The gypsy moth, Lymantria dispar, currently established in North America, is a European native that was accidentally introduced into New England in the late 1800's during an attempt to rear an alternative silk producing insect.
Life Cycle
The gypsy moth has one generation per year. From June to mid-July, the female attaches buff-colored, velvety egg masses to sheltered places on outdoor objects. These masses allow the insect to overwinter and may contain up to 1,000 eggs. Masses are also embedded with female abdominal hairs that may act as an allergen. The eggs hatch in April or May. Young larvae chew small holes in leaves, while older larvae consume entire leaves except for the larger veins and midribs. The whole tree may be defoliated, resulting in reduced growth and loss of vigor, as well as reduced aesthetic, recreational, and wildlife values. If total defoliation is experienced over several years, mortality may result. The older caterpillars are 1.5–2.5 in. (3.8-6.4 cm) long and are easy to identify by the tufts of hair on each segment and the pattern of blue and red dots on their backs. The gypsy moth pupates in dark brown pupal cases located in sheltered locations. Male gypsy moths have a 1.5 in. (3.8 cm) wingspread with light tan to brown wings marked with wavy, dark bands across the forewing. Females are white, larger than males with a wingspread of 2.5 in. (6.4 cm), and flightless. There is also an Asian strain of the gypsy moth (AGM) that was identified in 1991. AGM has a much broader host range and the females are active fliers due to their larger wingspan. These factors would allow AGM to spread much faster than the European strain and be even more damaging.
Distribution
L. dispar's current range extends from Maine to North Carolina and west across Pennsylvania and into Virginia, West Virginia, Ohio, Michigan, and Wisconsin. Spread occurs as a result of both natural flight of the moth and the attachment and transport of egg masses on vehicles. Gypsy moth is known to feed on over 300 trees and shrubs. Favored hosts include oak, apple, alder, basswood, birch, poplar, sweet gum, willow, and hawthorn. Less favored host species include hickory, maple, cherry, cottonwood, elm, black gum, larch, sassafras, and hornbeam. Some mortality even occurs in white pine. Many other plants may be fed upon.
Control Efforts
Use of tanglefoot or placement of burlap bands around the trunk of the tree can be used to trap larvae and can afford some protection to individual ornamental trees. Natural controls, including introduced insect parasites and predators, virus diseases, and adverse weather conditions, help control the gypsy moth. Chemical and microbial insecticides have been used, primarily in urban and recreation areas.