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Emerald ash borer found near Walla Walla, expanding Washington outbreak
Federal officials confirmed emerald ash borer larvae in ash trees in College Place, near Walla Walla, roughly a month after the destructive insect was first detected in Washington. State officials are asking residents to report suspected sightings and avoid planting ash trees.
Emerald ash borer has been confirmed in Eastern Washington, where state inspectors found the invasive beetle’s larvae and characteristic damage in several ash trees in College Place, next to Walla Walla.
An arborist first noticed signs of possible infestation. The Washington State Department of Agriculture inspected the trees and found multiple larvae and D-shaped exit holes in the bark. The U.S. Department of Agriculture confirmed the identification Wednesday, Oct. 14.
The discovery comes about a month after the pest was first reported in Washington, in Vancouver. Emerald ash borers have been established in Oregon since 2022 and British Columbia since 2023.
The beetle’s larvae feed beneath ash-tree bark, damaging the trees as they grow. They spend the winter in the trees and emerge as adults through the distinctive D-shaped holes in spring. The insect has killed more than 100 million ash trees across the United States in the past two decades, according to the state agriculture department. No U.S. effort to eradicate it has succeeded.
The pest can attack any true ash, including Oregon ash, the Pacific Northwest’s only native ash species. State officials advise homeowners not to plant new ash trees and to replace infested ones with other kinds of trees.
Washington began restricting the import of untreated firewood about two months ago as part of efforts to limit the spread of emerald ash borer and other invasive insects. “We anticipated it would only be a matter of time before emerald ash borer arrived in our state,” said Sven Spichiger, the agriculture department’s pest program manager.
Residents who suspect they have found the beetle can report it at invasivespecies.wa.gov, email invasivespeciesinfo@rco.wa.gov or use the state’s invasive species app. Officials ask people to preserve suspected specimens in a plastic bag in a freezer.