Lymantria dispar dispar
In the garden: Over 500 species of trees, shrubs and other plants
Europe and northeastern North America, with scattered outbreaks elsewhere
This imported pest is a major problem in forest trees, and easily becomes established on oak trees and many other tree species enjoyed in home landscapes. Some years are much worse than others. In bad years, the adult moths and their leaf-eating young are everywhere you look. In other years, you may hardly notice gypsy moths at all. The adult females are beige, with males darker brown, and both have faint dark markings on their wings, and prominent, feathery antennae. The females crawl from place to place, and do not fly. The larvae are dark, bristly caterpillars with pairs of dots down their backs.
Fast-growing gypsy moth caterpillars defoliate forest trees by eating leaves day after day. In early summer, the caterpillars can become a serious nuisance in yards by crawling everywhere and dropping unexpectedly from tree branches. Trees that are weakened year after year from gypsy moths can die from the repeated stress.
There are several ways you can help protect the trees in your yard. Starting in early winter, check tree trunks and outdoor decks or furniture for egg masses, which look like thumbnail-size blobs of dry orange-yellow foam. Scrape them off into a container of soapy water, or spray the egg masses with horticultural oil. In spring, place pheromone-baited traps in trees favored by the moths.
In late spring, place sticky bands around the trunks of trees at waist height: wrap the trunk with three widths of duct tape, press into place, and then spread a band of petroleum jelly over the middle of the band. Caterpillars that try to crawl up the trunks will be repelled, and can be swept into a collection can every few days. The use of pheromone-baited traps for several seasons can make a big impact on local populations.