, 1987); however, there is no current EPA registration for the use 

of this insecticide on rangeland.
Appendix A. Background Information on Grasshopper Programs

114 Grasshopper Environmental Impact Statement

3. Damage Compensation—Insurance Program. A Damage 

Compensation—Insurance Program approach could conceivably 

replace APHIS program activities with verification and compensation 

for agricultural losses caused by grasshopper damage. The 

responsibility for this approach would most likely be an agency other 

than APHIS. Verification and compensation of grasshopper damage to 

agricultural crops and rangeland forage could constitute a large 

undertaking involving complex considerations. A program to make 

available federally sponsored or subsidized insurance is another 

mechanism to compensate landowners for grasshopper damage. The 

insurance system could be similar to Federal crop, hail, or flood 

insurance programs. The legal and regulatory authority and 

legislation to implement this alternative does not exist at this time. 

4. Land Management Techniques. Land managers and land owners 

can take several actions in an attempt to prevent or reduce damage 

from grasshoppers. These preventative actions include cultural, 

mechanical, and biological methods that must be employed over a long 

period of time to reach effectiveness. It is the responsibility of the land 

managers, whether Federal, State, or private, to implement these 

management techniques. APHIS can assist the land managers with 

management decisions, but the ultimate responsibility for 

implementing grasshopper management actions rests with the land 

managers or land owners.

In some federally managed rangeland, grasshoppers pose a major 

threat to adjacent, privately owned croplands. Preventing the 

movement of these grasshoppers from rangeland onto neighboring 

lands and crops is a consideration land managers can often 

encounter. 
Appendix A. Background Information on Grasshopper Programs

Grasshopper Environmental Impact Statement 115

FIGURE 1-2: Road Warning Sign (Photo Credit USDA-APHIS)
Appendix A. Background Information on Grasshopper Programs

116 Grasshopper Environmental Impact Statement
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 117

Appendix B. Environmental Risk Assessment for Rangeland Grasshopper 

Suppression Programs—Insecticides 

A. Insecticide Risk Assessment Methodology

This section provides information about the basic methodology used to 

assess risk from the application of insecticides. Application 

procedures and basic background about the potential human health 

hazards of the program insecticides are discussed.

1. Human Health 

Assessment 

Methods

This section describes the human health effects that are possible from 

exposure to treatment insecticides that the Animal and Plant Health 

Inspection Service (APHIS) could apply to suppress grasshoppers on 

rangeland. The information contained herein summarizes the Human 

Health Risk Assessment for the APHIS 1996 Rangeland Grasshopper 

Cooperative Management Program (SERA, 1996) and updates that 

information. Analyses of the reduced rate applications were 

completed more recently using the same methodology. The risk 

assessment of each insecticide (i.e., carbaryl, diflubenzuron, and 

malathion) consists of: 

◆ an identification of the hazards associated with each agent,

◆ an assessment of potential human exposure to the agent,

◆ an assessment of the dose-response relationships of the agent, 

and

◆ a characterization of the risks associated with exposure to the 

agent.

These basic steps, used to prepare the Human Health Risk 

Assessment (SERA, 1996), are generally recommended by the National 

Research Council of the National Academy of Sciences in Risk 

Assessment in the Federal Government, Managing the Process (NRC, 

1983) for conducting and organizing risk assessments. In addition, 

information and analyses have been updated to make the presentation 

applicable to current program alternatives and application methods.

a. Hazard Identification. Hazard identification is the process of 

identifying what effects an agent is likely to induce in an exposed 

population. The hazard of each insecticide was examined by reviewing 

relevant toxicological and pharmacokinetic data from the published 

literature, manufacturers’ information, specific information from 

knowledgeable experts in the field, and reliable published information 

on exposed populations. The assessment was based on an analysis of 

in vivo and in vitro data for experimental animals as well as all 

available human data including epidemiology studies, case reports, 

and clinical investigations. The hazard of carriers and inert 

ingredients or possible contaminants in the insecticide formulations 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

118 Grasshopper Environmental Impact Statement

was also considered. The relative noncarcinogenic hazard of each 

treatment method is classified according to the level of severity as 

defined in table B–1.

In the risk assessment, a review of the toxicological and 

pharmacokinetics data for each insecticide was presented in the 

hazard identification and was intended to capture the dose-response 

and dose-severity relationships. The severity scale used for the risk 

assessment considered four levels of severity. These levels, defined in 

table B–1, include the no-observed-effect level (NOEL), 

no-observed-adverse-effect level (NOAEL), adverse-effect level (AEL), 

and frank-effect level (FEL). This scale, with minor differences in 

nomenclature, is used by many government agencies to classify the 

toxicological effects observed in experimental or epidemiology studies. 

The analysis involves making judgments about which effects are most 

relevant to the assessment of human health. 

The risk assessment uses common terminology to describe the acute 

toxicity of individual insecticides. The categories of acute toxicity as 

defined by the U.S. Environmental Protection Agency (EPA) are 

provided in table B–2 for description of relative toxicity.

Table B–2. Toxicity Categories

TABLE 1-1: Severity Definitions

Acronym Definition

NOEL No-observed-effect level: No biologically or statistically significant effects 

attributable to treatment.

NOAEL No-observed-adverse-effect level: Effects that are attributable to treatment but 

do not appear to impair the organism's ability to function and clearly do not 

lead to such an impairment.

AEL Adverse-effect level: Signs of toxicity that must be detected by invasive 

methods, external monitoring devices, or prolonged systematic observations.

Symptoms that are not accompanied by grossly observable signs of toxicity.

FEL Frank-effect level: Frank or clinically evident, gross and immediately 

observable signs of toxicity.

TABLE 1-2: Toxicity Categories

Habitat Category Toxicity Criteria
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 119

b. Exposure Assessment. Exposure assessment is the process of 

estimating the extent to which a population will come in contact with a 

chemical and the amount of the chemical in various media. Three 

general steps are involved in assessing population exposures: 

◆ characterizing exposure scenarios, 

◆ estimating levels in environmental media, such as soil, air, water, 

and vegetation, and 

◆ calculating dose rates.

The exposure scenarios selected were based on how the insecticides 

are applied and the biological, physical, and toxicological properties of 

the insecticides. Depending on the insecticide properties and 

application method, the following were also considered: oral, dermal, 

inhalation, or combined exposure to the insecticide; exposure of 

people living in or traversing treated areas and of grasshopper 

program workers; and acute, subchronic, or chronic durations of 

exposure.

Three types of exposure scenarios were considered: routine, extreme, 

and accidental. For routine exposures, assumptions were that the 

recommended application rates are used, that recommended safety 

precautions are followed, and that the estimated model parameter 

values, such as food or water consumption rates and skin surface 

area, are based on the most likely activities and circumstances. For 

extreme exposures, assumptions were that recommended procedures 

and precautions are not followed and that exposure parameters were 

based on different activities and circumstances that increased the 

estimate of exposure. For accidental exposures, the assumption was 

that some form of equipment failure or gross human error occurred. 

Not all three scenarios were used for each insecticide. The decision to 

Terrestrial Severely toxic

Moderately toxic

Slightly toxic

Very slightly toxic

LD50

1

_ 50 mg/kg2

50 mg/kg < LD50 < 500 mg/kg

500 mg/kg < LD50 < 5,000 mg/kg

5,000 mg/kg < LD50 < 50,000 mg/kg

Aquatic Very highly toxic

Highly toxic

Moderately toxic

Slightly toxic

Practically nontoxic

LC50

3

 _ 0.1 mg/L4

0.1 mg/L < LC50 < 1.0 mg/L

1.0 mg/L < LC50 < 10 mg/L

10 mg/L < LC50 < 100 mg/L

LC50 > 100 mg/L

1 Oral dose lethal to 50% of test organisms

2 Milligrams per kilogram

3 Concentration in water that is lethal to 50% of the test organisms

4 Milligrams per liter

TABLE 1-2: Toxicity Categories
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

120 Grasshopper Environmental Impact Statement

use a particular scenario was based on its applicability to the 

insecticide being assessed and the need to encompass uncertainties in 

the exposure.

The Human Health Risk Assessment also considered potential 

exposed or absorbed doses for individuals of different age groups, that 

is, adults and young children who may, under certain circumstances, 

be more vulnerable. Values such as body weights and food 

consumption rates were taken from standard sources (EPA, OHEA, 

ORD, 1988).

c.Dose-response Assessment. A dose-response assessment is the 

process of characterizing the relationship between a known dose of an 

agent and the incidence of an adverse health effect in an exposed 

population. It involves estimating the incidence and severity of the 

effect as a function of dose or exposure to the specific agent. It also 

takes into account the intensity of the exposure, the age range during 

exposure, and other variables that might affect the response, such as 

gender and lifestyle. Extrapolation from high to low dose and from 

animals to humans is often required (NRC, 1983). 

The dose-response assessments used an approach that involved a 

no-observed-adverse-effect level (NOAEL) and an uncertainty factor. 

Quantitative toxicological assessments involve deriving an estimate of 

the dose level that is unlikely to cause adverse health effects in 

humans. This dose estimate is called the reference dose (RfD). It is 

derived by taking the experimental no effect (or equivalent) dose 

associated with the most sensitive effect and applying a series of 

uncertainty factors to adjust for differences between the experimental 

design and the conditions for which the RfD is being derived.

d.Risk Characterization. Risk characterization is the process of 

estimating the incidence of a health effect in a human population 

under the different conditions of exposure represented in the exposure 

assessment (NRC, 1983). The risk characterization process detailed 

by EPA (OERR, 1989) generally was followed. It involved comparing 

the dose to which humans may be exposed with the RfD. This 

comparison produces a hazard quotient (HQ) which indicates the level 

of concern regarding one or more exposure scenarios. Because the 

RfD represents an exposure that is not expected to cause adverse 

effects, an HQ of 1 or less would not be a cause for concern. 

All relevant routes of exposure (mouth, skin, respiratory tract) were 

considered in deriving a composite HQ. An HQ greater than 1 (dose 

exceeds the RfD) was usually associated with a concern about an 

adverse effect. In some cases, however, uncertainties associated with 

the hazard identification and exposure assessment required a 

qualitative judgment to characterize the risk involved.
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 121

 1. Cumulative Effects

Some exposures, especially to workers, may occur over several 

days to several months. In addition, and in extremely rare 

situations, some program activities may be repeated more than 

once during a year or for several consecutive years under the full 

coverage control alternative. Such exposures are referred to as 

cumulative exposures.

Depending on the specific exposure scenario and the nature of 

the available data, the consequences of cumulative exposures are 

assessed in a variety of ways. For carcinogenic effects, total dose 

is assumed to be related directly to risk. Thus, the consequences 

of two applications at a given rate would be twice those of a 

single application. 

For toxic effects, concern is triggered by exposures that exceed 

the RfD. Only a limited amount of insecticide would be applied 

in a given year. Consequently, most exposure scenarios assume 

maximum application rates. If the RfD is not exceeded by 

multiple applications at maximum rates, it will not be exceeded 

by multiple applications at lower rates for comparable intervals. 

In addition, cumulative effects from exposures to persistent 

residues of diflubenzuron on vegetation are considered by using 

RfDs appropriate for chronic or lifetime exposure. If the daily 

exposure level does not exceed the daily level that would be 

tolerable for a lifetime, exposure for shorter periods will not 

present a hazard. It is expected that the program will seldom, if 

ever, need to retreat any sites within a given season.

 2. Connected Actions

Some individuals may be exposed to several treatment types, 

either in their job as applicators or because more than one type 

of treatment is used in the areas that they frequent. Such 

exposures are considered connected actions, that is, one or more 

actions that an individual may take that could affect the 

individual’s risk to the insecticides used to suppress the 

grasshopper. In addition, all individuals are exposed to a 

multitude of chemicals and biological organisms every day in 

foods, medicines, household products, and other environmental 

chemicals. 

Exposure to multiple chemical or biological agents may lead to 

interactions that are substantially toxic. For most of the 

grasshopper insecticides under review, relatively little 

information pertaining to this issue is available. The information 

that is available is included in the risk characterization for each 

insecticide.
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

122 Grasshopper Environmental Impact Statement

 3. Information Data Gaps

New data and more complete information are regularly obtained 

by APHIS about the program insecticides and application 

methods through independent researchers and monitoring data. 

This information is then incorporated into risk analyses and 

applied to environmental assessments prepared for site-specific 

programs as it is made available. 

The insecticides used by APHIS in this program are regulated by 

EPA. EPA has responsibility for pesticide registration and 

reregistration under the Federal Insecticide, Fungicide, and 

Rodenticide Act (FIFRA, as modified by the Food Quality 

Protection Act of October 1996). A variety of data, including 

product and residue chemistry, environmental fate, and human, 

wildlife, and aquatic toxicity, are required for this process (see 40 

Code of Federal Regulations (CFR) 158). EPA uses these data to 

make regulatory decisions concerning these pesticides. 

Data gaps (deficiencies) have been identified by EPA either 

because registration requirements have changed or because 

previously submitted data have been ruled inadequate under 

current registration guidelines. Data gaps are listed in EPA 

Registration Standards documents for each pesticide. In some 

cases, data have been submitted since the document and are 

under review by EPA.

Data considered inadequate for registration purposes, or data 

not submitted to EPA but available through the literature or 

other sources, may be adequate to provide indications of 

potential environmental effects. Because all data needed for a 

complete evaluation were not available, APHIS used the available 

data and made extrapolations when necessary. 

Nontarget 

Species 

Assessment 

Methods

a. Terrestrial Species. Organisms can be exposed to an insecticide 

used for grasshopper suppression through several exposure routes. 

These include dermal contact through direct spray applications as 

well as contact with contaminated soil and vegetation, ingestion of 

food and water that contains chemical residues, ingestion from 

grooming, and inhalation.

The potential risks to nontarget species posed by the grasshopper 

suppression program were determined quantitatively using a 

combination of the following: (1) a hazard analysis for each program 

insecticide, and (2) an exposure assessment based on estimated 

exposures to species representative of those found in regions where a 

grasshopper suppression program is likely to occur. Risk to nontarget 

species was assessed using available toxicological data for 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 123

representative species. Where toxicological data for representative 

species were not available, data for suitable surrogate species that 

exhibit similar biological characteristics were used.

 1. Nontarget Species Risk Assessment

A risk assessment, similar to the assessment of risks to human 

health, was prepared to analyze potential effects of the program 

insecticides, carbaryl, diflubenzuron, and malathion, on 

nontarget species.

A multiple-pathway exposure model developed by APHIS (USDA, 

APHIS, 1993) was used to estimate exposure levels for species 

through oral (ingestion) and dermal routes. Inhalation is also a 

route of exposure but to such a slight extent that it was not 

further considered. The model provides an estimate of total dose 

to nontarget species and attempts to quantify numerous direct 

and indirect routes of exposure. In so doing, the model makes 

assumptions considered a reasonable worst-case scenario. This 

use of a conservative model increases the likelihood that 

potential error will be “false positive” rather than “false negative.” 

(That is, the model is programmed to identify species at great 

risk, but it is unlikely that any species at risk would not be 

characterized as such.) Models predict which species may be 

potentially at risk; they do not predict which species will be 

definitely at risk from program treatments. 

 2. Exposure Estimates

Since it is unrealistic to attempt to estimate exposures to 

suppression insecticides for all species in the grasshopper 

program area, the analysis presented in this EIS is based on 

representative species. The species used for analytical purposes 

herein (see table B–3) are identical to those used in the 1987 EIS 

(USDA, APHIS, 1987). These species are considered to be 

adequately representative of bird, mammal, reptile, and 

amphibian species that inhabit the program area.

Table B–3. Representative Nontarget Terrestrial Species

TABLE 1-3: Representative Nontarget Terrestrial Species

Birds Mammals Reptiles and Amphibian

Lark bunting

Sage grouse

Bobwhite quail

American kestrel

Grasshopper mouse

Blacktail jackrabbit

Pronghorn antelope

Domestic cattle (Bovine spp.)

Coyote

Horned lizard

Eastern yellow-belly racer

Woodhouse’s toad
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

124 Grasshopper Environmental Impact Statement

Application rates and treatment areas in the grasshopper suppression 

program can vary considerably. Scenarios are designed to consider 

the impacts of conventional rates with full coverage and Reduced 

Agent Area Treatments (RAATs). Full coverage treatments are based 

upon label rates and complete coverage of infested sites. Although 

RAATs usually involves lower application rates and alternating swaths 

(incomplete coverage), it is not possible to analyze all possible 

combinations that could apply. The scenarios analyze nontarget 

species that are exposed within the treated swaths. The application 

rates analyzed for RAATs are considered typical of the rates that would 

be applied in this suppression program. It is possible for some 

site-specific programs that reduced rates could be even lower than 

those analyzed here, plus the reduced rates would be less than the full 

coverage application rates. Risk assessments will be prepared as part 

of site-specific program assessments to analyze other application rates 

and unique conditions at specific sites for suppression programs. 

Dose estimates were modeled based upon the representative 

application rates in table B–4.

Dermal exposures are estimated assuming that the animal is exposed 

over the entire body surface area at the per acre application rate. 

Additional exposure is also assumed to occur due to the animal 

coming in contact with treated vegetation while moving through a 

treated area. Ingestion is estimated based on a single day's diet of 

contaminated food items and an estimated daily consumption of 

contaminated drinking water (USDA, APHIS, 1996b). Diet items and 

water consumption rates are described in table B–5.

Table B–5. Diet Items and Water Consumption of Nontarget Species 1

TABLE 1-4: Representative Application Rates Used to Assess Potential Exposure

Insecticide Full Coverage Rate (lb a.i./acre)1

1 pound of active ingredient per acre

RAATs 

(lb a.i./acre)

Carbaryl 0.50 0.25

Diflubenzuron 0.016 0.012

Malathion 0.62 0.31
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 125

The dose estimates represent a daily dose of program insecticides for 

each animal. The dose estimate calculations are based upon the 

upper limits of exposures in short-grass prairie or rangeland. These 

calculations overestimate the dose to nontarget terrestrial species that 

would occur in tall-grass prairies. Studies of differences in potential 

exposure between short- and tall-grass prairies indicate more than a 

50 percent reduction in exposures in the tall grass at the upper limits 

of exposure (Kenaga, 1973). This difference will be considered in the 

documentation of any site-specific environmental assessments for 

programs in tall-grass prairie areas. 

Risks to exposed nontarget terrestrial species were calculated 

quantitatively by comparing the dose estimates to toxicity benchmark 

values, usually of a surrogate species. The benchmark toxicity value 

was extrapolated from the laboratory-derived dose determined to be 

lethal to half of the test organisms (median lethal dose or LD50). 

Populations of terrestrial species exposed to concentrations of 

insecticide at less than one-fifth of the LD50 are considered to be at 

negligible risk of adverse impacts. Populations of terrestrial species 

exposed to concentrations of insecticide in excess of the LD50 are 

considered to be at substantial risk of adverse impacts. Moderate risk 

to exposed populations would be anticipated for exposures between 

one-fifth of the LD50 and the LD50. In most cases, the dose estimates 

TABLE 1-5: Diet Items and Water Consumption of Nontarget Species1

1 Estimated daily consumption

Species Grass Insects

Small 

mammals Quail Seeds Toads Water

Birds

◆ Lark bunting 82

2 Food amount shown in grams

1 0.023

3 water amount in liters

◆ Sage grouse 70 0.10

◆ Bobwhite quail 30 4 0.05

◆ American kestrel 52 0.05

Mammals

◆ Grasshopper mouse 7 2 0.01

◆ Blacktail jackrabbit 300 0.05

◆ Proghorn antelope 2,763 1.00

◆ Domestic cattle

 (Bovine spp.)

11,250 58.00

◆ Coyote 40 320 340 0.80

Reptiles and Amphibian

◆ Horned lizard 4 0.05

◆ Eastern yellow-belly racer 9 22 0.10

◆ Woodhouse’s toad 8 0.10
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

126 Grasshopper Environmental Impact Statement

for the representative species are compared to LD50 values for 

surrogate species that have been selected based on their biological and 

metabolic similarities.

 3. Field Studies

One of the goals of the Grasshopper Integrated Pest Management 

(GHIPM) Program initiated in 1987 was to examine the effects of 

grasshopper treatments on nontarget organisms and the 

environment through the use of monitoring and field studies. 

Field studies were designed to determine not only the direct 

effects of program treatments, but the indirect impacts as well. 

For example, insectivorous species can be affected not only by 

coming in contact with a suppression insecticide or consuming 

contaminated food items, they also could be subject to indirect 

impacts due to the loss or alteration of their forage base. In fact, 

indirect impacts on birds and other insectivorous populations, 

due to fluctuations in forage base, have been shown to occur 

during GHIPM field investigations. The information describing 

the potential consequences for each insecticide is summarized in 

the sections on Nontarget Species (chapter 5).

b. Aquatic Species. Insecticide labels have protective measures 

designed to preclude exposures of aquatic organisms to insecticides 

from program applications. These are intended to prevent program 

insecticides from entering water bodies under routine applications. 

These measures do not apply to water bodies such as intermittent 

streams, vernal pools, cattle tanks, springs, and puddles which are 

often difficult, if not impossible, to avoid entirely. Insecticide 

concentrations following direct application to these small bodies of 

water were calculated. The theoretical insecticide concentrations 

calculated in this manner provide a conservative (maximized) estimate 

of exposure should any aquatic species be present. Exposure to 

aquatic species was equivalent to the potential concentration of 

insecticide in the organism’s habitat, that is, in the ambient water. 

Potential exposure to representative species in streams, wetlands, and 

small water bodies was analyzed. 

Risks to exposed nontarget aquatic species were calculated 

quantitatively by comparing the exposure estimates to toxicity 

benchmark values, usually of a surrogate species. The benchmark 

toxicity value was extrapolated from the laboratory-derived water 

concentration determined to be lethal to half of the test organisms 

(median lethal concentration or LC50). Exposures of aquatic species to 

concentrations of insecticides less than one-tenth of the LC50 are 

considered to pose negligible risk to the population present. 

Exposures of aquatic species to concentrations of insecticides in 

excess of the LC50 are considered to pose substantial risk to the 

population present. Moderate risk to exposed populations would be 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 127

anticipated for exposures between one-tenth of the LC50 and the LC50. 

In most cases, the exposure estimates for the representative species 

are compared to LC50 values for surrogate species that have been 

selected based on their biological and metabolic similarities.

3. Potential 

Hazards and 

Qualitative 

Assessment of 

Insecticide 

Suppression 

Agents

a. Carbaryl. 

 1. Toxic Mode of Action

Carbaryl is a carbamate insecticide. The mode of action of 

carbamates occurs primarily through acetylcholinesterase 

(AChE) inhibition (Smith, 1987; Klaassen et al., 1986). The 

AChE enzyme is responsible for the breakdown (hydrolysis) of 

acetylcholine, a neurotransmitter that permits the transmission 

of nerve impulses across the nerve synapse. Carbamates exhibit 

a reversible pesticide-enzyme binding reaction (carbamylation), 

which results in gradual decreases in binding as their 

concentration decreases through metabolism and excretion. 

Effects of AChE inhibition from carbamates may include 

weakness, blurred vision, headache, nausea, abdominal cramps, 

chest discomfort, constriction of pupils, sweating, muscle 

tremors, and decreased pulse. 

 2. Acute and Chronic Toxicity 

Carbaryl is of moderate acute oral toxicity to mammals. The 

acute LD50 is 270 mg/kg for rats (EPA, ECAO, 1984). The acute 

dermal LD50 was reported to exceed 4,000 mg/kg for rats and to 

exceed 5,000 mg/kg for rabbits (EPA, ECAO, 1984). Low doses 

can cause skin and eye irritation. The acute inhalation LD50 is 

721 mg/kg (HSDB, 1987). 

Based upon a 1-year dog feeding study, a systemic NOEL of 1.4 

mg/kg was determined. The NOAEL for this study was 3.83 mg/

kg based upon significant decrease in plasma and brain 

cholinesterase activity (EPA, OPPTS, 1994). The systemic 

reference dose (RfD) for carbaryl based upon this study is 0.01 

mg/kg/day.

 3. Neurotoxicity

Studies of carbaryl neurotoxicity were conducted with hens given 

subcutaneous injections (Carpenter et al., 1961; Gaines, 1969). 

Based upon their evaluation of these studies, EPA, OPTS (1980) 

concluded that carbaryl does not pose any neurotoxic human 

health hazard. At doses below the current RfD of 0.01 mg/kg/

day, no neurological or other adverse systemic effects are 

anticipated.

 4. Immunotoxicity
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Some relatively recent studies have suggested that carbaryl may 

inhibit the normal response of human natural killer cells (Casale 

et al., 1992) as well as T-cell activity in rats (Casale et al., 1993). 

Both of these studies involve in vitro exposures and cannot be 

used to quantify any immunologic risk. The toxicology of 

carbaryl has been studied extensively in vivo, and clinical 

consequences, if any, from any immunologic responses are likely 

to be encompassed by these study outcomes. The current 

information suggests that immunotoxic effects from carbaryl 

could only occur at doses in excess of those resulting in 

neurological or reproductive effects, so immunotoxic responses 

are not anticipated to be critical effects from program exposure 

to carbaryl.

 5. Carcinogenicity

Carbaryl has been classified by EPA as a “possible human 

carcinogen” based on an increased incidence of vascular tumors 

in a chronic study of male mice exposed at 46 mg/kg/day (1000 

parts per million (ppm)) (EPA, 1993). The EPA employs the 

default linear low dose extrapolation to risk assessments setting 

the Q1* value at 1.19 x 10-2 (mg/kg/day)-1 based on the mouse 

vascular tumors. Based upon use of this value in risk 

assessment of grasshopper programs, the potential for 

carcinogenicity is less than 1 in a million and much higher 

applications of carbaryl would be required to pose unacceptable 

risks of carcinogenicity. 

 6. Genotoxicity and Mutagenicity

A dominant lethal rat mutation assay was negative at 200 mg/kg 

(Epstein et al., 1972). Other chromosomal assays have caused 

some induction of mitotic effects and chromosomal aberrations 

(EPA, ECAO, 1984). The reproductive effects assessment group 

of EPA has concluded that data from mutagenicity studies 

indicate that carbaryl can be classified as a weak mutagen (EPA, 

OPP, 1984). Carbaryl does not pose any mutagenic risk at 

program application rates.

 7. Reproductive and Developmental Toxicity

A three-generation reproduction study of rats found a NOEL of 

200 mg/kg/day (highest dose tested) when carbaryl was 

administered in the diet (Weil et al., 1973). A teratologic study of 

beagle dogs determined a NOEL of 3.125 mg/kg/day and the 

lowest effect level (LEL) of 6.25 mg/kg/day. The defects observed 

included abdominal fissures, failure of skeletal formation, and 

the presence of extra toes (Smalley et al., 1968). A set of studies 

considered dietary and gavage exposure of mice and gavage 

exposure of rabbits (Murray et al., 1979). The teratogenic NOEL 
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for mice was 1,166 mg/kg/day for dietary exposure and 150 mg/

kg/day for gavage (highest doses tested). The maternal NOEL for 

each exposure to mice, based upon decreased weight gain and 

cholinesterase inhibition, was determined to be less than 1,166 

mg/kg/day for dietary exposure and less than 150 mg/kg for 

gavage. The teratogenic and maternal NOEL of 150 mg/kg/day 

was determined for rabbits. Based upon their review of available 

laboratory studies, EPA, OPP (1984) determined that carbaryl 

does not constitute a potential human teratogen or reproductive 

hazard under proper usage. 

The interpretation of reproductive risk is equivocal because of 

the qualitative judgment to derive a provisional RfD. EPA has 

determined qualitatively that carbaryl poses no teratogenic or 

reproductive risk to humans. EPA has also concluded that the 

dog is a poor model to use for teratogenicity testing (EPA, OPTS, 

1985). This position was also taken by the National Institute for 

Occupational Safety and Health (NIOSH) (Cranmer, 1986). In 

addition, none of the three published reviews (Baron, 1991; 

Cranmer, 1986; Mount and Oehme, 1981) suggest that carbaryl 

is a potential human teratogen. However, the basis for this 

determination is unclear and additional investigation calls these 

conclusions into question (SERA, 1996). Without further 

documentation, the position is not sufficiently well supported to 

allay concern for potential reproductive effects given the number 

of species in which carbaryl has caused teratogenic effects or 

death in the embryo or fetus. The provisional RfD determined by 

EPA for reproductive effects is 0.002 mg/kg/day. 

 8. Inert Ingredients and Metabolites

The major hydrolytic metabolites of carbaryl are glucaronides 

andsulfates (Knaak et al., 1965). Most metabolites such as 

naphthol are considerably less toxic than carbaryl. There has 

been some concern expressed about the reaction of carbaryl with 

nitrite under certain circumstances. This may result in the 

formation of N-nitrosocarbaryl which has been shown to be 

mutagenic and carcinogenic in laboratory tests (Siebert and 

Eisenbrand, 1974; Regan et al., 1976). 

Although the formulations of carbaryl in some previous 

programs had oil-based carriers (i.e., Sevin® 4-oil), current 

programs have converted to water-based carriers (i.e., SEVIN®

XLR PLUS). Some information about inert ingredients in these 

formulations is available, but actual concentrations of inert 

ingredients was not located. One inert ingredient is propylene 

glycol or propanediol (antifreeze agent). It degrades readily to 

carbon dioxide and water in soil and water environments after 

applications, so actual exposures from the grasshopper 
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130 Grasshopper Environmental Impact Statement

suppression program would only be acute. The low exposures to 

humans would not expect to have human health effects except to 

those few individuals experiencing allergic contact dermatitis. 

Program safety procedures preclude applications when 

unprotected people are present in the treatment area, so any 

adverse effects from program applications are unlikely. 

Propylene glycol is practically nontoxic to fish and daphnia 

(Pillard, 1995). Concentrations of propylene glycol from program 

application rates would not be anticipated to result in adverse 

effects to wildlife. 

 9. Synergistic Effects

The only studies of chemical interactions with carbaryl indicate 

that toxicity of organophosphates combined with carbaryl is 

additive not synergistic (Keplinger and Deichmann, 1967; 

Carpenter et al., 1961).

There may be situations where it is appropriate to use one 

insecticide or formulation in one part of a treatment area and a 

different insecticide or formulation in another part of that same 

treatment area with all applications conducted according to the 

label directions. For example, ultra-low-volume (ULV) malathion 

may be used over the majority of a treatment area, but areas of 

special consideration may be treated with carbaryl bait. Should 

these situations occur, no area would be treated with more than 

one insecticide, and there would be no mixing or combination of 

insecticides. 

 10. Carbaryl Baits

The nature of the carbaryl baits used to suppress grasshoppers 

suggests that the bait formulations will be less hazardous than 

liquid formulations. The carbaryl in the bait formulations is 

absorbed by the bran or other carrier, and will be less 

bioavailable, particularly in dermal exposures. The magnitude of 

this difference, however, cannot be quantified. Although 

separate exposure assessments are made for workers applying 

carbaryl baits, these assessments reflect differences in 

application rates between the baits and the liquid sprays but use 

the same exposure rate estimates as those used for the liquid 

formulations. Thus, the quantitative risk assessment for the 

baits probably overestimate risk; however, the extent of the 

overestimation cannot be quantified. 

Some carbaryl baits include certain additives to preserve the bait 

(i.e., silica gel) or provide an attractive carrier to the 

grasshoppers (i.e., n-amyl acetate). The primary concerns with 

silica gel relate to inhalation of dusts (potential for silicosis). The 
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concentration of silica gel is very low in the formulation. Proper 

application and adherence to pesticide labels preclude any 

concern for exposures to silica gel. 

N-amyl acetate or "banana oil" can be used as a solvent and 

flavor additive. It occurs naturally in fruits. N-amyl acetate 

readily volatilizes to the atmosphere. Biodegradation occurs 

readily in soil, but there is moderate potential for 

bioconcentration in aquatic organisms. Although this compound 

is a primary irritant of skin, eyes, and mucus membranes, the 

low potential exposures from program applications of carbaryl 

bait are not expected to result in any adverse effects to humans. 

Although it may bioconcentrate in aquatic organisms, the toxicity 

to those species is low relative to the active ingredient (carbaryl) 

in the formulation.

b.Diflubenzuron. 

 1. Toxic Mode of Action

Diflubenzuron is classified as an insect growth regulator. 

Diflubenzuron is toxic to insects through inhibition of chitin 

synthesis (interference with the formation of the insect's cuticle 

or shell). The likely mechanism is through blockage of chitin 

synthetase, the ultimate enzyme in the biosynthesis pathway of 

chitin (Cohen, 1993). Exposure of insect life stages to 

diflubenzuron can result in larvicidal and ovicidal effects. The 

larvae are unable to molt properly due to a lack of chitin in the 

new cuticle. Exposure of larvae may occur through dermal 

contact, but the primary route of intoxication is as a stomach 

poison. Ovicidal effects may occur through direct contact of eggs 

or through exposure of gravid females by ingestion or dermal 

routes. The larva develops fully in the egg, but is either unable to 

hatch or dies soon after hatching due to chitin deficiency in the 

cuticle. This inhibition of chitin synthesis affects primarily 

immature insects, but can also affect other arthropods and some 

fungi. Chitinous algae (diatoms) are not adversely affected by 

diflubenzuron (Antia et al., 1985). Most other organisms lack 

chitin and are not affected by exposure to diflubenzuron.

The main sources of uncertainty regarding diflubenzuron risk 

assessment are estimates of dermal absorption, dose-severity 

relationships for effects on the blood, and the potential cancer 

risk. These uncertainties have been addressed by using 

conservative estimates that are over-protective of human health. 

The overall quality of the data on diflubenzuron can be 

categorized as being moderate to good (SERA, 1996).

 2. Acute Toxicity
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Diflubenzuron has only very slight to slight acute oral toxicity to 

humans. Acute toxicity through dermal and inhalation routes is 

also low. There are no reports of skin sensitization from 

diflubenzuron, and it is only a mild skin and eye irritant.

 3. Effects on the Blood/Hematopoietic System

The most sensitive effect from exposure to diflubenzuron is the 

occurrence of methemoglobinemia, a condition that impairs the 

ability of the blood to carry oxygen. Hematological effects from 

exposure to diflubenzuron pose the greatest concern. The 

formation of substantial amounts of methemoglobin and 

sulfhemoglobin following exposure to diflubenzuron requires 

exposures higher than those in the grasshopper suppression 

program, but some subgroups of the population (i.e., smokers) 

could be at increased risk due to low viable hemoglobin counts 

from other nonprogram exposures. Clinical signs of toxicity do 

not normally begin to occur until the level of methemoglobin 

exceeds 10 percent in the blood. Levels above 50 percent can be 

fatal. Studies of chronic exposure to diflubenzuron indicate that 

hematological effects are the issue of greatest potential concern 

to humans. The toxic effect resulting from excessive exposure to 

diflubenzuron is the induction of methemoglobin and 

sulfhemoglobin. These modified forms of hemoglobin are unable 

to function normally in the transport of oxygen by blood. The 

NOEL for the formation of these modified forms of hemoglobin in 

a 1-year dog-feeding study of diflubenzuron was determined to 

be 2 mg/kg/day (Duphar, 1985), but actual toxic effects were not 

noted at this exposure level. Based upon this NOEL, the RfD 

determined by EPA for hematopoietic effects from diflubenzuron 

is 0.02 mg/kg/day.

 4. Neurotoxicity

Diflubenzuron has been shown to be negative in tests for 

neurotoxicity (Eisler, 1992; Maas et al., 1981).

 5. Carcinogenicity

Diflubenzuron has no reported carcinogenic effects. Neither a 

2-year feeding study of rats (Keet, 1984a) nor a 2-year feeding 

study of mice (Keet, 1984b) found any evidence of carcinogenic 

effects. Although EPA has not formally classified diflubenzuron, 

these negative studies indicate that this compound meets the 

criteria for EPA's group E classification (evidence of 

noncarcinogenicity).

 6. Genotoxicity and Mutagenicity
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Diflubenzuron has very limited evidence of mutagenic effects. 

Diflubenzuron had negative findings in a dominant lethal study 

of mice (Arnold, 1974), a cell transformation assay, an assay of 

induction of unscheduled deoxyribonucleic acid (DNA) synthesis 

(Brusick and Weir, 1977a), transplacental hamster cell 

transformation assays (Quarles et al., 1980), and Ames 

mutagenicity assays (Brusick and Weir, 1977b). The only 

positive finding was in a study of cell transformations that 

showed weak mutagenic effects in the absence of metabolic 

activation (Perocco et al., 1993). These mutagenic effects were 

not observed with metabolic activation. Immunotoxic, 

mutagenic, and genotoxic effects are only recorded for exposures 

much higher than would be anticipated in the grasshopper 

suppression program. 

 7. Reproductive and Developmental Toxicity

Reproductive and teratogenic effects were not reported in several 

teratogenicity and multigeneration reproduction studies of 

mammals conducted by the World Health Organization (1985). 

Only one study has noted a dose-related decrease in testosterone 

in chickens (Smalley, 1976), but this study is inconsistent with 

the full report for the same facility (Kubena, 1982) and with other 

studies (Cecil et al., 1981). 

 8. Inert Ingredients and Metabolites

The primary metabolites of diflubenzuron are 

4-chlorophenylurea (CPU) and 2,6-difluorobenzoic acid. The acid 

metabolite is further metabolized by microorganisms in 1 to 2 

weeks in soil. The CPU degrades in soil in about 5 weeks. The 

rapid metabolism and degradation of this metabolite's low 

concentrations make it highly unlikely that there would be 

sufficient exposure to cause any of the adverse toxicological 

effects noted in these studies. 

There are various carriers and adjuvants used with 

diflubenzuron to enhance the pesticide applications. These are 

primarily synthetic and naturals oils. These inert ingredients 

may include light and heavy paraffinic oils, polyethylene glycol 

nonylphenyl ether, alkylaryl polyether-ethanols, vegetable oil 

surfactants, and canola oil. Food-grade canola oil would not be 

expected to pose any noteworthy hazards, but some of the 

heavier oils could affect birds and other wildlife. (Use of 

formulations that use the paraffinic oils may not be appropriate 

in some habitats with nesting birds, particularly if endangered or 

threatened species are present or protection of game birds is an 

issue.) Although the paraffinic oils have been shown to decrease 

egg-hatch of nesting birds, these effects have only been observed 

from spills or exposures higher than are anticipated from 
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134 Grasshopper Environmental Impact Statement

program applications. Polyethylene glycol nonylphenyl ether has 

generally not been of human health concern except for a few 

cases of allergic contact dermatitis. This should not be an issue if 

proper program safety precautions are followed. This compound 

does not persist in natural environments and is unlikely to show 

bioconcentration of residues. 

 9. Synergistic Effects

Diflubenzuron is only reported to be synergistic with the 

defoliant DEF (NLM, 1988). Because the defoliant is unlikely to 

be applied concurrently with grasshopper suppression 

treatments, there is minimal risk of synergistic effects. However, 

diflubenzuron has potential for cumulative or synergistic effects 

with other (nonpesticidal) compounds known to bind 

hemoglobin. For example, exposure to cigarette smoke and 

carbon monoxide from incomplete combustion can result in 

binding of hemoglobin. Exposure to diflubenzuron after these 

exposures can result in additional binding of hemoglobin and the 

greater risk associated with less oxygen transport by blood. 

Malathion. 

 1. Toxic Mode of Action

Malathion is an organophosphate insecticide whose mode of 

toxic action is primarily through acetylcholinesterase (AChE) 

inhibition (Smith, 1987; Klaassen et al., 1986). At low doses, the 

symptoms of AChE inhibition in humans include effects such as 

nausea, sweating, dizziness, and muscular weakness. The 

effects of higher doses of malathion may include irregular 

heartbeat, elevated blood pressure, cramps, convulsions, and 

respiratory failure. However, AChE inhibition can be measured 

in blood at levels much below that which causes symptoms; 

therefore, adverse health effects do not necessarily result from all 

levels of AChE inhibition.

Complete toxicity data are unavailable for individual 

formulations of malathion. In these cases, regulatory values 

established by EPA and other agencies have been based on the 

toxicity characteristics of the technical grade (or pure) chemical 

or other similar formulations of the pesticide. It is this 

information that has been reviewed and incorporated into this 

hazard assessment of malathion. 
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 2. Acute and Chronic Toxicity

The acute oral toxicity of malathion is slight to humans (DHHS, 

NIOSH, OSHA, 1978). Malathion's acute toxicity by the dermal 

route is minimal, and malathion is considered one of the least 

dermally toxic of the organophosphorus insecticides (EPA, OPP, 

1989b). Malathion is a very slight dermal irritant and a slight 

eye irritant (EPA, OPP, 1989b).

Testing also indicates relatively low chronic toxicity. The human 

RfD was established at 0.02 (mg/kg/day) based upon no AChE 

inhibition (NOEL) at a higher concentration (2.3 mg/kg/day) and 

applying an uncertainty factor of 100 to that study of human 

exposure (Moeller and Rider, 1962; EPA, OPP, 1989b).

 3. Neurotoxicity

Neurotoxicity is any toxic effect on any aspect of the central or 

peripheral nervous system. Such changes can be expressed as 

functional changes (such as behavioral or neurological 

abnormalities) or as neurochemical, biochemical, physiological, 

or morphological alterations. Malathion poses a neurotoxic risk 

only as a consequence of inhibition of AChE. Studies of acute 

delayed neurotoxicity or structural neuropathy have been 

negative (EPA, OPP, 1989a). The quantitative risk assessment of 

AChE inhibition analyzes only the neurotoxic risks associated 

with AChE inhibition.

 4. Immunotoxicity

Immunotoxicity is any toxic effect mediated by the immune 

system, such as dermal sensitivity, or any toxic effect that 

impairs the functioning of the immune system. Malathion may 

be immunosuppressive and immunopathologic in vitro at high 

concentrations (Desi et al., 1978; Thomas and House, 1989). 

More recent studies have shown that malathion may alter 

immune functions in mammals in vivo (Rodgers and Ellefson, 

1992). The implications of this information with respect to 

human immune system toxicity remain unclear.

 5. Genotoxicity and Mutagenicity

Genotoxicity is a specific adverse effect on the genome (the 

complement of genes contained in the haploid set of 

chromosomes) of living cells that, upon the duplication of the 

affected cells, can be expressed as a mutagenic or a carcinogenic 

event because of specific alteration of the molecular structure of 

the genome. It results from a reaction with DNA that can be 
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136 Grasshopper Environmental Impact Statement

measured either biochemically or, in short-term tests, with end 

points that reflect on DNA damage. DNA is the genetic material 

of a cell.

Mutagenicity is an adverse effect that produces a heritable 

change in the genetic information stored in the DNA of living 

cells. There is some evidence that malathion may pose a genetic 

hazard at high concentrations based upon some in vivo and in 

vitro cytogenetic studies where chromosomal aberrations and 

reactivity with DNA had a weak association to exposure, but the 

majority of studies do not support a finding of any genetic hazard 

from malathion exposure (WHO, IARC, 1983; Griffin and Hill, 

1978). The potential risk of clastogenic injury increases if the 

high doses of malathion formulation contain sufficient 

impurities. The premium grade malathion is of high purity, and 

exposures resulting from applications are relatively low 

compared to the thresholds for genotoxicity. Based upon this, 

there should be no unacceptable risks of genotoxicity or 

mutagenicity from program applications of malathion.

 6. Carcinogenicity

Carcinogenicity is an adverse effect that causes the conversion of 

normal cells to neoplastic cells and the further development of 

neoplastic cells into a tumor (neoplasm). A neoplasm is an 

altered, relatively autonomous growth of tissue composed of 

abnormal (neoplastic) cells, the growth of which is more rapid 

than, and not coordinated with, the growth of other tissues. EPA 

has classified malathion as having “suggestive evidence of 

carcinogenicity, but not sufficient to assess human carcinogenic 

potential.” This indicates that any carcinogenic potential of 

malathion cannot be quantified based upon EPA’s weight of 

evidence determination used in this classification. 

Guidelines for the expression of potential carcinogenic hazard 

are being revised by EPA to accommodate the increased 

understanding of the nature and causation of cancer. 

Historically, it was widely believed that cancer was caused by a 

limited number of discrete chemical, physical, or biological 

agents. It was assumed that this limited number of carcinogenic 

agents could be readily determined and regulated to eliminate 

cancer risks. This assumption that only certain compounds 

cause cancer led to a nonthreshold approach to regulation. The 

finding of a positive result for cancer in an acceptable animal 

study, human study, or through epidemiological study presumed 

the agent to be a carcinogen. The finding of a negative result for 

cancer in these studies was interpreted as indicative that the 

agent was either not carcinogenic or the data were inadequate to 

classify the carcinogenic potential. This widespread assumption 
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Grasshopper Environmental Impact Statement 137

that potential initiation and promotion of cancer related to 

specific agents led EPA to issue guidelines on September 24, 

1986 (51 Federal Register (FR) 33992–34054), to rank those 

agents according to carcinogenic hazard potential based upon 

the weight of evidence. Under these guidelines, chemical and 

other agents were identified as human carcinogens (Group A), 

probable human carcinogens (Group B), possible human 

carcinogens (Group C), not classifiable (Group D), or having 

evidence of noncarcinogenicity (Group E). Although this 

classification based upon positive or negative results could be 

used readily for regulation of agents, it is widely recognized by 

the scientific community that this approach does not adequately 

use the advances in knowledge of carcinogenesis and risk 

assessment. 

Today, scientists recognize that cancer is a highly complex, 

multifactorial disease caused, in part, by endogenous (intrinsic) 

metabolic or other imbalances associated with age or genetic 

makeup and, in part, by a wide variety of exogenous (external) 

factors including diet, lifestyle, exposure to ionizing radiation, 

and exposure to chemicals of natural or man-made origin. It is 

now known that initiation of cancer may be caused by cell 

damage resulting from excess exposure to one or multiple agents 

and that promotion of genetic errors from the cell damage may 

also be caused by conditions or agents other than those causing 

the initial cell damage. It is also widely recognized that there is a 

threshold for all agents to cause carcinogenicity, and the 

threshold for a given agent may be affected by the endogenous 

and exogenous factors mentioned above. This realization has led 

to changes in carcinogen regulation by some international 

organizations. Likewise, EPA has prepared new categories to 

address these issues and other advances in the understanding of 

carcinogenesis. Their narrative descriptors of carcinogenic risk 

for potential agents in the 1999 proposed guidelines on June 25, 

1996 (61 FR 32799–32801) include carcinogenic to humans, 

suggestive evidence of carcinogenicity but not sufficient to assess 

human carcinogenic potential, not likely to be carcinogenic to 

humans, and data are inadequate for an assessment of human 

carcinogenic potential. Classification of pesticides into a given 

category is based upon a weight of evidence approach. These 

new rankings recognize the potential risk of all agents to cause 

cancer, even if the actual occurrence is “not likely.”

Uses of most insecticides in APHIS' grasshopper suppression 

programs are expected to be classified by EPA under the new 

guidelines as “not likely to be carcinogenic to humans” or data 

are inadequate for an assessment of human carcinogenic 

potential based upon the weight of evidence. As part of EPA’s 

Pesticide Reregistration process (for all pesticides registered prior 
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138 Grasshopper Environmental Impact Statement

to 1984) and in compliance with the Food Quality Protection Act 

of 1996, it is expected that carcinogenic potential will be 

reclassified for all chemicals. Depending upon the registration 

review status, references to carcinogenic potential of pesticides 

in this document use classifications according to either the 1985 

classification or the 1999 proposed guidelines. Based upon 

existing data including recent reviews, there are no unacceptable 

risks of carcinogenicity anticipated for this program. 

 7. Ocular (Eye) Toxicity

Information on the ocular effects of malathion have been based 

mostly on anecdotal data. Reports from Japan in the early 1970s 

associated eye disease in a number of people with agricultural 

use of malathion (as well as other pesticides) at extremely high 

concentrations (the syndrome was called Saku Disease after the 

region in which it occurred). A review of the data by the 

Malathion Public Health Effects Advisory Committee, a 

committee formed by the California Department of Health 

Services (CDHS) in 1990, found fundamental flaws in the original 

study and subsequent papers and determined that the reported 

association between malathion and eye disease had not been 

established (CDHS, 1991).

However, because data from various studies have demonstrated 

adverse ocular effects from other organophosphates, EPA has 

issued a data call-in to the registrant for ocular toxicity testing of 

malathion. The study is required to confirm or deny the 

potential for malathion to cause adverse eye effects.

 8. Reproductive and Developmental Toxicity

Reproductive toxicity is any adverse effect that produces changes 

in the capacity to produce viable offspring, for example, by 

affecting the reproductive organ systems or hormonal 

functioning. Developmental toxicity is any adverse effect in the 

parent or the offspring that produces changes in fetal or neonatal 

growth and development, including physiological, morphological, 

biochemical, or behavioral changes.

Reproductive and teratology studies are outstanding data 

requirements of EPA for reregistration of malathion (EPA, OPTS, 

1990). The lowest NOEL determined for these effects from 

malathion exposure was a developmental NOEL of 25 mg/kg/day 

in rabbits (EPA, OPP, 1989a). This exposure level is considerably 

higher than the NOEL for AChE inhibition (0.23 mg/kg/day) 

analyzed in the quantitative risk assessment, so these effects 

would not be anticipated unless other effects were noted first. 
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There are no unacceptable risks of reproductive or 

developmental toxicity to workers or to the general public from 

any exposure scenario.

 9. Inert ingredients and Metabolites

The main impurities of concern in malathion formulations are 

isomalathion (95 times as toxic as malathion) and malaoxon (68 

times as toxic as malathion) (CDHS, 1991; Aldridge et al., 1979; 

Ryan and Fukuto, 1985; Fukuto, 1983). Isomalathion formation 

results from improper storage or handling of malathion 

formulations. Malaoxon is formed from malathion's oxidation, 

which has been reported to occur in air and from volatilization 

from the bait droplets on various surfaces. A recent pilot study 

by the CDHS (Brown et al., 1991; Brown et al., 1993) found that, 

following aerial malathion applications, malaoxon and other 

transformation products were detectable in air and on various 

test surfaces for hours and, in some cases, days after the 

treatment. Levels of malaoxon increased, presumably via 

oxidation of malathion on some test surfaces for the 9 days of the 

study. However, another study (Ross et al., 1990) indicated that 

the dermal uptake of a pesticide can be highly dependent on the 

amount that is bioavailable (i.e., the amount of residue that can 

be dislodged or assimilated) and that the amount can decrease 

substantially over a 12-hour period. The variances in test data 

and the absence of any scientific accord over the interpretation of 

the results point to the need for further studies in this area. 

There is some petroleum-based oil that occurs in some ULV 

formulations. The exposure of birds’ eggs and humans to this oil 

has been shown to have no adverse effects at program 

application rates.

 10. Synergistic Effects

Although the toxicity of malathion may be potentiated by some 

other organophosphates and carbamates (Knaak and O'Brien, 

1960; Cohen and Murphy, 1970), it is impossible to predict 

multiple exposures and synergism from applications not related 

to this program. Dichlorvos and naled were not found to be 

synergistic with malathion, but only additive (Cohen and Ehrich, 

1976). Diazinon is synergistic with malathion (Keplinger and 

Deichmann, 1967). In addition, organophosphate insecticides 

are routinely used in various public health applications such as 

mosquito control programs. There is some potential for 

synergistic effects resulting from the combination of malathion 

and inadvertent simultaneous pesticide application by the 

public; however, public notification about program treatments 

helps to minimize this risk. 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

140 Grasshopper Environmental Impact Statement

B. Insecticide Applications at Conventional Rates and Complete 

Area Coverage

This section describes the potential consequences of the full coverage 

suppression alternative to affect human health, environmental 

quality, and nontarget species. The consequences are based upon the 

maximum field rates of application of each insecticide anticipated for 

this program as described in table B–4. The risks to human health are 

assessed quantitatively and characterized by potential health outcome 

for each of the program insecticides. The risks to environmental 

quality of the physical environment are presented qualitatively. 

Quantitative information about environmental fate and modeling data 

are provided in the chemical background paper on environmental fate 

and transport modeling (USDA, APHIS, 1996b; see appendix C). The 

risks to nontarget species include a review of the hazards of each 

insecticide, a quantitative presentation of potential risks, and review of 

the findings of field studies. 

1. Efficacy of 

Insecticide 

Controls

Grasshoppers and crickets comprise one of the major insect groups 

capable of a rapid response to habitat disturbance, due in a large part 

to their high fertility rate, prolific reproduction, and short generation 

time (Uvarov, 1966). Numerous reports have documented the capacity 

of grasshopper population "explosions" to cause significant 

destruction of vegetation (Uvarov, 1977). This aggressive colonization 

of uninfested (treated) sites by economically damaging grasshoppers 

assures that no limited program can eradicate these species with 

control agents alone. Insecticide treatments have only suppressed 

native grasshopper and cricket populations briefly. Although there are 

temporary decreases in grasshopper populations on treated sites, 

studies indicate that there is rapid recolonization of the disturbed 

(treated) sites by populations from untreated sites nearby (Parmenter 

et al., 1991). This rapid recolonization also assures that long-term 

suppression of grasshopper populations at given locations is highly 

unlikely. The only suggested extinction of a pest grasshopper in North 

America (Rocky Mountain grasshopper) has been attributed to 

agricultural destruction of the insect's habitat and the introduction of 

nonnative species (Lockwood and DeBrey, 1990).

The toxic properties of insecticides remain active against grasshoppers 

until the active ingredient in the formulated compound degrades. 

Populations of grasshoppers recover from the toxic effects of these 

insecticides as the frequency of contact decreases. This generally 

coincides with decreasing concentrations of the insecticides on the 

treated site. The selective nature of the insecticide may favor survival 

of certain species of grasshoppers over other species. This may result 

in higher populations of resistant species on certain treated sites, but 

this selective advantage would only last as long as the toxicant 

remained active. The selective nature of the insecticides determines 

which grasshopper populations would be affected, and the selection 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 141

pressure would determine the extent of population reduction and the 

length of suppression. Although some data about toxicity are available 

for these agents, not all program insecticides have been tested for 

efficacy against all species of economically damaging grasshoppers. It 

is, however, clear from the completed research that application of 

these chemical agents would not result in any permanent changes in 

the ecological relationships that exist between grasshopper species 

and other components of the rangeland.

2. Human Health Included in this risk assessment are the potential effects on 

grasshopper program workers, the general public, and groups of 

people who may be at special or increased risk. The potential high 

risk group includes those who are sensitive to specific chemicals, 

those with multiple chemical sensitivity, those whose health status 

may make them more susceptible to effects, and those whose lifestyles 

may make them more prone to come into contact with the chemicals 

in the treatment areas.

a. Carbaryl. For the general public, none of the exposures exceed the 

systemic RfD of 0.01 mg/kg/day. Therefore, the estimated exposures 

that might occur to the public as a result of involvement in an event 

similar to the scenarios that were analyzed are not cause for concern.

For workers, on the other hand, all of the estimated exposure levels 

associated with the normal application of carbaryl sprays exceeds the 

RfD, with estimated doses resulting in HQs of 2 to 4000. This 

variability probably reflects differences in individual work habits 

(SERA, 1993). Workers who handle insecticides with proper care can 

reduce their exposure substantially. Conversely, poor work habits can 

increase exposure substantially. 

At the lower and mid-ranges of exposure, it is unlikely that there 

would be overt signs of toxicity, even when the RfD is exceeded 

considerably (i.e., by factors of about 40 to 400). There are 

experimental studies in humans suggesting that doses of up to about 

3 mg/kg (Gold et al., 1982) will not be associated with signs of toxicity 

in humans. 

At the high range of occupational exposure (i.e., about 36 mg/kg), the 

nature of potential adverse effects is less clear. Carbaryl has been 

used for many years, and reports of occupational poisoning, either 

published or anecdotal, were not encountered. On the other hand, no 

rigorous worker monitoring or epidemiology studies were found on the 

aerial application of carbaryl. Consequently, a precise characterization 

of risk is not possible. However, with good personal work practices, 

carbaryl may be handled safely. Poor work practices may present 

risks, but the likelihood of observing adverse effects cannot be well 

characterized. If such effects are observed, they would be those that 

are characteristic of AChE inhibitors.
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

142 Grasshopper Environmental Impact Statement

Under most exposure scenarios, members of the general public do not 

appear to be at any risk to the potential reproductive effects of 

carbaryl, even using relatively conservative assumptions. The one 

exception may be exposure from the consumption of contaminated 

vegetation immediately after aerial applications. In this case, the 

upper range of projected exposure exceeds the provisional RfD for 

reproductive effects by a factor of 1.5. Although the exposure levels 

would diminish rapidly as the carbaryl degrades and disperses, the 

initial residues could plausibly result in dose levels that exceed the 

provisional RfD. The specific instance where this may cause concern 

would be for individuals either with gardens in the vicinity of a spray 

application, or for individuals, particularly Native Americans, who 

might forage for food, herbs, or medicinal plants immediately after an 

application. However, the provisional RfD is designed to protect 

against adverse effects from chronic exposure at that level. The rapid 

degradation and infrequent applications in the grasshopper 

suppression program would not be routinely (or chronically) expected 

to result in exposures in excess of the provisional RfD. The only 

exposures from program applications would be acute and not expected 

to cause adverse reproductive effects with the short duration of 

potential exposure. 

For workers, under the least conservative exposure assumptions, 

levels of plausible exposure are far greater than the provisional RfD for 

reproductive effects. For the application of carbaryl sprays, the 

central estimate of the absorbed dose, 3.6 mg/kg/day, is in the range 

of doses associated with fetotoxicity in dogs and the upper range of the 

estimated absorbed dose, 36 mg/kg/day, is above the level associated 

with teratogenic effects in dogs.

This does not necessarily mean that teratogenic effects or reproductive 

impairment in humans can be predicted from or attributed to carbaryl 

exposure. Nonetheless, standard criteria and procedures are used for 

estimating the provisional RfD. Plausible levels of exposure are far 

above this provisional RfD.

 1. Cumulative Effects

For the general public, repeated exposure to carbaryl is a 

relatively minor concern. The risk characterization is based on 

exposure that is likely to be transient and the RfD is intended to 

be protective over very prolonged periods of exposure. 

Applications for suppression of grasshoppers are unlikely to be 

repeated within a given season and outbreaks are not an annual 

occurrence, so exposures would be infrequent and effects would 

only be acute. Because the RfD for neurotoxic effects is not 

exceeded even in short-term accidental exposures such as direct 

sprays, it is unlikely that repeated brief exposure, even over 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 143

several seasons, would lead to neurotoxic effects. Based on 

estimated exposures from contaminated vegetation, the 

provisional RfD for reproductive effects is exceeded slightly.

As with the general public, effects that would be associated with 

repeated exposure to carbaryl are encompassed by the risk 

assessment. Workers will be exposed to higher doses of carbaryl 

than the general public will be, and the exposure may occur over 

a relatively prolonged period of time—during the work week of a 

treatment season or several treatment seasons. The 

reproductive studies on dogs differ from the reproductive studies 

on most other species in that the dose schedule spans the period 

from conception to birth. While it is not clear that this difference 

contributes to the apparently higher sensitivity of dogs to the 

reproductive effects of carbaryl, the use of the data on dogs in 

characterizing potential risks to workers does encompass an 

exposure schedule that is similar to that for workers who could 

be exposed.

 2. Connected Actions

Baron (1991) has reviewed the literature regarding the 

interaction of carbaryl with other compounds. Very little 

information is available on the interaction of carbaryl with other 

agents used to control the grasshopper. In a study of acute 

lethal toxicity, no interactions were apparent with the 

co-administration of malathion and carbaryl to rats (Carpenter et 

al., 1961). In a pharmacokinetic study, however, 

co-administration of these compounds to rats altered the action 

of both insecticides so that the elimination of carbaryl from 

gastrointestinal tissues was delayed (Lechner and 

Abdel-Rahman, 1986).

Many toxicological interactions occur as a result of changes in 

the metabolism of the toxicant because of the induction or 

inhibition of an enzyme system, microsomal mixed function 

oxidase (MFO), which is involved in the metabolism of many 

different chemicals. Some studies have found that pretreatment 

with an agent that induced MFO decreased the acute toxicity of 

carbaryl to mice while pretreatment with an inhibitor of MFO 

enhanced the toxicity (Neskovic et al., 1978). As with many 

compounds, carbaryl appears to induce enzymes that are 

involved in its metabolism.

These data suggest that some compounds, including carbaryl 

itself, may increase the rate of metabolism of carbaryl and that 

this may reduce the acute toxicity of the compound. Conversely, 

other compounds that inhibit carbaryl metabolism may increase 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

144 Grasshopper Environmental Impact Statement

the acute toxicity of this compound. It is unclear how or if 

changes in metabolism would affect the reproductive toxicity of 

carbaryl.

 3. Groups at Special Risk

Very young children (that is, infants less than 6 months old) may 

be at special risk because they have incompletely developed 

AChE systems and immature livers and thus reduced MFO 

activity (ATSDR, 1993). As part of our compliance with Executive 

Order 13045 (Protection of Children From Environmental Health 

Risks and Safety Risks), the potential for adverse effects to 

children was considered carefully. The grasshopper treatments 

are conducted primarily on open rangeland and croplands where 

children would not be expected to be present or enter during the 

restricted re-entry period. Therefore, it is expected that 

grasshopper suppression applications would not usually be 

expected to result in exposures to children and that children 

would not have any adverse effects from these actions that are 

disproportionately different from the general population.

A small proportion of the population has an atypical variant of 

plasma cholinesterase. This condition is known to make these 

individuals sensitive to succinylcholine and may make them 

more susceptible to exposure to carbaryl as well as other AChE 

inhibitors. Other groups known to have low plasma AChE levels 

are long-distance runners, women in early stages of pregnancy, 

women using birth control pills, individuals with advanced liver 

disease, alcoholics, individuals with poor nutritional status, and 

individuals with skin diseases (ATSDR, 1993).

Several studies are available indicating that animals on a protein 

deficient diet tend to be more sensitive to carbaryl in terms of 

acute LD50 values compared with animals on a diet containing 

normal levels of protein (Baron, 1991). This sensitivity is 

probably related to the metabolism of carbaryl. Animals on a 

protein deficient diet generally will have lower levels of MFO, and, 

as discussed in the previous section, MFO appears to be involved 

in the detoxification of carbaryl, at least in terms of acute lethal 

potency.

b.Diflubenzuron. Values for the highest dose levels that will not induce 

methemoglobinemia have been derived for both workers and the 

general public. These values have been compared with estimates of 

doses derived from the exposure assessment to calculate HQs.

HQs determined for aerial spray workers, for both routine and extreme 

exposures, were all less than 1, indicating that these workers are not 

at risk of adverse effects from the grasshopper program operations 
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Grasshopper Environmental Impact Statement 145

that use diflubenzuron. Scenarios representing workers involved in 

accidental exposures also resulted in HQs less than 1 if they washed 

within 1 hour. Therefore, accidents would not cause concern about 

the health effects on these workers. Circumstances that prevent a 

worker from washing until 24 hours after spilling diflubenzuron on the 

lower legs would be cause for concern. In this case, the HQ could be 

as high as 40. 

A number of scenarios were analyzed to help characterize risk to the 

general public. The calculated HQs were less than 1 for most of these 

public exposures; therefore, adverse health effects clearly are not 

anticipated. The HQs for a few of the extreme scenarios ranged from 1 

to 7. Even in these cases, no clinically significant effects are likely. At 

the highest exposure, increases in certain blood pigments may be 

detected, but they will not be long lasting.

 1. Cumulative Effects

Any cumulative effects from the use of diflubenzuron are likely to 

be additive if the exposures are in the same treatment season, 

that is, diflubenzuron is applied twice in one season. Because 

there is a relatively short "window of opportunity" to suppress 

grasshoppers using diflubenzuron (early instars), it is highly 

unlikely that diflubenzuron would be applied twice in one 

season. No cumulative effects are expected from one year to the 

next. Therefore, the risks of a single exposure at 7 g a.i./acre is 

identical to two applications at 3.5 g a.i./acre. Since the risk 

assessment used maximum application rates in determining risk 

and any effects are likely to be additive rather than synergistic, 

cumulative effects due to diflubenzuron essentially have been 

addressed. 

This risk assessment is based on single applications at a rate of 7 

g a.i./acre. This approach is used to estimate maximum daily 

exposure and daily absorbed dose. Because the dispersal rate 

for diflubenzuron in the environment is relatively fast, multiple 

applications at lower rates per application will result in risks that 

are less than those associated with a single application at the 

maximum approved rate. Given the narrow range of application 

rates compared with the variabilities and uncertainties in the 

exposure and dose-response assessments, the risks of toxic 

effects associated with a single application at less than the 

maximum rate will be related directly to the application rate. 

Thus, an application at 3.5 g a.i./acre will entail risks that are 

approximately one half of those expected at the maximum 

application rate. Two applications at 3.5 g a.i./acre will entail 

risks that are less than the risks from a single application at 7 g 

a.i./acre due to degradation, but greater than a single 

application at 3.5 g a.i./acre. 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

146 Grasshopper Environmental Impact Statement

 2. Connected Actions

No data were found to indicate that exposure to diflubenzuron 

will affect the way people respond to other insecticides used in 

the grasshopper suppression program. The most sensitive effect 

of diflubenzuron, methemoglobinemia, is not associated with 

exposure to any of the other insecticides. Therefore, the other 

insecticides are not expected to interact with diflubenzuron or 

result in an additive response. If other compounds in the 

environment induce methemoglobinemia, then an additive effect 

may be noticed. Individuals exposed to combustion smoke or 

carbon monoxide may be at increased risk of developing 

methemoglobinemia (Hoffman and Sauter, 1989; Laney and 

Hoffman; 1992). Also, individuals exposed to high levels of 

nitrates, in either air or water, will have increased levels of 

methemoglobin (Woebkenberg et al., 1981) and may be at 

increased risk from exposure to compounds such as 

diflubenzuron.

 3. Groups at Special Risk

Some individuals are born with a form of congenital 

methemoglobinemia and may be at increased risk of adverse 

effects from compounds that induce methemoglobinemia 

(Barretti et al., 1984). Infants less than 3 months old have 

higher levels of methemoglobin than do older children or adults 

(Centa et al., 1985; Khakoo et al., 1993; Nilsson et al., 1990) and 

may be at increased risk if exposed to diflubenzuron 

contamination. Some infants with an intolerance to cow's milk 

or soy protein exhibit methemoglobinemia (Murray and Christie, 

1993; Wirth and Vogel, 1988). This condition may decrease the 

likelihood that those infants would be exposed to diflubenzuron 

through contaminated milk. Nonetheless, the infants may be at 

increased risk if exposed to any materials contaminated with 

diflubenzuron or any compound that induces 

methemoglobinemia. As with carbaryl, the likelihood of exposure 

of children to insecticides used in grasshopper suppression 

programs is very slight, and no disproportionate adverse effects 

to children are anticipated over the negligible effects of 

diflubenzuron to the general population.

The most significant exposure scenarios for diflubenzuron 

involve dermal contact. Individuals with diseased or damaged 

skin may absorb chemicals such as diflubenzuron at a 

substantially greater rate than do normal individuals. Those 

individuals may be at higher risk, but the magnitude of this risk 

will depend on the type and severity of skin damage.
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Grasshopper Environmental Impact Statement 147

Other individuals who may be considered at increased risk of exposure 

to chemicals in general include those with various disease conditions 

(for example, immunosuppression; immunodeficiency; allergies; and 

impaired liver, kidney, lung, or other organ functions), the very young 

or the very old, individuals with poor diets, pregnant women, or 

individuals suffering from multiple chemical sensitivity. Other than 

infants and individuals with damaged skin, there are no data to 

support an evaluation of the sensitivity of such individuals to 

diflubenzuron. 

c. Malathion. For the general public, none of the exposure scenarios 

involve levels that exceed the RfD and most are far below the RfD. The 

assessment of inhalation exposure is based on a threshold limit value 

(TLV) that was normalized for an exposure that would occur over an 

8-hour workday, 5 days per week. When normalized for this 

continuous exposure, this RfD is equivalent to a factor of about 6,000 

above plausible levels of estimated exposure. Therefore, although the 

adjusted TLV does not incorporate additional uncertainty factors for 

sensitive subgroups or data quality, even very conservative 

adjustments would not result in HQs of concern.

For workers, estimates of daily absorbed doses that are associated 

with the maximum application rate of malathion span the RfD: 0.01 

mg/kg to 1 mg/kg. The variability in the exposure estimates reflects 

the variability in the data upon which the assessment is based. Under 

routine conditions, aerial spray workers may be exposed to doses that 

result in HQs of from 0.5 to 50. All accidental scenarios, based on the 

estimated amount of malathion handled per day, result in HQs more 

than 1 (from 2.5 to 13).

The implications of these HQs greater than 1 are difficult to assess. 

Although AChE inhibition is possible at the estimated levels of 

exposure, it is far less certain that these exposure levels would be 

associated with any signs of toxicity. This is consistent with human 

experience. Aerial applications of malathion have been conducted 

since the early 1960s to control grasshoppers and other pests, and 

signs of severe nervous system impairment have not been reported in 

the open literature or in unpublished or anecdotal reports. Although 

the upper range of plausible exposure, 1 mg/kg/day, is above the level 

that has been demonstrated to cause AChE inhibition in humans, it is 

well below the range at which adverse effects have been demonstrated.

 1. Cumulative Effects

For both workers and the general public, the characterization of 

risk for most scenarios is based upon the exposure relative to the 

RfD. Since this RfD value is intended to be protective of daily 

exposure over a life span, the value is conservative when applied 

to the grasshopper program in that all exposures will occur over 
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148 Grasshopper Environmental Impact Statement

substantially less than a life span. The only exception is the risk 

characterization for inhalation exposure, which is based on the 

TLV time-weighted for continuous exposure. Although there are 

uncertainties to this approach, the very low HQ, 0.0002, 

suggests that these uncertainties do not affect the 

characterization of risk. In addition, as with the other exposure 

scenarios, the concentrations of malathion in air used for the 

exposure assessment are based on monitoring data collected 

shortly after a spray. These levels will diminish over time 

through dispersion and dissipation. Thus, the exposure 

assessment is conservative. Given these conservative 

approaches and the lack of any apparent hazard, concern for 

cumulative effects is minimal.

 2. Connected Actions

Relatively little information is available regarding the effects of 

exposure to malathion with other agents used to control 

grasshoppers. Keplinger and Deichmann (1967) noted that 

co-exposure to malathion and carbaryl resulted in a slight 

increase in the toxicity of the mixture. Another cholinesterase 

inhibitor, EPN (O-ethyl O-p-nitrophenylbenzenethiophasphonate) 

also has been reported to have a greater than expected toxicity 

on co-administration with malathion to rats and dogs (Frawley et 

al., 1957), although it is not possible to quantify the magnitude 

or nature (i.e., additive vs. synergistic) of the interaction. 

 3. Groups at Special Risk

Very young children (that is, infants less than 6 months old) may 

be at special risk because they have incompletely developed 

AChE systems and immature livers. As with carbaryl and 

diflubenzuron, the likelihood of exposure of children to control 

chemicals used in grasshopper programs is very slight and no 

disproportionate adverse effects to children are anticipated over 

the negligible effects of malathion to the general population. 

Several other groups may be at special risk to all cholinesterase 

inhibiting compounds, including malathion. A small proportion 

of the population has an atypical variant of plasma 

cholinesterase. This condition is known to make these 

individuals sensitive to succinylcholine and may make them 

more susceptible to the effects of exposure to malathion and 

other AChE inhibitors. Other groups known to have low plasma 

AChE levels are long-distance runners, women in early stages of 

pregnancy, women using birth control pills, individuals with 

advanced liver disease, alcoholics, individuals with poor 

nutritional status, and individuals with skin diseases (ATSDR, 

1993).
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 149

For the general public, none of the exposure scenarios involve 

levels that exceed the RfD, and most are far below the RfD. The 

assessment of inhalation exposure is based on a TLV that was 

normalized for an exposure that would occur over an 8-hour 

workday, 5 days per week. When normalized for this continuous 

exposure, this reference level is equivalent to a factor of about 

6,000 above plausible levels of estimated exposure. Therefore, 

although the adjusted TLV does not incorporate additional 

uncertainty factors for sensitive subgroups or data quality, even 

very conservative adjustments would not result in HQs of 

concern.

3. Environmental 

Fate and the 

Physical 

Environment

The effects on components of the physical environment may be direct 

or indirect. Direct impacts to soil, water, or air would include changes 

in chemistry and composition in such a way as to reduce the ability to 

support plant and animal growth and survival. Indirect impacts 

include negative effects on soil and water organisms and 

microorganisms that play a large role in ecological processes such as 

nutrient cycling and breakdown of organic matter to include 

pesticides. It has been shown in many instances that the major factor 

in the breakdown of organic matter is the presence of microorganisms. 

Characteristics such as bioaccumulation or bioconcentration of 

insecticides in vegetation and animals are important environmental 

quality indicators. 

Environmental 

Fate of 

Insecticides

The ability of a chemical to affect an environmental component is 

largely dependent on persistence. The persistence of a chemical will 

be affected to some extent by certain ambient conditions such as 

amount of organic material present, temperature, moisture content, 

and pH. In the case of compounds that bind readily with organic 

matter, the amount of organic material present in the soil will 

determine the extent of inhibition to chemical movement. Specific 

information pertaining to the fate and transport characteristics of 

grasshopper suppression insecticides can be found in the Hazard 

Analysis—Rangeland Grasshopper Cooperative Management Program 

(USDA, APHIS, 1996c). The following paragraphs identify how each 

specific compound affects components of the physical environment.

Carbaryl. 

 1. Soil

Carbaryl has a relatively short half-life in soil. The average 

half-life ranges from 7 days in aerobic soils to 28 days in 

anaerobic soils (EPA, OPTS, 1985). Carbaryl persistence in soil 

depends on the pH, moisture content, and microbial activity of 

the soil. Degradation of carbaryl in soil results primarily from 

the metabolic activity of microorganisms (Heywood, 1975), but 

hydrolysis and photolysis also occur. Biodegradation of carbaryl 
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150 Grasshopper Environmental Impact Statement

is a principle breakdown mechanism and as much as 80 percent 

has been shown to mineralize (degrade) within 4 weeks (Howard, 

1991). 

Soil microorganism densities have been shown to be slightly 

reduced following carbaryl treatments, with recovery to 

normal population densities occurring within 3 weeks 

(Moulding, 1972). Carbaryl bait, due to its application 

method, will exhibit reduced soil effects relative to spray 

applications (USDA, APHIS, 1987).

Little transport of carbaryl through runoff or leaching to 

groundwater is expected due to the low water solubility, 

moderate sorption, and rapid degradation in soils. There are 

no reports of carbaryl detection in groundwater and less than 

1 percent of carbaryl applied to a sloping plot was detected in 

runoff (Caro et al., 1974). Groundwater Loading Effects of 

Agricultural Management Systems (GLEAMS) modeling (Davis 

et al., 1990) indicates minimal soil movement of carbaryl. 

A. Water

Degradation of carbaryl is rapid in both freshwater and 

saltwater. Carbaryl applied over open freshwater was found 

to degrade completely in 1 to 2 days (California Department of 

Fish and Game (CDFG), 1963; Lichtenstein et al., 1966). All 

carbaryl degraded from seawater in 17 days at 20 o

C (Karinen 

et al., 1967). Kinetic studies determined the half-life for 

hydrolysis in neutral to alkaline freshwater to be 1.3 to 1.5 

days (Wolfe et al., 1978; Aly and El-Dib, 1971). The photolysis 

half-life in water was determined to be 6.6 days (Wolfe et al., 

1978). Carbaryl concentrations following a 1.5-inch 

rainstorm are projected to have less than 5 parts per billion 

(ppb) in streams and less than 13 ppb in ponds based upon 

GLEAMS modeling (USDA, APHIS, 1996b; see appendix C). 

B. Air

Carbaryl has a half-life in air of 1 to 4 months. The low vapor 

pressure of carbaryl makes it unlikely that there will be any 

volatilization from soil, water, or treated surfaces (Dobroski et 

al., 1985).

Criteria pollutants (pollutants for which maximum allowable 

emission levels and concentrations are enforced by State 

agencies) will be produced by internal combustion engine fuel 

consumption during suppression application activities. 

Effects will be localized and minimal compared with other 

vehicular activities in treatment areas. 
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Grasshopper Environmental Impact Statement 151

C. Vegetation

Carbaryl has a short residual life on plant surfaces. 

Insecticidal properties are retained for 3 to 10 days (EPA, 

OPTS, 1985). The major metabolite is 1-naphthol. Although 

carbaryl is a polar compound, bioconcentration in plants is 

not of concern due to limited plant uptake relating to the low 

water solubility and rapid degradation (Nash, 1974). 

The effects of carbaryl on vegetation can be either direct 

toxicity (phytotoxicity) or indirect. Carbaryl can adversely 

affect plant growth and produce phytotoxic effects at high 

application rates. However, exposure of vegetation to carbaryl 

at the proposed program application rates is lower and would 

not be expected to result in any phytotoxic effects. Indirect 

effects include the beneficial impact of reducing numbers of 

grasshoppers that consume vegetation as well as the negative 

impacts on plant reproduction associated with reduced 

numbers of plant pollinators. The effects of reduced plant 

pollinators is discussed in the section entitled Arthropods 

Pollinator Issues (see section B.4.d. of this appendix).

Carbaryl can adversely affect plant growth and produce 

phytotoxic effects at certain application rates. However, the 

application rate used in grasshopper suppression programs is 

less than would result in phytotoxicity to rangeland 

vegetation. 

D. Animal

Most mammals, including humans, readily break down 

carbaryl and excrete it in the urine and feces. An estimated 

70 to 80 percent is eliminated within 24 hours (Dorough, 

1970). Water-soluble metabolites taken up by mammals are 

also quickly eliminated, mainly in the urine (Casida and 

Lykken, 1969). Carbaryl is not subject to significant 

bioaccumulation due to its low water solubility and low 

octanol-water partition coefficient (Dobroski et al., 1985). 

Uptake of carbaryl in fish has been detected with 95 percent 

excreted within 8 hours (Tompkins, 1966). 

 2. Diflubenzuron

A. Soil

Diflubenzuron has been shown to bind readily with organic 

matter in soils and is relatively immobile in the environment. 

GLEAMS modeling indicates no percolation to groundwater, 

but some transport in runoff is possible. The persistence of 

diflubenzuron in soils depends a great deal on the presence of 
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152 Grasshopper Environmental Impact Statement

microorganisms. The half-life of diflubenzuron under field 

conditions ranges from 7 days to about 19 days (Nigg et al., 

1986).

Some soil dwelling organisms may be at risk from 

diflubenzuron applications. Reductions in mite populations 

have been observed following applications of 35 g a.i./ha 

(Perry et al., 1993). Although soil dwelling species may be at 

risk, at least one field study suggests decomposition rates are 

not affected by diflubenzuron (Rockwood, 1995). 

Toxicological testing concerning fungal, bacterial, and soil 

invertebrate population effects from exposure to 

diflubenzuron on soil fertility and productivity has not been 

published.

B. Water

Diflubenzuron seldom persists more than a few days in water, 

so the toxic effects from direct exposure anticipated at 

program locations all would be acute. However, 

diflubenzuron indirectly entering water on foliage in the fall 

(cold water temperatures) is more persistent and can result in 

chronic toxicity to aquatic invertebrates that frequent the leaf 

packs as grazers (Wimmer et al., 1993). GLEAMS modeling 

predicts that concentrations of diflubenzuron after a 1.5-inch 

rainstorm will all be less than 0.1 ppb in streams and ponds. 

Directly sprayed, 1-foot deep ponds are projected to have 

diflubenzuron concentrations of less than 6 ppb (USDA, 

APHIS, 1996b; see appendix C).

C. Air

The vapor pressure of diflubenzuron is relatively low 

(Wauchope et al., 1992), so exposure to substantial 

concentrations of diflubenzuron in air is unlikely. 

Criteria pollutants (pollutants for which maximum allowable 

emission levels and concentrations are enforced by State 

agencies) will be produced by internal combustion engine fuel 

consumption during suppression application activities. 

Effects will be localized and minimal compared with other 

vehicular activities in treatment areas. 

D. Vegetation

Diflubenzuron does not directly affect vegetation through any 

phytotoxic effects, even though it may remain on leaf surfaces 

for several months following application. Diflubenzuron 

applied to foliage tends to remain adsorbed to leaf surfaces 

for several weeks with little or no absorption or translocation 
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Grasshopper Environmental Impact Statement 153

from plant surfaces (Eisler, 1992). This persistence on leaves 

may result in exposure and toxic effects to nontarget species 

as late as the time of fall foliage drop (Harrahy et al., 1993; 

Wimmer et al., 1993). Loss from foliage occurs mainly by 

wind, rain, and shedding of leaves in the fall. Chronic toxicity 

is possible for animals that feed on leaves or have regular 

contact with treated leaf surfaces.

E. Animal

Metabolism of diflubenzuron in mammals is rapid (EPA, 

OPTS, 1987). Diflubenzuron is not well absorbed by skin 

with only 0.2 percent absorption within 48 hours from shaved 

skin of a treated rabbit (Keet et al., 1982). Little, if any, 

bioconcentration or bioaccumulation would be expected for 

any animals (Booth, 1978). The rapid metabolism and lack of 

bioconcentration indicate that only acute toxic effects would 

be expected for diflubenzuron exposures. Metabolism of 

diflubenzuron by mammals and birds occurs through 

hydroxylation, conjugation, and cleavage of the urea moiety 

(Opdycke et al., 1982). 

 3. Malathion

A. Soil

The persistence of malathion in soils depends primarily on 

microorganism activity, pH, and organic matter content. The 

half-life of malathion in natural soil varies from less than 1 

day (Walker and Stojanovic, 1973) to 6 days (Neary, 1985). 

The character of a soil is dependent not only upon its physical 

and chemical components, but also upon the presence of 

microorganisms. Breakdown of malathion in soil has been 

determined to be largely mediated by soil microorganisms. 

The principle degradation products are monocarboxylic and 

dicarboxylic acids (Walker and Stojanovic, 1973).

Malathion has been shown in laboratory studies to exhibit 

slight toxicity to some soil microorganisms. Toxicity to some 

nitrifying bacteria is variable. Malathion is slightly toxic to 

Nitrobacter sp. and can cause complete inhibition of 

Nitrosomas sp. (Bollen, 1961; Garretson and San Clemente, 

1968). Malathion applied to soils has not affected the growth 

of several fungi or their ability to degrade other pesticides 

(Anderson, 1981). Malathion application to a forested 

watershed resulted in no observed effects on bacteria or fungi 

(Giles, 1970).
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154 Grasshopper Environmental Impact Statement

Inorganic degradation of malathion may be more important in 

soils that are relatively dry, alkaline, and low in organic 

content, such as those that predominate in the western 

program areas. Malathion is subject to hydrolysis under 

neutral and alkaline conditions, but is more stable under 

acidic conditions. It does not penetrate much beyond the soil 

surface and does not adsorb tightly to inorganic soil particles, 

although it binds tightly with organic matter (Jenkins et al., 

1978). Adsorption to organic matter and rapid degradation 

make it unlikely that detectable quantities of malathion 

would leach to groundwater (LaFleur, 1979; HSDB, 1991). 

Because of agricultural and other uses, low-level background 

residues of malathion may occur in certain areas.

Modeling of environmental fate of malathion indicates that 

less than 1 ppb is projected to percolate to a depth of 1 foot in 

soil, but some runoff is possible with heavy rainstorms 

(USDA, APHIS, 1996b; see appendix C).

Malathion degradation products also have short half-lives. 

Malaoxon, the major malathion degradation product of 

concern in soil, has half-lives of 4 and 5 days in soils of pH 

7.2 and 8.2, respectively (Paschal and Neville, 1976). 

B. Water

Surface water contamination may occur from direct 

applications or runoff from treated plants and soils, 

particularly if a rainfall occurs soon after application. 

Degradation of malathion in water is mostly by photolysis 

(decomposition induced by light), microbial degradation 

under acidic conditions, and chemical transformations under 

alkaline conditions (Wolfe et al., 1977). The half-life of 

malathion in water with pH values from 5 to 8 ranges from 6 

to 18 days (Paris and Lewis, 1973). The half-life of malathion 

was calculated from program monitoring data for natural 

waters during the 1997 Medfly Cooperative Eradication 

Program in Florida to be 8 hours in a retention pond and 32 

hours in the Hillsborough River (USDA, APHIS, 1997). 

Half-life in seawater at pH 8 was 2.6 days (Horvath, 1982). 

Malathion in chlorinated swimming pool water degrades 

readily to the more toxic metabolite malaoxon. The half-life of 

malaoxon in chlorinated swimming pool water has been 

determined to be 37 hours (CDFA, 1991). Monitoring of four 

aerial bait spray applications in the 1991 study showed no 

cumulative concentrations of malathion or malaoxon in 

freshwater or chlorinated swimming pools. Because of 

agricultural and other uses, low-level background residues of 

malathion may be present in water in certain areas.
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Various sources have set different water quality criteria for 

malathion in freshwater and saltwater habitats. EPAs 

chronic water quality criterion for malathion is 0.1 μg/L 

(equivalent to 

0.1 part per billion) for both freshwater and saltwater. This 

criterion is near or below the limit of detection for malathion 

using standard analytical techniques. By comparison, the 

CDFG water quality criteria for malathion (based on acute 

exposure) are 3.54 μg/L for freshwater and 10 μg/L for 

saltwater (CDFG, 1982). The criteria for aquatic life are quite 

a bit lower than for human drinking water—CDHS has 

established a Health Advisory Level of 160 μg/L for malathion 

in human drinking water (CDHS, 1991).

Some directly sprayed water within the treatment area could 

have malathion concentrations exceeding the EPA chronic 

freshwater and saltwater criteria immediately following 

malathion aerial application; however, program applications 

are not made to water bodies. The concentrations of 

malathion in unprotected freshwater bodies immediately after 

treatment during the 1997 Cooperative Medfly Eradication 

Program in Florida ranged from below the detection limit (less 

than 0.1 ppb) to 460 ppb (USDA, APHIS, 1997). 

Environmental fate modeling predicted that in directly 

sprayed water bodies greater than 6 feet deep, malathion 

concentrations immediately after spraying were 11 μg/L or 

less. Shallow water bodies were estimated to have higher 

concentrations (e.g., greater than 64 μg/L in water less than 

1-foot deep). The modeling data are consistent with 

monitoring data from past programs. Malathion 

concentrations in aquatic habitats would decrease readily 

over time because of the chemical degradation, biological 

metabolism, and water flow into and out of the water body. 

Modeling predicts that malathion concentration decreases 

rapidly in flowing water and in water bodies with drainage 

outlets. For shallow water bodies in which CDFG water 

quality criteria may be exceeded for a short time, natural 

degradation processes make it unlikely that chronic 

exposures could result from program activities. 

Malathion is predicted to occur in ponds and streams at 

concentrations less than 10 ppb following a 1.5-inch 

rainstorm within 24 hours after an application of 8 oz a.i./

acre. Directly sprayed ponds of 1-foot in depth are projected 

to have concentrations as high as 224 ppb (USDA, APHIS, 

1996b; see appendix C).

C. Air
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156 Grasshopper Environmental Impact Statement

Because of malathion's low volatility, high concentrations are 

unlikely to be detected in air. However, because of 

agricultural and other uses, low-level background residues of 

malathion may be present in the air at certain locations. The 

atmospheric vapor phase half-life of malathion is 1.5 days 

(HSDB, 1990). 

Criteria pollutants (pollutants for which maximum allowable 

emission levels and concentrations are enforced by State 

agencies) will be produced by internal combustion engine fuel 

consumption during suppression application activities. 

Effects will be localized and minimal compared with other 

vehicular activities in treatment areas. 

D. Vegetation

The effects of malathion on vegetation can be either direct 

toxicity (phytotoxicity) or indirect. The half-life of malathion 

on foliage ranges from 1 to 6 days (Matsumara, 1985; Nigg et 

al., 1981; El-Refai and Hopkins, 1972). Indirect effects 

include the beneficial impact of reducing numbers of 

grasshoppers that consume vegetation as well as the negative 

impacts on plant reproduction associated with reduced 

numbers of plant pollinators. The effects of reduced plant 

pollinators is discussed in the section entitled Arthropod 

Pollinator Issues (see B.4.d of this appendix). 

Malathion can adversely impact plant growth and produce 

phytotoxic effects at certain application rates. However, 

program application rates are lower than would result in 

phytotoxicity to rangeland vegetation. 

E. Animal

Metabolism of malathion in mammals occurs primarily by 

hydrolytic cleavage to yield urinary metabolites such as 

malathion monoacid that are readily excreted (WHO, IARC, 

1983). The half-life of malathion in humans was determined 

to be 3 hours and 90.2 percent of the total dose is excreted in 

the urine (Feldmann and Maibach, 1974). This accounts for 

the lack of bioaccumulation in mammals. The primary 

metabolism in insects occurs by oxidation to form malaoxon, 

a more potent inhibitor of acetylcholinesterase and a more 

toxic compound (O'Brien, 1957). This accounts for the 

greater toxicity to insects and high efficacy of malathion. 

Bioconcentration factors for fish range from 7.36 in lake trout 

to 34.4 in willow shiners (HSDB, 1990; Tsuda et al., 1989). 

The concentration in fish tissues decreases readily and 
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Grasshopper Environmental Impact Statement 157

consistently with decreasing of malathion in water. No 

concerns about bioaccumulation are anticipated for 

grasshopper suppression programs. 

4. Nontarget 

Terrestrial 

Species

4. Carbaryl. 

 1. Potential Hazards

A. Mammals

Carbaryl is of moderate acute oral toxicity to mammals. The 

acute oral LD50 is 270 mg/kg for rats. The acute dermal 

toxicity is low with an LD50 in excess of 4,000 mg/kg for rats 

and in excess of 5,000 mg/kg for rabbits (EPA, ECAO, 1984). 

B. Birds

Carbaryl is slightly toxic to birds. The acute oral LD50 of 

carbaryl to avian species ranges from 707 mg/kg to 3,000 

mg/kg (Hudson et al., 1984). A number of studies have 

reported no effects on bird populations in areas treated with 

carbaryl (Richmond et al., 1979; McEwen et al., 1962; 

Buckner et al., 1973). Some applications of carbaryl were 

found to cause depressed AChE levels (Zinkl et al., 1977; 

Gramlich, 1979). This temporary inhibition of AChE may 

reduce the ability of the birds to avoid predation and conduct 

adequate foraging. 

AChE inhibition at 40 to 60 percent affects coordination, 

behavior, and foraging ability in vertebrates. This could lead 

to death from weather, predators, or other stresses of survival 

in the wild. Studies over several years for multiple 

grasshopper treatment areas have shown AChE inhibition at 

levels of no more than 40 percent with most at less than 20 

percent (McEwen et al., 1996). 

C. Reptiles and Amphibians

Data about effects of carbaryl to these organisms is limited to 

toxicologic information about the bullfrog. The acute oral 

LD50 of carbaryl to bullfrogs is greater than 4,000 mg/kg 

(Hudson et al., 1984). This indicates that carbaryl is probably 

slightly toxic to most of these species. 

D. Terrestrial Invertebrates

Carbaryl, in its action as an insecticide, is severely toxic to 

many insects. Honey bees are particularly sensitive to 

carbaryl (Atkins et al., 1981). Carbaryl applied to turfgrass at 

labeled rates decreased earthworms by 60 to 99 percent 

(Potter et al., 1990). Spiders are not severely affected in 
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158 Grasshopper Environmental Impact Statement

carbaryl-treated fields, and recovery occurs within 3 weeks 

after spraying (Shepard and Sterling, 1972; Barrett, 1968). 

Carbaryl is severely toxic to predatory mites, but less toxic to 

phytophagous mites (Bartlett, 1968).

 2. Quantitative Risk Assessment

The output from terrestrial vertebrate exposure modeling of 

doses from carbaryl full coverage treatments is summarized in 

table B–6. The highest potential doses to representative 

vertebrates are shown for the lark bunting, grasshopper mouse, 

horned lizard, and Woodhouse's toad. These insectivorous 

species consume considerable quantities of grasshoppers and 

other rangeland invertebrates, so they would be expected to 

receive higher doses than omnivores, herbivores, and vertebrate 

carnivores. The highest potential doses of carbaryl to wildlife 

species would be received by the target insects (grasshoppers 

and crickets) and other nontarget invertebrates present within 

the treatment areas.

Based upon the quantitative calculations of doses of carbaryl to 

vertebrate species, most animals have negligible risk of adverse 

toxicological effects from full coverage treatments. The only 

species that shows greater risk is the grasshopper mouse, which 

has a potential dose just in excess of 1/5 of the LD50. The risk to 

TABLE 1-6: Estimated Daily Doses of Carbaryl from Full Coverage Treatments to 

Vertebrate Nontarget Species and Corresponding Reference Levels

Representative

Estimated Dose 

(mg/kg)

Reference Dose

1/5 LD50 LD50 Reference Species

Birds

 Lark bunting 66.97 156 780 Sharp-tailed grouse

Sage grouse 11.90 156 780 Sharp-tailed grouse

Bobwhite quail 48.93 458 2290 Japanese quail

American kestrel 43.20 156 780 Sharp-tailed grouse

Mammals

Grasshopper mouse 60.37 55 275 Mouse 

Blacktail jackrabbit 11.67 142 710 Rabbit

Pronghorn antelope 5.97 40 200 Mule deer

Domestic cattle (Bovine

spp.)

2.51 40 200 Mule deer

Coyote 3.47 30 150 Cat

Reptiles and Amphibians

 Horned lizard 66.38 156 780 Sharp-tailed grouse

Eastern yellow-belly racer 12.80 800 4,000 Bullfrog

Woodhouse’s toad 62.95 156 780 Sharp-tailed grouse
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 159

this species would be characterized as moderate, but this dose is 

at the lower end of the moderate effects and would not be 

expected to permanently affect local populations within the 

treated areas. 

The toxic effects of carbaryl full coverage treatments will be most 

evident as decreases in susceptible invertebrate populations. 

The immediate effect of a treatment results in more limited 

predator avoidance by susceptible insects within the treatment 

area and easier foraging for insectivorous species there. This is 

followed by rapid decreases in population density of the 

susceptible species and the need for more widespread foraging by 

the insectivorous species. The decrease in populations of 

susceptible insects following carbaryl treatments is expected to 

be temporary with rapid recolonization of the treated areas from 

surrounding range and croplands. 

 3. Field Studies

The use of Sevin® 4-Oil, at the formulation rate of 1.25 lbs a.i./

acre, has demonstrated little possibility of toxicity-caused 

mortality of upland birds, mammals, or reptiles, and none has 

been observed as part of the grasshopper IPM monitoring effort 

(McEwen et al., 1996). These observations are consistent with 

the modeling results for carbaryl shown in table B-6, which 

indicate negligible impact on representative mammalian, bird, 

and reptile species due to carbaryl treatments.

 4. Community Effects

Most potential community effects in terrestrial habitats appear to 

relate to the reduction in insect populations. Reduction of the 

insect populations on sites treated with carbaryl in New Jersey 

was correlated to reduced bird populations (Moulding, 1972). 

Removal of insects has been suggested as cause for bird 

migrations (Doane and Schaefer, 1971).

Field studies in North Dakota were conducted to determine the 

effects of Sevin® 4-Oil treatment on killdeer populations. At 

treatment rates of 0.5 and 0.4 lb a.i./acre, no toxic signs and no 

mortality were observed in the killdeer population. Effects on 

foraging and diet of the killdeer were examined by both direct 

observation and analysis of stomach contents (Fair et al., 1995b). 

The insect capture rate by foraging killdeer increased during the 

2-day period after treatment when affected insects were easily 

obtainable (Fair et al., 1995a). There were no other differences or 

changes in food habits observed.

 5. Carbaryl Bait Treatments
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160 Grasshopper Environmental Impact Statement

Bait treatments were not analyzed as part of the modeling effort. 

The methodology used to model the exposures was not 

considered to be applicable in determining exposures to carbaryl 

baits.

The modeling results determined in this analysis are based on 

ULV applications of treatment chemicals and take into account 

various transport mechanisms that are not applicable to carbaryl 

bait treatments. 

There are several factors, however, that could favor the use of 

carbaryl bait treatments. Carbaryl incorporated into bran flakes 

or other solid media acts only upon ingestion by the organism 

and is considered to be a more selective and environmentally 

benign than other chemical control means (Peach et al., 1994). 

This suppression method may offer a viable alternative when 

grasshopper treatment is required in close proximity to 

endangered and threatened species, water bodies, or other 

sensitive sites. The inert ingredients known to be present in bait 

formulations (e.g., silica gel and n-amyl acetate) occur at low 

concentrations or pose less risk than the active ingredients in the 

formulated product (see section A.3.a.(8)) on inert ingredients 

and metabolites of carbaryl). 

As part of the grasshopper IPM monitoring studies, a test was 

conducted in North Dakota of the effect of carbaryl bait on the 

nestling growth and survival of vesper sparrow (Adams et al., 

1994). This study was designed to simulate the treatment of a 

small grasshopper infestation with carbaryl bait. There was no 

difference reported in any of the productivity parameters between 

nests on treated and untreated sites (Adams et al., 1994). Adult 

sparrows on treated sites had to forage farther from the nests to 

obtain food but did so successfully (McEwen et al., 1996). Any 

effects on nontarget species due to bait treatments can be 

considered indirect; that is, the prey populations are affected, 

while no direct toxicity to the nontarget species is likely to occur.

b.Diflubenzuron. 

 1. Potential Hazards

A. Mammals

Diflubenzuron is slightly to very slightly toxic to mammals 

(Maas et al., 1981). The acute oral median lethal dose of 

technical diflubenzuron to mice and rats is 4,640 mg/kg. 

The acute dermal median lethal dose to rats is 10,000 mg/kg 

and to rabbits is 4,000 mg/kg (Eisler, 2000). 

B. Birds
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Grasshopper Environmental Impact Statement 161

Diflubenzuron is slightly to very slightly toxic to birds. The 

acute oral median lethal dose of diflubenzuron to birds 

ranges from 3,762 mg/kg for red-winged blackbird to in 

excess of 5,000 mg/kg for bobwhite quail and mallard duck 

(Willcox and Coffey, 1978). The primary concern for bird 

species has related to the effects of decreases in insect 

populations from insecticide applications on insectivorous 

species rather than to the direct toxicity to birds from 

diflubenzuron exposure. 

C. Reptiles and Amphibians

No information was located about toxicity of diflubenzuron to 

reptiles or amphibians, but it is likely that diflubenzuron is of 

low toxicity to these species based upon the selective nature 

of the toxic mode of action. Based upon this, the relative 

toxicity of diflubenzuron to these species is anticipated to be 

similar to that of mammals and birds.

D. Terrestrial Invertebrates

Toxicity of diflubenzuron to terrestrial arthropods varies, but 

most species show adverse effects at high exposures. The 

most evident toxic effects occur when diflubenzuron is 

ingested immediately prior to molting. As a result, 

diflubenzuron is moderately to severely toxic to larval stages 

(molting stages) of terrestrial insects, but is practically 

nontoxic to most adult stages such as adult honey bees 

(Kuijpers, 1989). Immature grasshoppers, beetle larvae, 

lepidopteran larvae, and chewing herbivorous insects are the 

most susceptible. The acute toxicity from topical exposure of 

the first instar caterpillar of the large white butterfly (Pieris 

brassicae) is 2.5 μg/insect or 1.07 mg/kg (Sinha et al., 1990). 

Honey bees, parasitic wasps, predatory insects, and sucking 

insects show greater tolerance to diflubenzuron exposure. 

Diflubenzuron is moderately toxic to spiders and mites. 

However, diflubenzuron is only slightly to very slightly toxic to 

earthworms.

E. Plants and Microorganisms

Phytotoxicity has not been found to be of any concern to 

green plants when diflubenzuron is applied at the 

recommended rates of application. Most fungi contain chitin 

and, therefore, may be affected by diflubenzuron. Some fungi 

have shown growth inhibition at 50 ppm, but most species 
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162 Grasshopper Environmental Impact Statement

have not (Booth, 1978). The no-observed effect concentration 

for phytotoxicity in duckweed is 190 μg/L (Thompson and 

Swigert, 1993). 

 2. Quantitative Risk Assessment

The output from terrestrial vertebrate exposure modeling of 

doses from diflubenzuron full coverage treatments is 

summarized in table B–7. The highest potential doses to 

representative vertebrates are shown for the lark bunting, 

grasshopper mouse, horned lizard, and Woodhouse's toad. 

These insectivorous species consume considerable quantities of 

grasshoppers and other rangeland invertebrates, so they would 

be expected to receive higher doses than omnivores, herbivores, 

and noninsect carnivores. The highest potential doses of 

diflubenzuron to wildlife species would be received by the target 

insects (grasshoppers and crickets) and other nontarget 

invertebrates present within the treatment areas.

Based upon the quantitative calculations of doses of diflubenzuron to 

vertebrate species, all vertebrates have negligible risk of adverse 

toxicological effects from full coverage treatments. The toxic effects of 

diflubenzuron full coverage treatments will be most evident as 

decreases in susceptible invertebrate populations. The immediate 

effect of a treatment results in more limited predator avoidance by 

susceptible insects within the treatment area and easier foraging for 

insectivorous species there. This is followed by rapid decreases in 

population density of the susceptible species and the need for more 

widespread foraging by the insectivorous species. The decrease in 

populations of susceptible insects following diflubenzuron treatments 

is expected to be temporary with rapid recolonization of the treated 

areas from surrounding range and croplands. The specificity of the 

toxic mechanism of action of diflubenzuron results in adverse effects 

to fewer susceptible species (primarily immature grasshoppers, beetle 

larvae, lepidopteran larvae, and chewing herbivorous insects) than 

carbaryl or malathion (general oral and dermal toxicants to all 

insects). This results in fewer insect populations affected and less 

effect on foraging of insectivorous vertebrates for diflubenzuron 

treatments than for the other grasshopper suppression insecticides.
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Grasshopper Environmental Impact Statement 163

 3. Field Studies

Diflubenzuron is unique among the grasshopper suppression 

insecticides in that it is not a cholinesterase inhibitor; that is, it 

is not a neurotoxin but acts as a growth regulator. The mode of 

insecticidal action of diflubenzuron is described in detail in the 

Hazard Analysis—Rangeland Grasshopper Cooperative 

Management Program (USDA, APHIS, 1996c). Because of its 

mode of action, diflubenzuron is more target-specific and can be 

expected to pose a reduced threat to nontarget species relative to 

the other grasshopper suppression insecticides.

A. Invertebrates

Previously conducted research, as well as field studies carried 

out as part of the grasshopper IPM project, indicate that 

diflubenzuron spares most terrestrial nontarget arthropods 

(Catangui et al., 1996). Results of these studies indicate that 

the effects of diflubenzuron normally range from nonexistent 

to slight. Any reductions in nontarget populations have been 

shown to be of short duration, usually measured in days.

TABLE 1-7: Estimated Daily Doses of Diflubenzuron from Full Coverage Treatments to 

Vertebrate Nontarget Species and Corresponding Reference Levels

Representative Species Estimated Dose

Reference Dose

1/5 LD Reference Species 50 LD50

Birds

◆ Lark bunting 4.25 752 3762 Red-winged blackbird

◆ Sage grouse 0.60 >1000 >5000 Mallard duck

◆ Bobwhite quail 2.21 >1000 >5000 Bobwhite quail

◆ American kestrel 2.15 >1000 >5000 Mallard duck

Mammals

◆ Grasshopper mouse 3.44 928 4640 Mouse

◆ Blacktail jackrabbit 0.59 928 4640 Rabbit

◆ Pronghorn antelope 0.26 928 4640 Rabbit

◆ Domestic cattle (Bovine

spp.)

0.11 928 4640 Rabbit

◆ Coyote 0.23 928 4640 Rabbit

Reptiles and Amphibians

◆ Horned lizard 2.41 752 3762 Red-winged blackbird

◆ Eastern yellow-belly 

racer

1.15 752 3762 Red-winged blackbird

◆ Wooehouse’s toad 16.56 752 3762 Red-winged blackbird
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164 Grasshopper Environmental Impact Statement

Grasshopper IPM field studies have shown diflubenzuron to 

have a minimal impact on ants, spiders, predatory beetles, or 

scavenger beetles. There was no significant reduction in 

populations of these species from 7 to 76 days after 

treatment. Although ant populations exhibited declines of up 

to 50 percent, these reductions were temporary, and 

population recovery was described as immediate (Catangui et 

al., 1996). 

No significant reductions in flying nontarget arthropods, 

including honey bees, have been reported. Within 1 year of 

diflubenzuron applications in a rangeland environment, no 

significant reductions of bee predators, parasites, or 

pollinators were observed for any level of diflubenzuron 

treatment (Catangui et al., 1996).

B. Vertebrates

Modeling results described in this EIS indicate that there is 

little or no direct impact on mammalian species as a result of 

diflubenzuron applications. Results of field studies reinforce 

these results. Acute dosages of diflubenzuron were found to 

have no direct effects on terrestrial wildlife (McEwen et al., 

1996). Although indirect effects do occur as a result of 

reduced populations of prey for insectivorous species, these 

impacts have been shown to be temporary.

IPM monitoring studies have shown the effects of suppression 

insecticides on small mammals such as mice and squirrels to 

be slight. Since many of these species are nocturnal, they are 

not as readily exposed to spray treatments as other larger 

mammals or birds (McEwen et al., 1996). 

c. Malathion. 

 1. Potential Hazards

A. Mammals

The acute oral toxicity of malathion is very slight to moderate 

for mammals. The acute oral median lethal doses of 

malathion range from 250 mg/kg in rabbits to 12,500 mg/kg 

in rats. The acute toxicity of malathion by the dermal route is 

one of the lowest of the organophosphorus insecticides (EPA, 

OPP, 1989b).
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 165

B. Birds

Malathion is slightly to moderately toxic to birds. The acute 

oral median lethal doses range from 150 mg/kg to chickens 

(EPA, 1975) to 1,485 mg/kg to mallard ducks (Hudson et al., 

1984). The 5-day dietary median lethal concentrations for 

wild birds all exceed 2,500 ppm (Smith, 1987).

Several reproductive and developmental studies have been 

conducted with birds. The lowest median lethal dose to 

chicken embryos (eggs) was 3.99 mg per egg for 4-day 

embryos (Greenberg and LaHam, 1969). The median lethal 

concentration for field applications of malathion to mallard 

duck eggs was found to be 4.7 lbs a.i./acre (Hoffman and 

Eastin, 1981). No effect on reproductive capacity of chickens 

was found at dietary concentrations as high as 500 ppm in 

feed (Lillie, 1973). 

C. Reptiles and Amphibians

The toxicity of malathion is relatively low to adult reptiles and 

amphibians, but is highly toxic to the immature aquatic 

stages. Studies of adult salamanders and lizards exposed to 

field applications (up to 6 oz a.i./acre) of malathion found no 

observable adverse effects and no AChE inhibition (Baker, 

1985; McLean et al., 1975). The 96-hour median lethal 

concentration of malathion is 420 μg/L for tadpoles of 

Fowler's toad and 200 μg/L for tadpoles of the western 

chorus frog (Mayer and Ellersieck, 1986). 

D. Terrestrial Invertebrates

Malathion is moderately to severely toxic to terrestrial 

invertebrates. The median lethal concentration of malathion 

to earthworms ranges from 0.27 to 13.5 μg/cm2 (Roberts and 

Dorough, 1985). The median lethal dose to honey bees is 

0.709 μg per bee (Atkins et al., 1973). Median lethal 

concentrations of malathion to insects range from 23 mg/kg 

for carpenter ants (Gibson and Scott, 1989) to 124.1 mg/kg 

for lacewings (Pree et al., 1989). A lowest effect level based 

upon increased excretion and decreased tissue protein 

content was determined for snails to be 5 ppm malathion 

(Sivaiah and Ramano Rao, 1978).

E. Plants and Microorganisms

Malathion has low phytotoxicity to most plants. 

Concentrations above field application rates are required for 

adverse effects to conifers, clover, and pea plants (Ilnytzky 

and Marshall, 1974; Archer, 1971; Chakraborti et al., 1983). 
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166 Grasshopper Environmental Impact Statement

 2. Quantitative Risk Assessment

The output from terrestrial vertebrate exposure modeling of 

doses from malathion full coverage treatments is summarized in 

table B–8. The highest potential doses to representative 

vertebrates are shown for the lark bunting, grasshopper mouse, 

horned lizard, and Woodhouse's toad. These insectivorous 

species consume considerable quantities of grasshoppers and 

other rangeland invertebrates, so they would be expected to 

receive higher doses than omnivores, herbivores, and noninsect 

carnivores The highest potential doses of malathion to wildlife 

species would be received by the target insects (grasshoppers 

and crickets) and other nontarget invertebrates present within 

the treatment areas.

Based upon the quantitative calculations of doses of malathion 

to vertebrate species, many animals are at negligible risk of 

adverse toxicological effects from full coverage treatments. The 

species that are at greater risk include the bobwhite quail, 

American kestrel, and Woodhouse's toad. The risk to these 

species would be characterized as moderate. Although their 

doses are at the lower end of the moderate effects, some 

individuals of these species could suffer mortality. The mortality 

TABLE 1-8: Estimated Daily Doses of Malathion from Full Coverage Treatments to 

Vertebrate Nontarget Species and Corresponding Reference Levels

Representative Species Estimated Dose

Reference Dose

1/5 LD Reference Species 50 LD50

Birds

Lark bunting 79.20 81 403 Horned lark

Sage grouse 13.91 30 150 Chicken

Bobwhite quail 56.67 30 150 Chicken

American kestrel 50.46 30 150 Chicken

Mammals

Grasshopper mouse 71.80 115 775 Mouse

Blacktail jackrabbit 13.65 50 250 Rabbit

Pronghorn antelope 6.96 11 53 Cattle

Domestic cattle (Bovine

spp.)

 2.90 11 53 Cattle

Coyote 3.50 72 360 Dog

Reptiles and Amphibians

Horned lizard 77.14 465 2324 Carolina anole

Eastern yellow-belly racer 15.16 30 150 Chicken

Woodhouse’s toad 74.02 30 150 Chicken
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would be considerably less than 50 percent and recovery of the 

populations of these species within the treatment area from 

these adverse effects would be expected to be rapid. 

The toxic effects of malathion full coverage treatments will be 

most evident as decreases in susceptible invertebrate 

populations. The terrestrial invertebrates are likely to have 

depressed populations for a given period of time following 

spraying. The treatment area and number of treatments will 

influence the ability of the population to become reestablished, 

but in most every case application is made only once. The ability 

to reestablish the population is also influenced by the distance 

from the treatment area to similar, untreated habitats containing 

potential colonists, and the ability of these potential colonists to 

disperse. The immediate effect of a treatment results in more 

limited predator avoidance by susceptible insects within the 

treatment area and easier foraging for insectivorous species 

there. This is followed by rapid decreases in population density 

of the susceptible species and the need for more widespread 

foraging by the insectivorous species. The decrease in 

populations of susceptible insects following malathion 

treatments is expected to be temporary with rapid recolonization 

of the treated areas from surrounding range and croplands. 

 3. Field Studies

The grasshopper IPM Program investigated the effects of 

malathion. A 3-year study was conducted to determine the 

indirect effects of malathion on nesting birds in Idaho (Howe, 

1993). Although the total invertebrate availability was 

significantly reduced by standard malathion spray applications 

(0.5 lb a.i./acre), nesting birds were shown to switch their diets 

to the remaining insects and reproduce as successfully as birds 

on untreated control plots. Adults had to forage longer on 

treated plots, and nestlings demonstrated an increased 

propensity for parasitic blowfly infestations. Either of these 

indirect effects might impact survival in some situations. 

However, this particular field study did not show these particular 

effects to be significant. Prespray grasshopper densities were 

relatively low (1 to 4 per square yard) on all plots and were 

significantly reduced in the post spray period. This probably 

made the food availability test even more rigorous than would be 

posed by an actual operational grasshopper suppression project, 

where prespray densities are much higher and even post spray 

grasshopper densities usually exceed 1 or 2 per square yard 

(McEwen et al., 1996).

The results of field studies involving malathion are consistent 

with the modeling results shown in table B–8. 
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168 Grasshopper Environmental Impact Statement

A. Arthropod Pollinator Issues

The majority of rangeland plants require insect-mediated 

pollination. Native, solitary bee species are the most 

important pollinators on western rangeland (Tepedino, 1979). 

Potential negative effects of insecticides on pollinators are of 

concern because a decrease in their numbers has been 

associated with a decline in fruit and seed production of 

plants. This decline may have repercussions throughout the 

rangeland food chain. Rangeland species populations that 

depend on plants for food may be indirectly affected due to 

changes in vegetation patterns (Alston and Tepedino, 1996).

Malathion and carbaryl are broad spectrum insecticides and 

are both considered to be highly toxic in their effects on bees 

(Johansen and Mayer, 1990, Johansen et al., 1983). Contact 

sprays can be very toxic to small, native bees because of 

direct contact with the insecticide or insecticide residue. 

More selective insecticides are desirable in order to reduce the 

negative effects on bee populations (Alston and Tepedino, 

1996). Although negative effects of diflubenzuron on honey 

bees have been demonstrated at high application levels and 

relatively long periods of exposure, these application rates far 

exceed the prescribed rate for grasshopper suppression. 

Diflubenzuron application rates as high as 0.125 to 0.25 lb 

a.i./acre resulted in no effects on adult mortality and brood 

production (Robinson and Johansen, 1978). Therefore, 

applications of diflubenzuron are preferable over carbaryl or 

malathion at locations where pollinating bees are active.

Any negative effects of grasshopper program insecticides on 

bee populations may also be mitigated by the use of carbaryl 

bran baits. Studies with carbaryl bran bait have found no 

sublethal effects on adults or larvae (Peach et al., 1994). 

There appears to be little cause for concern that any carbaryl 

eaten by foraging adult females from the nectar of open 

flowers will affect any aspect of reproduction (Alston and 

Tepedino, 1996).

5. Nontarget 

Aquatic Species

Aquatic organisms are protected from exposure to program chemicals 

by the protective operational measures and adherence to insecticide 

labels. These measures are intended to prevent program insecticides 

from entering water bodies under conventional applications. The 

site-specific protective measures may include (1) prohibiting direct 

application to water bodies, (2) no-spray buffer zones around water 

bodies, (3) restrictions to application when rain is forecast, and (4) 

measures to reduce pesticide drift during aerial applications.
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However, despite the protective measures, there is still a potential for 

aquatic organisms to be exposed to program insecticides. Water 

bodies cannot be completely protected from insecticide applications 

because human error in insecticide application, unaccounted drift, 

and runoff from treated areas would all result in insecticides entering 

water. This section describes the effects to aquatic organisms that 

may be exposed to program insecticides.

a. Carbaryl. 

 1. Fish

Carbaryl is moderately toxic to most fish. The 96-hour median 

lethal concentration of carbaryl ranges from 0.35 mg/L in a 

static test of yellow perch to 39 mg/L in a flow-through test of 

bluegill (Mayer and Ellersieck, 1986). Species of catfish and 

minnow are generally 10 times more tolerant than salmonids. 

Acetylcholinesterase depression in brook trout has been 

observed following 1 lb/acre treatments, but AChE levels 

returned to normal within 48 hours (Hurlbert, 1978). 

 2. Aquatic Invertebrates

Carbaryl is very highly toxic to all aquatic insects and highly to 

very highly toxic to most aquatic crustaceans. The toxicity from 

96-hour static tests ranged from 1.7 μg/L in the stonefly, 

Pteronarcella badia, to 1.9 mg/L in the shrimp, Procambarus sp. 

(Mayer and Ellersick, 1986). Treated streams may have a 50 to 

100 percent reduction in aquatic insect populations (Burdick et 

al., 1960), and recolonization may require up to 30 months after 

spraying (Gibbs et al., 1984). Treatments with carbaryl may 

enhance aquatic algae growth (Murray and Guthrie, 1980).

 3. Qualitative Assessment and Field Studies

Laboratory studies indicate that in aquatic ecosystems carbaryl 

would mostly affect the invertebrates and have little to no effect 

on the vertebrates. Based on the values included in the 

chemical background paper on environmental fate and transport 

modeling (USDA, APHIS, 1996b; see appendix C), carbaryl 

concentrations in water would be expected to range from 5 ppb 

in a stream receiving runoff from a treated area to 184 ppb in a 

shallow body of water directly sprayed with carbaryl. At those 

concentrations, the organisms that are at high risk and that are 

most likely to be found in the affected environment are 

cladocerans (Daphnia spp.). The amphipods (Gammarus spp.) 

and stonefly larvae (Pteronarcys sp., Pteronarcella sp., Isogenus

sp.) are at moderate (streams) to high risk (ponds/wetlands). 
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Chironomid midges and fish such as trout, salmon, minnows, 

catfish, and bluegills are at negligible to low risk of adverse 

effects from carbaryl applications at the expected exposure rates.

In an ecological risk assessment, Sheehan et al. (1992) predicted 

the effects of carbaryl on nontarget organisms in aquatic 

ecosystems. According to their analysis, carbaryl would cause a 

30 to 80 percent reduction in the invertebrate populations in 

prairie ponds. The populations would be expected to recover to 

normal levels in about 5 months. Carbaryl would potentially 

eliminate the most sensitive invertebrates, such as amphipods, 

for an extended period; chironomids (midges) would become 

dominant in the ponds, and there would be seasonal reductions 

in the invertebrates available as food for waterfowl.

Carbaryl’s effects on nontarget aquatic organisms have been 

reported from field studies on prairie ponds (Beyers and 

McEwen, 1996) and the Little Missouri River (Beyers et al., 1995) 

that were done in association with grasshopper control 

programs. These pond-monitoring studies showed that 

amphipod abundance declined in all ponds exposed to carbaryl. 

However, other taxa in the ponds were not affected (Beyers and 

McEwen, 1996).

In the Little Missouri River study (Beyers et al., 1995), the 

maximum mean carbaryl concentrations were 85.1 ppb in a 

drought year and 12.6 ppb in a nondrought year. When the 

carbaryl concentrations were highest, invertebrate drift 

(invertebrates dislodged from the river bottom) was more variable 

in the Little Missouri River than at a reference site. This 

response was not considered to be biologically significant 

because natural events can cause greater effects than those 

attributed to the insecticide, and because only a small part of the 

Little Missouri River was affected. No effects were noticed in the 

fish in the Little Missouri River.

Carbaryl has the potential to affect the invertebrate assemblages 

in aquatic ecosystems. Although invertebrates may be reduced 

or possibly eliminated locally, these changes would not be 

permanent. Over the course of several months, it is likely that 

most, if not all, invertebrates would recover to levels that existed 

prior to the exposure to carbaryl. However, the loss of aquatic 

insects as food items for fish through carbaryl treatments has 

been associated with decreases in fish (DOI, FWS, 1986). 
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b. Diflubenzuron. 

 1. Fish

Toxicity of diflubenzuron to aquatic organisms varies by taxa. 

Diflubenzuron is slightly to practically nontoxic to fish. The 

median lethal concentration of diflubenzuron in water ranges 

from 10 mg/L for smallmouth bass to 660 mg/L in bluegill 

sunfish (Willcox and Coffey, 1978; Julin and Sanders, 1978). 

 2. Aquatic Invertebrates

Diflubenzuron is slightly to practically nontoxic to fish, aquatic 

snails, and most bivalve species. It is very highly toxic to most 

aquatic insects, crustaceans, horseshoe crabs, and barnacles. 

The median lethal concentration of diflubenzuron in water to 

immature stages of aquatic insects ranges from 0.5 μg/L in the 

mosquito Aedes nigromaculatum (Miura and Takahashi, 1974) to 

57 mg/L in the perlodid stonefly Skwala sp. (Mayer and 

Ellersieck, 1986). The median lethal concentration of 

diflubenzuron in water to crustaceans ranges from 0.75 μg/L in 

Daphnia magna (Majori et al., 1984) to 2.95 μg/L in the grass 

shrimp Palaemonetes pugio (Wilson and Costlow, 1986). The 

median lethal concentration of diflubenzuron in water to the 

snail Physa sp. is greater than 125 mg/L (Willcox and Coffey, 

1978).

 3. Qualitative Assessment and Field Studies

Although diflubenzuron has been shown to produce relatively 

benign effects to most terrestrial arthropods, the same is not the 

case for aquatic organisms, particularly freshwater crustaceans 

and aquatic insects. Tadpole shrimp, clam shrimp, water fleas, 

copepods, cladocerans, mayfly naiads, and midge larvae all 

showed temporary population reductions following diflubenzuron 

treatments (0.1 lb a.i./acre) (Miura and Takahashi, 1974, 1975). 

Adult aquatic beetles, spiders, and mosquito fish were not 

affected by diflubenzuron even at the highest rates tested. These 

results are consistent with the mode of action of diflubenzuron in 

that it effects primarily insects in immature life stages.

Effects on invertebrates in aquatic ecosystems depend upon the 

exposure and type of water body. In freshwater lakes, ponds, and 

marshes, the types of invertebrates most susceptible to 

diflubenzuron are amphipods (scuds), cladocerans, some midges, 

caddisflies, and mayflies (Ali and Mulla, 1978a, b; Apperson et 

al., 1978; Eisler, 1992; Fischer and Hall, 1992; Hansen and 

Garton, 1992; Sundaram et al., 1991). In flowing water 

ecosystems, diflubenzuron application rates of 0.4 to 0.8 oz a.i./

acre reduced numbers of dipterans as well as cladocerans, 
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172 Grasshopper Environmental Impact Statement

copepods, mayfly nymphs, corixids, and springtails (Eisler, 

1992). In particular, cladocerans (Daphnia sp.) and caddisflies 

(Clistoronia sp.) are at high risk of adverse effects from full 

coverage applications of diflubenzuron. Mayflies (Callibaetis sp.), 

amphipods (Gammarus sp.), and some midges (Tanytarsus sp.) 

are at moderate risk. Dragonfly larvae, stonefly larvae, aquatic 

beetles, crayfish, bivalves, chironomid midges, and snails are at 

low risk.

Vertebrates in freshwater ecosystems are not directly susceptible 

to diflubenzuron (Eisler, 1992). Fish such as trout, salmon, 

catfish, bluegill, and perch are at low risk from full coverage 

applications. However, when preferred food items of fish are 

reduced by diflubenzuron, the fish may respond by switching to 

other prey until the preferred items have returned to 

pretreatment abundances (Apperson et al., 1978; Colwell and 

Schaefer, 1980).

In marine and brackish ecosystems, the grass shrimp, mysid 

shrimp, and crabs are at high risk from exposures to 

diflubenzuron at full coverage application rates. Other species 

such as snails and bivalves are at low risk. In one study, blue 

crabs were reduced nearly 50 percent after diflubenzuron was 

applied in a tidal pool (Hester et al., 1986). However, it is 

unlikely that the grasshopper program would occur in marine or 

brackish water areas that support aquatic organisms such as 

crabs.

Diflubenzuron used for the grasshopper suppression program is 

unlikely to cause long-term damages to aquatic ecosystems. 

Some aquatic invertebrate assemblages could temporarily 

decrease if exposed to diflubenzuron. However, this decrease 

would not be permanent because of the rapid generation time of 

aquatic invertebrates.

Residues of insecticides entering flowing water (i.e., creeks) 

dissipate more readily than in ponds due to constant movement 

of water from upstream that lowers the potential exposure 

concentration. There are some aquatic insects that are at 

potential risk in ponds. The dissipation of insecticide residues in 

creeks diminishes the likelihood of exposure relative to ponds. 

Risks to wildlife species in creeks are generally negligible from 

program use of diflubenzuron.

c. Malathion . 

 1. Fish
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The acute toxicity of malathion varies widely from slightly toxic to 

some species of fish to very highly toxic to other species. The 

median lethal concentration of malathion in water ranges from 

10 μg/L for the common shiner (Domanik and Zar, 1978) to 

38,000 μg/L for the Indian catfish (Singh and Singh, 1980). An 

analysis of the relative toxicity of malathion to taxonomic families 

(Macek and McAllister, 1970) determined that the least 

susceptible families include the catfish and minnows, and the 

most susceptible families include trout, salmon, perch, and 

sunfish. 

 2. Aquatic Invertebrates

Malathion is moderately to very highly toxic to most aquatic 

invertebrates. The median lethal concentration of malathion 

ranges from 0.5 μg/L in the scud (Mayer and Ellersieck, 1986) to 

3,000 μg/L in the aquatic sowbug (Johnson and Finley, 1980). 

The median lethal concentration of malathion to insects ranges 

from 0.69 μg/L in the stonefly nymph to 385 μg/L in snipe fly 

larvae (Mayer and Ellersieck, 1986). The median lethal 

concentration of malathion to a bivalve is 12 μg/L (Mane et al., 

1984). A No Effect Concentration was determined for mud snail 

to be 22,000 μg/L (Eisler, 1970). Decreases in primary 

production and increases in respiration were found in aquatic 

phytoplankton at as low as 16 μg/L, but no effects on long-term 

survival were observed at concentrations as high as 200 mg/L 

(Rajendran and Venugopalan, 1983; Saha and Singh, 1981).

 3. Qualitative Assessment and Field Studies

Malathion residues in water would vary according to the size of 

the water body and the amount of malathion applied. The 

amount of water-borne malathion residue that aquatic 

organisms would potentially be exposed to could range from 4.5 

ppb in runoff water to 224 ppb in a directly sprayed small water 

body (USDA, APHIS, 1996b; see appendix C).

Malathion toxicity to aquatic organisms has been reported by 

Mayer and Ellersieck (1986). According to these laboratory 

studies, the aquatic organism most sensitive to malathion is the 

amphipod, Gammarus, which has a 96-hour LC50 of <1 ppb. 

Therefore, amphipod populations would be reduced if water was 

exposed to full coverage treatments. Other species at high risk 

from malathion full coverage applications in standing water 

include cladocera (Daphnia sp.), caddisflies (Limnephilus and 

Hydropsyche sp.), and damselfly larvae (Lestes sp.). Other insect 

larvae in flowing water such as stonefly larvae (Pteronarcys, 

Pteronarcella, and Isoperla sp.) are at moderate risk. In addition, 

snipe fly larvae (Atherix sp.) and shrimp (Palaemonetes sp.) are at 

moderate risk. Water sowbugs (Asellus sp.) are at low risk. 
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174 Grasshopper Environmental Impact Statement

Fish are anticipated to show low to moderate risk from malathion 

in full coverage applications. Fish such as bluegill in shallow, 

standing water are at moderate risk, but catfish and largemouth 

bass are at low risk. Malathion in flowing waters would be 

rapidly diluted to concentrations that would not affect fish such 

as trout present in those waters. The greatest malathion 

concentrations and risk is to those species that inhabit ponds 

less than 1-foot deep that are directly sprayed.

A study of the effects of malathion applications in a worst-case 

scenario was conducted at Stewart’s Creek in Alabama ((Kuhajda 

et al., 1996). This study included surveillance of fish and aquatic 

invertebrate populations. The applications were made to cotton 

fields up to the edge of the creek bed. The conclusion based 

upon their data was that no adverse acute or long-term effects of 

malathion were evident in either the fish or aquatic invertebrate 

communities based upon numbers of individuals, numbers of 

taxa, and diversity indices over the 3-year study period. Based 

upon this study, it is anticipated that any applications of 

malathion in grasshopper programs, designed to avoid water, 

would not be expected to have any adverse acute or long-term 

effects on fish and aquatic invertebrates.

Malathion applied for grasshopper suppression could affect 

invertebrates, especially amphipods in aquatic ecosystems. 

These effects would soon be compensated for by the survivors, 

given the rapid generation time of most aquatic invertebrates and 

the rapid degradation of malathion in water. Therefore, 

malathion used for the grasshopper suppression program would 

not be likely to cause long-term, lasting effects to aquatic 

ecosystems. Organisms that feed on amphipods would likely 

switch temporarily to an alternate food source. If no alternate 

food source is available, the rapid generation time of amphipod 

assemblages means that the amphipod population would likely 

recover to pretreatment levels before the predator populations 

would be permanently affected. 

Consequences of the Reduced Agent Area Treatments 

Alternative (RAATs)

This section describes the potential consequences of the reduced 

agent area treatments alternative to affect human health, 

environmental quality, and nontarget species. The consequences are 

based upon the representative field rates of application of each 

insecticide anticipated for this alternative as described in table B–4. 

The risks are assessed quantitatively and likelihoods of occurrence 

characterized. Relative risks of insecticide applications are 

characterized by comparison to comparable outcomes from the full 

coverage alternative to provide adequate information for informed 

decisions about potential risk. Basic hazard information already 
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Grasshopper Environmental Impact Statement 175

presented in the human health section (A.3.) and in the hazard and 

field studies descriptions (B.5.) is not repeated in this section except 

when this information pertains specifically to potential insecticide 

impacts under the RAATs. 

1. Efficacy of 

Chemical 

Controls

Recent studies by Foster et al. (2000) have shown that the three 

insecticides APHIS could apply at conventional rates reduced 

grasshopper populations at 14 days after treatment by the following 

percentages: carbaryl spray, a 96 to 97 percent reduction; carbaryl 

bait, 35 to 85 percent reduction; diflubenzuron, a 98 percent 

reduction; and malathion, an 89 to 94 percent reduction.

The goal of grasshopper suppression under the RAATs alternative is to 

economically and environmentally suppress grasshopper populations 

to a desired level rather than to reduce those populations to the 

greatest possible extent. The efficacy of the RAATs alternative in 

reducing grasshoppers is therefore less than conventional treatments. 

The RAATs efficacy is also variable. Foster et al. (2000) reported that 

grasshopper treatment mortality using RAATs was reduced 2 to 15 

percent from conventional treatments while Lockwood et al. (2000) 

reported 0 to 26 percent difference in mortality between the 

conventional and RAATs alternatives.

2. Human Health The human health risks for each insecticide under RAATs alternative 

are similar to those under the full coverage suppression treatments, 

but the risk is diminished commensurate with the anticipated 

decreases in exposure. This section presents the risks relative to the 

reference doses for each insecticide and relative to comparable 

application scenarios under the full coverage suppression treatments 

for comparison of human health effects between the alternatives.

a. Carbaryl. 

The lower application rates analyzed for the RAATs alternative result 

in lower potential for exposure than the full coverage suppression 

treatments. Therefore, just as with the general public under the full 

coverage suppression treatments, no exposures under the RAATs 

alternative exceed the systemic RfD of 0.01 mg/kg/day. Likewise, the 

estimated exposures that might occur to the public as a result of 

involvement in an event similar to the scenarios that were analyzed 

are not cause for concern.

For workers, on the other hand, all of the estimated exposure levels 

associated with the conventional application of carbaryl ULV exceed 

the RfD, with estimated doses resulting in HQs of 1 to 2000. This 

variability probably reflects differences in individual work habits 
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176 Grasshopper Environmental Impact Statement

(SERA, 1993). In other words, workers who handle insecticides with 

proper care can reduce their exposure substantially. Conversely, poor 

work habits can increase exposure substantially. 

At the lower and mid-ranges of exposure, it is unlikely that there 

would be overt signs of toxicity, even when the RfD is exceeded 

considerably (i.e., by factors of about 20 to 2,000). There are 

experimental studies in humans suggesting that doses of up to about 

3 mg/kg (Gold et al., 1982) will not be associated with signs of toxicity 

in humans. 

At the high range of occupational exposure (i.e., about 18 mg/kg), the 

nature of potential adverse effects is less clear. Carbaryl has been 

used for many years, and reports of occupational poisoning, either 

published or anecdotal, were not encountered. On the other hand, no 

rigorous worker monitoring or epidemiology studies were found on the 

aerial application of carbaryl. Consequently, a precise characterization 

of risk is not possible. However, with good personal work practices, 

carbaryl may be handled safely. Poor work practices may present 

risks, but the likelihood of observing adverse effects cannot be well 

characterized. If such effects are observed, they would be those that 

are characteristic of AChE inhibitors.

Under all exposure scenarios, members of the general public do not 

appear to be at any risk to the potential reproductive effects of 

carbaryl, even using relatively conservative assumptions. Unlike the 

exposures under the full coverage treatments, exposure from the 

consumption of contaminated vegetation immediately after aerial 

applications under the RAATs alternative does not exceed the 

provisional RfD for reproductive effects of carbaryl. The exposure 

levels would diminish rapidly as the carbaryl degrades and disperses 

after application, so there are no concerns about exposures to the 

general public from applications under RAATs. 

For workers, under the least conservative exposure assumptions, 

levels of plausible exposure are far greater than the provisional RfD for 

reproductive effects. For the application of carbaryl ULV, the central 

estimate of the absorbed dose, 1.8 mg/kg/day, is in the range of doses 

associated with fetotoxicity in dogs and the upper range of the 

estimated absorbed dose, 18 mg/kg/day, is above the level associated 

with teratogenic effects in dogs.

This does not necessarily mean that teratogenic effects or reproductive 

impairment in humans can be predicted from or attributed to carbaryl 

exposure. Nonetheless, standard criteria and procedures are used for 

estimating the provisional RfD. Plausible levels of exposure are far 

above this provisional RfD.
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Grasshopper Environmental Impact Statement 177

The lower application rate under the RAATs strategy results in 

commensurately lower overall exposures. The rapid degradation of 

carbaryl and infrequent program applications makes it unlikely that 

high enough doses to induce cumulative toxic responses could occur 

to workers and the general public. Proper protective measures and 

routine monitoring can prevent excessive exposures and adverse 

effects to workers. Although effects from connected actions and 

effects to groups at special risk remain possible, the lower potential 

exposures resulting from actions taken under this alternative make 

these effects less likely than under the full coverage suppression 

alternative.

b. Diflubenzuron. The same reference doses derived for 

methemoglobinemia protection under the full coverage control 

treatments derived for both workers and the general public are used 

for comparison to the estimates of dose from the exposure assessment 

at the RAATs rate to calculate hazard quotients for each exposure 

scenario. 

HQs determined for aerial spray workers, for both routine and extreme 

exposures, were all less than 1, indicating that these workers are not 

at risk of adverse effects from grasshopper program operations that 

use diflubenzuron. Scenarios representing workers involved in 

accidental exposures also resulted in HQs less than 1 if they washed 

within an hour. Therefore, accidents would not cause concern about 

the health effects on these workers. Circumstances that prevent a 

worker from washing until 24 hours after spilling diflubenzuron on the 

lower legs would be cause for concern. In this case the HQ could be as 

high as 20. 

A number of scenarios were analyzed to help characterize risk to the 

general public. The calculated HQs were less than 1 for most of these 

public exposures; therefore, adverse health effects clearly are not 

anticipated. The HQs for a few of the extreme scenarios ranged from 1 

to 5. Even in these cases, no clinically significant effects are likely. At 

the highest exposure, increases in certain blood pigments may be 

detected, but they will not be long-lasting.

The lower application rate under the RAATs alternative results in 

commensurately lower overall exposures. Although cumulative 

effects, effects from connected actions, and effects to groups at special 

risk remain possible, the lower potential exposures resulting from 

actions taken under this alternative make these effects less likely than 

under the full coverage control alternative. 

c. Malathion. For the general public, none of the exposure scenarios 

under the RAATs alternative involve levels that exceed the RfD and 

most are far below the RfD. The assessment of inhalation exposure is 
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178 Grasshopper Environmental Impact Statement

based on a TLV that was normalized for an exposure that would occur 

over an 8-hour workday, 5 days per week. When normalized for this 

continuous exposure, this reference level is equivalent to a factor of 

about 6,000 above plausible levels of estimated exposure. Therefore, 

although the adjusted TLV does not incorporate additional uncertainty 

factors for sensitive subgroups or data quality, even very conservative 

adjustments would not result in HQs of concern.

For workers, estimates of daily absorbed doses that are associated 

with the maximum application rate of malathion span the RfD: 0.006 

mg/kg to 0.6 mg/kg. The variability in the exposure estimates reflects 

the variability in the data on which the assessment is based. Under 

routine conditions, aerial spray workers may be exposed to doses that 

result in HQs of from 0.3 to 30. All accidental scenarios, based on the 

estimated amount of malathion handled per day, result in HQs more 

than 1 (from 2 to 8).

The implications of these HQs greater than 1 are difficult to assess. 

Although AChE inhibition is possible at the estimated levels of 

exposure, it is far less certain that these exposure levels would be 

associated with any signs of toxicity. This is consistent with human 

experience. Aerial applications of malathion have been conducted in 

previous years to control grasshoppers and other pests, and signs of 

severe nervous system impairment have not been reported in the open 

literature or in unpublished or anecdotal reports. Although the upper 

range of plausible exposure, 0.6 mg/kg/day, is above the level that 

has been demonstrated to cause AChE inhibition in humans, it is well 

below the range at which adverse effects have been demonstrated.

The lower application rates under the RAATs alternative result in 

commensurately lower overall exposures. The rapid degradation of 

malathion and infrequent program applications makes it unlikely that 

high enough doses to induce cumulative toxic responses could occur 

to the general public. Proper protective measures and routine 

monitoring can prevent excessive exposures and adverse effects to 

workers. Although effects from connected actions and effects to 

groups at special risk remain possible, the lower potential exposures 

resulting from actions taken under this strategy make these effects 

less likely than under the full coverage control strategy. 

3. Physical 

Environment

The impacts to the physical environment from the RAATs alternative 

are expected to be similar, but of less intensity than those from the full 

coverage treatments. Projections of the intensity are all based upon 

output using the Forest Service Cramer Barry Grim (FSCBG) 

(Curbishley and Skyler, 1989) and GLEAMS modeling as described in 

the environmental fate background paper (USDA, APHIS, 1996b; see 

appendix C). 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 179

The primary environmental fate considerations for carbaryl relate to 

water issues. Carbaryl is unlikely to percolate to groundwater, but 

may occur in runoff waters following rainstorms. The concentrations 

following a 1.5-inch rainstorm are predicted to be 3 ppb in streams 

and 8 ppb in 6-foot-deep ponds. Directly sprayed 1-foot-deep ponds 

are projected to have carbaryl concentrations from 84 to 112 ppb. The 

program protective measures are designed to avoid direct treatment of 

water bodies, so these concentrations are not expected when 

monitoring most control programs. Carbaryl has low vapor pressure, 

and volatilization to the atmosphere is minimal. The rapid rate of 

degradation, metabolism, and excretion of carbaryl results in minimal 

capacity to bioconcentrate or bioaccumulate. Concentrations in 

organisms generally decrease consistent with the rapid rate of 

metabolism and degradation.

Diflubenzuron concentrations in most components of the physical 

environment are expected to be low and its persistence minimal. 

Diflubenzuron is not predicted to enter groundwater. Concentrations 

in streams and ponds receiving runoff following a 1.5-inch rainstorm 

are projected to be well below 0.1 ppb, and most aquatic habitats 

should not be adversely affected by runoff. Directly sprayed ponds of 

1-foot in depth are predicted to have concentrations of less than 3 

ppb, which could affect the more sensitive nontarget aquatic species. 

Diflubenzuron is readily metabolized by animals but is persistent on 

leaf surfaces where it can bioaccumulate. This persistence on 

vegetation results in residues from leaves falling into water in fall and 

exposing aquatic organisms throughout the winter (Wimmer, et al., 

1993). These conditions are unlikely to occur in most rangeland and 

croplands where the grasshopper program will occur. 

Malathion is unlikely to persist in any component of the physical 

environment. Rapid degradation, metabolism, and excretion prevent 

bioconcentration and bioaccumulation. Malathion is not expected to 

reach groundwater in detectable concentrations. Concentrations of 

malathion in waters receiving runoff from a 1.5-inch rainstorm are 

predicted to be 6 ppb in 6-foot-deep ponds and less than 3 ppb in 

streams. Directly sprayed 1-foot-deep ponds are projected to have 

concentrations as high as 137 ppb. The program procedures and 

adherence to pesticide labels are designed to avoid direct treatment of 

water bodies, so these concentrations are not expected when 

monitoring grasshopper suppression programs. 

4. Nontarget 

Terrestrial 

Species

The assessment of nontarget terrestrial species concentrates on 

quantitative calculations of exposures to vertebrate species from the 

RAATs alternative and the potential for toxic effects from those 

exposures. These effects are less than those anticipated from full 

coverage treatments. Some qualitative statements are given about the 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

180 Grasshopper Environmental Impact Statement

effects on invertebrate populations from applications and how these 

lower exposures under RAATs application affect predators and other 

organisms that depend upon invertebrates for prey or other needs. 

a. Carbaryl. The output from terrestrial vertebrate exposure modeling 

of doses from carbaryl at RAATs rates is summarized in table B–9. 

The highest potential doses to representative vertebrates are shown for 

the lark bunting, grasshopper mouse, horned lizard, and Woodhouse's 

toad. These insectivorous species consume considerable quantities of 

grasshoppers and other rangeland invertebrates, so they would be 

expected to receive higher doses than omnivores, herbivores, and 

vertebrate carnivores. The highest potential doses of carbaryl to 

wildlife species would be received by the target insects (grasshoppers 

and crickets) and other nontarget invertebrates present within the 

treatment areas.

Based upon the quantitative calculations of doses of carbaryl to 

vertebrate species, vertebrate animals are at negligible risk of adverse 

toxicological effects from the RAATs alternative. Unlike at the full 

coverage treatments, even populations of the grasshopper mouse are 

at low risk of adverse effects from the RAATs alternative. 

The toxic effects of carbaryl from the RAATs alternative will be most 

evident as decreases in susceptible invertebrate populations. The 

immediate effect of a treatment results in more limited predator 

avoidance by susceptible insects within the treatment area and easier 

foraging for insectivorous species there. This is followed by rapid 

decreases in population density of the susceptible species and the 

need for more widespread foraging by the insectivorous species. The 

decrease in populations of susceptible insects following carbaryl 

treatments is expected to be temporary with rapid recolonization of the 

treated areas from surrounding range and croplands. The use of 

alternate swaths as part of the RAATs alternative will be expected to 

increase the rate of recolonization and result in less drastic 

fluctuations in nontarget insect populations within the treatment 

areas following carbaryl applications.
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 181

b. Diflubenzuron. The output from terrestrial vertebrate exposure 

modeling of doses from diflubenzuron from the RAATs alternative is 

summarized in table B–10. The highest potential doses to 

representative vertebrates are shown for the lark bunting, grasshopper 

mouse, horned lizard, and Woodhouse's toad. These insectivorous 

species consume considerable quantities of grasshoppers and other 

rangeland invertebrates, so they would be expected to receive higher 

doses than omnivores, herbivores, and vertebrate carnivores. The 

highest potential doses of diflubenzuron to wildlife species would be 

received by the target insects (grasshoppers and crickets) and other 

nontarget invertebrates present within the treatment areas. The use 

of alternate swaths as part of the RAATs alternative will be expected to 

increase the rate of recolonization and result in less drastic 

fluctuations in nontarget insect populations within the treatment 

areas following diflubenzuron applications. 

Table B–10.Estimated Daily Doses of Diflubenzuron from Reduced 

Agent Area Treatments to Vertebrate Nontarget Species and 

Corresponding Reference Levels

TABLE 1-9: Estimated Daily Doses of Carbaryl from Reduced Agent Area Treatments 

to Vertebrate Nontarget Species and Corresponding Reference 

Levels

Representative Species Estimated Dose

Reference Dose

1/5 LD50 LD50 Reference Species

Birds

Lark bunting 40.85 156 780 Sharp-tailed grouse

Sage grouse 7.26 156 780 Sharp-tailed grouse

Bobwhite quail 29.85 458 2,290 Japanese quail

American kestrel 26.35 156 780 Sharp-tailed grouse

Mammals

Grasshopper mouse 36.83 55 275 Mouse

Blacktail jackrabbit 7.12 142 710 Rabbit

Pronghorn antelope 3.64 40 200 Mule deer

Domestic cattle (Bovine

spp.)

 1.53 40 200 Mule deer

Coyote 2.12 30 150 Cat

Reptiles and Amphibians

Horned lizard 40.49 156 780 Sharp-tailed grouse

Eastern yellow-belly racer 7.81 800 4,000 Bullfrog

Woodhouse’s toad 38.40 156 780 Sharp-tailed grouse
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

182 Grasshopper Environmental Impact Statement

TABLE 1-10: Estimated Daily Doses of Carbaryl from Reduced Agent Area 

Treatments to Vertebrate Nontarget Species and Corresponding 

Reference Levels

Representative Species Estimated Dose

Reference Dose

1/5 LD50 LD50 Reference Species

Birds

Lark bunting 3.19 752 3762 Red-winged blackbird

Sage grouse 0.45 >1000 >5000 Mallard duck

Bobwhite quail 1.66 >1000 >5000 Bobwhite quail

American kestrel 1.61 >1000 >5000 Mallard duck

Mammals

Grasshopper mouse 2.58 928 4640 Mouse

Blacktail jackrabbit 0.44 928 4640 Rabbit

Pronghorn antelope 0.20 928 4640 Rabbit

Domestic cattle (Bovine

spp.)

 0.08 928 4640 Rabbit

Coyote 0.17 928 4640 Rabbit

Reptiles and Amphibians

Horned lizard 1.81 752 3762 Red-winged blackbird

Eastern yellow-belly racer 0.86 752 3762 Red-winged blackbird

Woodhouse’s toad 12.42 752 3762 Red-winged blackbird
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 183

c. Malathion. The output from terrestrial vertebrate exposure 

modeling of doses from malathion from the RAATs alternative is 

summarized in table B–11. The highest potential doses to 

representative vertebrates are shown for the lark bunting, grasshopper 

mouse, horned lizard, and Woodhouse's toad. These insectivorous 

species consume considerable quantities of grasshoppers and other 

rangeland invertebrates, so they would be expected to receive higher 

doses than omnivores, herbivores, and vertebrate carnivores. The 

highest potential doses of malathion to wildlife species would be 

received by the target insects (grasshoppers and crickets) and other 

nontarget invertebrates present within the treatment areas.

Based upon the quantitative calculations of doses of malathion to 

vertebrate species, most animals are at negligible risk of adverse 

toxicological effects from the RAATs alternative. The species that are 

at greater risk include the bobwhite quail, American kestrel, and 

Woodhouse's toad. Although the risk to these species would be 

characterized as moderate, their potential doses are at the lower end of 

the moderate effects. It is considerably less likely that any individuals 

of these species at risk would suffer mortality from the use of the 

RAATs alternative than from the full coverage alternative. However, 

neurological effects from exposure to malathion could affect feeding 

efficiency, predator avoidance, and other necessary survival 

techniques of those species. 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

184 Grasshopper Environmental Impact Statement

The toxic effects of malathion from the RAATs alternative will be most 

evident as decreases in susceptible invertebrate populations. The 

immediate effect of a treatment results in more limited predator 

avoidance by susceptible insects within the treatment area and easier 

foraging for insectivorous species there. This is followed by rapid 

decreases in population density of the susceptible species and the 

need for more widespread foraging by the insectivorous species. The 

decreases in populations of susceptible insects following malathion 

treatments under the RAATs alternative are expected to be minimal 

with rapid recolonization of the treated areas from the surrounding 

range and croplands. The use of alternate swaths and reduced 

application rates as part of the RAATs alternative will further limit the 

adverse effects to nontarget insect populations and thereby, minimize 

any potential adverse effects on foraging of insectivorous vertebrate 

species.

Nontarget 

Aquatic Species

This section describes the potential risks to nontarget species from the 

RAATs alternative. The risk and the likelihood of occurrence is 

characterized qualitatively. Basic toxicological information and 

results of field studies were described in the section covering 

consequences of full coverage treatments to nontarget aquatic species. 

This information will not be repeated here except as it can be directly 

applied to the RAATs alternative. 

TABLE 1-11: Estimated Daily Doses of Malathion from Reduced Agent Area 

Treatments to Vertebrate Nontarget Species and Corresponding 

Reference Levels

Representative Species Estimated Dose

Reference Dose

1/5 LD50 LD50 Reference Species

Birds

Lark bunting 48.31 81 403 Horned lark

Sage grouse 8.49 30 150 Chicken 

Bobwhite quail 34.57 30 150 Chicken

American kestrel 30.78 30 150 Chicken

Mammals

Grasshopper mouse 43.80 115 775 Mouse

Blacktail jackrabbit 8.33 50 250 Rabbit

Pronghorn antelope 4.25 11 53 Cattle

Domestic cattle (Bovine

spp.)

 1.77 11 53 Cattle

Coyote 2.14 72 360 Dog

Reptiles and Amphibians

Horned lizard 47.06 465 2324 Carolina anole

Eastern yellow-belly racer 9.25 30 150 Chicken

Woodhouse’s toad 45.15 30 150 Chicken
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 185

a. Carbaryl. Laboratory studies indicate that in aquatic ecosystems 

carbaryl would mostly affect the invertebrates and have little to no 

affect on the vertebrates. Based on the predicted water concentrations 

included in of the chemical background paper on environmental fate 

and transport modeling (USDA, APHIS, 1996b; see appendix C), 

carbaryl concentrations in water would be expected to range from 3 

ppb in a stream receiving runoff from a treated area to 112 ppb in a 

shallow body of water directly sprayed with carbaryl. At those 

concentrations, cladocerans (Daphnia spp.) are at moderate (streams) 

to high (ponds) risk. The amphipods (Gammarus spp.) and stonefly 

larvae (Pteronarcys sp., Pteronarcella sp., Isogenus sp.) in ponds and 

streams are at moderate risk. Chironomid midges and fish such as 

trout, salmon, minnows, catfish, and bluegills are at negligible to low 

risk of adverse effects from carbaryl applications at the expected 

exposure rates.

Carbaryl has the potential to affect the invertebrate assemblages in 

aquatic ecosystems, but is unlikely to affect vertebrates such as fish at 

any concentrations that could be expected in the water. Although 

invertebrate populations may be reduced, these changes would not be 

permanent. Over the course of several months, it is likely that most 

invertebrates would recover to levels that existed prior to the exposure 

to carbaryl. The use of alternate swaths as part of the RAATs 

alternative will be expected to further decrease exposure of aquatic 

species from the low effects under the conventional alternative. This 

decreased exposure will coincide with commensurate increases in 

rates of recolonization and decreases in the fluctuation of populations 

of aquatic organisms. 

b. Diflubenzuron. Effects on invertebrates in aquatic ecosystems 

depend upon the exposure and type of water body. Modeling results 

indicate that concentrations vary from 0.01 ppb in streams receiving 

runoff water following rainfall to 4.3 ppb in a 1-foot deep body of water 

receiving a direct application. In particular, caddisflies (Clistoronia sp.) 

in ponds are at high risk of adverse effects from full coverage 

applications of diflubenzuron. Mayflies (Callibaetis sp.) and 

cladocerans (Daphnia sp.) in streams are at moderate risk. Dragonfly 

larvae, stonefly larvae, aquatic beetles, crayfish, bivalves, chironomid 

midges, amphipods (Gammarus sp.), and snails are at low risk.

Fish such as trout, salmon, catfish, bluegill, and perch are at low risk 

from the RAATs alternative. However, when preferred food items of 

fish are reduced by diflubenzuron, the fish may respond by switching 

to other prey until the preferred items have returned to pretreatment 

abundances (Apperson et al., 1978; Colwell and Schaefer, 1980).
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

186 Grasshopper Environmental Impact Statement

In marine and brackish ecosystems, the grass shrimp, mysid shrimp, 

and crabs are at high risk from exposures to diflubenzuron at reduced 

agent area treatment rates. Other species such as snails and bivalves 

are at low risk. However, it is unlikely that grasshopper program 

activities would occur in marine or brackish water areas that support 

aquatic marine or estuarine organisms.

Diflubenzuron used for the grasshopper suppression program is 

unlikely to cause permanent, long-term damages to aquatic 

ecosystems. Populations of some aquatic invertebrates could 

temporarily decrease if exposed to diflubenzuron, but the rapid 

generation time of these aquatic invertebrates would ensure rapid 

recolonization. The use of alternate swaths as part of the RAATs 

alternative will be expected to further decrease exposure of aquatic 

species from the low effects under the conventional alternative. This 

decreased exposure will coincide with commensurate increases in 

rates of recolonization and decreases in the fluctuations of 

populations of aquatic organisms. 

Residues of pesticides entering flowing water (i.e., creeks) dissipate 

more readily than in ponds due to constant movement of water from 

upstream that lowers the potential exposure concentration. There are 

some aquatic insects that are at potential risk in ponds. The 

dissipation of pesticide residues in creeks diminishes the likelihood of 

exposure relative to ponds. Risks to wildlife species in creeks are 

generally negligible from program use of diflubenzuron.

c. Malathion. Malathion residues in water would vary according to the 

size of the water body and the amount of malathion applied. The 

amount of water-borne malathion residue that aquatic organisms 

would potentially be exposed to could range from 2.8 ppb in runoff 

water in a stream to 137 ppb in a directly sprayed small water body.

As with the full coverage treatments, amphipod populations 

(Gammarus sp.) and cladocera (Daphnia sp.) would be reduced from 

treatments applied under the RAATs alternative. However, other 

species such as caddisflies (Limnephilus and Hydropsyche sp.), 

damselfly larvae (Lestes sp.), and stonefly larvae (Pteronarcys, 

Pteronarcella, and Isoperla sp.) are at moderate risk. Snipe fly larvae 

(Atherix sp.), shrimp (Palaemonetes sp.), and water sowbugs (Asellus

sp.) are at low risk. 

All fish are anticipated to show low risk from malathion in RAATs 

applications. Malathion in flowing waters would be rapidly diluted to 

concentrations that would not affect fish present in those waters. The 

greatest malathion concentrations and risk is to those species that 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

Grasshopper Environmental Impact Statement 187

inhabit ponds less than 1-foot-deep that are directly sprayed. This 

could affect species such as minnows that occur in shallow ditches 

and temporary standing water bodies.

A study of the effects of malathion applications in a worst-case 

scenario was conducted at Stewart’s Creek in Alabama (Kuhajda et al., 

1996). This study included surveillance of fish and aquatic 

invertebrate populations. The applications were made to cotton fields 

up to the edge of the creek bed. The conclusion based upon their data 

was that no adverse acute or long-term effects of malathion were 

evident in either the fish or aquatic invertebrate communities based 

upon numbers of individuals, numbers of taxa, and diversity indices 

over the 3-year study period. Based upon this study, it is anticipated 

that any applications of malathion in grasshopper programs, designed 

to avoid water, would not be expected to have any adverse acute or 

long-term effects on fish and aquatic invertebrates.

Malathion applied for grasshopper suppression could affect 

invertebrates, especially amphipods and cladocerans in aquatic 

ecosystems. These effects would soon be compensated for by the 

survivors, given the rapid generation time of most aquatic 

invertebrates and the rapid degradation of malathion in water. 

Therefore, malathion applied at reduced agent area treatment rates 

would not be likely to cause long-term, lasting effects to aquatic 

ecosystems. Organisms that feed on amphipods would likely switch 

temporarily to an alternate food source. If no alternate food source is 

available, the rapid generation time of amphipod assemblages means 

that the amphipod population would likely recover to pretreatment 

levels before the predator populations would be permanently affected. 

The use of alternate swaths as part of the RAATs alternative will be 

expected to further decrease exposure of aquatic species from the low 

effects under the conventional alternative. This decreased exposure 

will coincide with commensurate increases in rates of recolonization 

and decreases in the fluctuations of populations of aquatic organisms. 
Appendix B. Environmental Risk Assessment for Rangeland Grasshopper Suppression Programs—Insecticides

188 Grasshopper Environmental Impact Statement
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 189

Appendix C. Environmental Fate and Transport Modeling for Grasshopper 

Insecticides 

Methodology

A. Residues on Vegetation and Soil/Litter Surface.The Forest Service 

Cramer Barry Grim (FSCBG) model simulates aerial dispersion of 

insecticides using the initial insecticide droplet size distribution, 

aircraft speed, aircraft type, and meteorological conditions to calculate 

the trajectory of a falling droplet of insecticide. The spatial area 

modeled includes all of the spray area (spray block) and a portion of 

the area adjacent to the spray block. The average mass of insecticide 

within the spray block was calculated, as well as the maximum, 

minimum, and standard deviation. Based on typical application rates, 

three rates of application were used for carbaryl (0.375, 0.400, and 

0.500 pound active ingredient/acre (lb a.i./acre)), two rates of 

application were used for diflubenzuron (0.0078 and 0.0156 lb a.i./

acre), and one rate of application was used for malathion (0.61 lb a.i./

acre). Carbaryl, diflubenzuron, and malathion residues were estimated 

by modeling a single application as well as a second application at the 

same rate 1 week later. This model does not apply to ground 

applications of the insecticides.

The parameter values chosen, mostly from handbooks on aerial 

application equipment and from insecticide labels, represent the 

environmental conditions and equipment commonly encountered 

during a spray program (table C–1). However, many combinations of 

aircraft, spray equipment, and meteorological conditions were not 

addressed. Residues predicted by FSCBG generally represent those 

expected from aerial spraying. Site-specific conditions may cause 

actual residues to deviate from those predicted using the parameter 

values given in table C–1.

The parameters that substantially affect model output include release 

height, wind speed, aircraft speed, aircraft type, and application rate 

(Teske and Curbishley, 1990). Although the model is not very 

sensitive to changes in temperature or humidity, it is very sensitive to 

wind speed and release height (Teske et al., 1991). The wind was 

modeled as a 2 miles per hour (mph) crosswind perpendicular to the 

flight lines. This wind speed was selected to result in the maximum 

deposition on vegetation and the soil surface. Greater wind speeds 

would cause more of the insecticide to drift away from the target area, 

whereas lower wind speeds would not allow the proper amount of 

turbulent mixing required for even coverage. A 4.92-foot story canopy 

was used to simulate a rangeland with sagebrush. The release height 

above the canopy varied among the insecticides (45 feet for carbaryl, 

50 feet for diflubenzuron, and 25 feet for malathion). The actual 
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

190 Grasshopper Environmental Impact Statement

release height can range from 25 to 50 feet in the grasshopper 

program. These release heights were selected to give the most even 

coverage of insecticide given the aircraft, nozzle type, and wind speed. 

The model was run in the "near wake" mode of FSCBG to calculate the 

percentage of the insecticide on the soil surface or in the canopy.

The model has been validated in the field using data obtained from an 

aerial application of the insecticide Asana® XL to a seed orchard (Teske 

et al., 1991). The validation results suggest that FSCBG adequately 

represented the spray system, although during the validation runs the 

model generally over predicted the average insecticide mass within the 

spray block by 12.9 percent. 

Several factors contribute to uncertainty in the results of the aerial 

dispersion model. Small differences in release heights resulted in 

large differences in the estimated concentrations of the insecticides. 

Since it is unlikely that a pilot would maintain a constant altitude 

during aerial application, the actual deposition may deviate from the 

model predictions. Meteorological conditions (wind, temperature, and 

relative humidity) vary throughout a spray application and may also 

affect deposition, although this variation is not considered by FSCBG. 

FSCBG assumes, unrealistically, that the canopy is homogeneous 

throughout the spray block. Even when using the same configuration 

of aircraft and spray equipment, these factors combine to create more 

variability in observed residue levels than predicted by the model. In 

addition, different spray equipment, aircraft, and aircraft speeds can 

be expected to produce dissimilar distributions of residues. Despite 

the uncertainties associated with the model, it produces reasonable 

TABLE 1-1: Forest Service Cramer Barry Grim (FSCBG) Model Parameters

Parameters Carbaryl Diflubenzuron Malathion

Wind speed (mph) 2 2 2

Wind direction (°) 90 90 90

Temperature (°F) 60 60 60

Humidity (%) 85 85 85

Release height (ft) 45 50 25

Emission rate (fl oz/acre) 12/12.8/16 3/7 8

Active fraction 0.49 0.90 0.95

Aircraft type Turbo Thrush Cessna 188 Cessna 188

Nozzle type 8010 8001 8001

Swath width (ft) 125 75 75

Aircraft speed (mph) 100 100 100

Density of carrier (g/cm3) 0.999 1.19 1.23

Canopy type 1.5 m brush 1.5 m brush 1.5 m brush

Model type ◆ Near Wake

◆ No evaporation

◆ Near Wake

◆ Evaporation

◆ Near Wake

◆ Evaporation
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 191

results when compared to monitoring results and can simulate 

residue levels following application rates for which no monitoring data 

are available.

B. Degradation of Insecticides on Vegetation Over the Growing 

Season

Carbaryl residues have a half-life on vegetation of 7 days, resulting in 

a 50 percent reduction after 1 week Groundwater Loading Effects of 

Agricultural Management Systems (GLEAMS). Diflubenzuron residues 

decrease over time due to degradation of the insecticide on vegetation. 

Diflubenzuron residues were determined for leaves immediately after 

application and at the end of the growing season. The half-life of 

diflubenzuron used in the GLEAMS model is 27 days, resulting in a 16 

percent reduction in residues after 1 week. Malathion residues have a 

half-life on vegetation of 1 to 2 days on onions and 3 to 4 days on 

lettuce. The half-life used in this analysis in the GLEAMS model was 3 

days, resulting in a 80 percent reduction after 1 week.

C. Insecticide Concentrations

 1. Insecticide Concentration on Leaves and in Leaf Litter

A. Insecticide Concentration on Leaves

Insecticide concentration on leaves was not explicitly 

calculated. Carbaryl and malathion residues are not 

expected to persist throughout the growing season, in 

contrast to diflubenzuron which will persist. If diflubenzuron 

is applied before leaves have fully expanded, concentration 

will decrease over the growing season, as leaf weight and 

surface area increase as the leaves expand. In an eastern 

deciduous hardwood, an average of 46 percent of the original 

residue remained on the upper canopy leaves at leaf-drop, 

while 62 percent remained on lower canopy leaves (Wimmer 

et al., 1993).

B. Insecticide Concentration in Leaf Litter

Of the three proposed program insecticides (carbaryl, 

diflubenzuron, and malathion), only diflubenzuron is 

predicted to persist in leaf litter. Diflubenzuron may persist 

in leaf litter for the growing season following application; 

however, the concentration was not explicitly calculated.

 2. Insecticide Concentration in Soil

Concentrations of carbaryl, diflubenzuron, and malathion in the 

soil were estimated with the GLEAMS model. Model parameters 

were selected from insecticide profiles included with GLEAMS 

(table C–2). The soil parameters were selected to maximize 
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

192 Grasshopper Environmental Impact Statement

runoff following a storm, giving a conservative estimate of 

insecticide concentrations in receiving waters. The soil was a 

sandy loam covered with fair quality rangeland. Of the treatment 

area, 70 percent was covered with vegetation and 30 percent was 

bare soil. Comparing insecticide runoff 24 hours after 

application from a simulated treatment area containing only bare 

soil to a vegetated treatment area, resulted in a lower runoff 

concentration in bare soil for diflubenzuron, whose soil half-life 

was less than its foliar half-life. Otherwise, the bare soil 

treatment area had slightly greater insecticide runoff 

concentrations than the vegetated area. The greatest insecticide 

concentration in runoff water occurs when soils have high Soil 

Conservation Service (SCS) runoff coefficients, poor quality 

vegetative cover, high proportions of clay, high proportion of 

impervious surfaces within the watershed, and steep slopes.
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 193

TABLE 1-2: Summary of Groundwater Loading Effects of Agricultural Management Model (GLEAMS) Input 

Parameters

Input Parameters Carbaryl Diflubenzuron Malathion

Insecticide Data

Number of insecticides 1 1 1

Water solubility (mg/L) 120 0.08 130

Foliar half-life (days) 7 27 3

Soil half-life (days) 10 10 1

Partitioning coefficient 300 10000 1800

Initial concentration on foliage 0 0 0

Initial concentration on soil 0 0 0

Fraction available for washoff 0.55 0.05 0.9

Coefficient of uptake by plants 0 0 0.4

Depth of incorporation (inches) 0.3937 0.3937 0.3937

Fraction of insecticide applied to foliage 0.7 0.7 0.7

Fraction of insecticide applied to soil 0.3 0.3 0.3

Hydrology Data

Irrigation No No No

Area of field (acre) 61.776 61.776 61.776

Effective saturated conductivity below rooting zone 0.1181 0.1181 0.1181

Effective saturated conductivity above rooting zone (inches/hr) 0.3937 0.3937 0.3937

Fraction of plant available water 0.5 0.5 0.5

Soil evaporation 3.5 3.5 3.5

SCS Curve 82 82 82

Slope 0.1 0.1 0.1

Field length/width ratio 1.0 1.0 1.0

Effective rooting depth (inches) 12 12 12

Soil porosity (cc3/cc3) 0.43 0.43 0.43

Soil field capacity (cm/cm) 4.724 4.724 4.724

Wilting point (cm/cm) 0.30 0.30 0.30

Organic matter content 2.25 2.25 2.25

Soil type Silty clay Silty clay Silty clay

Percent Clay 45 45 45

Percent Silt 45 45 45

Specific surface area clay (m2/g) 20 20 20

Soil erodibility factor 0.495 0.495 0.495

Erosion Data

Soil loss ratio 0.4 0.4 0.4

Contouring factor 0.5 0.5 0.5

Manning’s n 0.06 0.06 0.06
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

194 Grasshopper Environmental Impact Statement

Following application, insecticides remained in the upper soil layer 

(0.39 inch) until a rainfall event. Rainfall (1 inch, 1.5 inch, or 2.5 

inch) on the day of spraying or the following day resulted in detectable 

insecticide concentrations in the lower soil layers. Malathion, at an 

application rate of 9.753 ounces (oz) a.i./acre, resulted in the highest 

soil concentrations (2.65 parts per million (ppm)) following a rainfall 

event. Higher concentrations of insecticides could be expected in soils 

with low SCS runoff coefficients, excellent quality vegetative cover, and 

gentle slopes. Arid conditions would tend to increase insecticide 

concentrations in soil and decrease them in runoff water.

 3. Insecticide Concentration in Waters

A. Insecticide Concentration in Directly Sprayed Waters

Insecticides are not applied directly to large bodies of water in 

grasshopper programs. Inevitably, however, small water 

bodies such as streams, vernal pools, cattle tanks, springs, 

and puddles are inadvertently sprayed. In order to provide a 

conservative (maximized) estimate of exposure, insecticide 

concentrations following direct application to these small 

water bodies are calculated. The pond was assumed to be 

cylindrical in shape. The concentration was determined by 

calculating the total residue falling on the surface and then 

dividing the mass by a volume of water, which varied 

according to depth of the water body. Mixing was assumed to 

be instantaneous. The stream was assumed to be triangular 

in cross section. The total mass of insecticide falling on the 

surface of a 3.28-foot long segment was calculated. 

Concentration was determined by dividing this mass by the 

volume of water in a 3.28-foot long stream segment.

B. Insecticide Concentration in Aquatic Sediments

Concentrations of diflubenzuron in the sediments were 

assumed to be 2 percent of the concentration in the water 

column based on a monitoring study by Kingsbury et al.

(1987). 

C. Metabolic Products of the Insecticides (4-chloroaniline and 

Malaoxon) 

Concentrations of 4-chloroaniline in the water column were 

assumed to be 10 percent of the water column concentration 

of diflubenzuron based on monitoring following diflubenzuron 

treatment of a flooded pasture (Schaefer et al., 1980). 

Malathion in chlorinated water bodies (swimming pools) 

readily metabolizes to malaoxon. Malaoxon concentrations in 

non-chlorinated waters are much lower than malathion 

concentrations.
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 195

D. d. Insecticide Concentration in Runoff Water

The GLEAMS model was used to estimate the insecticide 

concentration in runoff water from a sprayed watershed. 

Model parameters were selected to simulate the highest 

concentrations of insecticide that could reasonably be 

expected to provide a worst case scenario for aquatic 

organisms.

Parameter estimates were obtained from soil surveys, 

agricultural Insecticide handbooks, and from the GLEAMS 

insecticide data files (table C–2). For the simulation, the 

vegetation canopy coverage was assumed to be 70 percent. 

Insecticide was applied to fair-condition1 rangeland on a soil 

of hydrologic group D, thus minimizing infiltration and 

maximizing runoff to provide a conservative estimate of risk 

for aquatic organisms. 

Three different storm intensities were simulated (1 inch, 1.5 

inch, or 2.5 inch). Insecticide concentrations in the 1-inch 

storm were negligible. Maximum concentrations of 

insecticides in runoff water were observed when a 1.5-inch 

rainstorm occurred shortly after application. (This scenario 

was selected for the analysis.) Although more runoff was 

produced with the 2.5-inch storm, the insecticide 

concentrations in the runoff water, stream, and pond were 

lower than that observed with the 1.5-inch storm.

Many parameter values used in the GLEAMS model (i.e., 

slope, cover type, and soil composition) are site-specific; 

therefore, insecticide concentration in runoff from particular 

sites may be different from values predicted by the model. 

The GLEAMS model results used in this analysis could be 

considered a worst case scenario for silty clay soils. 

Therefore, the concentration of insecticide used in this 

analysis probably overestimates actual concentrations in 

many sites. This type of estimate is useful in the risk 

analysis because it sets an upper limit on the expected 

response of aquatic organisms to insecticide applications in 

the field.

E. e. Insecticide Concentrations in Waters Receiving Runoff 

Insecticides are not applied directly to large bodies of water, 

although small rangeland water bodies may inadvertently 

receive a direct spray or drift. For the purposes of this 

analysis, the concentration of insecticides in a small stream, 

1 Refers to SCS runoff curve, i.e., poor, fair, good, and excellent.
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

196 Grasshopper Environmental Impact Statement

directly sprayed, was determined as a worst case scenario. 

The concentration of insecticides in a small stream and 

shallow pond receiving runoff from the sprayed area, but not 

directly sprayed, were also determined. 

The surface-water model used in this analysis to estimate 

insecticide concentrations in streams and ponds was 

developed specifically to analyze the effects of nonpoint runoff 

in a watershed after aerial spraying. This model contains few 

site-specific parameters, and is used only to give an 

approximate estimate of insecticide in streams or ponds 

receiving runoff. Concentrations of insecticide at specific 

sites can reasonably be expected to vary from model 

predictions. The model predicts the concentration of 

insecticides in a stream and a pond in a small watershed 

(5,760 acres, or 9-square miles (mi2). The entire watershed 

was assumed to be sprayed with insecticide. The watershed 

consists of a 2.1-mile-long stream that drains 52.2 percent of 

the watershed before emptying into a 1,227-foot-diameter 

pond. The remaining 47.8 percent of the watershed drains 

directly into the pond via overland flow. The length of the 

stream was determined to be the average length of a second 

order stream draining a watershed of 3,008 acres (or 4.7 mi2) 

(van der Leeden et al., 1990). The surface area of the pond 

was determined by calculating the surface water body size for 

a watershed of 5,760 acres (or 9 mi2) using the average 

basin-to-lake ratio of 212 to 1 reported by Reckhow and 

Chapra (1983). The simulated pond is 6.56 feet deep. Water 

enters the pond from overland runoff and from the stream. 

Water leaves the pond through a drainage outlet and from 

evaporative loss. Water loss due to evaporation is based on 

the evaporation rate (van der Leeden et al., 1990) and the 

available surface area for evaporation (i.e., surface area of the 

pond). The water level of the pond is assumed to be constant, 

and the outflow from the pond varies with stream inflow. 

The model assumes that the stream has a base flow rate of 

3.60 meters (m) per second and an initial depth of 0.76 m at 

base flow. These values were selected because similar values 

have been reported for a second order stream of that length 

(van der Leeden et al., 1990). The stream channel was 

modeled as a triangular area; the depth and width vary, 

depending on the volume of water in the stream. The stream 

is assumed to be twice as wide as it is deep, making the 

cross-sectional area equivalent to depth squared. 

The model simulates the change in insecticide concentration, 

calculates the average concentration, and the maximum 

concentration over each 24-hour period within the first 96 
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 197

hours following a rainstorm. Insecticide concentration was 

calculated at each of the 1-second time steps until 96 hours 

had elapsed. The model may overestimate insecticide 

concentrations due to the assumption that all insecticide on 

impervious surfaces is carried into surface waters via runoff. 

Considerable uncertainty exists regarding the actual amount 

of insecticide that is not bound to organic impervious 

surfaces, such as asphalt. Some of the insecticide may not be 

available for transport via runoff water. 

At the first time step, the stream depth at base flow was used 

to calculate the cross-sectional area of the stream. The 

volume of water in the stream was calculated using the 

following equation:

V~=~l~times~xa #

ALIGNL where: #

STACKALIGN {

~~~V~&=~volume~of~water~\in~stream~(m^3)#

~~~l~&=~stream~length~(m)#

~~~xa~&=~cross-sectional~area~of~stream~(m^2)}

The volume of the stream is altered by the new volume of base flow 

entering the stream, the volume of runoff entering the stream, and the 

volume of water leaving the stream as discharge into the pond. With 

no runoff, the volume of base flow entering the stream is balanced by 

the volume of water discharged into the pond such that the stream 

volume does not change. When runoff occurs, the stream volume 

increases. Stream volume is calculated at each time step after the 

first using the following equation, which also accounts for runoff 

entering, volume of base flow entering, and volume of discharge 

leaving the stream:

V_t~=~V_{t-1}~+~V_{RO}~+~V_{BF}~-~V_{SD}#

ALIGNL where:#
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

198 Grasshopper Environmental Impact Statement

STACKALIGN {

~~~V_t~&=~volume~(m SUP 3)#

~~~V_{t-1}~&=~volume~at~previous~time~step~(m^3)#

~~~V_{RO}~&=~runoff~volume~entering~stream~(m^3)#

~~~V_{BF}~&=~base~flow~volume~(m^3)#

~~~V_{SD}~&=~stream~discharge~volume~(m^3)

}

The depth of the stream was calculated at each iteration after the first 

time step, using the following equation, assuming a stream channel 

twice as wide as it is deep:

d~ =~ sqrt{{V} OVER l}#

ALIGNL where: #

STACKALIGN {

~~~d~&=~depth~(m)#

~~~V~&=~volume~of~stream~(m^3)#

~~~l~&=~stream~length~(m)

}

Stream velocity and overland flow velocity were calculated with the 

following equation (Newberry, 1984):

v~ =~ {SQRT m~times~(p over xa) VERT 70 {2 OVERSM 3}} over {n}#
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 199

ALIGNL where:#

STACKALIGN {

~~~v~&=~velocity~(m/s)#

~~~p~&=~wettable~perimeter~of~stream~(m)#

~~~xa~&=~cross-sectional~area~of~stream~(m^2)#

~~~n~&=~Manning's~n#

~~~m~&=~slope

}

The maximum overland velocity in the model was determined by the 

highest overland flow velocity (greater than 0.61 m/second) reported 

for a land use type of residential dwellings and grass (USDA, SCS, 

1983). When the velocity calculated by the model exceeded the 

maximum reported velocity, the simulated velocity was taken to be the 

maximum value. 

The model assumes that there are no impervious areas (roads, 

high-density residential housing, commercial areas, or urbanized 

areas). The volume of runoff produced was determined by the 

following equations (USDA, SCS, 1983):

S~=~(1000 over SCS) - 10#

ALIGNL where: #

STACKALIGN {

~~~S~&=~runoff~parameter~derived~\from~~SCS~runoff~curve~num

ber#

~~~SCS~&=~the~SCS~runoff~curve~number~for~a~particular~cover~

class#

~~~98~&=~SCS~Impervious~areas~(pavement)#

~~~61~&=~SCS~Pervious~areas~(good~grass)~

}
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

200 Grasshopper Environmental Impact Statement

 Runoff~=~{sqrt{R~-~(0.2~times~S)}} over {R~+(0.8~times~S)}~times~ 

0.0254#

ALIGNL where: #

STACKALIGN {

~~~Runoff~&=~runoff~produced~(cm)#

~~~R~&=~rainfall~(inches)#

~~~S~&=~runoff~parameter~derived~from~SCS~runoff~curve

}

The model simulates the effect of insecticides entering a pond and 

stream by means of overland runoff after a relatively large storm event 

24-hours after application. The initial insecticide concentrations in 

the pond and stream 6 hours after application were assumed to be 

zero. Insecticide concentrations are expected to increase in the pond 

and stream as the overland flow enters them.

The surface-water model was designed to provide a generalized 

representation of insecticide transport in an aquatic system. This 

approach was selected over a more detailed site-specific model 

because of the difficulty in extrapolating from site-specific models to 

the geographically diverse program area. The predictions of the 

surface-water model are useful for comparing the expected 

concentrations of the insecticides; however, any spray may result in 

aquatic concentrations that differ from the model results because of 

site-specific factors. Ponds less than 6.56 feet deep are likely to have 

higher insecticide concentrations than the simulated pond; whereas 

larger, deeper ponds are likely to have lower insecticide 

concentrations.

The model assumes homogeneous and instantaneous mixing; thus it 

simplifies the hydrological conditions of a stream. Consequently, 

there is uncertainty regarding the residence time of insecticide in the 

stream. In reality, the concentration of insecticide in a pond or stream 

is likely to vary spatially. Insecticide residence time would vary if the 

model assumption of equal inflow and outflow of water in the pond 

were violated. Results of this model reflect the average insecticide 

concentration observed rather than the maximum concentration (table 

C–3). The maximum concentration persists for very short time periods 

(less than 6 hours). There are no toxicological data to determine 

whether the response of an organism to varying insecticide 

concentrations is more similar to that organism's response to the 

average concentration or the maximum concentration encountered. 

Therefore, in this analysis, the average concentration was used.
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 201

II. Results and Discussion

As expected, modeling results indicated the highest residues were 

associated with the highest of the application rates examined. 

Applying insecticide twice, rather than once, results in residue levels 

similar to those from a higher application rate used once (table C–4). 

TABLE 1-3: Carbaryl Bran Bait Estimated Environmental Residues

DEBUG-1 Application Rate 0.2 lb a.i. /acre

Expected residue based on application rate (lb/acre) 0.1814

DEBUG-1 Application Rate 0.02 lb a.i. /acre

Expected residue based on application rate (lb/acre) 0.01814

DEBUG 5% Application Rate 0.5 lb a.i. /acre

Expected residue based on application rate (lb/acre) 0.4536

DEBUG 5% Application Rate 0.05 lb a.i. /acre 

Expected residue based on application rate (lb/acre) 0.04536
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

202 Grasshopper Environmental Impact Statement

A. Carbaryl.Carbaryl is more likely to be transported offsite in runoff 

water than through percolation to the groundwater as suggested by 

GLEAMS modeling. Concentrations of carbaryl are predicted to be at 

least one order of magnitude greater for runoff water than percolating 

water (table C–5). Streams are predicted to have carbaryl 

concentrations of under 5 parts per billion (ppb), and ponds 6.56 feet 

deep are predicted to have less than 13 ppb in the 24 hours following 

runoff from rom a 1.5-inch rainstorm. Directly sprayed water bodies 

(1 foot deep) are predicted to have carbaryl concentrations that range 

from 138 to 184 ppb, depending on the application rate. Higher 

carbaryl concentrations occur in the upper soil layer (0 to 0.3937 inch) 

than the lower ones (0.3937 to 4.72 inches). Aerial dispersion 

modeling indicates most of the residues will be intercepted by the 

vegetation canopy, if there is one.

TABLE 1-4: Multiple Applications of Pesticide Within the Same Year

Carbaryl 0.5 lb a.i./acre

Surface residues (lb/acre) 0.7328

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 1.6467

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.3092

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.0282

Concentration in runoff water (1.5 inch storm) (ppm) 0.1266

Concentration in percolating water (1.5 inch storm) (ppm) 0.0073

Carbaryl 0.4 lb a.i./acre

Surface residues (lb/acre) 0.5863

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 1.4067

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.2684

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.0243

Concentration in runoff water (1.5 inch storm) (ppm) 0.1018

Concentration in percolating water (1.5 inch storm) (ppm) 0.0058

Carbaryl 0.375 lb a.i./acre

Surface residues (lb/acre) 0.5496

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 1.3128

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.2505

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.0226

Concentration in runoff water (1.5 inch storm) (ppm) 0.0950

Concentration in percolating water (1.5 inch storm) (ppm) 0.0054

Malathion 9.753 oz a.i./acre

Surface residues (lb/acre) 0.5573

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 2.6669

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.0523

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.0007

Concentration in runoff water (1.5 inch storm) (ppm) 0.0801

Concentration in percolating water (1.5 inch storm) (ppm) 0.00003
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 203

TABLE 1-5: Carbaryl Estimated Environmental Residues

Application Rate 0.5 lb a.i. /acre

Expected residue based on application rate (lb/acre) 0.4536

Vegetation mean residue from FSCBG (lb/acre) 0.4871

Soil/Litter surface residue beneath vegetation from FSCBG (lb/acre) 0.1843

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 1.2986

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.1752

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.0123

Concentration in runoff water (1.5-inch storm) (ppm) 0.1593

Concentration in percolating water (1.5-inch storm) (ppm) 0.0030

Average concentration in 0.76 m stream (ppb) 5.33

Average concentration in 2 m pond (ppb) 12.04

Directly sprayed water body 1 foot deep (ppb) 184.00

Directly sprayed water body 3.28 feet deep (ppb) 56.04

Application Rate 0.400 lb a.i. /acre

Expected residue based on application rate (lb/acre) 0.3629

Vegetation mean residue from FSCBG (lb/acre) 0.3895

Soil/litter surface residue beneath vegetation from FSCBG (lb/acre) 0.1735

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 1.0436

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.1407

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.0199

Concentration in runoff water (1.5-inch storm) (ppm) 0.0754

Concentration in percolating water (1.5-inch storm) (ppm) 0.0024

Average concentration in 0.76 m stream (ppb) 4.28

Average concentration in 2 m pond (ppb) 9.68

Directly sprayed water body 1 foot deep (ppb) 147.00

Directly sprayed water body 3.28 feet deep (ppb) 44.83

Application Rate 0.375 lb. a.i. /acre

Expected residue based on application rate (lb/acre) 0.3402

Vegetation mean residue from FSCBG (lb/acre) 0.3651

Soil/litter surface residue beneath vegetation from FSCBG (lb/acre) 0.1627

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 0.9740

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.1314

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.0092

Concentration in runoff water (1.5-inch storm) (ppm) 0.0704

Concentration in percolating water (1.5-inch storm) (ppm) 0.0022

Average concentration in 0.76 m stream (ppb) 4.00

Average concentration in 2 m pond (ppb) 9.03

Table C–5, continued.

Directly sprayed water body 1 foot deep (ppb) 138.00

Directly sprayed water body 3.28 feet deep (ppb) 42.03
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

204 Grasshopper Environmental Impact Statement

B. Carbaryl Bran Bait.Carbaryl residues resulting from bran bait 

applications (table C–3) are higher than those resulting from 

application of liquid carbaryl at the two lower application rates (table 

C–5). However, the residue is confined to the bran bait and is not 

found on vegetation or soil without the bait. Applying carbaryl in bait 

greatly reduces the number of organisms exposed to carbaryl. 

DEBUG 5 percent at 0.5 oz a.i./acre results in the highest carbaryl 

residues of the bran bait products used.

C. Diflubenzuron. GLEAMS does not predict any percolation of 

diflubenzuron to the groundwater; however, some transport off site is 

predicted in runoff water (table C–6). Streams and ponds in the 

treated watershed receiving runoff water following a 1.5-inch storm 

are predicted to have diflubenzuron concentrations less than 0.1 ppb. 

At the low application rates used, even directly sprayed water bodies of 

1-foot depth are predicted to have less than 6 ppb of diflubenzuron. 

Diflubenzuron concentrations in the soil are predicted to be greatest in 

the upper layer (0 to 0.3937 inch). Aerial dispersion modeling 

indicates most of the residues will be intercepted by the vegetation 

canopy, if there is one. Due to its persistence on vegetation, much of 

the diflubenzuron in the canopy can be expected to persist through 

leaf drop and beyond. Leaf litter in sprayed areas contains 

measurable diflubenzuron residues for more than one growing season 

(Wimmer, 1994a).

An extensive monitoring study of diflubenzuron residues was 

conducted in a mixed hardwood forest in West Virginia following 

application with 0.5 oz a.i./acre (Wimmer et al., 1993). Residues are 

reported throughout the growing season in both upper and lower 

canopy leaves. Insecticide concentrations in the litter in field studies 

(greater than 1 ppm spring, 1 ppm autumn, 1994) are similar to those 

estimated through modeling (1.4 ppm spring, 1.2 ppm autumn) 

(Wimmer, 1994b, unpublished data). 
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

Grasshopper Environmental Impact Statement 205

Malathion. GLEAMS predicts a very low concentration of malathion 

(>1 ppb) in water percolating to the groundwater. Some transport off 

site is predicted in runoff water (table C–7) resulting in malathion 

concentrations of 10 ppb or less in ponds and streams in the treated 

watershed receiving runoff water following a 1.5-inch storm. Directly 

sprayed water bodies of 1-foot depth are predicted to have 224 ppb of 

malathion. Malathion concentrations in the soil are predicted to be 

greatest in the upper layer (0 to 0.3937 inch). Aerial dispersion 

modeling indicates most of the residues will be intercepted by the 

vegetation canopy, if there is one. 

TABLE 1-6: Diflubenzuron Estimated Environmental Residues

Application Rate 0.0156 lb a.i. /acre

Expected residue based on application rate (lb/acre) 0.0142

Vegetation mean residue from FSCBG (lb/acre) 0.0150

Soil/litter surface residue beneath vegetation from FSCBG (lb/acre) 0.0020

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 0.040803

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.000140

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.000000

Concentration in runoff water (1.5 inch storm) (ppm) 0.000292

Concentration in percolating water (1.5 inch storm) (ppm) 0.000000

Average concentration in 0.76 m stream (ppb) 0.017

Average concentration in 2 m pond (ppb) 0.008

Directly sprayed water body 1 foot deep (ppb) 5.74

Directly sprayed water body 3.28 feet deep (ppb) 1.75

Application Rate 0.0078 lb a.i./acre 

Expected residue based on application rate (lb/acre) 0.0071

Vegetation mean residue from FSCBG (lb/acre) 0.0075

Soil/litter surface residue beneath vegetation from FSCBG (lb/acre) 0.0009

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 0.020401

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.000070

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.00000

Concentration in runoff water (1.5 inch storm) (ppm) 0.000146

Concentration in percolating water (1.5 inch storm) (ppm) 0.00000

Average concentration in 0.76 m stream (ppb) 0.008

Average concentration in 2 m pond (ppb) 0.019

Directly sprayed water body 1 foot deep (ppb) 2.87

Directly sprayed water body 3.28 feet deep (ppb) 0.87
Appendix C. Environmental Fate and Transport Modeling for Grasshopper Insecticides

206 Grasshopper Environmental Impact Statement

Multiple Applications.Carbaryl and malathion may potentially be 

applied to the treatment area twice in a season, with 7 days separating 

the two applications. Two applications would be considered if there 

was rainfall immediately following the first application. A second 

carbaryl application results in about a 30 percent increase in carbaryl 

concentrations in the upper soil layer (0 to 0.3937 inch), a 90 percent 

increase in the middle soil layer (0.3937 to 2.36 inches), and over a 

200 percent increase in the lower soil layer simulated (2.36 to 4.72 

inches) (table C–4). These concentrations are still below the soil 

concentration for a single application of malathion (table C–7). 

Carbaryl concentrations in runoff and percolating to groundwater are 

similar for one or two applications. A second malathion concentration 

does not increase either malathion concentrations in the soil, runoff 

water, or water percolating to the groundwater (table C–4). 

TABLE 1-7: Malathion Estimated Environmental Residues

Application Rate 0.61 lb a.i. /acre 

Expected residue based on application rate (lb/acre) 0.5529

Vegetation mean residue from FSCBG (lb/acre) 0.5137

Soil/litter surface residue beneath vegetation from FSCBG (lb/acre) 0.2183

Upper (0-1 cm) soil layer concentration from GLEAMS (ppm) 2.6480

Middle (1-6 cm) soil layer concentration from GLEAMS (ppm) 0.0518

Lower (6-12 cm) soil layer concentration from GLEAMS (ppm) 0.0007

Concentration in runoff water (1.5 inch storm) (ppm) 0.0795

Concentration in percolating water (1.5 inch storm) (ppm) 0.00003

Average concentration in 0.76 m stream (ppb) 4.51

Average concentration in 2 m pond (ppb) 10.2

Directly sprayed water body 1 foot deep (ppb) 224.00

Directly sprayed water body 3.28 feet deep (ppb) 68.00
Appendix D. References for Appendices A, B, and C

Grasshopper Environmental Impact Statement 207

Appendix D. References for Appendices A, B, and C

Adams, J.S., Knight, R.L., McEwen, L.C., and George, T.L., 1994. 

Survival and growth of nestling vesper sparrow exposed to 

experimental food reductions. The Condor 96:739–748.

Agency for Toxic Substances and Disease Registry, 1993. Case 

studies in environmental medicine #22: cholinesterase-inhibiting 

pesticide toxicity. U.S. Department of Health and Human Services, 

Public Health Service. September 1993.

Aldridge, W.N., Miles, J.W., Mount, D.L., and Verschoyle, R.D., 1979. 

The toxicological properties of impurities in malathion. Archives of 

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Branch II, October 7, 1993, 35 pp.

U.S. Environmental Protection Agency, Environmental Criteria and 

Assessment Office, 1984. Health and environmental effects profile 

for carbaryl. Environmental Protection Agency, Cincinnati, OH. 

January 1984.

U.S. Environmental Protection Agency, Office of Emergency and 

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superfund: vol. 1: human health evaluation manual (part A). 

Interim final. EPA/504/1–89/002. Washington, DC. December 

1989.

U.S. Environmental Protection Agency, Office of Health and 

Environmental Assessment, Office of Research and Development, 

1988. Reference physiological parameters in pharmacokinetics 

modeling. EPA/600/8-88/004. Washington, DC. 1–1. 

U.S. Environmental Protection Agency, Office of Pesticide Programs, 

1984. Guidance for the registration of pesticide products 

containing carbaryl as the active ingredient. Washington, DC.

U.S. Environmental Protection Agency, Office of Pesticide Programs, 

1989a. Inert ingredients in pesticide products: policy statement; 

revision and modification of lists. Federal Register 54(224): 

48314–48317; November 22, 1989.

U.S. Environmental Protection Agency, Office of Pesticide Programs, 

1989b. Toxchem no. 535–Malathion. Washington, DC. July 3, 

1989.
Appendix D. References for Appendices A, B, and C

232 Grasshopper Environmental Impact Statement

U.S. Environmental Protection Agency, Office of Pesticides and Toxic 

Substances, 1980. Carbaryl decision document. Environmental 

Protection Agency, Washington, DC. p. 1–78. December 1980.

U.S. Environmental Protection Agency, Office of Pesticides and Toxic 

Substances, 1985. Pesticide Fact Sheet Number 21: carbaryl. 

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1985.

U.S. Environmental Protection Agency, Office of Pesticides and Toxic 

Substances, 1987. Pesticide fact sheet no. 68.1: diflubenzuron. 

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U.S. Environmental Protection Agency, Office of Pesticides and Toxic 

Substances, 1990. Environmental Protection Agency 

memorandum. Peer review of malathion. Washington, DC.

U.S. Environmental Protection Agency, Office of Prevention, Pesticides 

and Toxic Substances, 1994. RfD/Peer review of carbaryl. 

Memorandum from George Ghali to Hack Housenger, Copy dated 

March 10, 1994 courtesy of Dr. George Ghali.

Uvarov, B., 1966. Grasshoppers and locusts. A handbook of general 

acridology, Vol. 2. Centre for Overseas Pest Research, London, 

England.

Uvarov, B., 1977. Grasshoppers and locusts. A handbook of general 

acridology, Vol. 1. Cambridge University Press, Cambridge, 

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van der Leeden, F., Troise, F.L., and Todd, D.K., 1990. The water 

encyclopedia. Lewis Publishers, Inc., Chelsea, MI. 808 pp.

Walker, W.W., and Stojanovic, B.J., 1973. Microbial versus chemical 

degradation of malathion in soil. J. Environ. Qual. 2(2):229–232.

Wauchope, R.D., Buttler, T.M., Hornsby, A.G., Augustijn-Beckers, 

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Weil, C.S., Woodside, M.D., Bernard, J.B., Condra, N.I., King, J.M., 

and Carpenter, C.P., 1973. Comparative effect of carbaryl on rat 

reproduction and guinea pig teratology when fed either in the diet 

or by stomach intubation. Toxicology and Applied Pharmacology 

26(4):621–638.

WHO—See World Health Organization.
Appendix D. References for Appendices A, B, and C

Grasshopper Environmental Impact Statement 233

WHO, IARC—See World Health Organization, International Agency for 

Research on Cancer.

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diflubenzuron (Dimilin) insecticide. Forest Insect and Disease 

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Broomall, PA. 18 pp.

Wilson, J.E.H., and Costlow, J.D., 1986. Comparative toxicity of two 

Dimilin formulations to the grass shrimp, Palaemonetes pugio. 

Bulletin of Environmental Contamination and Toxicology 

36:858–865.

Wimmer, M. 1994a. Professor, Department of Biochemistry, West 

Virginia University, Morgantown, WV. (Personal communication; 

comments from review of draft)

Wimmer, M. 1994b. (Unpublished data on file.) Environmental 

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Service, U.S. Department of Agriculture, Radnor, PA.

Wimmer, M.J., Smith, R.R., Wellings, D.L., Toney, S.R., Faber, D.C., 

Miracle, J.E., Carnes, J.T., and Rutherford, A.B., 1993. 

Persistence of diflubenzuron on Appalachian forest leaves after 

aerial application of Dimilin. Journal of Agricultural Food and 

Chemistry 41:2184–2190.

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infants with methemoglobinemia and diarrhea. European Journal 

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Carboxyhemoglobin and methemoglobin levels in residents living 

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Wolfe, N.L., Zepp, R.G., and Pacis, D.F., 1978. Carbaryl, propham, 

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World Health Organization of the United Nations, 1985. Pesticide 

residues in food—1985. Report of the joint meeting of the FAO 

panel of experts on pesticide residues in food and the environment 

and a WHO expert group on pesticide residues. Geneva, 

Switzerland.
Appendix D. References for Appendices A, B, and C

234 Grasshopper Environmental Impact Statement

World Health Organization of the United Nations, International Agency 

for Research on Cancer, 1983. International Agency for Research 

on Cancer monographs on the carcinogenic risk of chemicals to 

humans—miscellaneous pesticides (Vol. 30). International Agency 

for Research on Cancer, Geneva, Switzerland.

Zinkl, J.G., Henny, C.J., and DeWeese, L.R., 1977. Brain 

cholinesterase activities of birds from forests sprayed with 

trichlorfon (Dylox) and carbaryl (Sevin 4-oil). Bulletin of 

Environmental Contamination and Toxicology 17:379–386.
Appendix E. Federal Register Notices Associated With This Document

Grasshopper Environmental Impact Statement 235

Appendix E.Federal Register Notices Associated With This Document

Rangeland Grasshopper and Mormon Cricket Control Activities

Environmental Impact Statements; Notice of Availabilty

Environmental Impact Statements; Notice of Availability; Amended Notice

Environmental Impact Statements; Notice of Availability; Amended Notice
Appendix E. Federal Register Notices Associated With This Document

236 Grasshopper Environmental Impact Statement
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 237

Appendix F. Summary of Public Comments on the Draft Environmental Impact 

Statement

The Rangeland Grasshopper and Mormon Cricket Suppression 

Program, Draft Environmental Impact Statement (DEIS) was 

published on August 31, 2001. The U. S. Department of Agriculture 

(USDA), Animal and Plant Health Inspection Service (APHIS) originally 

provided a 45-day public comment period ending October 15, 2001. 

On October 15, 2001, APHIS received a request dated October 3, 

2001, from Terence N. Martin, Office of Environmental Policy and 

Compliance, U.S. Department of the Interior, to extend the public 

comment period. In accordance with that request, APHIS extended 

the public comment period in 66 Federal Register (FR) 53219 until 

November 14, 2001. On November 13, 2001, APHIS received a phone 

call from Arthur Totten, Office of Federal Activities, U.S. 

Environmental Protection Agency (EPA), who requested another 

extension of the public comment period. In accordance with that 

request, APHIS extended the public comment period in 66 FR 58734 

until November 28, 2001.

APHIS received 10 comment letters prior to the close of the comment 

period on November 28, 2001. Comments from the U.S. Fish and 

Wildlife Service were sent on March 6, 2002, and received by APHIS on 

March 29, 2002, after the close of the comment period, but have, 

nevertheless, been addressed in this document. Copies of the 

comment letters are included in this appendix. 

Many of the comment letters provided technical corrections that have 

been incorporated into the final environmental impact statement (EIS). 

The comments also pointed out areas where the DEIS was unclear. All 

of the comments received were carefully considered, and the DEIS has 

been revised and finalized accordingly. While considering the 

comments, APHIS identified 

25 primary issues that the commenters identified. Those issues are 

addressed in the following section and in no particular order. Each 

issue has been summarized and a response follows.

ISSUE 1: Some readers had difficulty with the organization of the 

document and locating the lists of references. 

RESPONSE: Several changes have been made to assist readers. A 

preface has been added that describes the organization of the 

document. References cited in chapters 1 through 6 are listed in 

chapter 7. References cited in the appendices can now be found in a 

single place, appendix D.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

238 Grasshopper Environmental Impact Statement

ISSUE 2: The distinction between what land managers do for 

grasshopper management and what APHIS does for grasshopper 

suppression was unclear to some commenters.

RESPONSE: The Plant Protection Act (PPA) directs APHIS to generally 

carry out a program to control grasshoppers and Mormon crickets on 

all Federal lands to protect rangeland. The PPA also states that, 

“Subject to the availability of funds. . .” on request of the 

administering agency or the agriculture department of an affected 

State, the Secretary of Agriculture, to protect rangeland, shall 

immediately treat Federal, State, or private lands that are infested 

with grasshoppers or Mormon crickets at levels of economic 

infestation, unless the Secretary determines that delaying treatment 

will not cause greater economic damage to adjacent owners of 

rangeland.”

Based on the above authority, APHIS directly intervenes and 

suppresses grasshopper and Mormon cricket populations only when 

requested, and only when those populations reach levels can cause 

economic damage to rangeland forage and/or adjacent cropland. In 

addition, APHIS conducts surveys and provides land managers 

technical assistance regarding grasshopper species composition, 

densities, and potential for economic damage to occur. 

The role of land managers is to implement management efforts that 

hopefully prevent or reduce the severity of grasshopper outbreaks. 

While APHIS can provide technical assistance to land managers, 

implementing the actual practices such as grazing management that 

are intended to prevent grasshopper outbreaks are the responsibilities 

of the land managers rather than APHIS. Land managers may choose 

from among a variety of cultural and biological approaches to prevent 

or lessen the severity of grasshopper outbreaks. Some of these 

approaches are described in appendix A.

ISSUE 3: Several comments were received regarding how the FEIS 

will be used by other Federal agencies to fulfill responsibilities they 

may have under the National Environmental Policy Act (NEPA). How 

this EIS can be restricted to the action of a single Federal agency 

(APHIS) was also asked.

RESPONSE: Information has been added to the EIS that contains 

information on the ways in which other Federal agencies may use this 

programmatic document to fulfill their responsibilities under NEPA, 

including site-specific programs against grasshopper outbreaks. The 

information is also reiterated in chapter 1, Purpose of and Need for the 

Proposed Action and chapter 2, Background. 

There are four methods from which Federal agencies may choose. One 

method is adoption 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 239

(§ 1506.3). NEPA regulations state “An agency may adopt a Federal 

draft or final environmental impact statement or portion thereof 

provided that the statement or portion thereof meets the standards for 

an adequate statement under these regulations.” Another method is 

combining documents. Section 1506.4 states that “Any environmental 

document in compliance with NEPA may be combined with any other 

agency document to reduce duplication and paperwork.” A third 

method is incorporation by reference (§1502.21) which says “Agencies 

shall incorporate material into an environmental impact statement by 

reference when the effect will be to cut down on bulk without impeding 

agency and public review of the action. The incorporated material 

shall be cited in the statement and its content briefly described. No 

material may be incorporated by reference unless it is reasonably 

available for inspection by potentially interested persons within the 

time allowed for comment. Material based on proprietary data which 

is itself not available for review and comment shall not be incorporated 

by reference.” 

A last method is tiering (§ 1502.20). “Agencies are encouraged to tier 

their environmental impact statements to eliminate repetitive 

discussions of the same issues and to focus on the actual issues ripe 

for decision at each level of environmental review (§ 1508.28). 

Whenever a broad environmental impact statement has been prepared 

(such as a programmatic or policy statement) and a subsequent 

statement or environmental assessment is then prepared on an action 

included within the entire program or policy (such as a site-specific 

action), the subsequent statement or environmental assessment need 

only summarize the issues discussed in the broader statement and 

incorporate discussions from the broader statement by reference and 

shall concentrate on the issues specific to the subsequent action. The 

subsequent document shall state where the earlier document is 

available. . . (§ 1508.28).” 

Adoption, combining, incorporation by reference are the methods best 

suited when using the data provided by this EIS. State agencies also 

can use the information provided by this EIS. 

This document is not restricted to the actions of a single agency; 

rather, it deals with a program, treating it by stage of technological 

development (40 Code of Federal Regulations (CFR) 

§ 1502.4 (c)(3)), in which other Federal land management agencies and 

State agriculture departments may cooperate, as needed, in more 

localized operations.

ISSUE 4: To some readers the DEIS did not provide enough 

information on how site-specific environmental assessments (EAs) will 

be prepared.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

240 Grasshopper Environmental Impact Statement

RESPONSE: The appropriate environmental documentation for a 

site-specific program, usually an EA, will be prepared prior to 

implementing a specific grasshopper suppression program. If a 

Federal land management agency is proposing the program, that 

particular agency will prepare, or be involved in preparing, the EA. 

For State agriculture departments proposing a grasshopper program, 

the environmental documentation will be provided by APHIS. Should 

a grasshopper program be requested by private groups or individuals 

through their State agriculture department, APHIS would undertake 

the appropriate environmental process. 

When site-specific grasshopper programs are proposed, the 

corresponding environmental documentation will include a thorough 

review of such subjects as alternatives; the affected environment; 

species of concern, including biological control insectary sites for 

noxious weeds; endangered and threatened species; cumulative 

impacts; compliance with the Executive Orders on minorities and 

low-income populations and children; and any required monitoring.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 241

ISSUE 5: Commenters questioned whether there is a need for 

grasshopper treatments, if those treatments were economically 

justified, and whether the long-term benefits of grasshopper 

suppression outweigh the long-term costs. In particular, one 

commenter repeatedly suggested that grasshopper outbreaks were 

analogous to natural disasters such as fires and floods and that 

policies and management practices should recognize the benefits of 

allowing natural cycles to take place with a minimum of human 

interference. 

RESPONSE: Congress directed USDA to protect rangeland from 

economic infestations of grasshoppers and Mormon crickets in the 

PPA. The need for a grasshopper suppression program in a particular 

rangeland location is evaluated on a case-by-case basis. For example, 

if the grasses in a rangeland area are abundant and the cattle have 

adequate forage—despite a high number of grasshoppers per square 

yard—a treatment may not be warranted. On the other hand, a lower 

grasshopper number per square yard under drought conditions may 

warrant a treatment. 

Other scenarios in which a grasshopper treatment would not be 

warranted include the following: (1) in an area that has naturally high 

numbers of grasshoppers and ranchers have adjusted the number of 

livestock for the amount of forage available, and (2) in an area where 

grasshoppers are primarily species that pose little threat to rangeland 

forage.

The areas where a request for a grasshopper treatment would 

probably occur would be in areas where there are periodic outbreaks 

of grasshopper species that consume and destroy forage that livestock 

and range-consuming wildlife could use. In these areas it is difficult 

to adjust to the periodic swings in available forage that would be 

caused by grasshopper outbreaks. 

In some regards, grasshopper suppression and forest fires are 

analogous. Just as not every forest fire is controlled by the Federal 

government, not every grasshopper outbreak is suppressed by APHIS. 

While it is likely that APHIS would be requested to intervene in 

widespread and severe grasshopper outbreaks, there may also be 

smaller outbreaks in areas of high value agricultural lands that would 

justify treatments. Additionally, assistance is available to the victims 

of disasters from groups and agencies such as nonprofit organizations, 

local relief agencies, and the Federal Emergency Management Agency. 

There are no such relief groups for grasshopper outbreaks.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

242 Grasshopper Environmental Impact Statement

ISSUE 6: Some commenters were unclear about when and where 

APHIS would conduct treatments and the criteria that will be used to 

determine if treatments are needed.

RESPONSE: The decision to conduct grasshopper treatments is 

based on many factors, some of which are difficult to quantify. Among 

the factors APHIS considers are: the number of grasshoppers present 

in the area, grasshopper and plant species composition, life-cycle 

stage of the grasshoppers, range condition, the economic significance 

of the infestation, and whether it would be feasible to conduct an 

effective treatment program. When State and private lands are 

involved, the land manager/land owner must cost-share from 33 to 67 

percent of the total treatment costs, and they are not likely to request 

treatments, through their State agriculture departments, unless they 

are reasonably certain their investment is worthwhile. 

There are many APHIS activities that precede any decision to conduct 

a grasshopper treatment. Every year APHIS conducts surveys and 

provides ongoing technical assistance to Federal, State, and private 

land managers. Federal land management agencies and State 

agriculture departments will frequently request that APHIS investigate 

complaints regarding damage that is being caused to rangeland by 

grasshoppers. In most every year, and in the majority of instances, 

the decision reached by APHIS is to not conduct a grasshopper 

treatment. For example, in Idaho in 2000, 

26 requests for treatment resulted in only 4 treatments.

To assist in decisionmaking, APHIS developed a computerized decision 

support system named HOPPER in the mid-1990s. HOPPER 

evaluated the validity and cost-effectiveness of treating rangeland 

grasshopper outbreaks on Western rangeland. It would be necessary 

to update HOPPER and include technological advances, such as the 

use of diflubenzuron and the RAATs strategy, before HOPPER could 

again be implemented to its fullest extent in deciding whether 

grasshopper treatments are biologically and economically warranted. 

APHIS conducts surveys for grasshopper populations on rangeland in 

the Western United States. In addition, APHIS provides technical 

assistance on grasshopper management to land owners/managers. In 

situations where direct intervention may be necessary to suppress 

grasshopper populations to below economically damaging levels, 

Federal land management agencies and State agriculture departments 

may request APHIS to assess the situation. The decision to conduct a 

grasshopper suppression program involves both APHIS and the land 

owner/manager.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 243

APHIS would only treat grasshoppers that have reached a level of 

economic infestation. In some cases APHIS rangeland treatments 

protect not only the rangeland, but reduce the likelihood that the 

grasshoppers will move from the rangeland onto crops and other lands 

that border rangeland. There are also situations where APHIS has 

been requested to treat a rangeland area that has small amounts 

(typically less than 10 percent of the infested area) of infested 

croplands. In those situations the crop owner pays the entire 

treatment cost on the croplands.

ISSUE 7: A need for spring surveys and a better ability to predict 

grasshopper outbreaks before they occur were suggested.

RESPONSE: APHIS has historically conducted spring (nymphal) 

surveys in years when funds were available. While these surveys 

provided much valuable information regarding the status of 

grasshopper populations, the ability to accurately predict grasshopper 

outbreaks is based upon numerous factors. Among these are 

temperature, precipitation, vegetation, soil qualities, and natural 

enemies. There may also be other factors not yet known that help 

determine if grasshopper populations will become economically 

damaging. The Grasshopper Integrated Pest Management (GHIPM) 

Program concluded that as more information becomes known, the 

task of forecasting outbreaks becomes more complex.

Although economically damaging grasshopper outbreaks cannot yet 

be accurately predicted, APHIS does conduct nymphal surveys in the 

spring and adult surveys in the fall. Early in the season, the locations 

where the grasshopper species composition and densities indicate a 

high likelihood of becoming an economic problem are identified. 

Those “hot spots” could then be treated to prevent grasshopper 

populations from developing and spreading. Such an approach would 

require early and accurate surveys and was proven to be economical 

in North Dakota during the GHIPM Program. 

In 2002 APHIS will conduct a comprehensive spring survey in the 

Western United States. This information will then be made available 

to land managers. APHIS will also provide technical support and 

expertise to cooperate in treatment of “hot spots” upon request of a 

Federal land management agency or State agriculture department and 

subject to the availability of funds.

ISSUE 8: Some commenters requested APHIS to publish the 

operational procedures that will be used when conducting 

grasshopper treatments.

RESPONSE: Operational procedures for conducting grasshopper 

treatments have not been included in this document because 

operational procedures are intended to be developed on a site-specific 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

244 Grasshopper Environmental Impact Statement

basis rather than in a programmatic document of this type. 

Operational procedures will be implemented to ensure that all 

treatments will be efficacious, cost-effective, conducted with 

restrictions according to the product label, and to protect sensitive 

areas identified in site-specific documents.

ISSUE 9: Some commenters wanted information on whether 

retreatments would occur and whether more than one insecticide 

would be used at a particular treatment site. 

RESPONSE: When requested by a Federal land management agency 

or State agriculture department, APHIS’ role in the suppression of 

grasshoppers may be the application of insecticides. APHIS typically 

applies either carbaryl, diflubenzuron, or malathion one time to a 

treatment site. Retreatments seldom occur for both scientific and 

economic reasons. The goal of a treatment is to reduce grasshopper 

populations to below those levels that cause economic damage. A 

single treatment according to either Alternative 2 or Alternative 3 is 

intended to sufficiently reduce grasshopper populations, and there 

should be no need for another treatment. In addition, while a single 

treatment must be cost-effective, there are very few situations where 

multiple treatments would be cost-effective. An exception could be 

migrating Mormon crickets that may sometimes require a second 

treatment. 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 245

There may, however, be situations where it is appropriate to use one 

insecticide or formulation in one part of a treatment area and a 

different insecticide or formulation in another part of that same 

treatment area with all applications conducted in accordance to the 

label directions. For example, ultra-low-volume (ULV) malathion may 

be used over the majority of a treatment area, but areas of special 

consideration may be treated with carbaryl bait. Should these 

situations occur, no area would be treated with more than one 

insecticide, and there would be no mixing or combination of 

insecticides.

State agencies, counties, and private groups or individuals may 

conduct their own grasshopper suppression programs. APHIS has no 

control over those activities, although technical assistance can be 

provided. Yet, it is highly unlikely that APHIS would be requested to 

treat areas that had already been treated by State, county, or private 

interests because of the cost involved, and there would be no need to 

further suppress the grasshopper populations. 

Pesticides may also be applied on rangeland by States, local 

governments, and private groups or individuals to control weeds, 

pests, or insects other than grasshoppers. Again, APHIS has no 

control over those activities, and the multitude of treatments that 

could be made are too numerous to analyze in this document. 

Site-specific environmental documents will describe any synergistic 

and cumulative effects should APHIS be aware of other pesticide use 

in an area proposed for grasshopper treatments. 

ISSUE 10: Many comments stated that the DEIS did not contain a 

reasonable range of alternatives. Mechanical control, biological 

control, and cultural control were among the alternatives suggested 

for analysis in this document, and many commenters proposed 

integrated pest management (IPM) as a preferred approach to 

grasshopper outbreaks. Others suggested which of the three 

alternatives contained in the DEIS they would prefer.

RESPONSE: In accordance with NEPA, alternatives relate to the 

underlying purpose and need to which the agency is responding (40 

CFR § 1502.13). In the case of a programmatic EIS that is examining 

pest suppression issues by stage of technological development and not 

applying that technology to meet identified needs on the ground, the 

range of alternatives that have to be considered is somewhat limited. 

This EIS is intended to generally explore new information on 

insecticides and technological advances and their effects. No decision 

regarding the application of any technologies or alternatives that may 

be available to the affected land manager or owner will be made until 

such time as a “proposal” exists. It is when an agency becomes aware 

of a growing localized grasshopper problem that the purpose and need 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

246 Grasshopper Environmental Impact Statement

for action becomes clear. When an agency “has a goal and is actively 

preparing to make a decision on one or more alternative means of 

accomplishing that goal and the effects can be meaningfully evaluated 

(40 CFR § 1508.23), a proposal exists.” APHIS does not contemplate 

an action, nor does it have an operational goal; therefore, a “proposal,” 

as such, does not exist. 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 247

APHIS’ role in direct intervention of grasshopper infestations is to use 

an insecticide treatment to reduce grasshopper populations to a level 

below that which constitutes an economic infestation. APHIS’ 

treatment alternatives analyzed in this EIS (see chapter 3, 

Alternatives) generally are carried out in conjunction with and 

complement Federal, State, and private efforts to prevent, control, or 

suppress grasshopper outbreaks. When a harmful grasshopper 

infestation reaches a level of economic infestation, direct intervention 

may be the most viable option. 

ISSUE 11: Some commenters asked about the use of biological 

control agents, such as Beauvaria, to suppress grasshoppers.

RESPONSE: APHIS is aware that there are many natural enemies of 

grasshoppers in North America, and that using those natural enemies 

for the suppression and maintenance of grasshopper populations is a 

widely supported concept. Biological control was a major aspect of the 

APHIS GHIPM Program with specific emphasis on Beauvaria. GHIPM 

findings as well as research conducted in other countries has 

furthered the search for an effective biocontrol agent for grasshoppers. 

APHIS continues to have an interest in any grasshopper suppression 

strategy or method that reduces the reliance on insecticide use, but, 

thus far, biological control has not yet been proven to be consistently 

efficacious or cost-effective in reducing grasshopper outbreaks below 

economically damaging levels in the United States.

ISSUE 12: Technological advances in grasshopper suppression since 

the 1987 Rangeland Grasshopper Cooperative Management Program 

EIS were not evident to some readers.

RESPONSE: A discussion of the GHIPM Program is included in 

appendix A. This program conducted in the1990s addressed the main 

issues associated with grasshopper management. Among the 

technologies developed during the GHIPM Program and included in 

this EIS was the Reduced Agent Area Treatments (RAATs) strategy 

that can reduce insecticide loads by 

75 percent or more. Another product of the GHIPM Program was 

research into the use of diflubenzuron, a chitin-inhibiting growth 

regulator, which is substantially less toxic to vertebrates than 

acetylcholinesterase-inhibiting chemicals. There have also been many 

other changes to the technical assistance APHIS provides as a result of 

the GHIPM Program.

ISSUE 13: The description of RAATs was confusing to some readers.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

248 Grasshopper Environmental Impact Statement

RESPONSE: The RAATs alternative is described in chapter 3 section 

C and the environmental consequences of that alternative are 

described in chapter 5, sections D and G. Figures have been added to 

chapter 3 of this document to visually depict this alternative. 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 249

In brief, the RAATs strategy is an approach to rangeland grasshopper 

suppression that reduces the insecticide application rate by 25 to 50 

percent (or more) and swaths not directly treated (refuges) are 

alternated with treated swaths. By using the RAATs strategy, 

insecticide loads over the area being treated can be reduced by 75 

percent compared to the rates that conventionally would be used in a 

blanket coverage of the treated area. The RAATs alternative works 

through both the action of the insecticide—meaning grasshoppers 

mortality occurs in the treated swaths—and conservation biological 

control—meaning the natural grasshopper predators and parasites 

remain in the untreated swaths.

A likely source of confusion in the EIS is that the risk assessment in 

appendix B was conducted using a set of reduced insecticide 

application rates, but the risk assessment assumes a blanket coverage 

of the reduced rates rather than reduction in the insecticide 

application area which would be an important part of the RAATs 

strategy. This was done to simplify the risk assessment because there 

is an almost unlimited number of combinations of reduced rates and 

reduced areas that could be considered. Therefore, the risk 

assessment for alternative 3 assumed the worst-case scenario in 

terms of insecticide load to an area, that being insecticide applied at a 

reduced rate, but over 100 percent of the entire treatment area with 

no untreated swaths. This does not mean that RAATs applications 

described in site-specific environmental documents will have 100 

percent coverage; those site-specific RAATs will certainly cover less 

than 100 percent of the treatment area. However, this means that 

RAATs with less than 100 percent coverage will be expected to have 

environmental consequences that are no greater than the effects 

described in this EIS.

ISSUE 14: One commenter stated that the affected environment has 

been inadequately described in the DEIS.

RESPONSE: The description of the affected environment is adequate 

given the nature of the programmatic EIS. In the context of this 

document a fuller description of the affected environment would be 

tantamount to emphasizing background material, something the 

NEPA implementing regulations discourage (40 CFR § 1500.4(f)).

Once a suppression area has been identified, the site-specific 

environmental documentation prepared for that particular program 

will include the detailed information on the affected environment. As 

stated in chapter 4, Affected Environment, the characteristics of the 

program that may be analyzed include the potential effects of the 

program on human health, nontargets and socioeconomic issues. In 

addition, special considerations for minorities, low-income 

populations, and children will be examined, as well as cumulative 

effects and monitoring.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

250 Grasshopper Environmental Impact Statement

ISSUE 15: Additional information regarding carbaryl was requested 

in the comments. Questions were also raised regarding the use of 

carbaryl in both bait and ULV spray form.

RESPONSE: Additional information regarding carbaryl was 

submitted by the manufacturer and that information has been 

included in the document. Carbaryl can be applied as either a bait 

form, which is most often wheat bran that has been mixed with liquid 

carbaryl and is applied by either ground or aerial application, or in 

liquid form that is a ULV spray that is most commonly applied by 

airplane.

ISSUE 16: Some requested additional information on the 

environmental effects of diflubenzuron, and one commenter supplied 

additional information on diflubenzuron. The effects of diflubenzuron 

on aquatic invertebrates was of special concern.

RESPONSE: Additional information was supplied by the registrant for 

diflubenzuron. Much of this information served to update the 

analyses and has been included in the FEIS. There is considerable 

information about the effects of diflubenzuron (including on aquatic 

invertebrates) in the environmental risk assessment in appendix B of 

this document. Field studies involving diflubenzuron have also been 

summarized in chapter 5 sections B, C, and D.

As one commenter pointed out, EPA has estimated that diflubenzuron 

poses some risk to invertebrates when applied at the lowest rate for 

forestry applications. It should be noted that the lowest forestry 

application rate is 0.02 lb active ingredient per acre (a.i./acre) while 

the rangeland application rate for grasshopper suppression in 

Alternative 2 is 0.016 lb a.i./acre. In 

Alternative 3 the rate is 0.012 lb a.i./acre but the total amount applied 

in a RAATs strategy will be reduced even further because 

diflubenzuron would only be applied directly to part of the treatment 

area.

ISSUE 17: A comment letter stated that the DEIS was unclear in its 

presentation of the effects of malathion on human health.

RESPONSE: The analysis of potential program effects of malathion on 

human health reveals comparable risks to those in EPAs recent risk 

assessments of malathion to comply with the Food Quality Protection 

Act. Readers are asked to refer to the Environmental Risk 

Assessment, appendix B, for details about human health effects that 

are summarized in chapter 5 of this final EIS.

ISSUE 18: More information contained on labels for carbaryl, 

diflubenzuron, and malathion was requested.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 251

RESPONSE: Because insecticide product labels frequently change, 

labels have not been included in this FEIS. The most recent labels for 

these products can be found at: www.cdms.net/manuf/manuf.asp. 

However, many commenters were concerned about protecting water 

bodies. All labels for carbaryl, diflubenzuron, and malathion prohibit 

application directly to water, and it is highly unlikely that this 

requirement will change. APHIS will adhere to all label restrictions. 

ISSUE 19: Some comments requested more information on how 

APHIS would protect the health, safety, and aesthetic concerns of 

workers as well as the public residing in areas where treatments could 

occur, including the need for a formal notification process to let 

allergic or hypersensitive individuals be informed before treatments.

RESPONSE: The effects of grasshopper treatments on humans and 

the measures APHIS will take to protect workers and the public are 

contained in several sections of the document such as chapter 5, 

section C. and appendix B.

An important aspect of protecting humans from the effects of 

insecticides used for grasshopper suppression is that APHIS will not 

conduct any suppression program unless requested to do so by the 

responsible land management agency. Those agencies would have 

their own procedures for protecting humans that APHIS will abide by. 

APHIS also conducts stakeholder meetings involving the wide range of 

land managers, land owners, and the public before any suppression 

programs are conducted and where health and safety issues can be 

addressed. In addition, APHIS complies with all product label 

requirements for human health and safety including the Worker 

Protection Standard (40 CFR § 170). 

ISSUE 20: The effects of grasshopper suppression treatments on 

nontarget organisms, and ecosystems in general, were a concern to 

many. Specific concerns were raised regarding the toxicity of carbaryl, 

diflubenzuron, and malathion to birds, nontarget insects, including 

those used as biological control agents, and fish. In addition, a 

comment was made regarding the environmental effect of oils used 

during treatments.

RESPONSE: The effects of carbaryl, diflubenzuron, and malathion on 

nontarget organisms have been described in chapter 5 and appendix 

B. Except for those atypical instances when the effects of program 

insecticides were known for a particular species, the analyses in this 

document relied on representative nontarget species. Refer to 

appendix B, table B–3 for a list of the representative species. Both 

laboratory and field studies were used to describe the effects of 

grasshopper treatments on nontarget organisms. This document 

contains some information on nontarget organisms that was not 

available for the DEIS. 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

252 Grasshopper Environmental Impact Statement

The available toxicity data from research on given pesticides is limited 

to a finite number of wildlife species. The determination of risk to a 

given species from potential program action is made by selection of 

toxicity data for that species or the most closely related surrogate 

species. The review of the quality of data from available research may 

influence the decision to select a given study or specific data for a 

given surrogate species over other available data. The decision to 

select specific data for a given surrogate for use in the grasshopper 

program risk assessments was made by a diverse team of scientists. 

The surrogate data were selected to best represent the species risk 

based upon the concensus of the team. This approach may not always 

portray the most sensitive outcome, but is designed to provide the 

decisionmaker with a realistic description of impacts of potential 

program alternatives. This information allows the risk manager to 

make an informed decision about differences in potential impacts 

among available alternatives to the program. 

In Chapter 5, section E, Species of Concern, protected species, and 

threatened and endangered species were addressed. Each of those 

categories contain descriptions of the environmental consequences of 

grasshopper programs on an individual species. These species were 

intended to be examples and the findings will not necessarily apply to 

all species that could be of special concern. Site-specific documents 

will provide more detailed information on any species that may be of 

special concern for a given grasshopper suppression effort.

In response to the oil that would be used, the amount of oil used will 

be within the labeled rate which for diflubenzuron which currently 

allows for, but does not mandate, the use of emulsified vegetable or 

paraffinic crop oil. The maximum rate that oil would be applied for 

grasshopper suppression is 10 ounces of oil per acre. The risk of toxic 

effects from oil at this rate is extremely low. 

ISSUE 21: Some comments asked about the effect of grasshopper 

treatments on bees.

RESPONSE: APHIS is well aware of the risks to bees in the vicinity of 

grasshopper suppression programs. The insecticides APHIS would 

use to suppress grasshoppers have varying degrees of toxicity to bees 

based on the insecticide’s mode of action. In general, bee mortality 

could be expected for bees exposed to carbaryl and malathion in spray 

form. However, bees are unlikely to be exposed to carbaryl in bait 

form. The insect growth regulator, diflubenzuron, is nontoxic to adult 

bees and immature bees would not likely be exposed to toxic levels of 

diflubenzuron residues returned by adults. 

Grasshopper suppression carried out under Alternative 2 would have 

a greater effect on bees than would suppression programs that use a 

RAATs strategy, Alternative 3. Native and foraging bees in areas left 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 253

untreated in a RAATs application would much less likely be directly 

exposed to any of the insecticides. Any beekeepers in the treatment 

area that could be affected will be notified. Site-specific environmental 

documents will describe what, if any, protective measures will be 

taken to protect bees from program insecticides. 

ISSUE 22: Many comments pertained to federally listed threatened 

and endangered species, State listed species, and other special species 

of concern, and the process by which APHIS proposes to protect those 

species.

RESPONSE: Federally listed species are being addressed in the 

Endangered Species Act section 7 consultation, which will include 

listed and proposed species that occur within the 17 Western States 

where grasshopper treatments could occur. APHIS will implement all 

measures to minimize any adverse impacts on those species that are 

identified in the consultation. The potential effects of a particular 

grasshopper treatment may also be evaluated for State listed species 

and species of concern in the environmental document prepared for 

that site. In addition, APHIS will abide by all restrictions that land 

managers may impose. 

ISSUE 23: Many commenters asked APHIS to describe what the 

effects of grasshopper treatments will be on threatened and 

endangered species. 

RESPONSE: A biological assessment is a document prepared by the 

Federal agency to determine the potential impacts of its action on 

endangered and threatened species and their habitats. APHIS is 

preparing the biological assessment that will evaluate the potential 

effects of the use of the three insecticides on listed and proposed 

endangered and threatened species and their habitats that occur 

within the 17 Western States. Through the consultation process, 

protection measures will be developed that when implemented will 

ensure the grasshopper program will not adversely affect endangered 

or threatened species or their habitats.

ISSUE 24: The extent to which cumulative impacts were analyzed in 

the DEIS was questioned by some.

RESPONSE: The EIS could not analyze cumulative impacts because 

it is a programmatic EIS for 17 Western States. Cumulative impacts 

will be considered at the site-specific, operational level when the 

parameters of the program area can be identified. The application of 

an insecticide by APHIS will be added to the past, present, and 

reasonably foreseeable future actions that have or will occur in the 

treatment area. These will be the components evaluated under 

cumulative impacts. 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

254 Grasshopper Environmental Impact Statement

ISSUE 25: Comments were received regarding the need for 

posttreatment monitoring to assess impacts on nontarget organisms.

RESPONSE: The GHIPM Program conducted studies on the effects of 

insecticide treatments on nontarget organisms. This information can 

be found in the IPM Manual available on line at 

www.sidney.ars.usda.gov/grasshopper/index.htm. Should 

environmental monitoring be conducted, a monitoring plan will 

describe the where, when, what, and how many samples should be 

collected. The types of samples collected might include flowing or 

stationary water, soil, sediment, fish, insects, and vegetation, as well 

as measuring airborne drift using dye cards. 
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

Grasshopper Environmental Impact Statement 255

Precision monitoring could be utilized to limit pesticide use to areas 

where pests actually exist or are reasonably expected and where 

economically and technically feasible. Samples will be analyzed for 

insecticide residues, and monitoring reports will be written should 

monitoring be conducted.

ALL COMMENT LETTERS SUBMITTED TO APHIS HAVE BEEN 

REPRODUCED HERE.
Appendix F. Summary of Public Comments on the Draft Environmental Impact Statement

256 Grasshopper Environmental Impact Statement
Appendix G. Preparers and Reviewers

Environmental Services

USDA, APHIS, PPD

4700 River Rd., Unit 149

Riverdale, MD 20737–1238

Carl Bausch

Deputy Director

Dr. Dave Bergsten

Toxicologist

Mary R. Biddlecome

Secretary

Kenneth Dial

Environmental Protection 

Specialist

Betsey L. Garver

Writer/Editor

Margaret I. Huggins

Program Analyst

Leslie G. Rubin

Toxicologist

Nancy E. Sweeney

Project Leader

Vicki L. Wickheiser

Environmental Protection 

Specialist

Office of Risk Assessment and Cost 

Benefit Analysis

USDA

1400 Independence Avenue

Washington, DC 20250

Dr. Linda C. Abbott

Senior Risk Analyst

Invasive Species Pest Management

USDA, APHIS, PPQ

4700 River Road, Unit 134

Riverdale, MD 20737 

Charles L. Brown

National Grasshopper Program 

Manager

Regulatory Coordination

USDA, APHIS, PPQ

4700 River Rd., Unit 141

Riverdale, MD 20737

Charles H. Bare

Senior Staff Officer

USDA, APHIS, PPQ

Phoenix Plant Protection Center

3645 E. Wier Avenue

Phoenix, AZ 85210

R. Nelson Foster

Supervisory Entomologist

USDA, APHIS, PPQ

1629 Blue Spruce Drive, Suite 204

Fort Collins, CO 80524

Timothy J. McNary

Senior Regional Program Manager

USDA, APHIS, PPQ

1629 Avenue D., Suite A–5

Billings, MT 59102

Craig E. Thomson

Plant Protection and Quarantine 

Officer
USDA, APHIS, PPQ

3509 Miriam Avenue, Suite A

Bismarck, ND 58501

Keith Winks

State Plant Health Director

David C. Hirsch

Plant Protection and Quarantine 

Officer

USDA, APHIS, PPQ

P.O. Box 250

Pierre, SD 57505

J. Bruce Helbig

State Plant Health Director

USDA, APHIS, PPQ

504 West 17th Street, Suite 200

Cheyenne, WY 82001–4348

John C. Larsen

State Plant Health Director

University of Wyoming

Department of Renewable Resources

Laramie, WY 82071

Dr. Jeffery A. Lockwood

Professor
Appendix H. Distribution List

State Plant Health Director

USDA, APHIS, PPQ

3658 East Chipman Road

Phoenix, AZ 85040

State Plant Health Director

USDA, APHIS, PPQ

9505 Micron Avenue, Suite G

Sacramento, CA 95827

State Plant Health Director

USDA, APHIS, PPQ

3950 North Lewiston, Suite 330

Aurora, CO 80011

State Plant Health Director

USDA, APHIS, PPQ

9134 West Blackeagle Drive

Boise, ID 83709

State Plant Health Director

USDA, APHIS, PPQ

1947 NW. Topeka Blvd.

Topeka, KS 66608

State Plant Health Director

USDA, APHIS, PPQ

1220 Cole Ave.

Helena, MT 59601

State Plant Health Director

USDA, APHIS, PPQ

2301 University Drive, Bldg. 23 B

Bismark, ND 58504–7595

State Plant Health Director

USDA, APHIS, PPQ

5940 South 58th Street

P.O. Box 81866

Lincoln, NE 68501

State Plant Health Director

USDA, APHIS, PPQ

6200 Jefferson Street, NE. Suite 130

Albuquerque, NM 87109–3434

State Plant Health Director

USDA, APHIS, PPQ

1550 South Wells Ave., Room 204

Reno, NV 89502

State Plant Health Director

USDA, APHIS, PPQ

4020 North Lincoln Blvd., Suite 101

Oklahoma City, OK 73105

State Plant Health Director

USDA, APHIS, PPQ

Airport Business Center

6135 NE. 80th Ave., Suite A–5

Portland, OR 97218–4033

State Plant Health Director

USDA, APHIS, PPQ

P.O. Box 250

Pierre, SD 57501

State Plant Health Director

USDA, APHIS, PPQ

903 San Jacinto Blvd., Suite 270

Room A–151

Austin, TX 78701–2450

State Plant Health Director

USDA, APHIS, PPQ

1860 West Alexander, Suite B

West Valley, UT 84119

State Plant Health Director

USDA, APHIS, PPQ

22000 Marine View Dr. South, Suite 201

Des Moines, WA 98198
State Plant Health Director

USDA, APHIS, PPQ

5353 Yellowstone Rd., Suite 208

Cheyenne, WY 82009

C. John Caravetta, Associate Director

Plant Services Division

Arizona Dept. of Agriculture

1688 West Adams

Phoenix, AZ 85007

Bill L. Callison, Assistant Director

Plant Health & Pest Prevention Services

California Dept. of Food & Agriculture

1220 N St.

Sacramento, CA 95814

Mitch Yergert, Acting Director

Division of Plant Industry

Colorado Department of Agriculture

700 Kipling St., Suite 4000

Lakewood, CO 80215–5894

Dr. Roger R. Vega, Administrator

Division of Plant Industry

Idaho Department of Agriculture

P.O. Box 790

Boise, ID 83701–0790

Thomas Sim, IV, Administrator

Plant Protection & Weed Control Program

Kansas Dept. of Agriculture

P.O. Box 19282

Topeka, KS 66619–0282

Steve Baril, Bureau Chief

Agricultural Sciences Division

Montana Dept. of Agriculture

P.O. Box 200201

Helena, MT 59620–0201

Stephen V. Johnson, State Entomologist

Bureau of Plant Industry

Nebraska Dept. of Agriculture

P.O. Box 94756

Lincoln, NE 68509–4756

Robert Gronowski, Bureau Chief

Bureau of Plant Industry

Nevada Division of Agriculture

350 Capitol Hill Ave.

Reno, NV 89502–2992

Sherry Sanderson, Bureau Chief

Bureau of Entomology & Nursery Industries

New Mexico Dept. of Agriculture 

MSC 3BA

P.O. Box 30005 

Las Cruces, NM 88003–0005

David Nelson, State Entomologist

North Dakota Dept. of Agriculture

State Capitol 600 East Blvd.

Bismarck, ND 58505–0020

Sancho M. Dickinson, Program Manager

Plant Industry & Consumer Services

Oklahoma Dept. of Agriculture

2800 North Lincoln Blvd.

Oklahoma City, OK 73105

Bob Shoemaker, Supervisor

Wyoming Weed & Pest, Platte County

P.O. Box 775

Wheatland, WY 82201–0775

Daniel J. Hilburn, Ph.D.

Administrator, Plant Division

Oregon Dept. of Agriculture

635 Capitol St. NE.

Salem, OR 97301–2532

Kevin Fridley, Administrator

Office of Plant Industry

South Dakota Dept. of Agriculture

Division of Agricultural Services

523 East Capitol, Foss Bldg.

Pierre, SD 57501–3182

Shashank Nilakhe, Director

Agri-Systems

Texas Dept. of Agriculture

P.O. Box 12847, Capitol Station

Austin, TX 78711
G. Richard Wilson, Director

Division of Plant Industry

Utah Dept. of Agriculture & Food 

350 North Redwood Rd.

Box 146500

Salt Lake City, UT 84114–6500

Clinton Campbell, Program Manager

Plant Services Division

Washington State Dept. of Agriculture

P.O. Box 42560

Olympia, WA 98504–2560

Jim Bigelow, Manager

Consumer & Compliance Division

Wyoming Dept. of Agriculture

2219 Carey Ave.

Cheyenne, WY 82002

Don Joy

Uniroyal Chemical Company

4205 Barge St.

Yakima, WA 98908

John Bruce

Cheminova, Inc.

3323 198th Pl. SE.

Bothell, WA 98012

Richard Shaw

Aventis CropScience

P.O. Box 475

Smithville, MO 64089–0475

Nina Garcia

U.S. Department of the Interior

Bureau of Land Management

1849 C St., NW. (LS 201)

Washington, DC 20240

R. Timothy Weiland, Ph.D.

Technical Manager

Crop Protection Division

Uniroyal Chemical Company

Benson Rd.

Middlebury, CT 06749

Kevin L. Kelley

Uniroyal Chemical Co.

Crompton Corporation

Benson Road

Middlebury, CT 06749

Dann Watson

Van Diest Supply Co.

North Highway 83

P.O. Box 410

McCook, NE 69001–0410

Dick Lindenmuth

USDA, Forest Service

Forest and Rangeland Management 

Sidney R. Yates Bldg.

3 South, MS–1103

P.O. Box 96090

Washington, DC 22090–6090

Allen R. Dedrick 

Associate Deputy Administrator

Natural Resources & Sustainable Agric. Sys. 

USDA, ARS

Room 4–228

5601 Sunnyside Ave.

Beltsville, MD 20705–5140

Rhey M. Solomon, Assistant Director

Ecosystem Management Coordination

USDA, Forest Service

201 14th St., SW.

Washington, DC 20250–1100

Adree DuVarney

National Environmental Coordinator

USDA, NRCS

Room 6158–S

1400 Independence Ave., SW.

Washington, DC 20250

Len Richeson

Department of Defense

Environmental Security–EQ

300 Defense, Pentagon

Washington, DC 20301–3400
Carol M. Borgstrom, Director

Department of Energy

Office of NEPA Policy and Compliance

Office of Environment, Safety, and Health

Room 3E–094

1000 Independence Ave., SW.

Washington, DC 20585–0119

Donald R. Sutherland

Department of the Interior

NEPA Coordinator/Federal Preservation 

Officer

Bureau of Indian Affairs

1849 C Street, NW. (MS 4516)

Washington, DC 20240–0001

Ann B. Aldrich, Group Manager

Planning, Assessment, & Community 

Support

DOI, Bureau of Land Management

1849 C Street, NW. (MS 1050LS)

Washington, DC 20240–0001

Jacob Hoogland, Chief

Environmental Quality Division

Department of the Interior

National Park Service

Room 2749

1849 C Street, NW.

Washington, DC 20240–0001

Don Peterson

Environmental Coordinator

Department of the Interior

Fish and Wildlife Service

1849 C Street, NW.

400 Arlington Sq. Bldg.

Washington, DC 20240–0001

Anne Norton Miller, Director

Office of Federal Activities

Environmental Protection Agency

Room Code 2251–A

1200 Pennsylvania Ave., NW.

Ariel Rios Bldg,

Washington, DC 20460

EPA Region 6 Office

1445 Ross Ave., Suite 1200

Dallas, TX 75202

EPA Region 7 Office

901 North 5th Street

Kansas City, KS 66101

EPA Region 8 Office

999 18th St., Suite 300

Denver, CO 80202–2466

EPA Region 9 Office

75 Hawthorne St.

San Francisco, CA 94105

EPA Region 10

1200 6th Ave.

Seattle, WA 98101

Kathleen J.R. Johnson, Ph.D.

Supervisor, Plant Pest and Disease Prog.

Oregon Dept. of Agriculture

635 Capitol St., NE.

Salem, OR 97301–2532

Larry E. Gabriel, Secretary

South Dakota Dept. of Agriculture

523 East Capital Ave.

Pierre, SD 57501–3172

Ann M. Bartuska, Director 

Forest and Rangeland Staff

USDA, Forest Service

14th & Independence Ave., SW.|

P.O. Box 96090

Washington, DC 20090–6090

Susan Child, Planning Consultant

Office of Federal Land Policy 

Herschler Bldg, 1West

122 West 25th Street

Cheyenne, WY 82002–0600
Danielle A. Larochelle

Registration Manager

Aventis CropScience

2 T.W. Alexander Dr.

Research Triangle Park, NC 27709

Neil Wagner

Peacock Industries, Inc.

Box 557

Hague, Saskatchewan SOK 1X0 Canada

Judith Thompson

Haco, Inc.

P.O. Box 7190

Madison, WI 53707

Jim Olivarez

USDA, Forest Service

Northern Region, Federal Bldg.

P.O. Box 7669

Missoula, MT 59807

Tom McClure

USDA, Forest Service

Rocky Mountain Region

P.O. Box 25127

Lakewood, CO 80225

Gene Onken

USDA, Forest Service

Southwestern Region

333 Broadway SE.

Albuquerque, NM 87102

Curt Johnson

USDA, Forest Service

Intermountain Region, Federal Bldg.

324 25th St.

Ogden, UT 84401

Cheri Rohrer

USDA, Forest Service

Pacific Southwest Region

1323 Club Dr.

Vallejo, CA 94592

Gary Smith

USDA, Forest Service

Pacific Northwest Region

P.O. Box 3623

Portland, OR 97208–3623

Levester Pendergrass

USDA, Forest Service

Southern Region

1720 Peachtree Rd., NW.

Atlanta, GA 30309

Christine Frisbee

USDA, Forest Service

Eastern Region

310 West Wisconsin Ave., Room 580

Milwaukee WI 53203

Jesus Cota

USDA, Forest Service

Forest Health Protection

Sydney R. Yates Bldg.

2 South, P.O. Box 96090

Washington, DC 22090–6090

Craig E. Thomson

USDA, APHIS, PPQ

1629 Avenue D., Suite A–5

Billings, MT 59102

Keith Winks

State Plant Health Director

USDA, APHIS, PPQ

3509 Miriam Ave., Suite A

Bismarck, ND 58501

David C. Hirsch 

USDA, APHIS, PPQ

3509 Miriam Ave., Suite A

Bismarck, ND 58501

Timothy J. McNary

USDA, APHIS, PPQ

1629 Blue Spruce Dr., Suite 204

Ft. Collins, CO 80524
J. Bruce Helbig

State Plant Health Director

USDA, APHIS, PPQ

P.O. Box 250

Pierre, SD 57505

R. Nelson Foster, Supervisory Entomologist

USDA, APHIS, PPQ

Phoenix Plant Protection Center

3645 East Wier Avenue

Phoenix, AZ 85210

Dr. Jeffrey A. Lockwood

University of Wyoming

Dept. of Renewable Resources

Laramie, WY 82071

Dr. Michael Catangui

South Dakota State University

Dept. of Plant Science

Box 2207A

Brookings, SD 57007

John Cooper

South Dakota Dept. of Game, Fish, & Parks

523 East Capitol, Foss Building

Pierre, SD 57501

Pat Keatts

DOI, Bureau of Indian Affairs

115 4th Ave., SE.

Aberdeen, SD 57401

Jim Glade

DOI, Bureau of Indian Affairs

Pine Ridge Agency

P.O. Box 1203

Pine Ridge, SD 57770

Roy Teachout

DOI, Bureau of Indian Affairs

Rosebud Agency

P.O. Box 550

Rosebud, SD 57570

Alan Lien

DOI, Bureau of Indian Affairs

Lower Brule Agency

P.O. Box 190

Lower Brule, SD 57548

Daigre’ Douville

DOI, Bureau of Indian Affairs

Crow Creek Agency

P.O. Box 139

Ft. Thompson, SD 57339

Robert Demery

DOI, Bureau of Indian Affairs

Standing Rock Agency

P.O. Box E

Ft. Yates, ND 58538

Paul Roe

DOI, Bureau of Indian Affairs

Yankton Agency

Box 570

Wagner, SD 57380

Jamie Murray

DOI, Bureau of Indian Affairs

Cheyenne Agency

Box 325

Eagle Butte, SD 57625

Curt Johnson

South Dakota Dept. of School 

 & Public Lands

500 East Capitol

Pierre, SD 57501

Greg Bourland

Cheyenne River Sioux Tribe

P.O. Box 590

Eagle Butte, SD 57625

Roxanne Sazue

Crow Creek Sioux Tribe

P.O. Box 50

Ft. Thompson, SD 57339
Michael Jandreau

Lower Brule Sioux Tribe

P.O. Box 187

Lower Brule, SD 57548

Harold D. Salway

Oglala Sioux Tribe

P.O. Box H

Pine Ridge, SD 57770

William Kindle

Rosebud Sioux Tribe

P.O. Box 430

Rosebud, SD 57570

Charles W. Murphy

Standing Rock Sioux Tribe

P.O. Box D

Ft. Yates, ND 58538

Madonna Archambeau

Yankton Sioux Tribe

P.O. Box 248

Marty, SD 57361

Tony DeToy

USDA, Forest Service

Ft. Pierre National Grasslands

P.O. Box 417

Pierre, SD 57501

Bill Perry

USDA, Forest Service

Buffalo Gap National Grasslands

Box 425

Wall, SD 57790

Robert Anderson

Grand River National Grasslands

Box 390

Lemmon, SD 57638

George Foley

USDA, Forest Service 

Sioux Ranger District

P.O. Box 37

1st & Main

Camp Crook, SD 57724

John Twiss

USDA, Forest Service

Black Hills National Forest

R R 2, Box 200

Custer, SD 57730

Lyle Chase

DOI, Bureau of Land Management

310 Roundup Street

Belle Fourche, SD 57717

William R. Supernaugh

DOI, National Park Service

Badlands National Park

P.O. Box 6

Interior, SD 57760

Nell McPhillips

DOI, Fish & Wildlife Service

420 South Garfield, Suite 400

Pierre, SD 57501

District Ranger

USDA, Forest Service

McKenzie Ranger District

1901 South Main Street

Watford City, ND 58854–6705

District Ranger

USDA, Forest Service

Medora Ranger District

161 21st Street West

Dickinson, ND 58601

Grasslands Supervisor

USDA, Forest Service 

Dakota Prairie Grasslands Office

240 West Century Avenue

Bismarck, ND 58503
Endangered Species Biologist

Ecological Services Field Office

DOI, Fish & Wildlife Service

3425 Miriam Avenue

Bismarck, ND 58501

Dr. William P. Kemp

USDA, ARS

Bee Biology and Systematics Laboratory

5310 Old Main Hill

Logan, UT 84322–5310

Dr. David Branson

USDA, ARS

Northern Plains Agricultural Research Lab.

1500 North Central Avenue

Sidney, MT 59270

Richard Hill

DOI, Fish & Wildlife Service 

Eastside Federal Complex

911 NE. 11th Avenue

Portland, OR 97232

Regional Director

USDA, APHIS

1629 Blue Spruce Drive, Suite 204

Ft. Collins, CO 80524

Dr. Tom Royer

Dept. of Entomology & Plant Pathology

Oklahoma State University, 225P NRC

Stillwater, OK 74078–3033

Roy Reichenback

Wyoming Weed & Pest Coordinator

Wyoming Department of Agriculture

2219 Carey Avenue

Cheyenne, WY 82002–0100

Steve Brill, Supervisor 

Wyoming Weed & Pest, Goshen Co.

P.O. Box 757

Torrington, WY 82240

Mike Willie, Supervisor 

Wyoming Weed & Pest, Washakie Co.

P.O. Box 936

Worland, WY 82401

Allen Pomeroy, Supervisor 

Wyoming Weed & Pest, Big Horn Co.

355 East 5th Street

Lovell, WY 82431

Allen Mooney, Director 

Campbell County Weed and 

 Pest District

P.O. Box 191

Gillette, WY 82717–0191

Ken Henke, Leader

Weed Management

DOI, Bureau of Land Management

5353 Yellowstone Road, Suite 208

Cheyenne, WY 82009

Worland Field Office

DOI, Bureau of Land Management 

P.O. Box 119

Worland, WY 82401–0119

Casper Field Office

DOI, Bureau of Land Management

2087 Prospector Drive

Casper, WY 82604–2968

Dr. Robert Pfadt

Dept. of Renewable Resources

University of Wyoming

P.O. Box 3354

Laramie, WY 82071

Frank Cross, Group Leader

Forest Health Protection

USDA, Forest Service

P.O. Box 25127

Lakewood, CO 80225–0127
Curt Allen

USDA, Forest Service

803 Soo San Drive

Rapid City, SD 57702

Ray Nation, Supervisor 

DOI, Bureau of Indian Affairs

P.O. Box 158

Ft. Washakie, WY 82514

Shoshone Tribal Council

P.O. Box 217

Ft. Washakie, WY 82514

Northern Arapahoe Tribal Council

P.O. Box 396

Ft. Washakie, WY 82514

Joint Business Council 

Tribal Complex

P.O. Box 217

Ft. Washakie, WY 82514

Biodiversity Associates

P.O. Box 6032

Laramie, WY 82073

Sierra Club

Northern Plains Region

23 North Scott, Suite 27

Sheridan, WY 82801 

Norman Wagoner, District Ranger

USDA, Forest Service, Douglas District

Medicine Bow/Routt National Forest

Thunder Basin National Grassland

2250 East Tichards

Douglas, WY 82633

Gary D. Carpenter

USDA, APHIS, PPQ

1629 Blue Spruce Drive, Suite 204

Ft. Collins, CO 80524

Dick Jackson

P.O. Box 723

Hermiston, OR 97838–0723

Dave McNeal

USDA, APHIS, PPQ

9134 West Blackeagle Drive

Boise, ID 83709

Laird J. Lucas

Land & Water Fund of the Rockies

P.O. Box 1612

Boise, ID 83701

William M. Eddie

Land & Water Fund of the Rockies

P.O. Box 1612

Boise, ID 83701

Melinda K. Harm

Land & Water Fund of the Rockies

P.O. Box 1612

Boise, ID 83701

Wyoming Farm Bureau

P.O. Box 1348

Laramie, WY 82073

Jerry W. Thomas

Natural Resources Manager

Shiprock Agency

P.O. Box 3538

Shiprock, NM 87420

Luke Kinese

222 9th Ave. South, Apt. 4.

St. Cloud, MN 56301

David Batts

3775 Iris Ave., #4

Boulder, CO 80301

Peter Galvin

P.O. Box 83

Garberville, CA 95542
Uintah National Forest

USDA, Forest Service

Forest Supervisor’s Office 

88 West 100 North

P.O. Box 1428

Provo, UT 84601

USDA, APHIS, PPQ

Plant Protection Laboratory

Moore Air Base, Bldg., S–6414

Route 3, Box 1014

Edinburg, TX 78539

Katie Fite, Conservation Director

Committee for Idaho’s High Desert

P.O. Box 2863

Boise, ID 83701

Angie Young

Biodoversity Associates

P.O. Box 6032

Laramie, WY 82073

Jeanne Wade Evans, Deputy Director, Forests & 

Rangelands

USDA, Forest Service

14th and Independence, SW.

P.O. Box 96090

Washington, DC 20090–6090

William E. Knapp

Acting Assistant Director, Fisheries 

 & Habitat Conservation

Fish & Wildlife Service

Dept. of the Interior

Washington, DC 20240

Office of Federal Land Policy

Herschler Building, 1 West

122 West 25th St.

Cheyenne, WY 82002–0600

Willie Taylor, Director 

DOI, Office of Environmental Policy 

 & Compliance

1849 C Street, NW. (MS 2340 Interior)

Washington, DC 20240–0001

Terry Ely, State Operations Staff Officer

USDA, APHIS, PPQ

3658 East Chipman Rd.

Phoenix, AZ 85040

Bud C. Criblef

Acting Assistant Director, 

Renewable Resources and Planning

DOI, Bureau of Land Management

Washington, DC 20240

Terence N. Martin, Team Leader 

Natural Resources Management 

DOI, Office of Environmental 

 Policy and Compliance

1849 C Street, NW.

Washington, DC 20240
Appendix I. Acronyms and Glossary

Grasshopper Environmental Impact Statement 269

Appendix I. Acronyms and Glossary

A

Acetylcholinesterase (AChE)—An enzyme produced at junctions in 

the nervous system that inactivates acetylcholine, thereby ending 

transmission of a nerve impulse once it has passed the junction.

Active Ingredient (a.i.)—The effective control agent of a pesticide 

formulation or the actual amount of the technical material present in 

the formulation.Acute Toxicity The potential of a substance to cause 

injury or illness when given in a single dose or in multiple doses over a 

period of 24 hours or less; in aquatic studies, exposure to a given 

concentration would be for 96 hours or less.

Amphipod—Any of a large group of small, aquatic crustaceans, 

commonly called scuds, with laterally compressed bodies.

Animal and Plant Health Inspection Service (APHIS) —An agency 

of the U.S. Department of Agriculture.

Arthropod—Members of the phylum Arthropoda include the insects, 

the crustaceans (crabs, lobsters, and shrimp), the arachnids (spiders, 

ticks, and scorpions), the millipedes, and centipedes. The arthropod is 

characterized by a rigid external body covering called a cuticle or 

exoskeleton, a segmented body, and paired, jointed appendages with 

at least one pair of functional jaws.

B

Bureau of Indian Affairs (BIA)—An agency of the U.S. Department of 

the Interior.

Bioaccumulation—The process of a plant or animal selectively taking 

in or storing a persistent substance over a period of time; a higher 

concentration of the substance is found in the organism than in the 

organism’s environment.

Biological Assessment (BA) —The document prepared to assess the 

potential impacts of a program on endangered and threatened species 

and their habitats.
C

270 Grasshopper Environmental Impact Statement

Bureau of Land Management (BLM) —An agency of the U.S. 

Department of the Interior.

C

Carbaryl —A broad-spectrum carbamate insecticide that inhibits 

acetylcholinesterase.

Carcinogen —Substance that causes cancer.

Council on Environmental Quality (CEQ) —The agency that 

oversees implementation of the National Environmental Policy Act.

CFR—Code of Federal Regulations (U.S.).

Chemical Degradation—The breakdown of a chemical substance into 

simpler components through chemical reactions.

Chitin—A polysaccharide, hard substance that forms the outer cover 

of insects, crustaceans, and some other invertebrates.

Cholinesterase (ChE)—Any enzyme that catalyzes the hydrolysis of 

choline esters; for example, acetylcholinesterase catalyzes the 

breakdown of acetylcholine to acetic acid and choline.

Chronic Toxicity—Harmful effects of a chemical from prolonged 

exposure or repeated administration.

Cooperator —A landowner, Federal, State, or private individual, 

agency, or group that is involved in a grasshopper or Mormon cricket 

control program as a codecisionmaker or financially through an 

established cost-sharing formula.

Cropland —Any area planted with the intent to harvest. Crops 

planted and then grazed because of drought or insufficient growth will 

be considered cropland. Fallow land also will be considered cropland.

Cumulative Impacts—“. . . the impact on the environment which 

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

past, present, and reasonably foreseeable future actions regardless of 

what agency (Federal or non-Federal) or person undertakes such other 

actions. Cumulative impacts can result from individually minor but 

collectively significant actions taking place over a period of time.” (40 

CFR 1508.7)
D

Grasshopper Environmental Impact Statement 271

D

DEIS—Draft environmental impact statement. See Environmental 

Impact Statement.

Diapause—A period of spontaneous dormancy independent of 

environmental conditions interrupting developmental activity in an 

embryo, larva, or pupa, or arresting reproductive activity in an adult 

insect and usually occurring during hibernation or estivation.

Diflubenzuron—An insect growth-regulating insecticide that inhibits 

the formation of chitin.

Diptera—Flies, mosquitoes, midges, and the like, that constitute a 

group of insects characterized by having only one pair of functional 

wings; a second nonfunctional pair is reduced to small knobbed 

structures called halteres.

Drift—That portion of a sprayed chemical that moves off a target site 

because of wind.

E

Economic Infestation—A measurement of the economic losses caused 

by a particular population level of grasshoppers or Mormon crickets to 

the designated rangeland.

Endangered Species —Any species of animal or plant that is in 

danger of extinction throughout all or a significant portion of its range.

Endangered Species Act (ESA) —A Federal law that regulates the 

conservation of endangered and threatened species and their habitats.

Environmental Assessment (EA) —An environmental document, 

prepared to comply with the National Environmental Policy Act of 

1969, wherein the environmental impacts of a planned action (in this 

case grasshopper control programs) are objectively reviewed.

Environmental Impact Statement(EIS)—A document prepared by a 

Federal agency in which anticipated environmental effects of 

alternative planned courses of action are evaluated; a detailed written 

statement as required by section 102(2)(C) of the National 

Environmental Policy Act (NEPA).
F

272 Grasshopper Environmental Impact Statement

Executive Order (E.O.)—A form of executive lawmaking implemented 

by the President.

Exoskeleton—The hard outer casing of an insect that is made of 

chitin.

Exposure Analysis—The estimation of the amount of chemicals that 

organisms receive during application of pesticides.

F

Family —A group of related plants or animals forming a category 

ranking above a genus and below an order, usually comprising several 

to many genera, but sometimes including a single genus of notably 

distinctive characters.

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA)—A 

Federal law that provides the overall framework for the Federal 

pesticide program. 

Fish and Wildlife Service (FWS) —An agency of the U.S. 

Department of the Interior.

Forage—All browse and nonwoody plants available to livestock or 

wildlife for grazing or harvesting for feed.

Forage Production—The weight of forage that is produced within a 

designated period of time on a given area. The weight may be 

expressed as either green, air-dry, or oven-dry. The term may also be 

modified as to time of production such as annual, current year's, or 

seasonal forage production. 

Forb—A herbaceous plant other than a grass, especially one growing 

in a field or meadow.

Forest Service (FS)—An agency of the U.S. Department of Agriculture.

Federal Register (FR)—The official daily publication for Rules, 

Proposed Rules, and Notices of Federal agencies and organizations, as 

well as Executive Orders and other Presidential documents.

Formulation—The form in which a pesticide is packaged or prepared 

for use. A chemical mixture that includes a certain percentage of 

active ingredient (technical chemical) with an inert carrier.
H

Grasshopper Environmental Impact Statement 273

G

Genus —A taxonomic category ranking below a family and above a 

species; used in taxonomic nomenclature, either alone or followed by a 

Latin adjective or epithet, to form the scientific name of a species.

Grasshopper Integrated Pest Management (GHIPM)—The 

Grasshopper Integrated Pest Management Program.

Granivorous—Feeding on grains and seeds. 

H

Half-life —The time required for a substance (such as an insecticide) 

in or introduced into a living or nonliving system to be reduced to half 

of its original amount whether by excretion, metabolic decomposition, 

or other natural process.

Hazard Analysis —The determination of whether a particular chemical 

is or is not causally linked to particular harmful effects.

Herbivore —An animal that feeds exclusively on plants.

Hydrolysis —Decomposition or alteration of a chemical substance by 

water.

Hymenoptera —A large order of insects comprised of the ants, bees, 

sawflies, and wasps. The typical adult has four membranous wings 

and chewing-type mouth parts.

I

Integrated Pest Management (IPM)—The selection, integration, and 

implementation of pest control actions on the basis of predicted 

economic, ecological, and sociological consequences; the process of 

integrating and applying practical methods of prevention and control 

to keep pest situations from reaching damaging levels while 

minimizing potentially harmful effects of pest control measures on 

humans, nontarget species, and the environment.

Insectivorous— Insect-eating; in common usage, includes animals 

that eat insects and sometimes other selected invertebrates.
L

274 Grasshopper Environmental Impact Statement

Instar —The term for an insect before each of the moults (shedding of 

its skin) it must go through in order to increase in size. Upon 

hatching from its egg, the insect is in instar I and is so called until it 

moults, when it begins instar II, and so forth.

Invertebrate Drift—Movement of aquatic insects and crustaceans 

downstream with the current in flowing water that results from 

exposure to substances that elicit repellant or toxic responses.

Isopod —Any of a large order (Isopoda) of small crustaceans with the 

body composed of seven free thoracic sections, each bearing a pair of 

similar legs. Commonly called sowbugs.

L

Leach —Usually refers to the movement of chemicals through soil by 

water; may also refer to the movement of herbicides out of leaves, 

stems, or roots into the air or soil.

Lepidoptera —A large order of insects, including the butterflies and 

moths, characterized by four scale-covered wings and coiled, sucking 

mouthparts.

M

Malathion—A broad-spectrum organophosphate insecticide that 

inhibits acetylcholinesterase.

Metabolite — A product of the chemical changes in living cells that 

provides energy and assimilates new material.

Methemoglobin—The compound in blood responsible for transport of 

oxygen.

Methemoglobinemia—The condition where the heme iron in blood is 

chemically oxidized and lacks the ability to properly transport oxygen.

Microbial Degradation—The breakdown of a chemical substance into 

simpler components by bacteria.

Microgram—One-millionth of a gram; abbreviated as μg.
N

Grasshopper Environmental Impact Statement 275

Mixed Function Oxidase (MFO)—Enzyme responsible for the oxidation 

of organophosphorous insecticides, such as malathion, to compounds 

that are stronger inhibitors of acetylcholinesterase.

Molt—To shed or cast off hair, feathers, shell, horns, or an outer layer 

of skin in a process of growth or periodic renewal with the cast-off 

parts being replaced by new growth.

Moribund—At or near the point of death.

N

National Environmental Policy Act of 1969 (NEPA) —The act 

whereby Federal agencies evaluate the potential effects of a proposed 

action and its alternatives on the human environment.

National Marine Fisheries Service(NMFS) —An agency of the U.S. 

Department of Commerce.

Nontarget Organisms—Those organisms (species) that are not the 

focus of insecticide treatments.

Nymph—Any insect larva that differs chiefly in size and degree of 

differentiation from the adult.

O

Omnivorous—Eating both animal and plant substances.

Oncogenic—Capable of producing or inducing tumors, either benign 

(noncancerous) or malignant (cancerous), in animals.

Order—A category of taxonomic classification ranking above family 

and below class and often being made up of several families.

Orthoptera—An order of Insecta comprising insects with mouthparts 

fitted for chewing, two pairs of wings or none, and an incomplete 

metamorphosis.

Outbreak—An explosive increase in the abundance of a particular 

species that occurs over a relatively short period of time.
P

276 Grasshopper Environmental Impact Statement

P

Pesticide—Any substance or mixture of substances used in 

controlling insects, rodents, fungi, weeds, or other forms of plant or 

animal life that are considered to be pests.

Phytotoxic—Poisonous or harmful to plants.

Piscivorous—Habitually feeding on fish.

Plecoptera—An order of Insecta, stoneflies, characterized by aquatic 

nymphs that are mostly phytophagous.

Plant Protection Act (PPA)—The Plant Protection Act.

Plant Protection and Quarantine (PPQ)—A unit within the Animal and 

Plant Health Inspection Service, U.S. Department of Agriculture.

R

Reduced Agent Area Treatments (RAATs)—A grasshopper 

suppression method in which the rate of insecticide is reduced from 

conventional levels, and treated swaths are alternated with swaths 

that are not directly treated.

Rangeland—An area on which the vegetation consists of native or 

introduced grasses, legumes, grasslike plants, forbs, or shrubs, and 

that is developed for range (grazing) use. Also counted as rangeland is 

native pastures or meadows that are occasionally cut or mechanically 

harvested and are grazed by livestock.

Riparian Area—Land areas that are directly influenced by water. They 

usually have visible vegetative or physical characteristics reflecting 

this water influence. Stream sides, lake borders, or marshes are 

typical riparian areas.

Riparian Habitat—Those terrestrial areas where the vegetation 

complex and microclimatic conditions are products of the combined 

presence and influence of perennial or intermittent water, associated 

high water tables, and soils that exhibit some wetness characteristics. 

Includes riparian zones plus one-half the transition zone (or ecotone) 

between riparian zones and upland habitat.
S

Grasshopper Environmental Impact Statement 277

Runoff—That part of precipitation, as well as any other flow 

contributions, that appears in surface streams, either perennially or 

intermittently.

S

Shrubsteppe—A prairie ecosystem dominated by desert shrub 

vegetation.

Species—A fundamental taxonomic classification category, ranking 

after a genus and consisting of class or group with distinguishing 

characteristics and designated by a common name.

T

Threatened Species—Any species of animal or plant that is likely to 

become an endangered species throughout all or a significant portion 

of its range within the foreseeable future.

Toxicity—A characteristic of a substance that makes it poisonous.

Translocation—The transfer of substances from one location to 

another in the plant body.

U

Ultra-Low-Volume (ULV)—Sprays that are applied at 0.5 gallons or less 

per acre or sprays applied as the undiluted formulation.

Understory—Plants growing beneath the canopy of other plants. 

Usually refers to grasses, forbs, and low shrubs under a tree or brush 

canopy.

U.S.C.— United States Code.

U.S. Department of Agriculture (USDA) —The department in which 

the Animal and Plant Health Inspection Service and the Forest Service 

are located.
U

278 Grasshopper Environmental Impact Statement

U.S. Department of the Interior (DOI) — The department in which the 

Bureau of Indian Affairs, the Bureau of Land Management, and the 

Fish and Wildlife Service are located.

U.S. Department of Commerce (DOC)—The department in which the 

National Marine Fisheries Service is located.

U.S. Environmental Protection Agency (EPA)—The Federal agency 

that creates and enforces environmental regulations such as FIFRA.