The adult, European, female moth is a large white, flightless moth with a two inch wing span and dark saw-toothed patterns on the wings. The male is smaller (one and a half inch wingspan), has smaller markings on brown wings and is a strong flier. The larva stage is the most destructive. Later stages of the larvae develop a distinctive color pattern of five pairs of blue dots followed by six pairs of red dots along their backs. The eggs are laid in masses of 100 to 1,000 and are covered with hair, forming a soft tan patch about the size of a quarter. The Asian gypsy moth is the same species as that from Europe. The biology of the Asian gypsy moth is similar to that from Europe with the following differences: 1) female Asian gypsy moth can fly up to 20 miles and 2) the larvae do well on conifers.
European gypsy moth first became established in the United States in 1869, in Massachusetts. It spread rapidly throughout the Northeast and has become the destructive pest of hardwood forest and shade trees in the United States. When populations are high, the gypsy moth defoliates millions of acres of forest and urban trees. This defoliation not only kills and weakens trees, but also alters forest composition and destroys habitat for mammals and birds. Gypsy moth infestations affect recreational use of forests, parks and backyards. Swarms of caterpillars discourage tourism and many other outdoor activities. In urban areas, the economic impact includes clean-up costs, tree replacement costs and loss of property values.
Gypsy moth is a native to Europe, southern Asia and northern Africa. The current distribution in the United States includes the northeast states (i.e., Pennsylvania, New Jersey, New York, Delaware, etc.) expanding southward into West Virginia, North Carolina and Tennessee, and westward into Michigan, Ohio and Illinois. Isolated infestations have been treated in the states of Washington, Idaho, Colorado, Utah and Oregon.
Adults emerge between June and August. The female emits a sex attractant that allows the male to find her. After mating, the female lays a single egg mass on any available surface including trees, rocks, fences and other manmade outdoor articles. Adults do not feed and die shortly after mating and egg-laying. Gypsy moth spends the winter in the egg stage. Eggs hatch in late February through April. Emerging larvae move to the tops of trees and are carried many miles on wind currents; wind-aided dispersal is the primary dispersal mechanism for the gypsy moth.
Gypsy moth has over 150 primary hosts, but can feed on over 500 plants. Both hardwoods and conifers are defoliated. Young larvae feed primarily on oaks, aspen, birch, willows and alder. Older larvae feed on a broader range of trees including cedar, pine, spruce and fir. Recent tests on western plants have shown that native and common California species such as manzanita, western hemlock, Douglas fir and live oaks are also good hosts.