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QuickTake:
Arborists say the emerald ash borer is likely already in Lane County, and they urge residents to be informed and take action.
The Eugene City Club hosted a meeting Friday, June 26, on how residents can prepare for the invasive, ash‑tree‑killing beetle called the emerald ash borer.
Native to southeast Asia, Russia and the Korean peninsula, the half-inch-long beetle kills nearly all ash trees within three to seven years of infestation.
Since its detection in the U.S. in 2002, the beetle has been found in 38 states and the District of Columbia. In Oregon, scientists first found it in Washington County in 2022. Since then, it has been detected in Clackamas, Marion, Multnomah and Yamhill counties, according to the Animal and Plant Health Detection Service.
The city club hosted three arborists: Erik Burke, director of Friends of Trees Eugene-Springfield; Jeff Chandler, owner of Chandler’s Tree Service; and Alby Thoumsin of Sperry Tree Care. They discussed the reality of the insect, the future of ash trees in Eugene and how the community can prepare for their loss.
This year, the beetle has been spotted in three new locations in the Willamette Valley, as far south as Silverton. There are no confirmed cases in Lane County, but Chandler suspects it’s present here.
“The population that was found in Silverton was suspected to have been there for about a decade,” he said. “So, it is very likely that it’s here, and we haven’t found it.”
The arborists said that emerald ash borer larvae feed for one to two years on the inner bark, or phloem of ash trees, chewing galleries that cut off nutrient flow and slowly kill the trees. The emerald ash borer is visible as an adult for only about three to four weeks, typically emerging from an ash tree anywhere from May to August.
“It’s pretty grim when you think about what it can do to our trees in the valley,” Thoumsin said. “We have multiple groves of ashes, which is a crucial part of the ecosystem, especially the greenways and the drainages, the wetlands.”
Thoumsin said the best thing residents with ash trees can do is be preemptive: decide on good replacement species and start planting them now.
“They say the best time to plant a tree was 200 years ago,” Thoumsin said.
Treatment options
Chandler brought up another preemptive measure residents could take: chemical treatment, which kills emerald ash borers once they’ve ingested it.
He said emamectin benzoate is the current “gold-standard” for trunk injections into the tree. Another option is imidacloprid, which can be injected or applied as a soil drench. However, it must be applied annually and has higher risk to nontarget species.
“For healthy trees before they’re infested, we have a 95 to 99% success rate in keeping the survivors,” Chandler said. “But if the tree is more than 30 percent dead, I’m not going to treat it for you.”
Chandler advised attendees to make a game plan: have large ash trees inspected by a certified arborist, consider proactive treatment for healthy, high‑value trees once the emerald ash borer is confirmed nearby and budget for removals and replacements over the next decade.
Burke urged residents to weigh their decisions.
“The news tells us that EAB [emerald ash borer] is a catastrophe, and it is, but no one is telling us the fact that EAB is here because our lives demand it,” Burke said. “Container ships cross the oceans from other continents laden with pallets of consumer goods for us to buy online or in big stores. These pallets bring us invasive species.”
Important species such as aphids, birds and caterpillars will be negatively affected by chemical treatments, according to Burke. He said homeowners will have to weigh the decisions of either cutting down ash trees or possibly harming other important species from chemical treatment.
Signs to look for
Crown dieback: Thinning foliage and dead branches start in the upper canopy and progress downward over several years.
Bark splits and cracks: Peeling back the bark may reveal winding “S‑shaped” galleries in the inner wood.
D‑shaped exit holes: Tiny, roughly one‑eighth‑inch, D‑shaped holes in the bark where adult beetles emerge.
Epicormic sprouts: New shoots or small branches suddenly appear low on the trunk or from the base of the tree as the upper crown declines.
Increased woodpecker activity: Birds flake off the bark to feed on larvae.
Arborists suggest anyone who suspects emerald ash borer activity contact a trusted arborist and report sightings to state officials.
