Spongy moth treatments begin in King, Pierce counties

OLYMPIA – The Washington State Department of Agriculture (WSDA) plans to begin treatments to eradicate spongy moth caterpillars starting next week, weather permitting. In total, WSDA will aerially treat 498 acres in Pierce County near Lakewood and 333 acres in King County near Lake Youngs. The treatment product is a naturally occurring soil bacteria, Btk (Bacillus thuringiensis var. kurstaki), which is only toxic to caterpillars.
 
A low-flying airplane will apply Btk using GPS guidance to ensure on-target application. The sites will each be treated three times, with applications approximately 3 – 14 days apart. WSDA expects to complete all applications in May.

Because weather conditions heavily influence when treatments can occur, WSDA advises people in or near the treatment areas to visit agr.wa.gov/moths to sign up for e-mail, text or robo-call alerts that are issued the day before applications are scheduled to take place. Changes in scheduled treatments will also be shared through these notification systems. WSDA mailed multiple postcards to residents in and near the treatment areas advising them of the upcoming treatments. The public can enter an address in a map on the agency website to determine whether their residence is within or near the treatment area.

According to the Washington State Department of Health (DOH), Btk poses very low risk to humans, pets, birds, fish and bees. Btk is found naturally in the environment and has an excellent safety record while also being effective for spongy moth eradication. People who wish to minimize their exposure to the spray can remain indoors with doors and windows closed during spraying and for 30 minutes after the treatment ends. Let the spray dry before allowing children to play outside, wash with soap and water if you do have skin contact with the spray and rinse your eyes with water if eye contact occurs.

Btk is sticky. Residents in the treatment areas may choose to cover cars parked outside and bring in toys, lawn chairs, or other outdoor items to protect them from the spray. However, Btk can be cleaned off outdoor articles with soap and water.

WSDA has protected Washington from spongy moth introductions for over 50 years. It has been one of the most successful pest detection and eradication programs in the country, preventing spongy moths from establishing in the state and protecting our environment, communities and agriculture from this destructive, invasive pest.

The program has trapped for spongy moths (known as gypsy moths when the program started) since 1974 and conducted the first eradication program in 1979. The WSDA Pest Program has safely eradicated every spongy moth population attempting to establish in the state since the program began, protecting vital habitat for Washington’s pollinators and other wildlife.

Spongy moths pose a serious threat to Washington’s environment, with the caterpillars feeding on over 300 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, spongy moth caterpillars defoliated one-third of the entire state of Massachusetts and in 2018, that state lost about one-quarter of its hardwood trees, including three-quarters of its oak trees, in large part due to spongy moth infestations.

If spongy moth were to become established in Washington, it would threaten forest ecosystems, defoliate or kill trees and shrubs in backyards and parks, lead to quarantine restrictions on forest products and horticulture, and result in long-term increased homeowner pesticide use.

Visit the agency’s spongy moth web page at agr.wa.gov/moths to learn more or contact the WSDA Pest Program at pest@agr.wa.gov or 1-800-443-6684.

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