The Washington State Department of Agriculture is undertaking the largest eradication effort in the nation to eliminate the invasive and highly destructive Japanese beetle. To contain the infestation the WSDA is proposing 49 square mile quarantine in the Yakima Valley encircling the city of Grandview. The metallic-green beetles with bronze wings are firmly established in the eastern United States, where they are known for causing “extensive damage to ornamental trees shrubs and flowers” and cost an estimated $460 million each year.
The half-inch adult beetles devour leaves, petals, and fruit, skeletonizing plants above ground. Below the soil, the larvae eat through roots turning large patches of green turf brown. Hundreds of plants are on the menu for the beetles. They’ll wreak havoc on household roses, but also threaten large commercial farms and plant nurseries.
“We need to make the commitment to eradicate it. What it means to have a population of Japanese beetle is that anybody who grows grapes-and unfortunately where we found this, there are a lot of grapes in that part of Yakima and in Benton County, they will likely need to add a spray if we allow this population to go unchecked. That may not seem like a lot, but adding sprays in a year when you have a Japanese beetle outbreak can make the difference between a farm going under and a farm succeeding to the next year,” said Sven Spichiger, Managing Entomologist, Washington State Dept. of Agriculture. “They also impact hops. A lot of folks don’t know that Washington leads the world in hops production and there’s quite a few hops in the area as well.”
“The beetle itself feeds on over 300 different types of plants. Most impacted, of course generally, back east is grape. Grape usually requires a spray because the adults after hatching out will defoliate the leaves and this can lead to all kinds of problems. Nursery stock is a real issue. What I mean by that is, any potted plant that has soil, basically speaking, the beetle will start emerging towards the end of June, they will mate, they will lay eggs, and the eggs will hatch out, go down into the soil, and the larvae will actually eat the roots of plants. Well, in doing so, sometimes they will lay in potted plants and in my former life in Pennsylvania, I used to have to inspect plants before they were ready for shipment out here to the west. If we found any living in them, they wouldn’t be allowed to go. So any nursery trying to operate is going to find themselves to have some extra work to do or have to change their practices a little to be able to continue to do business,” said Spichiger.
Meanwhile, the return of warmer weather means giant hornets will emerge from their winter nests to spread out and start new colonies in the northern part of the state.
It’s been three years since the first “murder hornet” nest ever found in the United States was located and removed from a tree in Whatcom County near the border with Canada. Like the beetles, the invasive hornets pose a serious ecological threat to Washington that demands intensive surveillance and aggressive intervention. But it’s not all bad news.
“We ended last year successfully tracking down and eradicating three nests before any breeding cast was even produced. So we were kind of ahead of the curve last year, which is great. That’s what you expect. We did it for the first time in 2020, 2021 worked really well. One of the new things that we noticed is all of our detections last year weren’t necessarily from our trapping program, but from concerned citizens who believed they saw them feeding on paper wasp nests in the eaves of their houses,” said Spichiger. “And as it turns out, that is what led us to all three nests last year. So one thing we’re doing and in addition to the trapping that we will continue to do throughout the area, is we are adding a project where citizens can adopt a paper wasp nest and log in weekly and let us know what they’re seeing. And we believe this is actually going to really help us get to any potential nests a lot faster, because this really was, once we started observing the behavior, a great way to detect nests,” said Spichiger.
Although all of the nests have been located in an area comprising a few square miles in northern Whatcom County, there have been other confirmed hornet detections further south. A giant hornet queen was killed on a porch in Bellingham in 2020. In 2021, a deceased male hornet was found on a lawn in Marysville near an apple tree. That hornet was found to be genetically unrelated to the other giant hornets found in the US to date, which share a common lineage.
“The one queen that was killed on a porch in Bellingham that happened very early in the spring of 2020 and that is something you would expect. So one thing we don’t know is, we do not know how far queens disperse before they overwinter and then eventually emerge and make their nests,” said Spichiger. ”That’s something that is missing from the literature.”
“We’re actually going to be working with a professor in Korea and hooking some up to a flight mill at the least to see how far they can fly. It doesn’t tell you how far they will fly, but at least it gives us, you know, some limits to work with. But that is something that’s expected. So if a queen hatches out, mates, and then tries to disperse, she . . . you could end up with one lonely queen that dies on a person’s porch in Bellingham. So we’ve surveyed intensely that area for the last two seasons and if we go one more season will declare that part of Whatcom County free of hornets. In reality, collecting a queen in the spring basically destroys the nest. So we never really had an issue there other than if one got out there, others could get there. So we did that as a precaution,” said Spichiger.
Watch the full interview with WSDA Managing Entomologist Sven Spichiger here:
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