The gypsy moth (Lymantria dispar), also known as the spongy moth, was introduced in 1868 into the United States by Étienne Léopold Trouvelot, a French scientist living in Medford, Massachusetts. Because native silk-spinning caterpillars were susceptible to disease, Trouvelot imported the species in order to breed a more resistant hybrid species. Some of the moths escaped, found suitable habitat, and began breeding. The gypsy moth is now a major pest of hardwood trees in the Eastern United States. The first US outbreak occurred in 1889 in the New England states. In 1923 attempts were made to prevent the westward spread of the moth by maintaining a barrier zone extending from Canada to Long Island of nearly 27,300 km2. This barrier however broke down by 1939. By 1987, the gypsy moth had established itself throughout the Northeastern United States, southern Quebec, and Ontario. The insect has now spread into Michigan, Minnesota, Virginia, West Virginia, Illinois, and Wisconsin. Small, isolated infestations have sporadically occurred in Utah, Oregon, Washington, California, and British Columbia, but efforts have been taken to eradicate them. the Washington State Department of Agriculture is again trying to eradicate both L. d. d. and L. d. asiatica – using Bacillus thuringiensis kurstaki (Btk) toxin – to prevent their establishment in the state. Since 1980, the gypsy moth has defoliated over one million acres (4,000 km2) of forest each year. In 1981, 12.9 million acres (52,200 km2) were defoliated. In wooded suburban areas, during periods of infestation, gypsy moth larvae crawl over man-made obstacles and sometimes enter homes. When feeding, they leave behind a mixture of small pieces of leaves and frass, or excrement. During outbreaks, the sound of caterpillars chewing and dropping frass may be loud enough to sound like light to moderate rainfall. Gypsy moth populations usually remain low, but occasional increases to very high levels can result in partial or total defoliation of host trees. According to a 2011 report, the gypsy moth is now one of the most destructive insects in the Eastern United States; it and other foliage-eating pests cause an estimated $868 million in annual damages in the U.S. Host species Gypsy moth larvae prefer oak trees, but may feed on many species of trees and shrubs, both hardwood and conifer. In the eastern US, the gypsy moth prefers oaks, aspen, apple, sweetgum, speckled alder, basswood, gray and paper birch, poplar, willow, and hawthorns, amongst