March 2006 Forest Health Protection and State Forestry Organizations

6.21 Management WEB July 2010 Guide for

By Lee Pederson and Gypsy Steve Munson Lymantria dispar (Linnaeus) (: Lymatriidae) US Forest Service

Gypsy moth is a Perferred Hosts: Other hosts: polyphagous , the Quercus and Lodgepole host range of the North Populus Ponderosa American strain of gypsy pines moth consists of over 300 species of trees and Western larch shrubs compared to the Riparian habitat Spruce Topics Asian strain which has a hosts: Douglas-fir host range that exceeds Salix, Alnus and Overview 1 500 species. Betula History 1 Damage 2 Overview in the West Life History 3 Eradication projects have been distances up to 20 miles could Management 4 conducted for European gypsy result in an accelerated rate of moth populations throughout the infestation. AGM presents a more Other Reading 6 western United States including difficult challenge to eradicate Field Guide Utah and Idaho. Early detection, because of its broader host range delimitation trapping and the use and flight capabilities compared to Management Guide Index of a biological insecticide applied the North American strain when necessary have successfully established in the northeast and eliminated introduced populations north central portions of the United of this insect in the west. Sporadic States. introductions of the Asian gypsy moth (AGM) have occurred in the west primarily near west coast Key Points cities. However in 2004, an AGM  The Asian strain of introduction occurred in northern the gypsy moth is Idaho near Hauser Lake. native to Asia. Environmental consequences associated with the successful  Asian gypsy moth female’s flight establishment of an Asian gypsy capability and moth infestation are more larger host range threatening as the female moth is Adult female gypsy moth. USDA APHIS PPQ Archives, USDA APHIS PPQ, makes it a serious capable of flight. Dispersal www.forestryimages.org threat to western forests. History  This insect The European gypsy moth was outlying infestations found as far consumes both old accidentally introduced into the west as Minnesota and Iowa. In and new needles United States near Boston, some forested sites, forest on conifers which are not able to Massachusetts during the late composition has changed too less refoliate. 1860’s. This introduced defoliator susceptible species due to periodic has now expanded its range to heavy defoliation of susceptible include all of the northeastern states, hosts. south to North Carolina with Page 2 Back to menu Gypsy Moth Biology 6.21 History Various chemical insecticides In addition to the female’s flight including lead arsenate, DDT, capability the Asian gypsy moth has orthene, carbaryl, the insect growth a larger host range than its European ® Historical Archive Photo regulator Dimilin , biological counterpart. Some North American insecticides such as Bacillus western conifers are hosts for this thuringiensis (Bt) and a natural insect and the insect is better virus, Gypchek have been used in adapted to colder climates. These suppression and eradication efforts. traits make the Asian strain a more The Asian strain of the gypsy serious threat to our western forests moth is native to Asia. It was first if introduced populations of the identified in North America in late insect become established. 1991 near the Port of Vancouver, British Columbia, Canada. Ships infested with egg masses from Gypsy Moth Distribution—2005 Pacific ports in eastern Russia introduced the pest while visiting west coast ports when larvae hatched from eggs and were blown Photo shows use of ropes in climbing trees in treating ashore. These initial introductions gypsy moth egg clusters were eradicated using multiple and pruning dead branches from trees when cleaning applications of Bt and pheromone operations were considered traps. In the U.S. it has since been necessary. 1930. USDA Forest Service Archives, found in California, Washington, USDA Forest Service, Oregon, and most recently in Idaho. www.forestryimages.org Damage

Damage by gypsy moth occurs mortality occurs. when the leaves or needles of hosts Caterpillar silk strands, are consumed by developing droppings, destroyed leaves and caterpillars (Figure 1). During dead are a nuisance in severe outbreaks, complete homes, yards and recreation areas. defoliation of susceptible trees or Caterpillar hairs can result in an shrubs may result. Defoliated allergic reaction in some people deciduous trees usually refoliate, when exposed to larvae. but this depletes the trees’ stored energy reserves, making them more susceptible to pathogens and other . Since this insect consumes both old and new Photo of gypsy moth defoliation. Mark Robinson, needles on conifers and trees are USDA Forest Service, not able to refoliate, severe www.forestryimages.org defoliation may result in tree mortality. Because deciduous trees do refoliate, it generally takes 2-3 Figure 1. Late instars feeding on oak consecutive years of complete foliage. Photo by: Tim Tigner, Virginia Department of Forestry, defoliation before branch and tree www.forestryimages.org Page 3 Back to menu Gypsy Moth Biology 6.21 Life Cycle The gypsy moth life cycle has response to sunlight. Depending on four stages: egg, larvae, pupa and crowding and the suitability of the First instar larvae adult moth. Eggs of the North host, a percentage of the first instar will drop on silken American strain are laid on the bark larvae will drop on silken threads threads and of trees (Figure 2), female moths and disperse to a new location disperse by the lay egg clusters in virtually any propelled by wind. This dispersal wind called sheltered location including homes, behavior is known as “ballooning:” “ballooning” vehicles, firewood, and on outdoor Distances of dispersal usually items. For the Asian strain egg average less than ½ mile (0.80 km), masses can be deposited on the but can be as great as 12 miles same substrates but egg laying (19.3 km) or more. behavior varies greatly throughout Once finding a suitable host, its native range. the larvae begin to feed. As larvae In the Russian Far East, eggs are feed they go through a series of deposited on leaves, in Mongolia molts and increase in size with each eggs are laid near the forest floor consecutive molt. Instars are the and in Japan the females select larval stage between molts. Male trees with light colored bark larvae normally have five instars (primarily Betula) for egg and females six before entering the deposition. pupal stage. Older larvae have five pairs of raised blue spots and six pairs of raised brick-red spots along their dorsal (back) side (Figure 3). If populations are sparse, larvae move up and down the tree depending on light intensity. Larvae in the later instars feed in the top of the tree at night and crawl down the truck to rest during the day. When populations are high, larvae feed continuously day Figure 2. Egg mass on bark of tree. Photo by Daniela Lupastean, Faculty of and night until all the foliage is Forestry, University of Suceava, consumed. Romania, www.forestryimages.org McManus (1987) reports the time interval of individual instars Gypsy moth eggs hatch and can range between 4 to 10 days larvae emerge in the spring after depending on temperature. The overwintering in protected egg caterpillar stage can last from 8-12 masses consisting of 100-1000 weeks depending on temperature, individual eggs. In most cases food quality, and population levels. larvae hatch in synchronization Caterpillars feed from early May to with bud break of preferred hosts. mid-July in the western U.S Figure 3. Photo of older depending on elevation and the larvae displaying the bright However, egg hatch is red spots along dorsal side. predominantly determined by factors affecting growth mentioned Photo by: Cooperative temperature. After hatching first previously. Late instar larvae can Extension University of California instar larvae spend from 3 –5 days reach approximately 2 inches in on or near the egg mass, eventually length. the larvae climb vertically in Page 4 Back to menu Gypsy Moth Biology 6.21 Life Cycle A caterpillar may consume up to The North American strain one square foot of foliage during its generally deposits her eggs near her development. Once feeding is pupation site. Female moths of the completed, the caterpillars are ready Asian strain have flight capabilities to pupate which can occur from late up to 20 miles (32 km). Eggs are June to early August. Following deposited in a single mass and then pupation, which usually lasts from covered with dense layer of brown 10 to 14 days, adult moths emerge hair from the female’s body. The and mate. cycle is completed when the fully Adult moths of the North developed embryos hatch in the American strain are slightly smaller spring. (male wingspan about 1 inch, female wingspan up to 2 inches) compared to the Asian strain (male Photo shows a gypsy moth wingspan 1 ½ inches and female trap in the late 40’s. wingspan 3 ½ inches). Adult USDA Forest Service Archives, USDA Forest coloration is similar for both strains. Service, Males are light tan to dark brown www.forestryimages.org with blackish wavy bands across their forewings and arrowhead markings near the leading edge Figure 4 male(left) and female (right) (Figure 4). Female moths are nearly Asian gypsy moths - shown for white with faint, dark wavy bands comparison . USDA APHIS PPQ Archives, USDA APHIS PPQ, on the forewings (Figure 4). www.forestryimages.org

Management The risk of introduced North Occasionally egg mass and larval American strain populations surveys are also conducted near a becoming established in the west positive catch site if a suspected increases as more people move from introduction has occurred. the generally infested areas in the Detection and delimiting east to the uninfested west. As programs are conducted jointly by trade increases with Asian countries, State and Federal agencies placing the risk of introducing the Asian pheromone traps in areas of risk. strain to North America also High-risk areas include cities, increases. towns, National and State Parks, and Gypsy moth detection programs campgrounds where susceptible in the west rely on pheromone hosts occur and people are likely to Figure 5. Photo shows baited delta traps to locate arrive from the generally infested today's pheromone delta introduced populations (Figure 5). areas. Most of the North American traps being deployed in wooded area near high risk If a single male moth is caught in strain introductions occur in the waterway the detection grid, the trapping grid west as the result of humans moving USDA APHIS PPQ Archives, USDA APHIS PPQ, is refined the following year. This articles with egg masses from the www.forestryimages.org delimitation trapping grid is used to generally infested area in the east. locate developing populations. Page 5 Back to menu Gypsy Moth Biology 6.21 Management

Eradication programs are suppression/eradication programs. initiated in the west if multiple Non-target impacts and human male moth catches of the North health concerns resulted in American strain occur within discontinuing these products as detection or delimitation trapping suppression/eradication strategies grids or other life stages of the for gypsy moth. Suppression/ insect is found. If a single Asian eradication programs for gypsy gypsy moth adult is captured, moth typically involve an current APHIS (, Health integrated pest management (IPM) Plant Inspection Service) policy is approach. multiple applications of Bt within a one mile radius of the positive catch site. Historically, conventional pesticides such as DDT, carbaryl, Spraying DDT in the 1930’s. USDA Forest Service Archives, and acephate were used in the USDA Forest Service, northeastern states in gypsy moth www.forestryimages.org

Applying a barrier band used to capture migrating caterpillars. (Village of Hartland, 2001)

Integrated Pest Management The following products or methods are often considered in developing an IPM program for gypsy moth in the west:

 Mass trapping with pheromone baited traps.  Release of sterile male gypsy moths.  Mating disruption with a registered synthetic version of the pheromone disparlure in products such as Disrupt®II, Luretape Gypsy Moth®, and Luretape Plus®.  Diflubenzuron (Dimilin®), an insect growth regulator.  Nucleopolyhedrosis virus (NPV), a natural disease agent in gypsy moth caterpillars. Gypchek® is a registered NPV product that is available for use.  Bacillus thuringiensis kurstaki (Btk), a microbe that is a natural disease agent of caterpillars. Several registered Btk products are available for use.

Pesticide registrations change frequently; please contact County, State, or Federal pesticide coordinators for a list of registered insecticides. Page 6 Back to menu Gypsy Moth 6.21 Management Natural enemies play an important role in gypsy moth control during years of light infestations. Wasps, flies, ground During severe beetles, spiders, and ants are outbreaks, complete common predators. Birds such as defoliation of chickadees, bluejays, nuthatches, susceptible towhees, and robins serve as control trees or shrubs agents. Several woodland mammals may result. including mice, shrews, chipmunks, and squirrels are also predators. Over ten foreign biological control Biocontol for gypsy moth - parastic wasp laying eggs on gyspy moth pupal case. agents that includes parasites, Eggs will hatch into wasp larvae which predators, and disease organisms will feed and kill host. USDA APHIS PPQ Archives, USDA APHIS PPQ, specific to gypsy moths, have been www.forestryimages.org introduced for control purposes in North America.

Other Reading Bess, H..A., Sourr, S.H, and Littlefield, E.W. 1947. Forest site conditions and the gypsy moth. Harv. For. Bull. No 22. 56 pp.

Herrick, O. W. and Gansner, D.A. 1986. Rating forest stands for gypsy moth defoliation. USDA For. Serv. Res. Pap. NE-583. 4 pp.

Leonard, D.E. 1981. Bioecology of the gypsy moth. p. 9-29 in: The gypsy moth: Research toward integrated pest management. Doane, C.C. and M.L. McManus (eds.). USDA Tech. Bull. 1584

McManus, M.L. 1987. The gypsy moth problem: history, biology, spread. pp. 1-10. In Proceedings of “Coping With The Gypsy Moth In The New Frontier.” West Virginia University Books, Morgantown, West Virginia. 153 pp.

McManus, M.L., N. Schneeberger, and G. Mason. 1992. Gypsy moth. USDA Forest Service, Forest Insect and Disease Leaflet 162. Page 7 Back to menu Gypsy Moth 6.21 Other Reading

Miller, J.C. and P.E. Hanson. 1989. Laboratory feeding tests on the development of gypsy moth larvae with reference to plant taxa and allelochemicals. Agricultural Experiment Station Bull. 674. 63 pp. Oregon State University, Corvallis, OR.

Miller, J.C. and P.E. Hanson. 1989. Laboratory studies on development of gypsy moth Lymantria dispar (L.), (Lepidoptera: Lymantriidae), larvae on foliage of gymnosperms. Can. Ent. 121 (6): 425-429.

Internet References http://www.doh.wa.gov/ehp/Pest/egm/why-egm-problem.htm

http://www.hc-sc.gc.ca/cps-spc/pubs/pest/_pnotes/gypsy-spongieuse/index-eng.php

http://www.aphis.usda.gov/plant_health/plant_pest_info/gypsy_moth/index.shtml

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