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Karla Salp
P.O. Box 42560, Olympia, Washington 98504-2560

Gypsy moth treatments begin in Kitsap, Snohomish and King counties

OLYMPIA - The Washington State Department of Agriculture (WSDA) plans to begin treatments to eradicate gypsy moth introductions this Saturday, May 11, weather permitting. In total, WSDA will aerially treat about 1,700 acres with a naturally occurring soil bacteria, Btk (Bacillus thuringiensis var. kurstaki.)

WSDA plans to start treatments at two of the four sites - Gilberton and Martha Lake. The other two sites, Crosby and Union Hill-Novelty Hill, will begin later this month. WSDA has yet to determine the exact start dates for those sites.

A low-flying airplane will apply the Btk using GPS to ensure on-target application. Each site will be treated three times, with each application approximately 3 - 14 days apart. All treatments are weather dependent and the schedule is subject to change. WSDA expects to complete all applications by the middle of June.

Because weather conditions heavily influence when treatments occur, WSDA advises people in or near the treatment areas to visit and sign up for alerts via e-mail, text or robo call, which are issued the day before applications take place. Changes in scheduled treatments will also be shared through these notification systems. WSDA will use its Twitter account, @WSDAgov, to provide real-time information during operations as well.

WSDA mailed postcards to residents in and near the treatment areas advising them of the coming work. The public can also enter an address in a map on the agency website to verify whether their residence is within the treatment area.

Btk is not considered harmful to humans, pets, birds, fish or bees. Btk is found naturally in the environment and has an excellent safety record while also being effective for gypsy moth eradication. Although the risk to humans is low, the Washington State Department of Health says that people who wish to minimize their exposure can remain indoors during spraying and for 30 minutes afterwards as a precaution. The product washes off with soap and water.

Btk is sticky. Residents in the treatment areas may choose to cover cars parked outside and bring in toys, etc. Btk washes off outdoor articles with soap and water.

Gypsy moths pose a serious threat to Washington's environment, with the caterpillars feeding on over 500 types of trees, plants and shrubs. The pest is permanently established in 20 states across the Northeast and Midwest, where it has defoliated millions of acres of forest and urban trees. In 2017, gypsy moth caterpillars defoliated one-third of the entire state of Massachusetts and in 2018, they lost about one-quarter of their hardwood trees, including three-quarters of their oak trees, in large part due to gypsy moth infestations.

If gypsy moth were to become established in Washington, it would threaten forest ecosystems, lead to quarantine restrictions on forest products and horticulture, and result in long-term increased homeowner pesticide use.

WSDA has been trapping for gypsy moths for over 40 years and has successfully prevented them from establishing in Washington by safely eradicating reproducing populations. Visit the agency's gypsy moth web page at to learn more or call the WSDA toll-free hotline at 1-800-443-6684.