Gypsy Moth FAQs


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Gypsy Moth FAQs

For more information, e-mail us or call (800) 443-6684.
WSDA doesn’t want the worst forest pest insect ever to enter the U.S. to become permanently established in the state. We have seen the damage done to the environment and economy in the more than 20 states in the East and Midwest where permanent populations exist. We don’t want that to occur in Washington. It would have a catastrophic impact on our environment and economy.
Connecticut, Delaware, District of Columbia, Illinois, Indiana, Maine, Massachusetts, Maryland, Michigan, Minnesota, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, Vermont, Virginia, West Virginia, and Wisconsin.
Very extensive. Hundreds of thousands of acres are annually defoliated, quarantined, and sprayed. For example, in 2008 in New Jersey 30,900 acres of trees died in the state as a result of repeated gypsy moth defoliation. In 2009 in Maryland 37,000 acres of vegetation were aerially sprayed to suppress existing infestations. In 2015, gypsy moth caterpillars defoliated 180,000 acres of trees in Connecticut. In 2016, damage from gypsy moth caterpillars in New England was so vast that it could be seen from space. 
On an average year, about $1 million. Of that, about half is provided by the federal government. Approximately 75 percent of gypsy moth control money is spent on summer trapping, and 25 percent on eradication.
By weakening and killing trees and plants, destroying wildlife habitat, degrading water quality of creeks and streams,and reducing the use and aesthetic value of recreation areas.
By destroying or damaging plants, trees, and shrubs; by triggering costly quarantines of agriculture, nursery, and timber products; and by reducing tourism. Visitors don't visit locations infested with caterpillars.
We have conducted dozens of eradication treatments since the 1970's. For a complete overview of past eradication projects, visit our past control efforts page
All of them. Washington has never had a permanent population of gypsy moth.
Two consecutive summers of negative trapping following an eradication treatment if it is for European gypsy moth and three consecutive summers of negative trappling if it was for Asian gypsy moth. Eradication treatments occur in late spring. Summer trapping occurs from June-October. On rare occassions, subsequent treatments may be necessary to eradicate an area. 
Because it feeds on more than 500 species of trees and plants, and reproduces very rapidly. A single female moth can lay 1,000 or more eggs.
State law directs WSDA to survey for the presence of destructive pests; propose eradication treatments when infestations are located; prepare assessments of the impact of the eradication proposals on the environment; make the assessments available for public review and comment; and then approve or disapprove the proposals based on all evidence presented.
The people of the state of Washington. They exercise this authority through public officials they elect to office, the state's judicial system, and in some cases directly.
Where gypsy moths were caught, whether other evidence of gypsy moth activity in the area was detected, host vegetation in the area, and the type of gypsy moth caught (Asian or European.) Standard treatment for an Asian gypsy moth detection is one square mile with even one detection. Treatment areas for European gypsy moths can be much smaller and usually require more than one moth detection because the European female gypsy moth does not fly.
WSDA prefers to conduct treatments with ground treatments. However, WSDA will use aircraft when the size or typography of a proposed treatment zone make it prohibitively expensive, impractical, or impossible to administer the treatment with ground equipment.
An insect that infects people or domesticated animals with diseases, or competes with people for food, fiber, or living space.
An "introduction" is a first-time detection. An "infestation" is a conclusion by state entomologists that a reproducing population of gypsy moth is present. Most introductions of European gypsy moths die out on their own and WSDA does not treat every introduction. Conclusions that a reproducing population is present are based on multiple catches in close proximity to each other or evidence of other gypsy moth life stages in an area (e.g., egg masses, pupal cases, cast skins, or dead moths found on the ground.)
Oak, apple, hawthorne, poplar, willow, and maple. While European gypsy moths almost exclusively consume deciduous trees, Asian gypsy moths also readily consume evergreen trees, which is of great concern for Western Washington. European gypsy moths will also consume evergreen trees when an area is infested. 
We conduct extensive trapping throughout the state each summer to detect where gypsy moths have been introduced. 
Gypsy moth eradications take place in the late spring. The exact dates depend on the weather. To sign up for text, email, or robo call notifications when an eradication occurs, visit our current control efforts page.