A sample from an ash tree in Walla Walla County infested by the emerald ash borer. The invasive insect’s larvae chew through the wood, creating winding galleries that kill the tree, and, when the insects mature, exit through tiny D-shaped holes.
Courtesy of Mountain View Tree Service
Last month, arborist Isaac Long drove to a residence in Walla Walla County to see if he could save a green ash tree in the owner’s backyard. Based on how much the tree had defoliated, Long sensed it would probably have to be cut down.
He also knew to check for something else.
Long inspected the canopy, and there they were: tiny D-shaped holes. He found what became the first documented emerald ash borer infestation in Washington state.
Adult emerald ash borers measure about half an inch long and sport a shiny green exoskeleton. Originally from Asia and first identified in the U.S. in Michigan in 2002, the invasive pest has decimated ash trees in North America, according to the U.S. Department of Agriculture.
The beetles lay their eggs in the tree bark. The hatched larvae then chew through the wood, making sinuous galleries that girdle the tree — severing its vascular system — and kill it. Tunneling their way out, the beetles emerge fully grown.
Tens of millions of ash trees in the U.S. have died in this way, according to the USDA.
The first reported emerald ash borer in the state was seen in August in the Vancouver area on a windshield.
Long and his colleagues at Mountain View Tree Service had expected the bug to arrive in southeast Washington, but not so soon, he said.
Long broke the news to the property owner.
“He was hoping that I would have some miracle cure to have his tree come back,” Long said. “He didn’t want to remove it, so he was fairly bummed, but also understood that the tree needed to come down and be disposed of properly.”
Long took a small branch to WSU’s extension office in Walla Walla. He later got a call from an entomologist with the Washington State Department of Agriculture. WSDA staff visited the site, found the pale larvae in multiple trees and sent specimens to the USDA, which confirmed the insect species, according to a release.
These tiny D-shaped holes are signs of the emerald ash borer. This branch is from an ash tree in Walla Walla County, which has Washington State’s first documented tree infestation.
Courtesy of Mountain View Tree Service
The tree, meanwhile, was removed — and many more will follow. The WSDA is urging people to stop planting ash trees.
“Once emerald ash borer has been detected, it’s only a matter of time before you see large-scale mortality of ash on the landscape,” said Zeima Kassahun, an urban and community forestry specialist with the Washington State Department of Natural Resources.
Ash trees are used for lumber, but they also have deep cultural significance for Indigenous communities. Now, Kassahun said, the trees are going the way of the iconic American chestnut, which in the 20th century nearly died off because of an Asian blight fungus.
“It’s just unfortunate to see the loss of a tree species in our lifetime, especially something that we see so often,” Kassahun said. “Even if you don’t know what an ash tree looks like, you probably have interacted with one. It’s probably in your neighborhoods, in your parks.”
Emerald ash borers are usually spread by humans. The transporting of wood products is a common vector — earlier this year, Washington state enacted a firewood quarantine — but the bug “also has its own way of getting around,” Kassahun said.
The state’s Urban and Community Forestry Program at the state’s natural resources department can provide support to help landowners preserve some ash trees or buy time to replace them. Washington has also published an Urban Forest Pest Readiness Playbook and an Emerald Ash Borer Resource & Management Guide.
Over time, a dead ash tree becomes more brittle and more dangerous to remove.
Oregon ash is the Pacific Northwest’s only native ash tree. A riparian species, it helps keep waterways healthy. Many birds and insects rely on ash trees.
“We lose that, we lose a very specialized niche in our ecosystems,” Kassahun said.
Sightings can be reported to the state at invasivespecies.wa.gov, via email at invasivespeciesinfo@rco.wa.gov or on the Washington Invasives app; specimens can be collected in a plastic bag and frozen, the WSDA said in a release.
Erick Bengel is a reporter with Northwest Public Broadcasting.
This story comes to you from the Northwest News Network, a collaboration between public media organizations in Oregon and Washington.
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