Gypsy Moth Managementin the United States:a cooperative approach

Final

EnvironmentalImpactStatement

Summary

November 1995

United StatesDepartment ofAgriculture

Forest Service Animal and PlantHealth InspectionService

This is a summary of the final environmentalimpact statement. The complete final environmental impact statement is available, while

supplies last, from the USDA Forest Service,Northeastern Area State and Private Forestry, bycalling (610) 975-4150.

What is Being Proposedand Why

The Forest Service and Animal and Plant HealthInspection Service (APHIS) propose to adopt a newcomprehensive long-term national program to protectthe forests and trees of the United States from theadverse effects of the gypsy moth. Gypsy mothmanagement activities are conducted by theseagencies of the U.S. Department of Agriculture(USDA) under the authority of Federal laws.

The gypsy moth caterpillar disrupts people’slives, alters ecosystems, and destroys the beauty ofwoodlands by feeding on the foliage of trees, shrubs,and other plants. During outbreaks, when gypsymoth populations increase rapidly, caterpillars pose ahazard to human health and interfere with theenjoyment of hiking, camping, and other outdooractivities. Defoliation caused by the caterpillarsfeeding reduces the vigor and general health of forestsand shade trees, leads to tree death, alters wildlifehabitat, changes the quality and quantity of water,lowers property values, and reduces the economicvalue of timber.

Since its accidental introduction in easternMassachusetts in the late 1860’s, the European strainof the gypsy moth has been spreading. By 1994 it wasestablished as a permanent resident in all or parts of16 States (Connecticut, Delaware, Maine, Maryland,Massachusetts, Michigan, New Hampshire, NewJersey, New York, North Carolina, Ohio,Pennsylvania, Rhode Island, Vermont, Virginia, andWest Virginia) and the District of Columbia. Peoplealso spread the gypsy moth to areas of the countrywhere it is not established by unknowingly carrying

eggs, pupae, and caterpillars on recreational vehicles,campers, automobiles, nursery stock, logs, lumber,and outdoor household articles. This accidental spreadcan result in isolated infestations.

In 1991 the Asian strain of the gypsy moth wasdiscovered for the first time in the United States inOregon and Washington. It was traced to ships fromeastern Russian ports. Eradication in these States hasbeen achieved. In 1993 the Asian strain wasintroduced to North Carolina from a ship returningmilitary cargo from Germany. This introduction wastreated in 1994 and 1995, and is being monitored todetermine whether follow-up treatments will berequired. The Asian strain is of particular concernbecause it may spread faster than the European strain.Although both gypsy moth strains are the samespecies (Lyrnantria dispar), they have differentbehavioral characteristics. For example, some femalesof the Asian strain are known to fly up to 18 milesbefore depositing an egg mass, while females of theEuropean strain do not fly. The Asian strain also feedson a wider variety of trees and shrubs and may causemore damage than the European strain.

Six possible programs to protect the forests andtrees of the United States from the effects of thegypsy moth are being proposed. These programs

Even backyard trees are subject to gypsy moth feeding.

Gypsy Moth Life Cycle

Catepillar8 weeksduring springand earlysummer

Pupa2 weeks duringspring-summer

AdultSeveral daysduring summer

Egg Mass9 months,summer-spring

A young caterpillar isblack. As it matures,double rows of red andblue spots develop.Insecticides usually areapplied when foliageand caterpillars are atan early stage ofdevelopment.

The female pupa islarger than the male.Both are dark reddishbrown. Caterpillarspupate in protectedareas, and pupae canbe moved accidentallyby people.

The male adult is brownor gray and hasfeather-like antennae todetect the pheromoneemitted by the female,which is white withsmall black markings.

The female lays a buff-colored egg mass onalmost any object. Forthis reason andbecause the egg is thelongest lasting lifestage,it is most oftenmoved accidentally bypeople.

range from using no strategy to using one or morestrategies to reduce damage caused by outbreakswhere the gypsy moth is established (suppression),eliminate isolated infestations that are detected inother areas of the country (eradication), and slow theinsect’s rate of spread from the area where it isestablished (slow the spread).

No suppression, eradication, or slow-the-spreadprojects will be conducted as a direct result of thedecision on the environmental impact statement.Each decision to conduct a treatment project wouldbe made only after a site-specific environmentalanalysis of the treatment proposal has beenconducted. Project proposals will also be analyzedfor compliance with applicable Federal laws such asthe Endangered Species Act; Wilderness Act; Wild,Scenic, and Recreational Rivers Act; and NationalHistoric Preservation ACC and with presidential

executive orders concerning natural resource issues,such as environmental justi~e and floodplain andwetland protection; as well as any applicable Statelaws.

Proposed treatment projects will be analyzed onan individual basis to determine whether they areenvironmentally acceptable, biologically sound, andeconomically feasible. Suppression projects are oftencost efficient, depending on the resource manager’s orlandowner’s objectives and the values at risk. Benefitsof suppression include avoiding tree loss that wouldaffect recreation, property, watershed, wildlife habitat,or timber values. The greatest economic benefit oferadication is the absence of long-term suppressioncosts. A 1991 economic analysis indicated thatsignificant economic efficiency is possible with theslow-the-spread strategy.

Certain gypsy moth management activities areoutside the scope of this environmental impactstatement and, consequently, are not examined. Theseactivities include regulatory actions (such astreatment of quarantined items infested with gypsymoths), the boarding and inspection of ships enteringseaports, and research and methods developmentactivities carried out by the Forest Service andAPHIS, as well as actions against the gypsy moth byother agencies or individuals.

Parts of the EnvironmentThat May Be Affected

Within the United States all areas where thegypsy moth is established and could becomeestablished constitute the affected environment.Establishment of the gypsy moth in an area dependson the presence of shrubs and trees with leaves thatthe insect prefers to eat.

The foliage of hardwood trees, particularly ofoaks, is preferred by the gypsy moth. At risk fromdefoliation and damage are at least311 million acresof publicly and privately owned forests dominated by

Gypsy moth caterpillars feed on hundreds of tree species.

0 20 40 60 80 100 120 140

Millions of acres

Susceptible Forest Type Groups

Oak-hickory

Maple-beech-birch

Oak-gum-cypress

Oak-pine

Elm-ash-cottonwood

Aspen-birch

Western hardwoods

hardwoods. The Asian strain also feeds on coniferssuch as larch and Douglas-fir. Also at risk arecountless urban and rural forested areas throughoutthe country where plants susceptible to both gypsymoth strains grow naturally or have been planted,such as forested areas in cities, towns, andcommunities; greenways; parks; wildlife reserves;areas along streams and rivers; and small woodlots.

Strategies

The area of the United States where theEuropean strain of the gypsy moth is established iscalled the generally infested area. Next to this areais a band 50 to 100 miles wide, called the transitionarea, where the gypsy moth is spreading from thegenerally infested area. The area where the gypsymoth is not established, is called the uninfestedarea. Isolated infestations, the result of accidentalspread of the gypsy moth by people, are found in this Large numbers of caterpillars suddenly appear

during gypsy moth outbreaks.

area. Different management strategies apply in theseareas: suppression in the generally infested area, slowthe spread in the transition area, and eradication ofisolated infestations of the European strain in theuninfested area. In addition, the Asian strain maybeeradicated wherever feasible, including the generallyinfested area.

Suppression

The objective of suppression is to reduceoutbreak populations of gypsy moth caterpillars, thusminimizing heavy defoliation. Suppression does noteliminate the gypsy moth from the generally infestedarea, but reduces damage to ecosystems and effects onpeople in treated areas. Treatments available for usein suppression are application of the biologicalinsecticides Bacillus thuringiensis var. kurstaki andthe gypsy moth Nucleopolyhedrosis virus (Gypchek),and the chemical insecticide diflubenzuron.

Participation of State or other Federal agencies incooperative suppression projects is voluntary. Privatelandowners may participate by coordinating withState and local agencies.

Within the generally infested area, the U.S.Department of Agriculture would provide assistanceto cooperating Federal and State agencies forsuppression projects wherever gypsy moth outbreaksare likely to cause defoliation. Projects may beconducted in residential areas, recreation areas,uninhabited forests, and special-use areas such asscenic byways and watersheds.

Eradication

The objective of eradication is to eliminateisolated infestations of the gypsy moth that aredetected in the uninfested area of the United States, toprevent the insect from becoming established.Infestations of the European strain would beeliminated wherever they are detected in theuninfested area. In addition, infestations of the Asian

including the generally infested area when the time,location, and extent of the introduction can bedetermined or developed from deductive,circumstantial, or investigative information. Theobjective of treating infestations of the Asian strain inthe generally infested area is to eliminate all of thegypsy moths that exhibit traits characteristic of theAsian gypsy moth.

Treatments available for eradication areapplication of the biological insecticides Bacillusthuringiensis var. kurstaki and Gypchek the chemicalinsecticide diflubenzuron; as well as the use of masstrapping, mating disruption, and sterile insect release.The smaller the treatment area the more likely thatnoninsecticidal treatments can be used.

The most common cause of isolated infestationsis movement of outdoor household articles from thegenerally infested area to the uninfested area.Therefore, the most likely locations for future isolatedinfestations are wooded residential areas with highincidence of relocation by people. Sawmills,nurseries, mobile home parks, and tourist attractionssuch as campgrounds and State and National Parksare other likely locations for isolated infestations.

The U.S. Department of Agriculture does notrequire private landowners to participate ineradication projects. Participation is governed byState law and by the policies and regulations of thecooperating State agency. In some States,participation in eradication projects maybe

People unknowingly give gypsy moth a free ride.

mandatory. If it is determined that State actions areinadequate, the Secretary of Agriculture can declarean emergency and conduct an eradication project.

Slow the Spread

The objective of slow the spread is to slow therate of spread of the European strain of the gypsymoth from the generally infested area, to delay theimpacts and costs associated with gypsy mothoutbreaks. This strategy, which is being tested in apilot project, entails intensively surveying thetransition area and aggressively treating pockets oflow-level gypsy moth populations to keep them fromincreasing rapidly.

Treatments available for use in slow the spreadare application of the biological insecticides Bacillusthuringiensis var. kurstaki and Gypchek and thechemical insecticide diflubenzuron, as well as the useof mass trapping, mating disruption, and sterile insectrelease.

Alternatives Considered

The strategies of suppression, eradication, andslow the spread-or their absence—are the buildingblocks for six alternatives analyzed in theenvironmental impact statement:

Alternative 1. No suppression, no eradication, noslow the spread

Alternative 2. SuppressionAlternative 3. EradicationAlternative 4. Suppression and eradicationAlternative 5. Eradication and slow the spreadAlternative 6. Suppression, eradication, and slow

the spread (preferred alternative).

The alternatives describe how the U.S.Department of Agriculture could respond to the gypsymoth on State and private lands through Stateagencies, and on Federal lands through appropriateFederal land management agencies.

All alternatives have two elements in common:

• They offer USDA support for an integratedpest management approach to manage thegypsy moth in the United States.

• They include delivery of technical advice andsupport to State and Federal cooperators by theForest Service and APHIS.

Slow the spread involves intensive surveys to findthe gypsy moth.

No suppression,no eradication,no slow the spread

Alternative 1

The Alternatives

Alternative 3

Eradication

Alternative 5

EradicationSlow the Spread

Alternative 2

Suppression

SuppressionEradication

Alternative 5

Alternative 6 (Preferred)

SuppressionSlow the SpreadEradication

What Are People’sConcerns?

To learn the concerns of interested and affectedpeople across the country, the preparers of theenvironmental impact statement invited publiccomments for 120 days through a notice in theFederal Register, mailings, news releases, articles,and presentations to natural resource managers.

Most of the concerns that were within the scopeof the environmental impact statement were centeredaround the following issues:

1. How does the presence of the gypsy mothaffect people and the environment?

2. How do the insecticide treatments applied tothe gypsy moth affect people and theenvironment?

3. How do the noninsecticidal treatmentsapplied to the gypsy moth affect people andthe environment?

People’s concerns include spraying insecticides andlow flying aircraft.

A variety of specific concerns related to thegypsy moth was identified from more than 800 lettersreceived from the public. Specific concerns that arewithin the scope of the environmental impactstatement were analyzed. The following list of broadtopics by which the proposed alternatives could beevaluated and compared was developed:

Human health and safetySocial and economic characteristics

Perceptions and behaviorsEconomicsRecreation

Ecological characteristicsNontarget organismsForest conditionWater qualityMicroclimateSoil productivity and fertility.

What Would Be theConsequences of theAlternatives?

The alternatives were evaluated by comparingenvironmental consequences and how each alternativeaddressed these criteria:

• Meeting the USDA goal of reducing theadverse effects of the gypsy moth nationwideby protecting forests and trees

• Affording the U.S. Department of Agricultureflexibility in managing or assisting others inmanaging affected ecosystems.

• Estimated conditions throughout the UnitedStates by the year 2010 (conditions in 1994 areprovided for comparison-see box)

• How they respond to the three issues, that is,whether they pose risks to people or theenvironment from the gypsy moth,insecticides, or noninsecticidal treatments.

Conditions in 1994

Generally infested areaTotal size . . . . . . . . . . ...155,874,560 acresGypsy moth outbreaksand defoliation . . . . . . . . . 881,752 acresSuppression treatments. . .649,653 acres

Transition areaSlow-the-spread treatments. . .34,309 acres

Uninfested areaIsolated infestations. . . . . . . . . . 38 infestationsEradication treatments. . . . . .71,826 acres

Alternative 1.No Suppression, NoEradication, No Slow theSpread

Under alternative 1, the U.S. Department ofagriculture would do nothing to reduce the adverseeffects of the gypsy moth in the United States. Theeffects of implementing this alternative arise from thepresence of gypsy moth caterpillars and thedefoliation they cause. Because no strategies areavailable, natural resource professionals would havelittle flexibility to manage affected ecosystemsnationwide.

Caterpillar droppings are an unwanted addition toa picnic (Photo by Nate Bacon, photographer)

The generally infested area could grow to685million acres by 2010. Effects associated with thegypsy moth would be possible on 69 million of thoseacres.

In the transition area, the gypsy moth wouldcontinue to spread from the generally infested area. In2010, effects from the gypsy moth would be possibleon 5 million acres.

By 2010 additional areas within the uninfestedarea could become generally infested due to isolatedinfestations of the gypsy moth left untreated. Effectssimilar to those expected in the generally infestedarea could also occur on those acres. In 2010 alone,an estimated 76 new isolated infestations could occur.

Alternative 2. Suppression

Under alternative 2, the U.S. Department ofAgriculture would reduce the adverse effects of thegypsy moth only in the generally infested area.Flexibility to manage affected ecosystems would behigh in this area.

The generally infested area could grow to 685million acres by 2010. Gypsy moth outbreaks couldoccur on 69 million of those acres, and 12 millionacres likely would be treated with insecticides. Effectsassociated with insecticide treatments would bepossible in treated areas. Effects from the gypsy mothwould be possible on 57 million acres whereoutbreaks would probably not be treated.

In the transition area, the outlook would be thesame as under alternative 1.

By 2010 additional areas within the uninfestedarea could become generally infested due to isolatedinfestations of the gypsy moth left untreated. Effectssimilar to those expected in the generally infestedarea could also occur on those acres. In 2010 alone,76 new isolated infestations could occur.

Alternative 3. Eradication

Under alternative 3 the U.S. Department ofAgriculture would reduce the potential for adverseeffects of the gypsy moth in the uninfested area, andof the Asian strain anywhere in the United States.Flexibility to manage affected ecosystems would behigh in local areas with isolated infestations.

The generally infested area could grow to 305million acres by 2010. Effects associated with thegypsy moth would be possible on 14 million acres.

In the transition area, the gypsy moth wouldcontinue to spread. In 2010, effects from the gypsymoth would be possible on 500,000 acres.

In the uninfested area, all isolated infestationsfound since 1994 would have been eliminated.

There would be no effects from the gypsy moth inthe uninfested area. The 263 new isolated infestationsprojected for 2010 would be eradicated. Effects frominsecticide treatments could occur on 484,000 acres,and effects from noninsecticidal treatments would bepossible on 36,000 acres.

Alternative 4. Suppressionand Eradication

Alternative 4 represents no change from thecurrent gyps y moth program. The U.S. Department ofAgriculture would reduce the potential for adverseeffects of the gypsy moth in both the generallyinfested and uninfested areas, and of the Asian strainanywhere in the United States. With two strategiesavailable, flexibility to manage ecosystems would behigher than under alternatives 2 and 3.

The generally infested area could grow to 305million acres by 2010. Effects associated with thegypsy moth would be possible on 12 million acres.

Effects from insecticide treatments could occuron 2 million acres.

In the transition area, the outlook would be thesame as under alternative 3.

In the uninfested area, all isolated infestationsfound since 1994 would have been eliminated. Therewould be no effects from the gypsy moth in theuninfested area. The 263 new isolated infestationsprojected for 2010 would be eradicated. Effects frominsecticide treatments could occur on 484,000 acres,and effects from noninsecticidal treatments on36,000acres.

Alternative 5. Eradicationand Slow the Spread

Under alternative 5, the U.S. Department ofAgriculture would reduce the potential for adverseeffects of the gypsy moth in both the uninfested andtransition areas, and of the Asian strain anywhere inthe United States. With two strategies available,flexibility to manage ecosystems would be the sameas under alternative 4 and higher than underalternatives 2 and 3. To slow the spread of the gypsymoth from the generally infested area, pockets ofgypsy moths detected in the transition area could betreated with insecticides or noninsecticidaltreatments.

The generally infested area would grow to 204million to 271 million acres by 2010 depending on thesuccess of the slow-the-spread strategy. Effects fromthe gypsy moth could occur on 8 million to 12 millionof those acres.

In the transition area, slow-the-spread projectswould be conducted on 250,000 to 300,000 acres by2010. Effects from insecticide treatments could occuron 230,000 to 270,000 acres, and effects fromnoninsecticidal treatments would be possible on20,000 to 30,000 acres.

In the uninfested area, all isolated infestationsfound since 1994 would have been eliminated. Therewould be no effects from the gypsy moth in theuninfested area. In 2010, the number of isolatedinfestations would range from 284 to 324 dependingon the success of slow-the-spread projects.Eradication projects could result in effects frominsecticide treatments on 530,000 to 605,000 acres,and from noninsecticidal treatments on 40,000 to45,000 acres.

Alternative 6. Suppression,Eradication, and Slow theSpread

Under alternative 6 —the preferred alternative —the U.S. Department of Agriculture would fullypursue its goal of reducing adverse effects of thegypsy moth (including the Asian strain) anywhere inthe United States. A full range of strategies would beavailable, and flexibility to manage affectedecosystems would be high nationwide — higheroverall than under all other alternatives.

The generally infested area would grow to 204million to 271 million acres by 2010. Effects frominsecticide treatments would be possible on 1.0million to 2.0 million acres where gypsy mothoutbreaks would be suppressed. Effects from thegypsy moth would be possible on 7 million to 10million acres where outbreaks are not treated. Acresaffected would vary depending on the success of theslow-the-spread strategy.

In the transition area, the outlook would be thesame as under alternative 5.

In the uninfested area, all isolated infestationsfound since 1994 would have been eliminated. Therewould be no effects from the gypsy moth in theuninfested area. In 2010, 284 to 324 new isolatedinfestations could occur depending on the success ofthe slow-the-spread strategy. Effects from insecticidetreatments used in eradication projects could occur on530,000 to 605,000 acres, and from noninsecticidaltreatments on 40,000 to 45,000 acres.

Effects of the Gypsy Mothand Treatments

Effects associated with the gypsy moth andavailable treatments that could be used in the USDAgypsy moth program are described in general in thissection. Where the choice is made not to treat thegypsy moth, effects would be from the insect. In someparts of the generally infested area, gypsy mothpopulations will be too low to affect people or theenvironment.

Risk assessments were prepared to logically andscientifically examine how the gypsy moth,

insecticide treatments, and noninsecticidal treatmentsaffect human health and the environment.

How People May BeAffected by the Gypsy Moth

After being exposed to young caterpillars duringmoderate or heavy gypsy moth outbreaks, childrenand others who spend a lot of time outside maydevelop rashes or other skin irritation. Irritation to theeyes or respiratory tract is also possible. Someindividuals may develop an allergy to the gypsy mothafter repeated exposures over one or more years.

Insecticide treatment

Strategies and treatment options available under the alternatives

Alternative and strategy 1

Noninsecticide treatment

Treatment 2

options1 2 3 4 5 6

Bacillus thuringiensisvar. kurstaki

Diflubenzuron

Gypsy moth virus

Masstrapping

Matingdisruption

Sterile insectrelease

S E E STS S E STS

1 S = suppression strategy: Reduce damage caused by the gypsy moth in the generally infested area E = eradication strategy: Prevent establishment of isolated infestations of the gypsy moth STS = slow the spread strategy: Slow the spread of the gypsy moth in the transition area2 No treatment is an option in all the alternatives

S E

On rare occasions gypsy moth outbreaks cancreate a safety hazard, as caterpillars and theirdroppings can make roads and walkways slippery.Falling limbs can pose a hazard when trees die as aresult of defoliation.

Infestations that are particularly bothersome topeople or have a significant adverse effect on estheticvalues can induce stress in some individuals.

Because some people will spend less time inoutdoor activities to avoid contact with the gypsy

Contact with caterpillars may cause a rash. (Photo byNate Bacon, photographer)

moth, and repeated heavy defoliation can change thecharacter of an area, recreation and tourismbusinesses may suffer. Economic losses can alsoresult from the damage to trees on woodlots andsubsequent reduction in property values.

Property owners may incur costs for treating thegypsy moth, removing caterpillars or their droppings,removing or scraping egg masses, repaintingbuildings, pruning or removing trees, and replacingdamaged or dead trees and shrubs.

Homewowners are faced with cleanup after anoutbreak.

How the Environment MayBe Affected by the GypsyMoth

Ecological effects from the gypsy moth varydepending on population levels, the amount ofdefoliation, and the duration of an outbreak.Defoliation is light (less than 30 percent) when gypsymoth populations are at low levels. Defoliation ismoderate (30-60 percent) or heavy (more than 60percent) during population outbreaks, which may lastfor 1 to 3 years. Effects are noticeable after moderateand heavy defoliation.

Low Populations and Light Defoliation

In the absence of outbreaks, as gypsy mothpopulations build, the numbers of certain naturalenemies of the insect, such as the gypsy moth virus,parasites, and disease-causing fungi may increase.

Moderate Outbreaks and Defoliation

Nontarget Organisms

Changes in populations of nontarget organismsmay occur as a result of changes in habitat andavailability of food after moderate defoliation. Short-lived changes may include increases in gypsy mothparasites and in numbers and types of birds.Populations of some bird species, such as flycatchers,may decline, as may those of gray squirrel andvarious amphibians. Increases in water temperaturecould cause short-term increases in aquatic insects,but the habitat quality of some marginal trout streamsmay decline. Numbers and types of other insects maydecrease.

Long-term changes—after two or threeconsecutive years of moderate defoliation—mayinclude an increase or decrease in numbers of graysquirrel and white-footed mouse, depending onlongterm survival rates of trees and the capacity ofdominant oaks to produce acorns. Numbers ofnongame bird species may increase, but neotropicalmigrants may not be affected. Salamander populationsshould benefit from increases in dead and downbranches and trees. The numbers and types ofpollinators and other insects may increase in responseto greater variety within the plant community.

Forest Condition

Short-term impacts of moderate defoliation onforest condition may be slight. Tree health may beginto deteriorate, growth of wood in susceptible treesmay decline, and growth of vegetation beneath thetree canopy may increase. After 2 years of defoliation,oaks may begin to produce fewer acorns (hard mast),a situation that can persist for as long as 5 years.Production of berries and other fruit (soft mast) couldincrease should shrubs and herbaceous plantsincrease. If an outbreak continues for a third year, theabundance of organisms that attack weakened trees,such as shoestring fungus and two-lined chestnutborer, increases.

Oak trees may produce no new acorns the year ofheavy defoliation.

In the long term, after two or more years ofmoderate defoliation, some of the shortersubdominant trees may die, resulting in a moreonestoried forest. Tree species favored by the gypsymoth will probably decline and less-favored specieswill thrive. The growth of species that do well inshade, such as red maple, will accelerate. In survivingdominant oaks, the production of acorns eventuallywill return to predefoliation levels. The forest as awhole will probably become less susceptible tofeeding by the gypsy moth. .

Water Quality

Slight short-term increases in water temperatureand water yield, as well as decreases in dissolvedoxygen, may result from moderate defoliation.

Long-term effects should be few. Sustainedmoderate outbreaks could result in a seasonal increasein water temperature—for a decade or more—in smallstreams bordered by susceptible vegetation.

Microclimate, and Soil Productivity and Fertility

Moderate defoliation may cause an increase inthe seasonal temperature of soil and leaf litter, andincreased exposure to sunlight, resulting in shorttermincreases in biological productivity on the forest floor.

Heavy Outbreaks and Defoliation

Nontarget Organisms

Short- and long-term effects of heavy but notcomplete defoliation on nontarget organisms willprobably be similar to those of several years ofmoderate defoliation. Even 1 year of completedefoliation, however, will have dramatic effects oncaterpillars of moths and butterflies, which couldsuffer large-scale starvation.

Short-term impacts of two or more years ofheavy defoliation can be dramatic. The numbers of

Trees killed as a result of defoliation provide nestand den sites.

gray squirrel are likely to decline, as are those ofsome bird species, though woodpecker populationsmay increase. Populations of small mammals andamphibians such as salamanders will probablydecline, as may those of the timber rattlesnake. Troutmay decline or disappear from small streams, alongwith small crayfish and snails. Forest-feeding mothsand butterflies-particularly those that feed on oaks—and their parasites (and perhaps their predators) alsoare likely to decline, as may other forest-dwellinginvertebrates. Natural enemies of the gypsy moth mayincrease significantly. White-tailed deer will probablymigrate to undefoliated areas, and nesting failures ofgrouse and turkey may increase. Bear, turkey, and batsmay migrate to undefoliated or less defoliated areas.

In the long term, populations of gray squirrel andpossibly trout might be reduced or eliminated fromdefoliated areas for years due to changes in habitat.Other nontarget organisms will increase or remain atpredefoliation levels. Species that will increaseinclude those that do not require a closed canopy andmultistoried forest and those that associate withherbaceous plants and woody brush. Standing deadtrees will provide cavity nests and den sites foranimals, and dead and down trees will provide densites and habitat for a variety of animals. In streams,logs and debris will improve habitat conditions forsome species of fish and aquatic insects.

Forest Condition

The condition of trees in the forest canopy will bedegraded and mortality rates will increase even afteronly 1 year of heavy defoliation. Production of bothwood and hard mast (nuts and seeds) will declinetemporarily. The growth rate of many shrubs andherbaceous plants may increase.

Short-Term Changes—After 2 years of heavydefoliation, the production of wood, and hard and softmast will be greatly reduced. Shoestring fungus andtwolined chestnut borer, which attack and kill treesweakened by defoliation, will become more abundant.Mortality is likely within 5 years, both among oaksand among species that are less favored by the gypsymoth. After 3 years of heavy defoliation, mortalitywill be high in oaks and less favored hosts. Thegrowth of wood will be drastically reduced, andproduction of hard mast will probably cease for atleast 5 years. Shrubs and herbaceous plants, such asraspberry and sweetfern, will increase dramatically.

Long-Term Changes—After 1 year of heavydefoliation, many subdominant trees will be removedin the long term, but few other effects will likely beapparent. After 2 years of heavy defoliation, stands oftrees will become one-storied; however, survivingtrees will recover, growing at an accelerated rate and

Bats may move from defoliated areas. (Photo byCraig Stihler, West Virginia Division of NaturalResources)

Repeated defoliation reduces a tree’s ability to growand maintain a healthy condition.

producing mast crops. Shrub cover will increase, aswill red maple and other species that grow well inshade.

After three successive years of heavy defoliationon poor growth sites, many or most of the overstorytrees will die, and sites will revert to plants such asblueberry, sweetfern, and raspberry. Regeneration toyoung forests will take decades. In areas where treesless favored by the gypsy moth remain, stands will bedominated by species such as red maple and yellow orblack birch. If dead trees are not removed, the firehazard will increase. The resulting forest, particularlyon better sites, will be less susceptible to future gypsymoth outbreaks.

Water Quality

After heavy defoliation of trees along smallstreams, a short-term increase in water temperature islikely. Decomposition of leaf fragments andcaterpillar droppings in these small streams couldreduce oxygen levels and result in dramatic increasesin algae. The capacity to neutralize acids could bereduced in some upland streams. Watershed yieldswill increase.

In the long term, these same changes inwaterconditions may persist for years, though wateryields should return to predefoliation levels.

Microclimate, and Soil Productivity and Fertility

After heavy defoliation, increased exposure tosunlight will cause seasonal elevations in thetemperature of soil and leaf litter. Soil moisturecontent may increase temporarily. These factors couldresult in increased rates of soil decomposition,mineralization, and plant productivity. Such changesshould be short-lived.

Effects Associated WithInsecticide Treatments

Treatments available for use under all strategiesin all parts of the country are formulations of thebiological insecticides Bacillus thuringiensis var.kurstaki and the gypsy moth Nucleopolyhedrosisvirus product Gypchek, and the chemical insecticidediflubenzuron.

Bacillus thuringiensis var.kurstaki

Bacillus thuringiensis var. kurstaki (B.t.k.), abacterium that has insecticidal activity againstcaterpillars of moths and butterflies, is a variety ofBacillus thuringiensis (B.t.).

How People May Be Affected by B.t.k.

If directly exposed to B.t.k. spray, someindividuals (most likely project workers) maydevelop minor irritation of the skin, eyes, orrespiratory tract. These effects are relatively mild andtransient. Pathogenic effects are not likely, even inindividuals with impaired immune systems. Allergicresponses to B.t.k, are conceivable, but have not beendocumented.

The two-lined chestnut borer can kill treesweakened by defoliation.

How the Environment May Be Affected byB.t.k.

Due to the relatively short insecticidal activity ofB.t.k., the risks associated with its use are usuallylimited to the time immediately after application.

Nontarget Organisms

Some spring-feeding caterpillars of moths andbutterflies will be adversely affected by exposure toB.t.k. Large caterpillars eat more vegetation thansmall ones and are more likely to consume B.t.k. Thepotential for exposure to B.t.k. and mortality increaseswith an increase in the application rate and greaterheight in the tree canopy, because most B.t.k. spray isdeposited in the tops of trees. B.t.k. poses a riskprimarily to caterpillars present in spring because it isapplied at that time and has relatively shortinsecticidal activity. Not all of these caterpillars maybe affected due to wide differences in response toB.t.k. among species. Total numbers of moths andbutterflies maybe temporarily reduced. Some speciesappear to be particularly susceptible to B.t.k. andpopulations maybe eliminated from treatment areas.

Permanent changes in nontarget caterpillarpopulations are not likely following suppressionprojects, which usually consist of a single applicationof B.t.k. An exception might occur in certain habitattypes that support small isolated populations of mothsand butterflies that are highly susceptible to B.t.k. Ifunaffected individuals of the same species areunlikely to or cannot physically migrate fromuntreated areas to the treated area, a single applicationof B.t.k. may have a greater effect on the ability ofthose populations to recover.

Data are sparse on the effects of multiple B.t.k.applications in one year and sequential yearlyapplications commonly used in eradication projects. Itis reasonable to expect, however, that both thenumbers and types of nontarget caterpillars maybereduced after multiple applications of B.t.k., and thatthese effects could persist for 1 year or longer.Additional studies on this topic would help to betterquantify the effects on nontarget caterpillars.

The predominant effect of B.t.k. on someparasites of caterpillars is indirect through effects ontheir hosts. Caterpillars that are exposed to B.t.k. butdo not die eat less, grow more slowly, and remainlonger in the larval stage, increasing theirsusceptibility to parasites. Parasitism of the gypsymoth by at least two parasitic wasps increases in areassprayed with B.t.k. Few other species or groups areaffected.

Vertebrates that feed on caterpillars in spring willhave a reduced number of prey on which to feed forseveral weeks. Reductions in caterpillar numbers fromapplication of B.t.k. may force a switch in diet forbirds and mammals that eat them. In birds, thenumber of nesting attempts per year maybe reduced,but the overall number of fledglings per breedingterritory may not change. Bats that feed onnightflying moths in summer may have to expandtheir foraging territories and adjust their foraginghabits temporarily.

Use of B.t.k. reduces the incidence of infection bythe Nucleopolyhedrosis virus in gypsy mothpopulations. B.t.k. reduces both the number of earlystage caterpillars available for infection by the virusand the amount of virus released that can infect theresidual gypsy moth population.

The red-eyed vireo eats all life stages of the gypsymoth.

Forest Condition

B.t.k. reduces defoliation caused by somespringfeeding caterpillars. As a result, its use is likelyto maintain the forest condition.

Water Quality and Microclimate

By protecting tree foliage, B.t.k. reduces thelikelihood of changes in water quality andmicroclimate that might be associated with feeding bygypsy moth caterpillars.

Soil Productivity and Fertility

Changes in soil productivity and fertility due toB.t.k. are not likely. B.t.k. persists for a relativelyshort time, B t. is known to occur naturally in soilsworldwide, and applications of insecticidescontaining B.t. do not appear to increase levels of B.t.in soil. Some soil invertebrates maybe affected byB.t.k., but additional research is needed to determinewhat effects, if any, this might have on rates of soildecomposition.

Diflubenzuron

Diflubenzuron (Dimilin), a chemical insecticide,interferes with the growth of some immature insects.

How People May Be Affected byDiflubenzuron

No human health effects are likely from exposureto diflubenzuron as it is used in gypsy moth projects.At very high exposures, increases in methemoglobin,an abnormal blood pigment that reduces the oxygen-carrying capacity of the blood, might be detectable. Ifother compounds that raise levels of methemoglobin-cigarette or other combustion smoke, carbonmonoxide, nitrates in air or water— are present, theeffect may be additive.

A conservative estimate of cancer risk fromexposure to diflubenzuron or 4-chloroaniline, abreakdown product of diflubenzuron, is less than onein 1 million over a lifetime.

How the Environment May Be Affected byDiflubenzuron

Diflubenzuron is persistent on vegetationthroughout the growing season and may remain in leaflitter at least 1 year after spraying.

Nontarget Organisms

Moth and butterfly caterpillars, grasshoppers andother leaf- and litter-eating immature arthropods,parasitic wasps, some beetles, spiders, sawflies,aquatic insects, bottom-dwelling crustaceans, andimmature free-floating crustaceans could be adverselyaffected from the lowest application rate ofdiflubenzuron used in gypsy moth treatment projects(0.25 oz active ingredient per acre). Higherapplication rates reduce populations even more andaffect more types of species groups. More aquaticorganisms could be affected at the highest applicationrate registered for use (1.0 oz active ingredient peracre).

Terrestrial Organisms—Moths, butterflies, andgrasshoppers may be affected in both the upper andlower tree canopy in spring and fall. Mostdiflubenzuron spray is deposited in the upper canopy,

Aerial application of diflubenzuron may be used insuppression, eradicationn, or slow the spread.

and the amount of diflubenzuron residue begins todiminish after spraying in spring. As a result, thepopulation reduction is greater for species that feed inthe upper canopy.

Because diflubenzuron can kill caterpillars thatserve as hosts, parasitic wasps of caterpillars maybeindirectly affected. Diflubenzuron can have differenteffects on different species of parasites of nontargetinsects. Of predators that eat prey contaminated withdiflubenzuron, more of those in immature stages, suchas lacewings, die than do adults. In some groups suchas ladybird beetles, the adults may produce feweroffspring.

Ground spiders could be directly affected bydiflubenzuron applications or indirectly by areduction in prey. Overall species diversity wouldremain unchanged.

Vertebrates, adult beetles, and earthworms are notlikely to die from exposure to diflubenzuron.

Birds are not directly affected by exposure todiflubenzuron. Some insectivorous species may showsubtle changes, such as a switch in diet, reduced fatloads, and expanded foraging territories. Similarchanges may occur in bats that feed primarily onmoths and butterflies.

Aquatic Organisms—Aquatic organisms may beaffected by diflubenzuron treatments in bothundeveloped forest areas and developed residentialareas. Aquatic organisms that eat fallen leaves will beaffected by diflubenzuron that coats leaves thatl enterstreams in autumn. Bottom-dwelling insects may beaffected in all habitats except ponds in undevelopedforest areas, which have the lowest concentrations ofdiflubenzuron. Free-floating crustaceans may be lessaffected in undeveloped areas. Mollusks do not appearto be at risk.

Fish are not likely to be directly affected fromexposure to diflubenzuron as it is used in gypsy mothprojects. Fish could suffer indirect effects through areduction in prey but would likely compensate for thisby eating other organisms.

Multiple Applications and Recolonization—The effects on most organisms from exposure todiflubenzuron applied 1 to 2 weeks apart, as ineradication projects, would be similar to onetreatment at twice the application rate. Consecutiveannual applications of diflubenzuron may affectinvertebrates in leaf litter more than would a singleapplication, because some diflubenzuron residueswould persist into the following spring when the nexttreatment would be applied.

Some generalizations can be made about the riskof eliminating nontarget invertebrates from an areatreated with diflubenzuron:

• Susceptible invertebrates that produce morethan one generation per year and are exposedto persistent diflubenzuron (for example, onleaves or in leaf litter) are more likely to beaffected severely than similar organisms thatproduce a single generation per year.

• Invertebrates that disperse rapidly or in largenumbers will be able to recolonize treatedareas.

• Invertebrates whose populations are severelyreduced by diflubenzuron and have lowdispersal rates will be affected for the longestperiod.

Fish are not likely to be affected by exposure todiflubenzuron as used in gypsy moth projects.

• Low dispersal capabilities of invertebrates,treatment of a large area, and frequentretreatment of an area will hinder the recoveryof invertebrate populations.

Forest Condition

Diflubenzuron is not poisonous to plants and hasno direct effect on them. Diflubenzuron mayindirectly help maintain existing forest condition byreducing gypsy moth populations and protecting treefoliage.

Water Quality

Diflubenzuron may reduce numbers of twogroups of stream invertebrates: those that processparticulate organic matter from plant and animalremains, and those that feed on algae. Changes inwater quality due to reductions of organisms in thesegroups, however, have not been observed.

Microclimate

Diflubenzuron indirectly helps maintain theexisting microclimate by reducing the amount ofdefoliation by the gypsy moth and other insectdefoliators.

Soil Productivity and Fertility

Earthworms are not at risk from diflubenzuron.Other invertebrates in leaf litter, particularly mitesand ground dwelling spiders, may be affected byexposure to diflubenzuron, but decomposition rates ofleaf litter do not seem to be affected.

Nucleopolyhedrosis Virus(Gypchek)

The Nucleopolyhedrosis virus, which occursnaturally, is specific to the gypsy moth. Gypchek is aninsecticide product made from the gypsy mothNucleopolyhedrosis virus.

How People May Be Affected by Gypchek

Irritation of the eyes, skin, and respiratory tract ispossible from exposure to Gypchek, but thispossibility cannot be assessed due to limitations in theavailable data. Because Gypchek contains gypsy mothparts, irritant effects might be similar to those causedby the gypsy moth itself. Individuals with allergiesmay be at greater risk of developing irritation.Workers are more likely to be affected than thegeneral public because their exposure will be higher.

Caterpillars killed by the nucleopolyhedrosis virusappear wilted and shiny, and often hang limply inan inverted “v” position.

How the Environment May Be Affected byGypchek

The gypsy moth virus is not known to directlyaffect organisms other than the gypsy moth, and nochange in nontarget species or their populations islikely from the use of Gypchek. Gypsy mothparasitoids may be indirectly affected by loss of theirhost.

Changes in forest condition, water quality,microclimate, and soil productivity and fertility fromthe use of Gypchek will be minimal compared withthose that otherwise would occur from feeding by thegypsy moth.

Effects Associated WithNoninsecticidalTreatments

Noninsecticidal treatments available for use inslow-the-spread projects (in the transition area) anderadication projects (primarily in the uninfested area)are mass trapping, mating disruption, and sterileinsect release.

Mass Trapping

Mass trapping entails the deployment of largenumbers of male moth traps in the treatment area.The purpose is to attract male gypsy moths into thetraps and thereby prevent them from mating withfemale moths. The effect is population reduction andeventual elimination of the infestation.

Two types of traps could be used in masstrapping. Both contain a minute amount of disparlure,a synthetic version of the sex-attractant produced byfemale gypsy moths to attract male moths. Thesmaller delta trap has a sticky inside surface fortrapping moths. The larger milk-carton trap contains a

pest strip impregnated with the insecticide DDVP (2,2dichloroethenyl dimethyl ester phosphoric acid), alsocalled dichlorvos. To date only the delta trap, whichcontains no insecticide, has been used in masstrapping. It is possible, however, that the milk cartontrap would be effective for mass trapping in thetransition area because of its larger capacity. Milkcarton traps are commonly used for survey purposesin the transition area and where the estimated numberof male moths that would be caught exceeds thecapacity of the delta trap.

How People May Be Affected by MassTrapping

The insecticide DDVP as used in milk cartontraps would pose more than a negligible health risk tohumans only if an individual were to disassemble atrap and tamper with the DDVP-impregnated strip.Skin contact with the strip or eating the strip couldinhibit the production of acetylcholinesterase. Thisenzyme prevents the accumulation of acetylcholine,the buildup of which can impair the function of thenervous system. Obvious signs of toxicity to thenervous system are possible but unlikely. Exposure toother substances that inhibit acetylcholinesterase,including similar insecticides, could have an additiveeffect with DDVP. The cancer risk from eating thestrip or from skin contact with it is about one in 1million over a lifetime.

Milk carton traps contain the insecticide DDVP(dichlorvos).

The use of the smaller delta trap (which containsno insecticide) poses no known risks to people.

How the Environment May Be Affected byMass Trapping

Invertebrates that inadvertently enter delta ormilk carton traps are likely to die. Invertebrates thatcome into contact with a DDVP strip that hasaccidentally fallen on the ground, vegetation, or inwater might also be adversely affected. The potentialfor adverse effects decreases over time as DDVPdissipates from the strip. Large animals, such asbears, that may tamper with traps are not likely to beaffected by DDVP strips.

Mass trapping using either type of trap is notlikely to cause changes in forest condition, waterquality, microclimate, or soil productivity andfertility.

Mating Disruption

Mating disruption entails the aerial application oftiny plastic flakes or beads that contain disparlure, thesynthetic version of the gypsy moth sex attractant.The effect is to confuse male moths and prevent themfrom locating and mating with females.

How People May Be Affected by MatingDisruption

By analogy to other insect pheromones, the riskof toxic effects from exposure to disparlure isbelieved to be slight. After direct contact withdisparlure, a person (most commonly a projectworker) may attract male gypsy moths. Although thisattraction may last for years, and could be annoyingand particularly stressful for individuals with anaversion to insects, it is not known to pose a healthrisk. The general public is not likely to be exposed tosufficient amounts of disparlure to experience thisrare effect.

How the Environment May Be Affected byMating Disruption

Disparlure has low toxicity to vertebrates and isspecific to the gypsy moth. As used in matingdisruption (and as an attractant in mass trapping),disparlure is not likely to cause changes in nontargetorganisms, forest condition, water quality,microclimate, or soil productivity and fertility.

Sterile Insect Release

The purpose of sterile insect release is to addlarge numbers of sterile gypsy moth adults to atreatment area. The sterile adults will mate withfertile adults. The effect is population reduction andeventual elimination of the infestation. This techniquecan include the release of male pupae that weresterilized by a dose of radiation, male pupae

Female gypsy moths produce a chemical to attractmales.

that have been irradiated but not sterilized, or eggmasses that were produced from mating of irradiatedmales with nonirradiated females.

How People May Be Affected by Sterile InsectRelease

Because this treatment increases the number ofgypsy moths in the treatment area, it could increaseboth the chance of effects from the gypsy moth andcontact with gypsy moth caterpillars.

How the Environment May Be Affected bySterile Insect Release

Effects from releasing sterile male pupae occuronly in the year of treatment, while the effects fromreleasing irradiated male pupae or egg masses from anirradiated parent occur over 2 years.

Release of egg masses could add enough gypsymoth caterpillars to the treatment area to cause lightdefoliation in the year of release. Effects from thisdefoliation would be negligible.

None of the three release approaches has anyknown effect on other organisms, or on forestcondition, water quality, microclimate, or soilproductivity and fertility.

Mitigating AdverseEffects

In some cases, different treatments can be used toavoid possible adverse effects. When the use of analternate treatment is not possible on a treatment site,effects may be lessened and sometimes avoided byusing mitigating measures.

For example, applying insecticides when weatherconditions favor spray deposition and establishing anuntreated buffer zone around a treatment site canprevent the drift of insecticide spray into a habitat ofspecial concern, for example, a body of water or anorganic farm.

Informing the public about treatment projects canhelp avoid inaccurate perceptions and reduce anxiety.Notifying people of the insecticide applicationschedule allows those who live in treatment areas or

Balloons may be used to mark locations were sensitivespecies exist and that are off-limits to treatment

Sterile insect release often involves pupae.

who use recreation areas to plan their activities so thatexposure can be avoided.

Mitigating measures are largely project-specificand are developed on a site-by-site basis duringenvironmental analyses conducted for each proposedtreatment project.

Public InvolvementImproves theEnvironmental ImpactStatement

In April 1995 the Forest Service and APHISpublished a draft environmental impact statement andasked the interested public to review and comment onit. A public outreach effort was conducted through the

use of direct mail, newspapers, magazines,newsletters, radio, and the Internet, and in response146 letters were received.

The comments were analyzed and addressed inthe final environmental impact statement. Thecomments indicated that no significant changes to thedocument were needed, and provided information thatresulted innumerous improvements.

This summary is volume one of the five volumefinal environmental impact statement. To obtain thecomplete document, please contact the USDA ForestService at (610) 975-4150.