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Gypsy moth treatments wrap up across Western Washington

OLYMPIA – The Washington State Department of Agriculture (WSDA) concluded its gypsy moth treatments today, wrapping up with an application in Tacoma that ended just after 8 a.m., the last of 21 treatments that began on April 16.

“This was the most challenging gypsy moth eradication project we have had in many years due to the number of treatment sites, the multiple detections of the very destructive Asian gypsy moth, and the warm weather that caused the caterpillars to emerge earlier than in previous years,” Jim Marra, WSDA’s Pest Program manager, said. “We certainly appreciate the support of the people in the treated communities for this important project.”

WSDA will now plan its summer trapping to detect any new introductions of gypsy moths and evaluate the effectiveness of this year’s treatments. WSDA set 19,000 traps in Western Washington last year, but will set more this summer and include Eastern Washington in surveillance efforts.

In the past two weeks, WSDA has treated about 10,500 acres with a biological insecticide at seven sites in Western Washington to prevent this invasive pest from becoming established in the state. Each site was treated three times with an aerial application of the biological insecticide, Bacillus thuringiensis var. kurstaki (Btk), a product approved for use on food crops in organic agriculture and widely used for gypsy moth eradication for decades.

Vancouver, Lacey, Nisqually, Gig Harbor, Tacoma, Kent, and Seattle were all treated. Asian gypsy moths were found at each location, except Seattle, where WSDA detected 22 European gypsy moths.

Outreach to raise awareness of the gypsy moth eradication project included four postcards, each mailed to 38,000 addresses, open house events in each affected community, a webinar and other social media outreach. WSDA will soon mail a final postcard to these communities requesting feedback on project outreach.

WSDA trapped 32 European gypsy moths last year and 10 Asian gypsy moths, a more destructive variety of the pest that can also spread more quickly. It was the largest detection of Asian gypsy moth in Washington ever and the first time this variety of the invasive pest had been detected here since 1999.

The gypsy moth is a destructive, non-native pest that, in its caterpillar stage, feeds on hundreds of species of trees and bushes. The pest has destroyed millions of acres of forest lands in 20 states where it is established, primarily in the Eastern United States. An infestation in Washington would trigger costly quarantines for timber, Christmas trees and other forest and nursery products, as well as cause significant ecological damage to our forests and parks.

Gypsy moths have been detected in Washington every year since 1977, but no permanent populations have been established here due to WSDA’s consistently quick and successful treatment programs, along with annual trapping and surveillance efforts to detect introductions of the pest.

More information on gypsy moth is available at, where people can also sign up for periodic updates on gypsy moth related news and trapping updates.