WSDA gypsy moth trapper
WSDA setting Gypsy Moth traps. Photo by WSDA

Each year, the Washington State Department of Agriculture (WSDA) sets traps around the state to detect gypsy moths, a non-native, highly invasive pest that has destroyed millions of acres of trees and forests in 20 Eastern states with infestations. For 40 years, WSDA has successfully prevented the moth from becoming established here in Washington.

There are two types of gypsy moths that WSDA seeks to detect: the European (sometimes called the North American) gypsy moth and the Asian gypsy moth. While both moths are highly destructive, the Asian gypsy moth is of even greater concern because of two factors:

  • Asian gypsy moth females can fly, enabling them to spread more rapidly than the European gypsy moth.
  • Asian gypsy moths readily feed on both deciduous and conifer trees, putting more trees at risk than the European gypsy moth, which primarily feeds only on deciduous trees.
asian and european female gypsy moths
Female Asian and European gypsy moths. Photo by USDA APHIS PPQ,

This year, WSDA trapped 10 Asian gypsy moths and 32 European gypsy moths at several locations in Western Washington. This is the highest number of Asian gypsy moths ever detected in the state and the first time this variety of gypsy moth has been found in Washington since 1999.

In response to these findings, WSDA consulted a panel of scientific experts on the best methods to respond to this introduction. The panel made a recommendation to conduct aerial applications of the insecticide known as Btk (Bacillus thuringiensis kurstaki) at several locations where moths were found.

WSDA has not finalized a proposal for treatment but is developing a plan to treat the areas with a certified organic formulation of Btk. There is extensive research on Btk demonstrating its safety to humans, pets, bees, fish, and plants.

gypsy moth caterpillar us fish and wildlife service-ATTRI-REQ
Gypsy moth caterpillar. Photo by US Fish and Wildlife Service

An environmental review must be completed before a recommended treatment plan can be approved.  However, if treatment is approved, applications will be conducted in the spring when the moths are in their caterpillar stage. Residential areas are currently under consideration for treatment. WSDA plans extensive outreach to educate and inform local residents and before any treatment occurs, the public will have multiple opportunities to ask questions and comment on the WSDA proposal.

For the most current information on the agency’s response plan, visit the WSDA gypsy moth information webpage.

This article submitted by Karla Salp, community outreach and environmental education specialist, Washington State Department of Agriculture.