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Forest & Disease Leaflet 162 April 2020

U.S. Department of • Forest Service Gypsy Tom W. Coleman1, Laurel J. Haavik 2, Chris Foelker3, and Andrew M. Liebhold 4 Gypsy moth, forest composition toward dispar (Linnaeus) (: dominance by immune host species. ), is an exotic introduced from Europe Several related moth species, that is spreading south and west in including L. albescens, L. mathura, North America. In spring and early L. monacha, L. postalba, L. summer, gypsy moth umbrosa, and two other subspecies feed on the of many different of gypsy moth, L. dispar asiatica tree species, especially . During and L. dispar japonica, the outbreaks, caterpillars defoliate Asian gypsy moth, do not have entire forests. Most broadleaf trees established populations in North produce new foliage in response America. Of these, Asian gypsy to defoliation >50%, allowing moth subspecies, L. dispar asiatica them to resume photosynthesis. and L. dispar japonica, have been Defoliation weakens trees, which the most frequently intercepted renders them more susceptible to and accidentally introduced secondary mortality agents. Gypsy subspecies in North America. moth can also directly kill trees, Asian gypsy moth surveillance and especially if severe defoliation eradication have been particularly persists for multiple successive critical because these subspecies seasons. In some years, outbreaks have broader host ranges than can be massive with defoliation their European counterpart, and exceeding several million acres. unlike the European subspecies, If extensive tree mortality occurs, females are capable of flight. outbreaks can contribute to shifts in

1 USDA Forest Service, Forest Health Protection, Asheville, NC 2 USDA Forest Service, Forest Health Protection, Missoula, MT 3 Wisconsin Department of Agriculture, Trade, and Consumer Protection, Madison, WI 4 USDA Forest Service, Northeastern Research Station, Morgantown, WV Identification seek sheltered areas to rest and From fall through early spring, ultimately pupate. Pupae are dark gypsy moth exists as eggs in brown brown and affixed with silken to cream-colored hairy masses thread to trees, rocks, and other (approximately 1.5 inches long structures (Figure 1.B). Pupal cases and 0.75 inches wide) located on and old egg masses can remain on tree trunks and large branches or trees and other surfaces long after other objects such as rocks, logs, the have emerged. Adult homes, motor vehicles, and outdoor moths appear from early June to furniture (Figure 1). In spring, early October throughout its current young caterpillars hatching from range, and are sexually dimorphic. egg masses first appear dark and Males are mottled brown in color hairy, then develop characteristic with feathery antennae and black markings on their dorsal (upper) wing markings, whereas females surface as they increase in size (five are white or cream-colored with and six pairs of raised blue and distinct black markings on the red spots, respectively, Figure 2). wings and thin, wire-like antennae Mature caterpillars can range from (Figure 3). Females are larger than 1.5 to 2.5 inches long and frequently males with a wingspan of about 2.5

Table 1. Approximate seasonal occurrence of gypsy moth life stages in the established areas of North America (A) and approximate timing of various monitoring methods (B) and suppression techniques (C).

Month A. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Eggs Caterpillars Pupae Adults B. Egg mass surveys Pheromone trapping C. var. kurstaki (Btk) Nucleopolyhedrosis virus (NPV) Tebufenozide Broad spectrum Mating disruption

2 Figure 1 (left). A high density of gypsy moth egg masses laid at the base of a tree (A) and laid under a human-made structure (trailhead sign) (B). Old pupal cases secured with webbing can be seen near the egg masses under the shelter in the second photo.

Figure 2 (below). Newly hatched first instar caterpillars resting on their egg mass (A). A dark-colored second-instar (B) lacks the distinct red- and blue-colored markings possessed by fourth-, fifth- and sixth-instar caterpillars (C).

3 caterpillars are strongly photo- positive and crawl upward; some spin downward on long silken threads and disperse as their silken thread carries them on the wind. This behavior is called ballooning, and typically transports caterpillars for short distances (less than a mile), but sometimes further on strong wind currents. Young caterpillars chew holes in leaves in the upper canopy during the day and rest at night on foliage. Older caterpillars consume all tissue aside from the midrib (Figure 4.A), and actively feed at night, crawling downwards to protected resting sites Figure 3. Adult female gypsy moths lay eggs on the bark on or near the base of trees surface or in crevices. Note the brown to cream coloring of the egg mass under each female and at the bottom of during the day. A significant the image. Brown-colored male moths can be seen mating fraction of late-instar larvae with the white-colored females on the stem of a tree (inset). Female and male moths can lose their coloration on their crawl to the forest floor, forewings, as seen in the main image of the females, as resting under objects such as they and become more drab-colored. rocks, stumps, and logs, and inches, compared to the 1.5 inch may crawl up a different tree the wingspan of males. Though they next morning. During outbreaks, have wings, females do not fly. caterpillars will feed throughout the day because of the competition for Life History declining foliage. In early summer, Gypsy moth has one generation per gypsy moths enter the pupal stage year and the seasonal timing of its for one to two weeks, typically life cycle can vary across its wide located in their last larval resting range in North America depending site. These resting sites (Figure on climate (Table 1.A). Eggs hatch 1.B) are generally in branch and in early spring (Figure 2.A) in bark crevices and under rocks synchrony with the bursting of tree and human-made structures, but leaf buds. Caterpillars grow 1,000- during outbreaks, when caterpillar fold in weight as they progress densities are high, pupation may through five (males) or six (females) occur anywhere. Adults emerge larval instars (stages) during their from pupal cases in mid-summer six to eight week development and are active for one to seven days. period. After hatching, first-instar Males detect the female-produced 4 [(+)-disparlure] to to feed on the foliage of hundreds locate females and mate. Male adult of different tree and shrub species. gypsy moths are diurnal (daytime) Nevertheless, within North flyers and have a distinct erratic America, there is considerable flight pattern. Flightless females variation in suitability among tree lay eggs near where they pupated. species, which can be classified as In mid- to late summer, females lay susceptible, resistant, or immune 100-1,000 eggs in a brown to cream- (Table 2). Susceptible tree species colored hairy mass on tree trunks, are those which caterpillars are or on other objects. Gypsy moth capable of feeding on from the overwinters as a fully developed first instar through completion within the egg (embryos of larval development. Typical develop into larvae in four to six North American susceptible weeks but remain in the eggs over species include oaks, aspen, apple, winter). Dense hairs, the red and willow, basswood, hawthorns, and blue coloration on caterpillars, lack some birches and alders. During of web- or tent-building, and feeding outbreaks, susceptible species primarily during the early growing are generally the most heavily season can distinguish gypsy moth defoliated in mixed stands. Feeding larvae from other leaf-feeding forest by early instar larvae does not occur pests in the eastern USA, such on species classified as resistant; as tent caterpillars, spanworms, most feeding on resistant species is cankerworms, and webworms. only by late instar larvae and these hosts are generally only utilized Hosts once larvae have depleted most Gypsy moth caterpillars are known of the foliage of susceptible trees.

Table 2. Tree and shrub species susceptible, resistant, and immune to gypsy moth feeding in the USA. This is not a complete list of host genera and species for gypsy moth. Susceptible Resistant Immune alder, Alnus spp. beech, Fagus spp. arborvitae, Thuja spp. apple, Malus spp. dogwood, Cornus spp. ash, spp. aspen and poplars, spp. , Ulmus spp. black cherry, serotina basswood, Tilia spp. hemlock, Tsuga spp. fir, Abies spp. paper birch, Betula papyrifera hickory, Carya spp. , Ilex spp. hawthorn, Crataegus spp. , Acer spp. , Juniperus spp. hazelnut, Corylus spp. , Pinus spp. locust, Robinia spp. larch, Larix spp. Prunus spp. redbud, Cercis spp. mountain-ash, spp. serviceberry, Amelanchier spp. sumac, Rhus spp. , Quercus spp. spruce, Picea spp. , Platanus spp. willow, Salix spp. Viburnum spp. poplar, witch-, Hamamelis spp. walnut, Juglans spp. , Nyssa spp. See Liebhold et al. (1995) for a more complete gypsy moth host list. 5 Resistant species include maple, even during outbreaks, these trees beech, hickory, and black walnut. are completely free of defoliation. Immune species include tulip poplar, Most conifers are immune, though ash species, American sycamore, some (e.g., hemlock, white pine, and black cherry. Larvae essentially blue spruce) are resistant and can never feed on immune trees and be defoliated by late instar larvae;

Figure 4. Mature caterpillars can feed extensively on oak leaves (A) and cause severe defoliation and subsequent tree mortality especially of oaks (B). Uninjured resistant and immune host species can be seen in the understory (B) following a gypsy moth outbreak in the northeastern USA.

6 conifers (e.g., larch, bald Léopold Trouvelot, an immigrant cypress) are generally susceptible. to the USA from France living in Medford, MA, obtained gypsy Distribution and Spread moth egg masses from Europe The amateur entomologist Éttiene and reared gypsy moth larvae in

Figure 5. Historical spread of the gypsy moth from 1900 to 2018 to the south and west in North America (A). Range of susceptible hosts and habitat suitability of gypsy moth found in the USA (B).

7 cages on trees in the backyard of Outbreaks of the gypsy moth have his home. They escaped in 1868 primarily impacted susceptible host or 1869. Recognizing the potential tree species (Figure 4.B). Defoliation for damage, Trouvelot alerted from young caterpillars can be entomologists to this incident but difficult to detect, but feeding can no action was taken until 1890 resemble small holes in the interior when the State of Massachusetts of the leaf. Young caterpillars need initiated an unsuccessful campaign foliage from susceptible trees and to eradicate the population. shrubs to survive and commonly Since then, the gypsy moth has begin feeding on these species been slowly expanding its North in the understory. As caterpillars American range (Figure 5.A). mature, leaf feeding becomes The historically slow rate of more extensive and the entire leaf spread can be attributed to the can be consumed. Following low lack of female flight as well as to levels of defoliation (<50%), most several intensive efforts to limit broadleaf trees will experience only its spread. Beginning in 1912, the a minor reduction in radial growth. US Department of Agriculture Healthy trees can withstand one (USDA) implemented a quarantine or two consecutive years of severe that limited the movement of defoliation and will frequently re- objects, such as nursery stock, from foliate by mid-summer even after the invaded area; this and other experiencing >50% defoliation. management activities (see below) However, stressed trees and trees have greatly limited gypsy moth with poor crowns are more likely range expansion. Gypsy moth often to succumb to high levels of colonizes new areas when objects defoliation. Crown dieback can carrying egg masses (e.g., outdoor occur following extensive feeding furniture, firewood, recreational from gypsy moth and tree mortality vehicles, and trailers) are can result from repeated bouts of transported outside of the generally severe defoliation (>75%). Drought infested area. As described below, and secondary mortality agents on networks of pheromone traps oaks, such as twolined chestnut monitored annually by state and borer (Agrilus bilineatus) and fungal federal agencies are used to detect root diseases (e.g., Armillaria these populations so that they spp.), can interact with gypsy moth can be eradicated or contained defoliation to cause additional tree to prevent additional spread. The mortality three to five years later. current gypsy moth range only Conifer species (e.g., and encompasses about one-third hemlock), although generally less of the potentially susceptible preferred hosts of gypsy moth, are forests in the USA (Figure 5.B). less tolerant of defoliation and can be killed following a single year of Ecological and Economic complete defoliation. Forest stands Impacts dominated by oaks, particularly 8 Figure 6. Oak-dominated stands that experience repeated bouts of defoliation can lead to high levels of defoliation and tree mortality (>90%). Defoliation can be extensive across the landscape. Note the brown patches of trees in the foreground and background of the image (A). Interacting stressors (e.g., , disease, and dry sites) can result in tree mortality being delayed for three to five years following an outbreak (B).

chestnut oak, or other susceptible as south- and west-facing aspects, hosts (>50% of the forest canopy), and ridge-tops with sandy or experience the most defoliation and rocky and a preponderance mortality (Figure 6.A). In addition, of hiding places (e.g., bark flaps) forests located on xeric sites, such for caterpillars can contribute to 9 multi-year defoliations and high- levels of tree mortality caused by gypsy moth (Figure 6.B). Tree mortality can exceed 90% following gypsy moth outbreaks w h e n Figure 7. During outbreaks, high densities of caterpillars can be a nuisance additional and a health concern to homeowners, especially those in or adjacent to stressors forested areas. (e.g., drought, secondary mortality agents) are In North America, regional present, though, generally, <15% of gypsy moth outbreaks typically the total basal area is lost following occur every 8 to 12 years and most gypsy moth outbreaks. may persist for one to three years. Losses to the forest canopy can From 1920 to 2020, gypsy moth result in changes in understory has defoliated >95 million acres. vegetation and long-term canopy Economic impacts associated with composition where more shade- tree mortality include the loss of tolerant and less susceptible timber revenues and removal/ tree species, like red maple, typically replacement costs for homeowners, gain canopy dominance. Defoliation businesses, and governments. and tree mortality from gypsy moth The most serious impacts are can delay mast production in oaks, felt by private landowners who thus reducing food availability for experience loss of aesthetic and wildlife such as squirrels, mice, property values when ornamental and deer. During and following trees are defoliated or killed. High outbreaks, there may be short-term densities of caterpillars can also changes in the microclimate (e.g., be a nuisance when frass rains higher sun exposure, temperature, down from defoliated trees on and wind) on the forest floor and homeowners and in recreation in water quality because of the areas (Figure 7). Hairs from substantial loss of canopy cover caterpillars can trigger respiratory and the leaching of nutrients with problems, skin irritations, and leaf material and frass (insect allergic reactions in some people. excrement) to the forest floor and ultimately forest streams. State and federal governments have directed >$282 million dollars 10 from 1980 to 2020 to suppress infection cycles in a season but gypsy moth outbreaks on >14 are typically most prevalent and million acres. As gypsy moth noticeable with later instar larvae. continues to spread south and west from currently infested areas, Gypsy moth NPV is specific to counties are placed under a federal gypsy moth, and has been present quarantine to restrict the movement in North America since the early of gypsy moth life stages, resulting 1900s. It likely arrived from in additional costs to governments Europe with introduced and business to institute new for biological control. Gypsy monitoring, management, and moth NPV infects developing regulatory protocols. Since 2000, caterpillars upon ingestion of viral federal and state agencies have bodies present on the leaf surface contributed >$7 million annually or residing on the surface of egg to monitor and manage low density masses. After being consumed, the gypsy moth populations at the virus quickly replicates and ruptures transition zone between invaded cells throughout the internal organs and uninvaded areas to Figure 8. General symptoms of caterpillars killed from reduce its natural and human- gypsy moth nucleopolyhedrosis virus (A, the arrow points assisted spread rate through a to the “V” shape of the infected caterpillar) and the fungal national program (see below). pathogen Entomophaga maimaiga (B, the arrow notes the straight and limp infected body). These symptoms are not definitive nor mutually exclusive, as co-infection by both Natural Enemies pathogens can occur, as well as attack by parasitoids (C, eggs There are multiple pathogens, parasitized by an introduced wasp, Ooencyrtus kuvanae). parasitoids, and predators, introduced in the early 19th century from Europe and Asia, that attack gypsy moth in North America. The most important mortality agents affecting high density populations are two diseases: a viral pathogen, gypsy moth nucleopolyhedrosis virus (NPV), and a fungal pathogen, Entomophaga maimaiga Humber, Shimazu, and R.S. Soper (Entomophthorales: Entomophthoraceae), both of which can contribute to outbreak collapse. Both diseases can infect all stages of larvae and have multiple 11 of the caterpillar, resulting in death. infection. This fungus produces two The virus is transmitted when the types of spores: large resting spores dead caterpillar’s cuticle ruptures that overwinter in the and are and viral bodies are either spread viable for >10 years and smaller, by rainfall or drop onto leaves short-lived conidia which disperse below. These viral bodies are then in the wind. Caterpillars are infected eaten by uninfected caterpillars. upon contact by airborne conidia The diagnostic symptom of NPV- after which the fungus begins caused mortality in gypsy moth consuming the caterpillar. Mortality caterpillars is an inverted “V” body typically occurs within a few days position (Figure 8.A). Interactions and four to nine cycles of infection between NPV and host gypsy can occur within one season. The moth populations are considered general diagnostic symptom of to be one of the main drivers of E. maimaiga-caused mortality in the quasi-periodicity of gypsy late-instar gypsy moth are thin, outbreaks. Gypsy moth NPV has shriveled caterpillars in a downward been formulated into an aerially facing position (Figure 8.B). applied biopesticide, Gypchek. This product is costly and time- Early gypsy moth management consuming to produce because it efforts in North America included requires the large- rearing of introducing a variety of insect virus-infected caterpillars. Gypchek natural enemies (e.g., parasitic is used only in USDA Forest flies and wasps, and predatory Service-sponsored treatment areas beetles). At that time, there was where there are concerns about little regulation or research on the non-target effects, particularly to effectiveness or non-target effects threatened or endangered native of these introduced natural enemies. and moths (Lepidoptera). At least ten species established, and several of them were generalist Entomophaga maimaiga is a fungal predators and parasitoids that pathogen largely specific to gypsy offered little control of gypsy moth. moth and was first documented However, some were specialist causing significant mortality in parasitoids that may contribute to eastern North America in 1989. The regulation of low-density gypsy introduction date or origin of this moth populations (Figure 8.C). important pathogen is unknown; it may have been introduced Small mammals, particularly white- accidentally or intentionally at an footed mice, feed on both larvae and earlier date but remained undetected pupae, and are typically the most for many years. Infection by E. important cause of gypsy moth maimaiga is facilitated by wet mortality in low-density gypsy moth conditions, especially during populations. Temporal and spatial early spring, which are ideal for variation in their abundance, which spore propagation and caterpillar may be related to timing of mast 12 seeding, appears to be associated populations and reduce risk of with the release of low-density tree mortality from repeated gypsy populations to outbreak levels. moth defoliation. When developing a management plan, it is important Management and Treatment to consider the extent, severity, Options and context of the outbreak. For There are many management tactics homeowners, direct manual control available to suppress gypsy moth measures targeting outbreak

Figure 9. Many historical treatment options for gypsy moth [e.g., fogging (A), branch pruning and egg mass removal (B), tree banding (C), egg mass treatments, sterile male release, biological control augmentation, and mass trapping] are no longer extensively used primarily because more effective and environmentally safe measures are available.

13 populations may be feasible for large-scale treatment programs protecting high-value trees, but are because it is effective against generally ineffective at changing high-density populations and has the course of regional gypsy limited non-target effects. This moth outbreaks. Management of product primarily targets foliar- outbreak gypsy moth populations feeding, early instar Lepidoptera has been conducted for over a and is active in the environment century in North America, and for less than two weeks. Btk is many previous treatment options typically applied from aircraft but (e.g., broad spectrum insecticide can also be applied to the canopy applications, branch pruning, egg from the ground, such as in small mass removal and destruction, eradication projects. Gypchek, tree banding, egg mass treatments, which has a greater specificity, has sterile male release, augmentation similar impacts and application biological control, and mass timing as Btk and can be used in trapping) have been deemphasized treatment programs where impacts because they are too tedious and on sensitive species of Lepidoptera economically impractical over large are a concern (Tables 1 and 3). areas, ineffective for controlling gypsy moth populations or reducing Insect growth inhibitors (e.g., defoliation, or environmentally diflubenzuron and tebufenozide) unacceptable (Figure 9). are also effective at suppressing are an effective choice for treating high gypsy moth populations invading or outbreak gypsy moth (Tables 1 and 3). When ingested populations. Ground applications or contacted by caterpillars, are appropriate for small acreages; diflubenzuron inhibits the formation otherwise, most pesticides are of , a major component of applied aerially via helicopter or the insect exoskeleton, during fixed-wing aircraft. Large-scale molting. Tebufenozide is also aerial treatments for gypsy moth active at disrupting molting, but are typically conducted in areas of it mimics the action of a molting high recreation value, residential hormone in various terrestrial neighborhoods, high-value timber, and aquatic insects; however, along the leading edge of gypsy moths are generally more moth expansion, or in state/federal sensitive to the insecticide than cooperative programs (Table 3). non-target insects and .

Suppression strategies Application of broad spectrum Bacillus thuringiensis var. kurstaki insecticides to the tree crown can be (Btk) is a naturally occurring used to target feeding caterpillars, soil bacterium that has been but these materials are rarely used formulated into a commercial in large-scale treatment programs. biological insecticide for gypsy Immediate and persistent toxicity moth control. It is favored in many may make these products ideal for 14 Table 3. Frequently applied treatment options for gypsy moth population suppression.

Treatment Option Timing of Non-target Biological Mode of Action and Comments application Effects (Y/N) Bacillus Mix of 1st Feeding Y A naturally occurring soil bacterium thuringiensis var. and 2nd caterpillars of that breaks down the gut lining of kurstaki (Btk) instars all butterflies feeding caterpillars. Bacteria must and moths be ingested to cause mortality. Applications have a short period of efficacy; commonly applied twice in a season.

Gypsy Moth Mix of 1st None, Y Formulation of the naturally nucleopolyhedrosis and 2nd specific to occurring gypsy moth virus (NPV) instars gypsy moth nucleopolyhedrosis virus that ruptures internal organs. Manufacturing can be costly and time-consuming as it requires the rearing of live caterpillars. Product is only available for use in USDA Forest Service-sponsored programs.

Diflubenzuron 3rd instar Especially N A commercially available insect toxic to growth regulator that prevents aquatic caterpillars from molting. invertebrates

Tebufenozide 1st to 3rd Feeding N A commercially available insect instars caterpillars of growth regulator that prevents all butterflies caterpillars from molting. and moths

Broad spectrum All larval Most N Broad spectrum contact insecticides insecticides instars arthropods that inhibit normal function of the (carbaryl, bifenthrin) that nervous system. These products contact the are no longer used in large-scale insecticide treatment programs.

Mating disruption Pupation, Non-lethal, Y Pheromone-based product that prior to moth specific to limits male moth ability to locate emergence gypsy moth females. Used in the National in North Gypsy Moth Slow the Spread America program and occasionally in eradication; effective primarily for low density populations.

15 homeowners, but the non-target effective in areas with low and effects of these insecticides on isolated populations, and is used arthropods makes them unfavorable primarily along the invading edge for use in larger treatment programs. of the infestation in the National Gypsy Moth Slow the Spread Broad spectrum insecticides (STS) program (see below). were used frequently in earlier gypsy moth treatment programs, Prevention strategies but have not been used in Preventative silvicultural measures large gypsy moth treatment are a component of an effective programs since the late 1980s. long-term management strategy Mating disruption is a non-lethal for larger woodlots, particularly control strategy that saturates within generally infested areas with an area with a species-specific, a history of gypsy moth defoliation synthetically-produced sex or in high-risk stands adjacent to pheromone to inhibit mate finding the gypsy moth invasion front. and subsequent reproduction. Specific plans should be tailored This control strategy is only more precisely for an individual

Figure 10. Four strategies of the USDA National Gypsy Moth Management Program include 1) suppressing outbreak populations of European gypsy moth in quarantined areas, 2) slowing the spread of new populations of European gypsy moth along the expanding invasion front, 3) eradicating all new populations of the Asian and European subspecies, and 4) monitoring and regulating the movement of European life stages from quarantined areas (not pictured).

16 site, though general strategies to monitor and regulate the movement reduce the risk of outbreak include of the European subspecies life thinning to reduce basal area of stages from quarantined areas susceptible host species (e.g., oak, with regulatory inspections and paper birch, aspen) and increasing certifications (Figure 10). USDA basal area of resistant and immune Forest Service and state agencies species (e.g., conifers, maple, black cooperate to suppress gypsy cherry, black walnut). Maintaining moth outbreaks in quarantined general tree vigor is also important areas across all land ownerships for reducing stand vulnerability to (though not all states participate). tree mortality following outbreaks. Whereas, USDA Forest Service Intermediate cuttings targeting and and Health trees with poor crowns can reduce Inspection Service (APHIS) and stand vulnerability. Homeowners state agencies cooperate to slow can water trees during periods of the spread of European gypsy moth drought stress and remove ailing and eradicate new populations or undesirable understory trees of both subspecies. The USDA that are susceptible hosts. Figure 11. Networks of pheromone-baited traps are National Monitoring used to monitor gypsy moth populations, direct treatment actions, delineate treatment blocks, and determine and Management treatment efficacy (A). Aerial applications (B) are Programs frequently used to suppress gypsy moth populations for the three national program areas (suppression, slow the There is a comprehensive spread, and eradication). U.S. national monitoring and management program for both the European and Asian gypsy moth subspecies. The USDA National Gypsy Moth Management Program is comprised of four strategies: 1) suppress building populations of European gypsy moth in quarantined areas; 2) slow the spread of new populations of European gypsy moth along a 62 mile (100 km) wide action area along the expanding invasion front; 3) eradicate all new populations of the Asian subspecies and new populations >62 miles from quarantined areas for the European subspecies; and 4) 17 Forest Service manages the STS The USDA APHIS collaborates program, which is carried out in with state agriculture and/or collaboration with multiple state natural resource agencies to agencies in the central and eastern detect and eradicate new gypsy USA, a non-profit foundation, moth populations outside the two universities and APHIS. The quarantined area. Approximately STS program, implemented in 100,000 pheromone-baited traps 2000, represents a culmination of are deployed annually nationwide several previous pilot programs to provide early detection of new during which the monitoring populations. Human-assisted and management protocols dispersal frequently results in the used in STS were developed. movement of European gypsy moth out of quarantined areas in STS is intensive. It relies on the eastern USA, whereas egg tens of thousands of sex pheromone- masses of Asian gypsy moth are baited monitoring traps (e.g., delta sometimes introduced with cargo and milk carton) deployed annually and ships originating from eastern in quarantined areas and along Asia. Eradication efforts have the transition zone of infested and successfully eliminated every new uninfested areas (62 mile action population of both subspecies since area) to monitor population growth 1970. Dense trapping grids are and to detect new populations, typically deployed around newly respectively (Figure 11.A). High detected European gypsy moth densities of traps are used in some populations in uninfested areas prior areas to detect isolated growing to eradication in to confirm populations, delimit treatment the persistence of populations as boundaries, and assess treatment well as to delimit their spatial extent. efficacy. Biorational pesticides are Asian gypsy moth populations are then applied aerially to suppress typically treated the year following isolated populations in the detection; these eradication transition zone, which reduces the efforts occur most frequently near rate of spread (Figure 11.B). Trap US ports. APHIS also provides locations and catch data are used to regulatory certification of articles compute the program boundaries, (e.g., nursery stock, shipments of highlight potential problem areas lumber, firewood, plant material, (i.e., growing populations), adjust mobile homes, and household trapping densities, and recommend items) that may contribute to treatment applications. The STS spread of European gypsy moth program has reduced the annual out of quarantined counties. rate of gypsy moth spread by >60% during the 20 years that References the program has been in place. Doane, C.C., M.L. McManus (Eds). 1981. The Gypsy Moth: Research Toward Integrated 18 Research. USDA Forest Service, Forestry. Gypsy Moth Digest. Washington, D.C. 757 p. https://www.fs.usda.gov/ naspf/programs/forest-health- Elkinton, J.S., A.M. Liebhold. protection/gypsy-moth-digest (last 1990. Population dynamics of accessed 20 March 2020) gypsy moth in North America. Annual Review of Acknowledgements 35: 571-596 This publication is a revision of the previous version by McManus Liebhold, A.M., K.W. Gottschalk, et al. (1989). Their work provided R. Muzika, M.E. Montgomery, valuable guidance to the preparation R. Young, K. O’Day, and B. of this update. The authors also Kelley. 1995. Suitability of thank Paul Chaloux, USDA Animal North American Tree Species and Plant Inspection Service; to the Gypsy Moth: A Summary Robbie , USDA Forest of Field and Laboratory Service, Forest Health Protection- Tests. USDA Forest Service, Pacific Northwest Region; Northeastern Forest Experiment Michael McManus (retired), Station, Gen. Tech. Rep. NE-211 USDA Forest Service, Northern Research Station; and Steven J. Liebhold, A.M., K.W. Gottschalk, Seybold (deceased), USDA Forest E.R. Luzader, D.A. Mason, Service, Pacific Southwest Region R. Bush, D.B. Twardus. 1997. for their review of this leaflet. Gypsy moth in the United States: An Atlas. USDA Forest Service, Photo credit to Bugwood.org; L. Northeastern Forest Experiment Blackburn, USDA Forest Service Station, Gen. Tech. Rep. NE-233 (Fig. 5.A); S. Bauer, Agricultural Research Service (Fig. 9.C); T. Tobin, P.C., L.M. Blackburn. Coleman (Figs. 1.B, 2, 11); C. 2007. Slow the spread: a national Foelker (Figs. 1.A, 3, 7, 8); H. program to manage the gypsy Mannin Dodd, Virginia Polytechnic moth. Gen Tech Rep NRS-6. Institute and State University Newtown Square, PA; USDA (Fig. 10); K. Dodds, USDA Forest Forest Service, Northern Service (Fig. 4.B); Mark Robinson, Research Station. 109 p. USDA Forest Service (Fig. 6.A); K. Salp, Washington State Department USDA Forest Service and Animal of Agriculture (Fig. 4.A); and USDA and Plant Health Inspection Forest Service (Figs. 11.A, B) for Service. 2012. Gypsy Moth use of images. European gypsy Management in the United moth establishment suitability States: A Cooperative Approach, summary for 2014 (M.C. Downing, Final Environmental Impact I.I.F. Leinwand, J.R. Withrow, G.L. Statement, Vol 1-4., Newtown Cook, L.F. Kenneway, C. Jarnovich, Square, PA, NA-MB-01-12 F.J. Sapio) (Fig. 5.B) reproduced with permission from USDA Forest USDA Forest Service, Service, Forest Health Assessment Region 9, State and Private and Applied Sciences Team. 19 Pesticide Precautionary Statement This publication reports research involving pesticides. It does not contain recommendations for their use, nor does it imply that the uses discussed here have been registered. All uses of pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended.

CAUTION: Pesticides can be injurious to humans, domestic , desirable , and fish or other wildlife--if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides and pesticide containers.

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The Forest Insect and Disease Leaflet (FIDL) series provides information about insects and diseases affecting forest trees in the United States. FIDLs are produced through coordinated efforts of the US Forest Service’s Forest Health Protection staff and its partners from state forestry, academic and research organizations.

Learn more at www.fs.fed.us/foresthealth/publications/fidls/index.shtml 20