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GYPSY MOTH, Lymantria dispar (L.) -- Lymantriideae [ also called Porthetria dispar (L.) ]

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This insect is native to the Palearctic region where it is a pest of broadleaf forests in eastern and southern Europe. It was brought to North America and accidentally released in Medford, Massachusetts in 1868 by an astronomer, Dr. Leopold Trouvelot, who wished to study it in the laboratory for its potential in silk production. Since then it has become a serious pest of hardwoods throughout the northeastern United States and has a continually expanding range which currently extends into Ontario, Quebec and southward into Virginia with isolated infestations in Minnesota, Oregon and occasionally California.

A biological control project was organized by the U. S. Department of Agriculture, Bureau of Entomology in 1905 and extensive foreign exploration for parasitoids and predators was carried out in Europe, Japan, North Africa and Asia at various intervals since that time (Doane & McManus 1981). This was the first major classical biological control project against a forest insect, directed by Dr. L. O. Howard, Chief of the Bureau of Entomology. DeBach (1974) revealed that a large number of young American entomologists were employed on the gypsy moth project, some becoming famous later on, e.g., P. H. Timberlake (uncle of President Richard Nixon), H. S. Smith, W. R. Thompson and J. D. Tothill.

The gypsy moth project has revealed that (1) insect disease was recognized as an important biological control factor, (2) the sequence theory of natural enemies was introduced by W. F. Fiske, (3) a number of future important contributors to biological control were trained on the project (H. S. Smith, W. R. Thompson and W. D. Tothill), (4) sleeve cages were invented as well as other equipment and techniques that are still in use today and (5) L. O. Howard and W. F. Fiske were the first to clearly distinguish between those causes of mortality that act in relation to the density of the population and those that do not. L. O. Howard also stimulated the Canadian interest in biological control in the early 1900's by making available facilities and scientific assistance from the Melrose Highlands Parasite Laboratory of the U. S. Bureau of Entomology.

Early importations of natural enemies occurred between 1905-14 and again between 1922-33. While some collections were made in Japan, attention focused on Europe where temporary field laboratories were placed wherever gypsy moth outbreaks were sufficient to permit the rearing of parasitoids from a large number of hosts. Frequent shipments of parasitoids and predators were made to the gypsy moth laboratory at Melrose Highlands, Massachusetts and this resulted in the liberation of >690,000 living insects of more than 45 species during this period (Dowden 1962). The enormous importation and multiple release program enabled two larval/pupal predators, two egg parasitoids, six larval parasitoids and one pupal parasitoid to become established in the New England states. The two egg parasitoids were also subject to either large scale rearing releases in the case of Ooencyrtus kuwanae (How.), or to large scale relocation releases in the case of Anastatus disparis Ruschka. Most of the establishments occurred rapidly after the initial field releases but the tachinids Parasetigena silvestris (R.-D.) and Exorista larvarum (L.) were not recovered until 1937 and 1940 respectively and the chalcidid Brachymeria intermedia (Nees) was only recovered in 1965.

Biological control by established parasitoids and predators in New England was limited and large scale aerial applications of DDT were used until the early 1960's. Since 1960 renewed interest in the search for additional natural enemies has extended explorations in Europe, Japan, Morocco, India, Iran and Korea (Doane & McManus 1981). Since 1963 the USDA Agricultural Research Service Beneficial Insects Research Laboratory has continued to receive gypsy moth natural enemies in their quarantine facilities and have been able to distribute more than 200,000 individuals of about 60 species to other State and Federal facilities for culture, study and field release. From 1966 until 1971, the Gypsy Moth Methods Improvement Laboratory at Otis Air Force Base in Massachusetts was charged with the development of rearing procedures for the imported natural enemies. From 1963-71 in conjunction with the New Jersey Department of Agriculture about 7 million parasitoids of 17 species were reared and released in the forests of New Jersey and Pennsylvania. Then from 1971-77 a Gypsy Moth Parasite Distribution Program was established in which the New Jersey Dept. of Agriculture and the University of Maryland reared and released an additional two million parasitoids of 18 species throughout the New England states. Since the late 1970's more new parasitoids and a predator from Japan and Korea and from the Indian gypsy moth, Lymantria obfuscata Walk., have been imported (Coulson et al. 1986). More than 100,000 individuals of nine new species or strains have been released in the field in Delaware, Massachusetts and Pennsylvania.

Although much knowledge of the biology and rearing methods of the imported parasitoids was gained during this massive program of importation, propagation and release, it has resulted in the addition of only a single pupal parasitoid, Coccygomimus disparis (Vier.) to the complex of 10 species established during the initial importation program. This has prompted Tallamy (1983) to compare the establishment of gypsy moth parasitoids with island biogeography theory, suggesting that a dynamic equilibrium now exists between further introductions and the extinction of established parasitoids. In the last 30 years two of the parasitoids that were initially established, Anastatus disparis and Exorista larvarum have become very rare, while two pupal parasitoids Brachymeria intermedia and C. disparis have become established. However, the main reasons for the failure to establish additional parasitoids in recent years are the parasitoids' requirements for suitable alternative overwintering hosts for their second generation each year and the fact that several of the parasitoid species released during the 1960's were not closely associated with gypsy moth as a principal host in their areas of origin (Dahlsten & Mills 1999).

The failure of the established natural enemies to control expanding outbreaks of the gypsy moth encouraged attempts during the 1970's to augment the impact of previously established species. Through inundative releases of Cotesia melanoscelus (Ratz.), Weseloh & Anderson (1975) were able to show significantly increased rates of parasitism but this had little influence on foliage protection or egg mass counts for the following generation. On the other and several other inundative releases of this and other species failed to provide any evidence of increased parasitism in comparison to control plots (Doane & McManus 1981). The combined release of parasitoids and pathogens has been used as a method of augmentation. Wollam & Yendol (1976) were able to show a synergistic effect of the release of C. melanoscelus in plots treated with a double application of low concentration Bacillus thuringiensis over plots treated with each of these natural enemies alone. The resultant reduction in defoliation and subsequent egg mass densities has more recently been attributed to the retarding effect of B. thuringiensis on host larval growth which exposes the younger larvae to parasitism for a longer period of time (Weseloh et al. 1983). A similar effect of C. melanoscelus in conjunction with viral treatments is unlikely to occur since this parasitoid avoids oviposition in moribund host larvae (Versoi & Yendol 1982).

Augmentation through use of microbial pathogens has been of considerable importance against gypsy moth with significant advances in recent years. Early trials with B. thuringiensis in the 1960's were not effective in providing foliage protection; but the discovery of improved strains (Dubois 1985b) and successive improvements in formulation and application technology during the late 1970's and early 1980's led to greater success. The results of aerial applications during the 1970's remained highly variable but a recommendation of double application of low concentrations was developed and used operationally for the first time on a large scale in 1980. This also met with limited success but further experimental work in the early 1980's (Dubois 1985a) indicated that the use of higher concentrations and acrylamide stickers could provide not only good foliage protection but also could reduce subsequent egg mass densities significantly with a single application. This development reduced the cost of B. thuringiensis applications and has been used operationally with success on 40-70% of the 1.3-1.5 million ha. of hardwood forest treated since 1983.

Many field trials have been conducted with virus sprays against gypsy moth both in North America and Europe (Cunningham 1982). An NPV virus strain (Hamden standard) isolated from a natural epizootic in Connecticut in 1967 forms the basis for the commercially produced "Gypchek" that was registered for use against gypsy moth in North America in 1978. However, early trials of the baculovirus produced erratic results and while continued improvements in formulation and application have produced more positive results, it has never been accepted for operational use (Podgwaite 1985). Reasons for this are the relatively low virulence of the virus, its rapid degradation on foliage in the field and the more recent successes with the use of B. thuringiensis.

Dahlsten & Mills (1999) point out that the gypsy moth program has been spectacular in both the scale and the continued enthusiasm with which it has been conducted, but that the results have been disappointing and serve as a good example of the failure of classical biological control in situations where the introduced pest is also severe in its region of origin. Therefore the search for natural enemies in areas where gypsy moth is not a pest, in non-outbreak populations or from related non-pest Lymantria species may prove to be a better strategy.

For further details on biological control efforts and biologies of host and natural enemies, please see the following (Fiske 1910, Howard 1910, Howard & Fiske 1911, Burgess 1915, Burgess & Collins 1915, Culver 1919, Tothill 1919, Crossman 1922, 1925; Escaleva 1926, Webber & Schaffner 1926, Muesebeck & Dohanian 1927, Burgess & Crossman 1929, Lepiney 1933, Schaffner 1934, Baeta-Neva & Azeveda 1944, Templado 1957, Hitchcock 1959, Tadic & Bin…ev 1959, Dowden 1961a,b; Tadic 1962, Salatic 1963, Bjegovic 1964, Leonard 1966, 1967; Clausen 1978)

REFERENCES: [Additional references may be found at: MELVYL Library ]

Baeta Neves, C. M. & F. A. e Silva. 1944. Nota sobre a aplicacao da luta biologica na companha da Lymantria. Bol. Junta Nac. Cortica (Lisbon) 63: 101-03.

Bellows, T. S. & T. W. Fisher (eds.). 1999. Handbook of Biological Control: Principles and Applications. Academic Press, San Diego, New York. 1046 p.

Bjegovic, P. 1964. The dependence of the sex ratio of Anastatus disparis Ruschka on the phase of embrionic development of the host. Zast. Bilja 15: 569-76.

Burgess, A. F. 1915. Report on the gypsy moth work in New England. U. S. Dept. Agric. Bull. 204. 32 p.

Burgess, A. F. & C. W. Collins. 1915. The Calosoma beetle (Calosoma sycophanta) in New England. U. S. Dept. Agric. Bull. 251. 40 p.

Burgess, A. F. & S. S. Crossman. 1929. Imported insect enemies of the gypsy moth and the brown-tail moth. U. S. Dept. Agric. Tech. Bull. 86. 147 p.

Clausen, C. P. 1978. Lymantriidae. In: C. P. Clausen (ed.), Introduced Parasites and Predators of Arthropod Pests and Weeds: A World Review. U. S. Dept. Agric., Agric. Handbk. No. 480. 545 p.

Coulson, J. R., R. W. Fenster, P. W. Schaefer, L. R. Ertle, J. S. Kelleher, & L. D. Rhoads. 1986. Exploration for and importation of natural enemies of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), in North America: an update. Proc. Ent. Soc. Wash. 88: 461-75.

Crossman, S. S. 1922. Apanteles melanoscelus, an imported parasite of the gypsy moth. U. S. Dept. Agric. Bull. 1028. 25 p.

Crossman, S. S. 1925. Two impoirted egg parasites of the gypsy moth, Anastatus bifasciatus Fonsc. and Schedius kuvanae Howard. J. Agric. Res. 30: 643-75.

Culver, J. J. 1919. A study of Compsilura concinnata, an imported tachinid parasite of the gypsy moth and the brown-tail moth. U. S. Dept. Agric. Bull. 776. 27 p.

Cunningham, J. C. 1982. Field trials with baculoviruses: control of forest insect pests, p. 335-386. In: E. Kurstak (ed.), "Microbial and Viral Pesticides. Marcel Dekker, Inc., New York. 720 p.

Dahlsten, D. L. & N. J. Mills. 1999. Biological Control of Forest Insects. In: Bellows, T. S. & T. W. Fisher (eds.), Handbook of Biological Control: Principles and Applications. Academic Press, San Diego, New York. 1046 p

DeBach, P. 1974. Biological Control by Natural Enemies. Cambridge University Press, London & New York. 323 p.

Doane, C. C. & M. L. McManus. 1981. The gypsy moth: research toward integrated pest management. USDA Forest Service Tech. Bull. 1584. 757 p.

Dowden, P. B. 1961a. The persistence of gypsy moth parasites in heavy sprayed areas of Cape Cod, Msssachusetts. J. Econ. Ent. 54: 873-75.

Dowden, P. B. 1961b. The gypsy moth egg parasite Ooencyrtus kuwanai in southern Connecticut in 1960. J. Econ. Ent. 54: 876-78.

Dowden, P. B. 1962. Parasites and predators of forest insects liberated in the United States through 1960. USDA, Forest Service, Agric. Handbook No. 226, 70 pp.

Dubois, N. R. 1985a. Recent field studies on the use of Bacillus thuringiensis to control the gypsy moth (Lymantria dispar L.). Proc. Symposium Microbial Control of Spruce Budworms and Gypsy Moths. USDA For. Serv. GTR-NE-100. p. 83-85.

Dubois, N. R. 1985b. Selection of new more potent strains of Bacillus thuringiensis for use against gypsy moth and spruce budworm. Proc. Symposium Microbial Control of Spruce Budworms and Gypsy Moths, USDA For. Serv. GTR-NE-100. p. 99-102.

Escalera, F. M. de la. 1926. Un neuvo ensayo para combatir en Argelia la plaga de Lymantria dispar (Lep.). 3rd Internatl. Cong. Ent. Proc. 2: 414-16.

Fiske, W. F. 1910. Parasites of the Gypsy and Brown-tail Moths Introduced Into Massachusetts. Wright & Potter Printing Co., Boston. 56 p.

Hitchcock, S. W. 1959. Number of fall generations of Ooencyrtus kuwanae (How.) in gypsy moth eggs. J. Econ. Ent. 52: 764-65.

Howard, L. O. 1910. Technical results from the gypsy moth laboratory. I. The parasites reared or supposed to have been reared from the eggs of the gypsy moth. U. S. Dept. Agric. Bur. Ent. Tech. Ser. 19, pt. 1. 12 p.

Howard, L. O. & W. F. Fiske. 1911. The importation into the United States of the parasites of the gypsy moth and the brown-tail moth. U. S. Dept. Agric. Bur. Ent. Bull. 91: 344 p.

Leonard, D. E. 1966. Brachymeria intermedia (Nees) (Hymenoptera: Chalcididae) established in North America. Ent. News 77: 25-7.

Leonard, D. E. 1967. Parasitism of gypsy moth in Connecticut by Brachymeria intermedia. J. Econ. Ent. 60: 600-01.

Lepiney, J. de. 1933. Le role de la direction des eaux et forets du Maroc et de l'Institut Scientifique Cherifien dans la lutte biologique entreprise contre Lymantria dispar a laaide de Schedius kuwanae. 5th Internatl. Cong. Ent. Proc. (1932) 5: 807-12.

Muesebeck, C. F. W. & S. M. Dohanian. 1927. A study in hyperparasitism, with particular reference to Apanteles melanoscelus (Ratzeburg). U. S. Dept. Agric. Dept. Bull. 1487. 35 p.

Podgwaite, J. D. 1985. Gypchek: past and future strategies for use. Proc. Symposium: Microbial Control of Spruce Budworms and Gypsy Moths. USDA For. Serv. GTR-NE-100. p. 91-93.

Salatic, S. 1963. Results of investigations of some factors of effectiveness of gypsy moth egg parasites. Zastita Bilja, Belgrade 14: 693-99.

Schaffner, J. V., Jr. 1934. Introduced parasites of the brown-tail and gypsy moths reared from native hosts. Ann. Ent. Soc. Amer. 27: 585-92.

Tadic, M. 1962. Numerical relationship between Anastatus disparis R. and Ooencyrtus kuwanae How. in certain localities of Yugoslavia. Agron. Glasnik 5-7: 548-52.

Tadic, M. & B. Bin…ev. 1959. Gubar. Resultati rada na njegovom prou…avanju i suzbyanju kod nas u toku 1958 Godine. Plant Protect. 1959: 51-59.

Tallamy, D. W. 1983. Equilibrium biogeography and its application to insect host-parasite systems. Amer. Nat. 121: 244-54.

Templado, J. 1957. Datos sobre Ooencyrtus kuwanai How. (Calcidido parásito de Lymantria dispar L.) en España. Inst. Biol. Appl. Pub. 25: 119-29.

Tothill, J. D. 1916. The introduction and establishment in Canada of the natural enemies of the brown-tail and gypsy moths. Agric. Gaz. Canada 3: 111-16.

Versol, P. L. & W. G. Yendol. 1982. Discrimination by the parasite, Apanteles melanoscelus, between healthy and virus-infected gypsy moth larvae. Environ. Ent. 11: 42-45.

Webber, R. T. & J. V. Schaffner, Jr. 1926. Host relations of Compsilura concinnata Meigen, an important tachinid parasite of the gypsy moth and the brown-tail moth. U. S. Dept. Agric. Dept. Bull. 1363. 31 p.

Weseloh. R. & J. Anderson. 1975. Inundative release of Apanteles melanoscelus against the gypsy moth. Environ. Ent. 4: 33-36.

Weseloh, R. M., T. G. Andreadis, R. E. B. Moore, J. F. Anderson, N. R. Dubois & F. B. Lewis. 1983. Field confirmation of a mechanism causing synergism between Bacillus thuringiensis and the gypsy moth parasitoid, Apanteles melanoscelus. J. Invert. Path. 41: 99-103.

Wollam, J. D. & W. G. Yendol. 1976. Evaluation of Bacillus thuringiensis and a parasitoid for suppression of the gypsy moth. J. Econ. Ent. 69: 113-18.