Washington sees first substantial decline in Japanese beetles

YAKIMA — The Washington State Department of Agriculture Pest Program saw its first substantial decline in Japanese beetle numbers after trapping more than 19,000 beetles this summer in Yakima, Benton and Franklin counties, according to a WSDA announcement.  

According to the release, Japanese beetles pose a substantial threat to hops and grape growing in Central Washington. If the beetles permanently establish in the state, it will result in costly quarantines and limit the ability of growers to move products from the area. Additionally, both homeowners and farmers will be left to pay for managing the beetles on their property.

“The community is the solution,” said WSDA Pest Program Manager Sven Spichiger. “We can eradicate this beetle, but only if we all work together.”

The announcement stated that about half of the proposed treatment areas are allowing WSDA to treat their properties for the beetle. The beetle feeds on over 300 different types of crops, including grapes and hops, as well as turf grass, sweet corn, roses and many other locally grown crops, according to the statement. 

Japanese beetles were first detected in Grandview and Sunnyside in 2020 when just two beetles were caught, said the statement. Mass trapping helped keep the numbers steady at around 24,000 beetles in 2021 and 2022. 

According to the statement, WSDA was first able to conduct Japanese beetle treatments in 2022, but the effects of treatments are not seen until the following year, so WSDA saw the first decline in Japanese beetle catches this year with a total of 19,655 trapped. WSDA conducted another treatment for Japanese beetle this spring and hopes to see a further decline in beetle numbers next year.

Despite increased trapping, continued treatment, and declining overall total beetles, the beetles are being detected further from the “hot spot” in Grandview and in higher numbers. The announcement stated that this fall and winter, WSDA will look at expanding both the quarantine area and the number of target treatment properties.

"Our window for being able to eradicate this pest is closing,” Spichiger said. 

Visit agr.wa.gov/beetles to learn more about WSDA’s Japanese beetle project.