Control of Gypsy Moth, Lymantria dispar, in North America since 1878

Abstract

Gypsy moth is an outbreak species that was introduced to North America from Europe in 1869, with disastrous consequences. This species is a devastating defoliator in northeastern hardwood forests and continues to spread to the west and south. Four different types of pathogens are of interest for gypsy moth control, making this the invasive arthropod with the greatest diversity of pathogens being utilized for control. Bacillus thuringiensis kurstaki HD-1 is commercially available and is usually applied for control instead of synthetic chemical insecticides. Btk can provide excellent control of outbreak populations and also gives outstanding results in eradication campaigns when gypsy moth is introduced into new areas. The baculovirus LdMNPV, which is highly specific to gypsy moth, is also mass produced but because of its limited availability is only applied in environmentally sensitive areas. While Btk does not cause epizootics in natural gypsy moth populations, LdMNPV has a history of epizootics that have caused crashes in defoliating (high density) populations since the accidental introduction of the virus some time before 1907. The fungal pathogen Entomophaga maimaiga, originating from Japan, first reported in North America in 1989 and probably accidentally introduced, also causes dramatic epizootics in both low and high density gypsy moth populations; activity of this fungus is determined, at least in part, by environmental conditions. Several species of microsporidia are known from the native range of gypsy moth and programs are in place to introduce these microsporidia to North American gypsy moth populations to augment the natural enemies already present.