WSDA has monitored for and successfully and safely eradicated spongy moth introductions in Washington state since 1974. This consistent program has protected our state's valuable natural resources and our communities from this devastating pest.

When WSDA has evidence that there is a reproducing population in the area (usually by finding alternate life stages or trapping moths in the same area for more than one year) an eradication is proposed for that area. Most commonly, WSDA uses Btk (Bacillus thuringiensis var. kurstaki) –  which is an insecticide approved for use in organic agriculture. It has an excellent safety record with people, plants, pets, fish, birds, and bees and has been used globally for decades as a safe and effective treatment for combatting spongy moth. Treatments occur as spongy moth caterpillars emerge in the spring and begin to feed on vegetation.
 

What is Btk?

Btk (Bacillus thuringiensis kurstaki) is a naturally occurring bacteria. It commonly occurs in soils and on plants throughout the world. It is employed in a biological insecticide used to eradicate the spongy moth. Widespread use of Btk to control the spongy moth began in the 1970's. Since then, it has been applied to millions of acres of forest in the East and Midwest. For example, over 500,000 acres were treated in the eastern U.S. in 2008 - more than twice the area of Mount Rainier National Park.

Btk and Human Health

Btk has been used in forestry and agriculture for over 70 years and has been shown to have an excellent safety record. Public health officials across the U.S. and Canada periodically review research on Btk and have found there is very low risk to human health.

You can learn more about Btk by visiting the department of health's webpage.

Before an eradication proposal can be finalized, state and federal environmental reviews must be completed. The draft environmental reviews are made available for public comment before they are finalized.  

Click on the maps below to download printable pdf versions. Please note: while the map of the treatment area may include areas over water, the treatments themselves are not conducted over water and include a water buffer. 

You can also use our interactive, searchable map. In the interactive map, you can enter an address and see if it is in, near, or outside of a proposed treatment area. 

 

Before WSDA finalizes its treatment proposal, the Pest Program does extensive outreach to notify residents in and near the proposed treatment area to alert them to the proposed eradication. In addition to providing information and answering questions, WSDA provides opportunities to sign up for notifications about the project and specifically when treatments will occur if the plan is finalized and moves forward.