The females then lay oval-shaped egg masses which are covered with hairs from her body. The buff-colored egg masses contain 100 to 1,500 eggs and are laid on the underside of tree limbs, bark, rocks, and structures including buildings, campers, mobile homes, etc. Long distance spread of the gypsy moth occurs when egg masses are unknowingly transported from infested areas on vehicles . Repeated defoliation stresses trees and can lead to death. During outbreaks in residential areas gypsy moth caterpillars are an extreme nuisance.
Trees lose their foliage, caterpillars crawl everywhere, and their droppings rain from the trees.
When disease kills large numbers of caterpillars, as often occurs, the stench is overwhelming. In some cases, people develop an allergy to the hairs of the gypsy moth caterpillars. Bt is a naturally occurring disease that only kills caterpillars, and Dimilin is a chemical that interferes with gypsy moth growth and eventually kills the caterpillar.