Eastern Forest Threat Center - Gypsy Moth

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Adult male and female gypsy moths

Adult male and female gypsy moths

John H. Ghent, USDA Forest Service, Bugwood.org

Gypsy Moth
Lymantria dispar

The gypsy moth is an exotic insect first introduced into the U.S. in 1869 by a French scientist living in Massachusetts. It is now one of the most notorious pests of hardwood trees in the eastern U.S.

Keywords: moth, Lepidoptera, GM, hardwoods, egg masses, silken threads, defoliation, refoliation, twig dieback, sprouting of old buds

Distribution Map Distribution Source Image

Threat Description

Gypsy moth egg masses are laid on tree trunks and branches, but may be found in any sheltered location. Hatching coincides with budding of most hardwood trees. Newly hatched larvae hanging from host trees on silken threads can be carried by the wind for a distance of a mile or more. Larvae prefer hardwoods, but may feed on leaves of several hundred different species of trees and shrubs. In the East, the gypsy moth prefers oaks, apple, sweetgum, speckled alder, basswood, gray and white birch, poplar, willow, hawthorn, cottonwood, hemlock, southern white cedar, and native pines and spruces. During periods when gypsy moth populations are dense, larvae feed on almost all vegetation. If more than half of their crown is defoliated, most hardwoods will refoliate by midsummer. Trees use energy reserves during refoliation and thus are eventually weakened, exhibiting symptoms such as dying back of twigs and branches in the upper crown and sprouting of old buds on the trunk and larger branches. Healthy trees can usually withstand one or two consecutive defoliations. Trees weakened by previous defoliation or other stress are frequently killed after a single defoliation of more than 50 percent.