/A ' .11 : ;3pn 
 
 .^^>v United States 
 i] Department of 
 
 tffy Agriculture 
 
 Combined Forest Pest 
 Research and 
 Development Program 
 
 Home and Garden Bulletin 
 
 No. 227 
 
 Gypsy Moth 
 Handbook 
 
 ^ 
 
 The 
 
 Homeowner 
 
 and 
 
 the Gypsy 
 
 Moth: 
 
 Guidehnes for 
 
 Control 
 
Digitized by tine Internet Arclnive 
 
 in 2011 witln funding from 
 
 University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation 
 
 http://www.archive.org/details/gypsymothhandbooOOmcma 
 
Contents 
 
 In 1974 the U.S. Department of 
 Agriculture initiated the 
 Combined Forest Pest Research 
 and Development Program, an 
 interagency effort that 
 concentrated on the Douglas-fir 
 tussock moth in the West, on 
 the southern pine beetle in the 
 South, and on the gypsy moth 
 in the Northeast. The work 
 reported in this publication was 
 funded in whole or in part by 
 the program. This manual is 
 one in a series on the gypsy 
 moth. 
 
 Introduction 
 
 4 
 
 Life History and Life Stages 
 
 7 
 
 Egg masses 
 
 7 
 
 Egg hatch and spread of 
 larvae 
 
 8 
 
 Early-stage larvae 
 Late-stage larvae 
 Pupae 
 Adults 
 
 10 
 11 
 13 
 14 
 
 Detecting the Gypsy Moth 
 
 15 
 
 Egg masses 
 
 15 
 
 Larvae and pupae 
 
 17 
 
 Hosts of the Gypsy Moth 
 
 18 
 
 Effects of Defoliation on Trees 
 
 19 
 
 Tree condition 
 
 20 
 
 Number and severity of 
 
 20 
 
 previous defoliations 
 Mortality-causing organisms 
 
 22 
 
 Managing the Gypsy Moth 
 
 23 
 
 The natural enemy complex 
 Guidelines for tree survival 
 
 23 
 30 
 
 References 
 
 34 
 
The Homeowner and the 
 
 Gypsy Moth: 
 
 Guidelines for Control 
 
 by 
 
 Michael L. McManus, David R. 
 
 Houston, and William E. Wallner 
 
 Introduction 
 
 The gypsy moth is the most 
 important defoHating insect of 
 hardwood trees in the Eastern 
 United States (fig. 1). Since the 
 turn of the century, milhons of 
 dollars have been spent in efforts 
 to control or eliminate gypsy 
 moth populations and to retard 
 natural and artificial spread. In 
 the early decades of this century, 
 outbreaks occurred only in New 
 England; today defoliation by the 
 gypsy moth is far more severe 
 and widespread (fig. 2). 
 
 The gypsy moth has always been 
 a "people problem." Defoliation 
 often occurs in populated areas, 
 especially where homes and 
 developments are located in 
 previously forested land (fig. 3). 
 Under these conditions, the gypsy 
 moth defoliates not only 
 woodland trees but also valuable 
 park and ornamental trees. 
 Because the insect is firmly 
 established in the densely 
 populated regions of the Eastern 
 United States, it is very likely 
 that you, the homeowner in this 
 area, and the gypsy moth will 
 meet. 
 
 In urban situations, gypsy moth 
 larvae (caterpillars) are a major 
 nuisance as they defoliate shade 
 and ornamental trees, crawl over 
 everything — homes, outdoor 
 
 'Respectively, program coordinator, 
 principal plant pathologist, and research 
 entomologist, U. S. Department of 
 Agriculture. Northeastern Forest 
 Experiment Station, Hamden, Conn. 
 
Figure 1. — Late-stage gypsy 
 moth larva. 
 
 Figure 2. — Extensive defoliation 
 
 on ridgetops caused by gypsy moth. 
 
 Figure 3. — Partial defoliation 
 around suburban homesite. 
 
furniture, lawns — and leave debris 
 from their feeding (figs. 4 and 5). 
 Should it occur, the death of 
 defoliated trees and the often 
 substantial cost of their removal 
 and replacement can add to the 
 homeowner's distress. 
 
 Although the gypsy moth is well 
 established as a component of 
 the predominantly oak hardwood 
 forest community of North 
 America, there are ways to 
 minimize its adverse effects on 
 trees and to reduce its impact on 
 people. Use this guide to 
 acquaint yourself with the habits 
 of the gypsy moth, maintain 
 active surveillance for its presence 
 or increase, and use those 
 procedures that are most 
 appropriate for your situation. If 
 you are uncertain about which 
 actions to take, consult with a 
 representative of the county 
 cooperative extension office, the 
 State agriculture service, or the 
 U. S. Department of Agriculture, 
 or contact specialists at a nearby 
 university or agricultural 
 experiment station. 
 
 Figure 4. — Hungry larvae 
 crawling over home. 
 
 Figure 5. — Nuisance of larvae 
 and frass on picnic table. 
 
Life History and Life Stages 
 Egg Masses 
 
 The female gypsy moth deposits 
 her eggs in a well-formed egg 
 mass (fig. 6) in June or July and 
 dies shortly thereafter. An egg 
 mass may contain from 75 to 
 1,000 eggs. It is buff colored 
 when first laid but may bleach 
 out over the winter months when 
 exposed to direct sunlight and 
 weathering. 
 
 Egg-mass size is an indicator of 
 the status of a gypsy moth 
 infestation. Declining outbreaks 
 
 are characterized by the presence 
 of many small masses 
 (approximately 0.5 in long) that 
 contain as few as 75 to 100 eggs. 
 In static or growing populations, 
 the egg masses are fewer in 
 number but larger (1.5 in long) 
 and contain from 700 to 1,000 
 eggs. 
 
 Figure 6. — Female moth 
 depositing egg mass. 
 
Egg Hatch and Spread of Larvae 
 
 
 
 Gypsy moth larvae usually begin 
 emerging from individual egg 
 masses in late April or early 
 May. Initial hatch is determined 
 primarily by temperature and 
 usually coincides with budbreak 
 of most hardwood trees. The eggs 
 in an individual egg mass will 
 hatch completely over a period of 
 3 to 5 days, but in an infested 
 area eggs may hatch over a 
 period of 2 to 3 weeks, 
 depending on the location of egg 
 masses and their exposure to 
 sunlight. Newly hatched larvae 
 are buff colored but turn black 
 
 within 4 hours after emergence 
 (fig. 7). They remain on or 
 around the egg mass for several 
 days if temperatures are below 
 40° F or if it is raining. 
 
 When conditions are favorable, 
 larvae leave the egg mass and 
 climb trees in response to 
 overhead light. They produce silk 
 from glands located in their head 
 
 Figure 7. — Egg mass hatching in 
 early spring; bufT-colored larvae 
 have emerged most recently. 
 
and lay down a trail of silk 
 continually as they move (fig. 8). 
 When larvae reach the outer 
 branches or tops of trees, they 
 drop on silken threads (fig. 9) 
 that are easily fractured by slight 
 gusts of wind. Both the silk 
 strand and long lateral hairs 
 (fig. 10) add buoyancy to the 
 windborne insects. In woodland 
 situations, larvae may go through 
 several windblown dispersals 
 before settling down to feed. 
 Although some larvae may be 
 carried for long distances by 
 wind, most spread results in 
 
 massive redistribution of the 
 population within relatively local 
 areas. 
 
 Figure 8. — Newly hatched larvae 
 trailing silk prior to dispersing. 
 
 Figure 9. — Larva suspended on 
 a silken thread. 
 
 Figure 10. — First-stage larva 
 with long lateral hairs. 
 
Early-Stage Larvae 
 
 After dispersing, larvae begin 
 feeding when they encounter 
 acceptable food plants, which 
 include many species. In some 
 years, larval emergence and 
 dispersal may occur prior to leaf 
 expansion of favored tree species 
 such as the oaks; usually 
 however, larvae can sustain 
 themselves by feeding on tree 
 buds and on many understory 
 plants or shrubs until trees bear 
 leaves. 
 
 First-stage larvae, which usually 
 have two or three feeding periods 
 during the day, chew small holes 
 within the perimeter of the leaf 
 (fig. 1 1). When not feeding, they 
 rest on a mat of silk they have 
 
 made on the underside of a leaf. 
 Male larvae molt (shed the outer 
 skin) through five stages, females 
 through six. Each larval stage 
 lasts 4 to 10 days, the time 
 dependent mainly on temperature 
 during each developmental stage. 
 
 Second- and third-stage larvae 
 (fig. 12) feed at the leaf margins 
 and characteristically stay in the 
 tree tops, migrating to the 
 undersides of branches and twigs 
 when not feeding. 
 
 Figure 11.— Typical feeding 
 damage caused by young larvae. 
 
 Figure 12.— A third-stage larva. 
 
 10 
 
Late- Stage Lanae 
 
 After molt to the fourth stage 
 (fig. 13), larval behavior changes 
 dramatically. Larvae feed during 
 the night, then descend the trees 
 at dawn in search of protective 
 locations where they rest for the 
 remainder of the day. At dusk 
 they climb the trees again to 
 feed. The movement up and 
 down the tree is apparently 
 triggered by light intensity. It is 
 during this stage of development 
 that defoliation can be severe 
 enough to be noticed. 
 
 Larvae prefer to rest under bark 
 flaps or other structures on trees 
 (fig. 14). If no hiding place is 
 available on trees, the insects will 
 descend to the ground and rest 
 
 Figure 13. — Newly emerged 
 fourth-stage larva. 
 
 Figure 14.— A bark flap 
 provides protection for gypsy 
 moth larvae and pupae. 
 
 11 
 
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 beneath leaf litter (fig. 15), dead 
 stumps, or other nearby objects. 
 Here they are often vulnerable to 
 attack by small mammal 
 predators such as mice, shrews, 
 and insects such as ground 
 beetles. At very high densities, 
 the larvae follow a different 
 pattern of behavior — they remain 
 on the foliage and feed 
 
 continuously day and night 
 (fig. 16). 
 
 Figure 15. — Late-stage larvae 
 resting in leaf litter at base of 
 tree. 
 
 Figure 16. — Foliage being 
 stripped by many late-stage 
 larvae. 
 
 12 
 
Pupae 
 
 i». 
 
 Larvae usually complete their 
 development in late June or early 
 July, attach themselves to a 
 surface with strands of silk, and 
 then transform into pupae (fig. 
 17). Usually this is in the same 
 locations where they rested as 
 late-stage larvae. Pupation lasts 
 about 2 weeks. Males usually 
 pupate before females because 
 they pass through one less larval 
 stage. The mahogany-colored 
 pupae are immobile and 
 defenseless and are vulnerable to 
 many different predators and 
 parasites. Female pupae are 
 usually larger than male pupae 
 (fig. 18); however, in dense 
 populations where available 
 foliage is limited, female and 
 male pupae may be the same 
 size. 
 
 Figure 17. — Newly formed 
 pupae attached to bark with 
 silken threads. 
 
 Figure 18.— Male (left) and 
 female pupae. 
 
 13 
 
Adults 
 
 Male moths usually emerge 
 before females (fig. 19). Males 
 are strong fliers and are usually 
 most active within the forest 
 canopy during daylight hours. 
 They fly in zigzag patterns and 
 can be seen searching up and 
 down tree trunks for female 
 moths. 
 
 The female moth has well- 
 developed wings but cannot fly. 
 She compensates for this by 
 releasing a strong sex attractant 
 from her abdomen that lures 
 male moths to her location. Soon 
 after mating occurs, the female 
 deposits her eggs in a single 
 mass, usually in the same 
 location where she pupated. 
 
 \9A 
 
 Figure 19. — Adult moths: A, 
 Male; B, female. 
 
 \9B 
 
 14 
 
Detecting the Gypsy Moth 
 
 Egg Masses 
 
 The presence of the gypsy moth 
 often goes unnoticed until trees 
 are partially defoliated. This 
 section describes how and where 
 to find the insect's life stages 
 before they become so numerous 
 as to cause damage. 
 
 20 A 
 
 Figure 20.— Good places to 
 check for egg masses: A, Bark 
 flaps; B, holes in trees. 
 
 Gypsy moth egg masses are the 
 life stage most often observed, 
 mainly because they are present 
 in the field from July to May 
 and persist even after the larvae , 
 emerge. New egg masses are firm 
 to the touch; hatched egg masses 
 are soft and spongy. Although 
 egg masses may be found 
 anywhere from in the leaf litter 
 on the forest floor to the tops of 
 trees, most are laid on the trees, 
 especially in protected refuges 
 such as bark flaps, crevices, and 
 holes (fig. 20). 
 
 20 B 
 
 15 
 
In suburban areas, egg masses 
 are frequently found in 
 woodpiles, rock walls, or other 
 protected locations around or on 
 homes. Homeowners should also 
 check lawn furniture, behind 
 shutters, underneath tree houses, 
 and beneath lower rows of 
 shingles on a house or garage 
 (fig. 21). 
 
 Figure 21. — Suburban areas 
 where egg masses can be found: 
 A, Woodpile at the base of this 
 tree is a Ukely place to find egg 
 masses; B, stone walls may 
 contain many egg masses and 
 other life stages; C, old pupal 
 skins and a hatching egg mass 
 at base of same stone wall; D. 
 tree houses also make good 
 homes for gypsy moths. 
 
 \\A 
 
 16 
 
Larvae and Pupae 
 
 When the feeding and resting 
 behavior of late-stage larvae 
 changes, they search out places 
 to rest during the day either on 
 the trees or on the ground. 
 Ultimately the larvae pupate in 
 these same places (fig. 22). 
 Burlap bands or skirts placed 
 about tree trunks of preferred 
 species such as oaks can aid the 
 homeowner to detect the presence 
 of gypsy moth larvae before 
 noticeable defoliation occurs. 
 Larvae climbing down the trees 
 early in the morning will locate 
 and crawl beneath the burlap 
 where they can be observed or 
 periodically removed and 
 destroyed. 
 
 attached at about 5 ft above the 
 ground. The burlap should be 
 folded in half and either stapled 
 to the tree from within the fold 
 or draped over a piece of string 
 or rope which is then tied 
 around the tree (fig. 23). It is 
 important that the folded burlap 
 is loosely attached to the tree so 
 that the larvae are able to crawl 
 beneath it from either the bottom 
 or the sides. 
 
 Figure 22. — Larvae and pupae 
 readily use bark flaps for resting 
 sites. 
 
 Figure 23. — Burlap band 
 (attached with twine) containing 
 gypsy moth pupae. 
 
 Burlap bands or skirts should be 
 less than one-half the diameter of 
 the tree wide and should be 
 
 17 
 
Hosts of the Gypsy Moth 
 
 Various reports indicate that 
 gypsy moth larvae can feed on at 
 least 500 species of plants that 
 include trees, shrubs, and vines. 
 This host list will continue to 
 grow as the gypsy moth spreads 
 to the South and West. For 
 example, it has recently been 
 shown that gypsy moth larvae 
 can successfully feed and develop 
 on many cultivated trees, shrubs, 
 and vines important to agriculture 
 in California. 
 
 hemlock, southern white cedar, 
 and the pines and spruces native 
 to the East. 
 
 The gypsy moth avoids ash, 
 balsam fir, butternut, black 
 walnut, catalpa, red cedar, 
 flowering dogwood, American 
 holly, locust, sycamore, and 
 yellow or tulip poplar, and 
 shrubs such as mountain laurel 
 (fig. 24), rhododendron, and 
 arborvitae. 
 
 In the East, the gypsy moth's 
 favorite trees include apple, 
 speckled alder, basswood, gray 
 and river birch, hawthorne, oak, 
 poplar, and willow. Less desired 
 but still attacked are black, 
 yellow, and paper birch, cherry, 
 Cottonwood, elm, blackgum, 
 hickory, hornbeam, larch, maple 
 and sassafras. Older gypsy moth 
 larvae devour the foliage of 
 several species that younger 
 larvae normally avoid, such as 
 
 This list is provided only as a 
 guideline for possible 
 consideration in choosing 
 landscape plantings. The 
 susceptibility of less preferred 
 species to defoliation also 
 depends upon the species 
 composition of forests in the 
 surrounding area and the severity 
 of nearby infestations. 
 
 Figure 24. — Laurel was ignored 
 by larvae, although surrounding 
 trees were defoliated. 
 
 18 
 
Effects of Defoliation on 
 Trees 
 
 25 
 
 One must see an episode of 
 severe defoliation by the gypsy 
 moth to appreciate fully the 
 dramatic impact this insect can 
 have. Most noticeable, of course, 
 is the great change in appearance 
 of yards and gardens, when 
 autumn appears to have arrived 
 months ahead of time. Sometimes 
 these visual effects are temporary, 
 lasting but a few weeks until a 
 new set of leaves is produced. 
 
 Sometimes, however, because trees 
 may be seriously weakened by 
 defoliation, the effects are long 
 lasting. Tree tops may become 
 thin and off color, and buds and 
 
 branches may die (fig. 25); some 
 trees may die altogether. 
 
 Whether or not a tree succumbs 
 to defoliation by the gypsy moth 
 depends on three main factors: 
 Tree condition, the number and 
 severity of prior defoliations, and 
 the presence of organisms that 
 attack and kill stressed trees. 
 
 Figure 25.— Dieback of upper 
 branches on a stressed tree. 
 
 19 
 
Tree Condition 
 
 Number and Severity of Previous 
 Defoliations 
 
 Trees weakened by construction 
 (by being wounded, by water 
 being altered, or by sudden 
 exposure to drying winds or 
 bright, hot sun) or by other 
 stress agents such as too httle or 
 too much water, frosts, leaf 
 diseases, or herbicides are likely 
 to suffer more drastically from 
 gypsy moth defoliation than 
 healthy, nonstressed trees. But 
 even healthy trees can suffer 
 from defoliation if enough of 
 their leaves are removed in 
 successive years. 
 
 How severely can trees be 
 defoliated and not suffer? How 
 often can this occur before trees 
 are adversely affected? Although 
 there are no simple answers to 
 these questions, a general rule is 
 that a tree is seriously affected 
 by defoliation when enough 
 leaves are removed to cause it to 
 produce a second crop of leaves 
 in the same growing season. This 
 process is called refoliation. 
 
 Because leaves produce the tbod 
 required by the tree for life and 
 growth, any reduction in their 
 numbers, no matter how small, 
 reduces the amount of food 
 manufactured. But because most 
 trees produce more food than 
 they need to survive, they can 
 tolerate some loss of leaves. 
 Indeed, loss of up to about half 
 the leaves results in little more 
 than reduction in growth. But 
 when more than half of the 
 leaves are eaten, not enough food 
 and other substances needed for 
 growth are produced; this 
 situation triggers the process of 
 refoliation. When all the leaves 
 are eaten and no food is 
 produced, the tree must subsist 
 on its reserve foods until new 
 leaves are formed. Gypsy moth 
 defoliation is especially 
 detrimental because it occurs at 
 precisely the most critical time 
 for the tree — when growth is 
 most active and when food 
 reserves are at their lowest 
 normal levels. 
 
 20 
 
26 A 
 
 IbB 
 
 When enough leaves are eaten to 
 cause the tree to refohate, 
 changes occur both outside and 
 inside the tree. After 2 to 3 
 weeks, buds begin to open and a 
 second crop of leaves develops. 
 These leaves are often smaller 
 and are a lighter green than those 
 produced in spring (fig. 26). 
 Inside the tree, defoliation and 
 the refoliation process have 
 markedly reduced the amount of 
 food energy reserves, energy that 
 the tree needs to maintain itself 
 during the winter dormant period 
 and to produce buds and twigs 
 in the early spring. Low energy 
 reserves, together with the 
 desiccation of immature buds 
 produced during refoliation, will 
 result in the death of buds, twigs, 
 and branches during winter 
 months. 
 
 If no defoliation occurs the 
 following year, most trees (except 
 for trees already in poor 
 condition) will survive and regain 
 their former fullness. But 
 defoliation, even at low levels, 
 can be harmful if repeated for 
 several years; even healthy trees 
 may die if they go through the 
 defoliation/refoliation process for 
 2 or 3 years in succession. 
 
 Figure 26. — Refoliated leaves of 
 defoliated trees (A) are usually 
 smaller and lighter green than 
 normal leaves (B). 
 
 21 
 
Mortality-Causing Organisms 
 
 The final blow to most defoliated 
 trees is dealt by opportunistic 
 organisms that can successfully 
 attack and kill trees stressed by 
 defoliation. One of these 
 organisms, the shoestring root-rot 
 fungus, Armillaria mellea, enters 
 the bark and wood of weak, 
 dying, or dead roots. The fungus 
 grows rapidly between the bark 
 and wood of the roots and root 
 collar (fig. 27) and can kill the 
 tree quickly. Armillaria also can 
 decay tissues of the roots that 
 store food or that absorb and 
 transport food, water, and 
 minerals. In addition, death of 
 small roots may start a cycle of 
 decline that can result in the 
 tree's death. 
 
 Another organism that can 
 invade oaks weakened by 
 defoliation is the twolined 
 chestnut borer, Agrilus bilineatus. 
 This insect attacks and chews 
 feeding tunnels under the bark of 
 branches and tree trunks (fig. 28). 
 These tunnels in the outer wood 
 and inner bark interfere with the 
 passage of food, water, and 
 minerals causing the death of 
 more branches and roots. 
 
 The combined attacks by the 
 shoestring fungus in the roots 
 and root collar and the twolined 
 chestnut borer in the branches 
 and stems usually result in tree 
 death. Often, attacked trees die 
 so rapidly, especially in late 
 summer, that their leaves 
 suddenly wilt and turn brown. 
 
 Figure 27. — Dead oak tree with 
 bark removed to show white 
 fans of the shoestring root-rot 
 fungus. 
 
 Figure 28. — Dead oak tree with 
 bark removed to show feeding 
 tunnels of the twoHned chestnut 
 borer. 
 
 22 
 
Managing the Gypsy Moth 
 
 The Natural Enemy Complex 
 
 There are two approaches to 
 preventing or alleviating the 
 problems of gypsy moth 
 invasions: One is directed against 
 the insect; the other is designed 
 to improve the growing 
 conditions for trees around the 
 home. 
 
 In addition to knowing about the 
 gypsy moth and the damage it 
 inflicts, you should be aware of 
 the many natural enemies that 
 collectively destroy it, because the 
 actions you select to control the 
 gypsy moth may also affect these 
 many beneficial organisms. 
 
 The natural enemy complex, 
 which is composed of parasites, 
 predators, and disease, does not 
 control the gypsy moth in 
 outbreak situations but does aid 
 in maintaining certain sparse 
 gypsy moth populations at low 
 levels. It may also help to extend 
 the period of years between 
 outbreaks. Disease is the major 
 factor in halting outbreaks, but 
 unfortunately this occurs only 
 after the full impact of gypsy 
 moth defoliation has been 
 realized. 
 
 23 
 
Parasites 
 
 Parasites are living organisms that 
 make their homes on or in the 
 bodies of other Hving organisms 
 (hosts) from which they get 
 nourishment during at least one 
 stage of their life. A parasite 
 usually requires only a single 
 individual of the host species to 
 complete its development. 
 
 In North America, there are 
 about a dozen species of 
 parasites that attack various 
 gypsy moth life stages, and their 
 abundance varies greatly from 
 place to place and year to year. 
 
 Several species of small wasps 
 attack the various life stages of 
 the gypsy moth. One of the most 
 common species, Ooencyrtus 
 kuvanae, attacks the eggs 
 wherever they occur, resulting in 
 small pinholes on the surface of 
 the egg mass (fig. 29). Apanteles 
 melanoscelus attacks and kills 
 small larvae (fig. 30), and 
 Brachymeria intermedia (fig. 31) 
 stings gypsy moth pupae but is 
 most effective only when gypsy 
 moth populations are at 
 defoliating levels. 
 
 Three species of files that are 
 slightly larger than the common 
 house fiy attack large larvae and 
 are important parasites of the 
 gypsy moth. One of them, 
 Parasetigena agilis, lays its eggs 
 near the head of the larvae (fig. 
 32). The maggots (or larvae) of 
 these files develop to maturity 
 within gypsy moth larvae and 
 pupae, leaving only the outer 
 shells behind (fig. 33). 
 
 Figure 29.— Weathered egg mass 
 showing pinholes caused by egg 
 parasite. 
 
 Figure 30.— Attached cocoons of 
 a wasp that kills young larvae. 
 
 24 
 
Figure 31.— A small wasp that 
 stings gypsy moth pupae. 
 
 Figure 32.— Eggs of a fly 
 parasite attached to late-stage 
 larva. 
 
 Figure 33.— Maggots of parasite 
 fly eventually destroy the pupae, 
 leaving only the outer shell. 
 
 25 
 
Predators 
 
 Whereas parasites are usually 
 smaller than the host they attack 
 and develop within a single 
 individual, predators usually are 
 larger than their prey and 
 consume many host insects 
 during the course of their life. 
 They are very active, live longer, 
 and are opportunistic in that they 
 may prey upon a variety of 
 insects, depending on what is 
 available. 
 
 Although predators destroy many 
 life stages of the gypsy moth, 
 their importance has probably 
 been underestimated because they 
 consume their prey quickly and 
 leave few if any remains. 
 Woodland mammals can consume 
 large numbers of gypsy moth 
 larvae and pupae in forested 
 areas. Some mammals eat only 
 one life stage of gypsy moth, 
 while others may eat as many as 
 
 three. Some mammalian predators 
 of the gypsy moth include the 
 white-footed mouse (fig. 34), 
 shrews, chipmunks, voles, and 
 squirrels. Shrews, which are often 
 mistaken for mice, are voracious 
 insect feeders (fig. 35) that 
 consume their own weight in 
 prey each day. Unfortunately, 
 mice and shrews are probably 
 not important as predators in 
 suburban settings because they 
 are eliminated by domestic 
 animals such as the common cat 
 and because their natural habitat, 
 forest litter, is frequently 
 destroyed. 
 
 Figure 34. — White-footed mice 
 eating larvae. 
 
 26 
 
Many species of birds have been 
 observed feeding on gypsy moth 
 larvae or adults. Nuthatches, 
 chickadees (fig. 36), towhees, 
 vireos, northern orioles, catbirds, 
 robins, and blue jays are 
 probably more important in 
 sparse gypsy moth populations. 
 Cuckoos (fig. 37 ) and flocking 
 species such as starlings, grackles, 
 red-winged blackbirds, and crows 
 
 may be attracted to areas where 
 the gypsy moth exists in large 
 numbers. 
 
 Figure 35. — Shorttail shrew 
 eating larva. 
 
 Figure 36. — The black-capped 
 chickadee feeds on all gypsy 
 moth life stages. 
 
 Figure 37.— The black-billed 
 cuckoo prefers hairy caterpillars 
 like the gypsy moth. 
 
 27 
 
39 
 
 Less is known about the 
 importance of insect or insect- 
 related predators of the gypsy 
 moth, ahhough more is being 
 learned about their importance. 
 Ground beetle larvae and adults 
 feed readily on gypsy moth 
 larvae and pupae (fig. 38) and 
 are usually most evident when 
 gypsy moths are numerous. These 
 beetles are very active and 
 readily climb trees in search of 
 their prey. Many gypsy moth 
 larvae and pupae that rest on or 
 
 near the ground are destroyed by 
 spiders (fig. 39), ants, and 
 harvestmen (daddy longlegs). The 
 collective value of these 
 organisms has not been widely 
 recognized because they are less 
 conspicuous than other predators. 
 and their activities are difficult to 
 monitor. 
 
 Figure 38.— This ground beetle 
 destroys both larvae and pupae. 
 
 Figure 39. — Many kinds of 
 spiders kill gypsy moths. 
 
 28 
 
Disease 
 
 40 
 
 There are many diseases caused 
 by bacteria, fungi, or viruses that 
 kill gypsy moth larvae. Only one, 
 however, the nucleopolyhedrosis 
 virus (NPV), has a dramatic 
 effect on gypsy moth populations, 
 frequently resulting in the total 
 collapse of outbreaks. Virus-killed 
 larvae are commonly seen 
 hanging in an inverted V-shaped 
 form from trees (fig. 40); their 
 bodies are dark and flaccid and 
 contain only liquified material 
 composed mainly of the 
 
 infectious virus. Large numbers of 
 virus-killed larvae usually indicate 
 a general collapse caused by the 
 virus. 
 
 Figure 40. — Larva killed by 
 disease caused by a natural 
 virus. 
 
 29 
 
Guidelines for Tree Survival 
 
 Maintain Good Conditions for 
 Growing Trees 
 
 41 p'Mp™*'-'' m|-^.lnt! w,^-.f w !?,»- 
 
 Trees that are stressed are more 
 vulnerable to defoliation and the 
 opportunistic organisms that 
 frequently attack them, so efforts 
 should be made to keep trees in 
 a good state of health or vigor. 
 Nearly all the recommendations 
 discussed here emphasize the 
 importance of maintaining good 
 soil nutrient and moisture 
 relationships. 
 
 • Keep soil conditions favorable 
 for the development and survival 
 of the tree's fine feeder root 
 system. Construction activities 
 such as cutting and filling, 
 installing utility and septic tank 
 field lines, changing grades, 
 paving, and cutting down the 
 surrounding forest may have 
 harmful effects on soil/moisture 
 relations. A general rule is to do 
 no more than is necessary. 
 
 • In wooded backyards, or in 
 yards where lawns and forests 
 meet, an attempt should be made 
 to keep the forest floor surface 
 as natural as possible (fig. 41). 
 Because oaks thrive under acid 
 soil conditions, removal of their 
 organic acid-rich leaf litter can 
 
 be harmful. Layers of natural leaf 
 litter help prevent drying out 
 surface soil layers that contain 
 the bulk of the tree's feeder roots 
 and provide a natural habitat for 
 predators such as mice and 
 shrews that prey upon gypsy 
 moth larvae and pupae. 
 
 • Growth conditions for isolated 
 trees planted on lawns can be 
 enhanced by encircling them with 
 mulch or ground cover plants 
 (when practical) out to an area 
 delimited by the outer branches. 
 A dense grass layer over feeder 
 roots causes severe competition 
 for moisture and nutrients. 
 Applications of lime or weed 
 killers around forest trees can 
 seriously damage shallow tree 
 roots. 
 
 • In times of drought, stressed 
 individual trees can also benefit 
 from watering, fertilizing, and 
 judicious pruning to thin the tree 
 tops and reduce moisture 
 demands on the roots. 
 
 Figure 41. — Wooded areas 
 adjacent to lawns should be 
 kept in a natural state. 
 
 30 
 
Discourage Survival and Destroy Life 
 
 Stages 
 
 
 
 There are other practices that 
 directly affect the insect itself, 
 especially in sparse populations, 
 and that should be considered as 
 part of a total preventive 
 program around the home. 
 
 • Remove objects around the 
 yard that provide shelter for 
 gypsy moth larvae and pupae 
 and increase their chances for 
 survival. These include natural 
 objects such as bark flaps, dead 
 branches (fig. 42) and trees, 
 stumps, and debris on the ground 
 such as boxes, cans, or old tires. 
 
 • Diversify composition of trees 
 and plants or encourage those 
 species that are known to be 
 unpopular with the insect. Species 
 such as tulip or yellow poplar, 
 honeylocust, ash, maple, hickory, 
 dogwood, mountain ash, and 
 many conifers can be 
 incorporated into a landscaping 
 
 plan that will make your 
 property less susceptible to gypsy 
 moth and other defoliators as 
 well. Check first with your 
 nurseryman, arborist, or county 
 cooperative extension agent to 
 select those tree species that are 
 most compatible with your 
 particular climate and soil and 
 site situation. 
 
 • During the winter months, 
 remove and destroy egg masses 
 that are found on or around 
 homes and premises. Carefully 
 inspect buildings such as 
 toolsheds, garages, and tree 
 houses, as well as stone walls, 
 woodpiles, and fencing for hidden 
 egg masses. Check lawn chairs and 
 other yard equipment for egg 
 masses before storing them away 
 for the winter. 
 
 Figure 42. — Dead branches and 
 bark flaps should be removed. 
 
 31 
 
Figure 43. — Many gypsy moth 
 larvae resting beneath burlap 
 skirt. 
 
 Figure 44. — This maple was 
 disfigured where a homeowner 
 placed a band of sticky material 
 around the tree. 
 
 • Place burlap on trees, especially 
 oaks, and destroy gypsy moth 
 larvae and pupae that hide 
 beneath during daylight hours 
 (fig. 43). The burlap also aids in 
 keeping tabs on numbers of the 
 insect and encourages activity by 
 resident parasites and predators 
 that search out protected 
 locations for larvae and pupae. 
 
 • Placing a band of sticky 
 material (such as grease, tar, or 
 other petroleum product) around 
 trees to entrap gypsy moth larvae 
 is not encouraged. These 
 materials can cause injury 
 (swelling and cankering) on thin- 
 barked trees such as maples and 
 young oaks (fig. 44). 
 
 32 
 
Protect Foliage From Defoliation 
 
 Under normal circumstances, 
 when few insects are observed, 
 annual protective spraying of 
 pesticides on trees and shrubs 
 around the home to control the 
 gypsy moth is probably not 
 justified and may have an 
 adverse effect on the insect's 
 natural enemy complex. Your 
 decision to use or not use 
 pesticides should be influenced by 
 environment, economics, and 
 practical concerns as they relate 
 to the following: 
 
 Number of and kind of trees — Is 
 there a large proportion of 
 preferred hosts on your property? 
 
 Tree condition — Are your trees 
 showing signs of decline (dead or 
 dying branches) especially near 
 the top? 
 
 Proximity to other areas of 
 infestation — Is your property 
 located adjacent to areas heavily 
 infested with gypsy moth? 
 (Windblown first-stage larvae and 
 migrating late-stage larvae in 
 search of food can infest your 
 property.) 
 
 History of past infestation — Were 
 your trees recently defoliated by 
 gypsy moth or other insects? 
 
 Indications of anticipated severity — 
 Have you observed gypsy moth 
 larvae feeding on your trees, 
 resting under bark flaps, burlap 
 bands, or in other protected 
 locations? Are gypsy moth larvae 
 numerous enough to be 
 considered a nusiance to you on 
 your property? 
 
 If the answer to three or more of 
 these questions is yes, then you 
 should consider the use of a 
 chemical or biological pesticide to 
 protect foliage of your trees and 
 to reduce the number of gypsy 
 moths. There are several 
 pesticides registered for control of 
 the gypsy moth. To obtain the 
 most current recommendations on 
 pesticides and their application in 
 your area, you should contact a 
 county cooperative extension 
 agent. State entomologist, 
 nurseryman, arborist, city or St^te 
 forester, or specialists at your 
 State university or agricultural 
 experiment station. 
 
 33 
 
Acknowledgments 
 
 References 
 
 Figure 4 is used through the 
 courtesy of the Connecticut 
 Agricultural Experiment Station, 
 New Haven. 
 
 We thank the Encyclopaedia 
 Britannica Educational 
 Corporation for kindly allowing 
 the use of figures 36 and 37, 
 which were copyrighted 1962-64. 
 
 These publications may be of 
 interest to homeowners 
 confronted with the gypsy moth 
 problem: 
 
 Campbell, R. W. 1975. The gypsy 
 moth and its natural enemies. 
 U.S. Dep. Agric, Agric. Info. 
 Bull. 381. 
 
 McManus, M. L., and R. T. 
 Zerillo. 1979. The gypsy moth: 
 An illustrated biography. U. S. 
 Dep. Agric, Home and Garden 
 Bull. 225. 
 
 Smith, H. R., and R. A. 
 Lautenschlager. 1978. Predators of 
 the gypsy moth. U. S. Dep. 
 Agric, Agric Handb. 534. 
 
 Talerico, R. L. 1978. Major 
 hardwood defoliators of the 
 Eastern United States. U. S. Dep. 
 Agric, Home and Garden Bull. 
 
 224. 
 
 Wargo, P. M. 1978. Defoliation 
 by the gypsy moth: How it hurts 
 your tree. U. S. Dep. Agric. 
 Home and Garden Bull. 223. 
 
 Issued August 1979 
 
 Available from the Superintendent 
 
 of Documents 
 
 U. S. Government Printing Office 
 
 Washington, DC. 20402 
 
 Stock No. 001-000-03950-4 
 
 34 
 
 it U.S. GOVERNMENT PRINTING OFFICE : 1979 O— 275-407 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 08584 2978