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State forestry warns Oregon City: emerald ash borer detected nearby, major urban-tree losses possible
Summary
Oregon Department of Forestry specialists told the commission EAB was found in Oregon in 2022 and in metro-area traps this year; they urged residents not to move firewood, to report suspect trees and to remove ash from planting lists to avoid large canopy and fiscal losses.
State forestry staff told the Oregon City Commission on Nov. 19 that emerald ash borer (EAB), an invasive wood-boring beetle, poses a major risk to the city’s ash trees and urban canopy.
Kat Buffay, an EAB support specialist with the Oregon Department of Forestry, said EAB was discovered in Oregon in 2022 and that recent metro-area surveillance turned up positive traps and buffer detections within a few miles of Oregon City's urban growth boundary. "Since its introduction in the mid '90s, it has killed over a 100,000,000 ash trees," Buffay said, and warned that the insect’s life cycle and larval feeding lead to mortality that typically becomes apparent five to 10 years after infestation.
Buffay described how a single adult female can lay up to about 80 eggs and said native Oregon ash in riparian corridors are especially vulnerable; she cited an estimated 99.95% mortality for some native ash when EAB establishes. She explained common responses: do not move firewood, monitor trees for symptoms, report suspected finds via the Oregon Invasives hotline, and consult oregoneab.com for guidance and resources. Agencies regulate movement of infested material under quarantine rules enforced by the Oregon Department of Agriculture and by administrative rules (OAR).
Commissioners and staff discussed local inventory and mitigation: the city is surveying street trees, park trees and water-facility plantings to quantify ash presence and will coordinate a mitigation plan with the Oregon Department of Forestry and other stakeholders. City staff said the effort may require code changes to remove ash from approved planting lists and that treatment options include selective removal, trunk injections by licensed applicators and a "SLAM" (slow ash mortality) strategy that spreads costs over time.
Buffay said early detection and targeted treatment can preserve high-value ash but that treatment is not a one-time fix: insecticide injections must be repeated every two to three years for continued protection. She recommended that communities prioritize prevention, surveillance and strategic treatment to limit canopy loss and the city’s fiscal exposure.
The briefing concluded with a staff offer to provide additional resources, a bulletin on quarantine/OAR rules and follow-up information to help the city finalize an urban-forest mitigation plan.
