Defoliation by Lymantria dispar, the gypsy moth, has killed millions of oak trees across Pennsylvania. Although white, chestnut, black and red oak are preferred, gypsy moth caterpillars also eat hundreds of other tree and shrub species including apple, alder, aspen, basswood, birch, poplar, willow, hawthorn, hemlock, tamarack (larch), pine, spruce, and witch hazel. Gypsy moth usually avoids ash, butternut, black walnut, locust, sycamore, and tuliptree (yellow poplar). Although it usually takes more than one year of defoliation before trees die, conifers that are defoliated may be killed after a single season of defoliation.
Download a Homeowner's Guide to Gypsy Moth Management or detailed descriptions of the gypsy moth lifecycle, life stages and controls provided in a Forest Health Fact Sheet and the U.S. Forest Service Pest Alert for Gypsy Moth.
The most recent information on areas of defoliation and control programs is published in the 2012 Pennsylvania Forest Health Report.