WSDA: Japanese Beetle Numbers Increased in 2024, Spongy Moth Down

The Washington State Department of Agriculture has wrapped up seasonal trapping of invasive pests including Japanese beetles and spongy moths.

According to WSDA, after seeing a drop in trapped beetles last year, overall beetle numbers increased in 2024.  More than 26,600 beetles were collected this year this year, up from 19,655 in 2023.  Most beetles, over 24,700, were caught in Grandview and surrounding areas.  However, over 1,500 beetles were caught in the Wapato area and over 400 were caught in the Tri-Cities area.

The Department of Ag says trapping alone is not enough to eradicate Japanese beetles from Washington. WSDA has also been providing free beetle treatments to area residents to combat the pest.  To this point, treatments have been voluntary and property owners must give consent each year to have their property treated. Only about half of residents have given permission to have their property treated.

"So far the level of community participation has only been enough to slow, but not stop or eradicate Japanese beetles from our state,” noted Sven Spichiger, WSDA Pest Program manager. “If we aren’t allowed to treat most of the properties in the infested areas, it is only a matter of time before it is too late to eradicate.  Then homeowners, gardeners, and farmers will be left with the responsibility and expense of not only managing the pest but the burden of permanent quarantine regulations as well.”

WSDA is already accepting treatment consent forms for 2025. If you were in a treatment area previously, you can download a treatment consent for from the WSDA’s Website and sign up for treatments, starting in the spring.  The department is considering additional legal options to increase the number of treated properties, including seeking administrative warrants or an emergency proclamation.

“We hope that residents understand how important this is for their communities and will voluntarily sign up for treatments. But it is getting to the point where we may need to use all our legal options if we are to have any hope of eradicating this beetle,” Greg Haubrich, assistant director of the Plant Protection Division, said.

When it comes to spongy moth, the WSDA said trapping saw a significant decline in moths caught compared to 2023.  This year, the Department of Ag trapped just 32 moths, compared to over 100 spongy moths reported last year.  WSDA said the decline in moths is due in part to the spongy moth eradications conducted earlier this spring by the Pest Program.  No spongy moths were caught within the eradication sites at Concrete or the Steamboat Island Rd. area.

Over the next several weeks, the program will be analyzing the trapping results and conducting egg mass surveys to look for evidence of a reproducing population in areas where multiple moths were trapped. This information will be used to determine if spongy moth eradications might be warranted.

WSDA has not yet been able to obtain the reported Northern Giant hornet that was reportedly spotted near Port Orchard in October, although efforts continue.  In addition, the Pest Program has not received any other concerning hornet reports.  If the program obtains the hornet, DNA analysis will be conducted to attempt to determine the origin of the specimen.

Hornet trapping continues through the end of November, with traps being collected and final trap contents analyzed for potential hornets. The program expects to be able to make an announcement about whether any hornets were found in Whatcom County this year by mid-December.

Japanese beetles, spongy moths, and northern giant hornets are just three of over 130 different species that WSDA’s Pest Program surveys for each year. Visit the Pest Program Website for more information about some pests that WSDA monitors for each year.  The Department of Ag added the traps for these pests, which were set and checked several times throughout the summer, have now been removed.

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