Spongy Moth (Gypsy Moth)

Lymantria dispar (Linneaus)

Key Features

  • Significant defoliation
  • Shot-holes in chewed leaves
  • Blue and red spotted caterpillar
Gypsy moth caterpillar feeding (on oak)
Gypsy moth defoliation (on oak)
Adult gypsy moths mating


Infested trees can be completely defoliated by hairy, red and blue spotted caterpillars that grow up to 2 " long. Although many deciduous tree species will leaf out again, complete defoliation 2-3 years in a row is lethal. During heavy infestations, the rain of caterpillar excrement below trees can be a nuisance. White adult females can be found laying light brown egg masses from mid to late July through early August. On spruces, pines and Atlantic white cedar, loss of more than half the leaves can be lethal.

Gypsy moth caterpillars feeding on white pine Photo by E. Barnes
Gypys moth caterpillars feeding on spruce Photo by E. Barnes
Late stage gypsy moth caterpillars feeding on fir Photo by E. Barnes


Egg masses containing from 50 to 1500 eggs can be found on tree trunks and nearby sheltered areas including door jams, picnic benches, firewood, under vehicles, and at the bottom of nursery containers. Eggs hatch in late April into black caterpillars that climb to the top of a tree or structure so they can be blown by the wind to a new tree. When the caterpillars land on a tree they begin feeding on leaves. As caterpillars become large, they feed only at night. When full grown in late June, caterpillars will wander to sheltered areas to where they become adult moths after constructing an intermediate stage called a pupa. In mid July, white female and brown male moths emerge. Adult female gypsy moths do not fly. They sit on trees and release a scent that attracts males. After mating, females will walk to find a sheltered place to lay eggs.

Gypsy moth egg mass
Gypsy moth pupae and old caterpillar skins

Management Recommendations

These exposed caterpillars are easily killed by insecticides such as spinosad, or Bacillus thuringiensis, or insect growth regulators like tebufenozide. Most conventional insecticides like carbaryl, permethrin, and bifenthrin, can readily kill caterpillars while they are feeding. Gypsy moth can often be an emotional issue for a community. Defoliation can be greatly reduced if you wrap a folded burlap band on a tree trunk to trap caterpillars. This works best if caterpillars are collected and destroyed each morning. Be sure to contact your local extension educator to see how you can fit into the local gypsy moth management plan. If you find this pest in Indiana, please use the "useful links" button on the homepage of the detailed information about this pest to report your find to local authorities via the "Report Gypsy Moth Here" link or call 1-866-NO-EXOTIC.

Effective Pesticides

Active Ingredients include: Bacillus thuringiensis var. Kurstaki, Bifenthrin, Carbaryl, Chlorantraniliprole, Permethrin, Spinosad, Tebufenozide

landscape report
Purdue Landscape Report
Plant & Pest Diagnostic Laboratory