Gypsy moth catches at 20-year high in Washington

The Washington State Department of Agriculture (WSDA) trapped 117 male gypsy moths this year in its annual trapping program – the highest number caught in traps since 1995.

In addition to the moths caught in traps, for the first time in state history, WSDA also identified an infestation of actively reproducing gypsy moths in Pierce County. The infestation included live female moths and dozens of gypsy moth egg masses. This site is also believed to be the source of 83 of the 117 male gypsy moths caught in WSDA’s usual trapping.

In addition to the Pierce County infestation, another concentration of catches also occurred in Kitsap County.

The next step is for WSDA’s pest program to complete egg mass surveys, which provide data necessary to propose an eradication project. Of greatest concern is the high number of gypsy moth catches in Pierce and Kitsap counties, which WSDA will need to address next spring.

WSDA last conducted an eradication in 2016, when more than 10,000 acres were treated. No gypsy moths were caught in any of the 2016 eradication zones this year or last. The 2016 treatment for European gypsy moths in the Capitol Hill area has been determined to be a success based on the lack of catches. The remaining 2016 treatment areas were for the eradication of Asian gypsy moths and thus require one more year of trapping before those areas can be declared eradicated.

Gypsy moth is the most destructive invasive pest to be introduced to American forests. Last year in New England, where the moths are now permanently established, millions of acres of trees were totally defoliated and thousands of acres of trees were killed by gypsy moths.

The outbreak back East likely contributed to the increase in gypsy moths found in Washington. European gypsy moths are usually brought into the state by people moving to Washington from infested areas with egg masses on their belongings.

Visit WSDA’s website at agr.wa.gov/gypsymoth for a detailed list and map of the 2017 gypsy moth catches.