An invasive beetle that kills virtually every ash tree it infests now has a foothold in Portland, putting an estimated 94,000 ash trees across the city at risk.
The emerald ash borer, a metallic green insect first detected on the West Coast in Forest Grove in June 2022, was confirmed in Portland's Hazelwood neighborhood in 2025, according to the city's Urban Forestry division. A local arborist spotted a declining green ash near the David Douglas Aquatics Center and reported it through the Oregon Invasive Species Hotline. The city installed monitoring traps, and state and federal agencies confirmed the beetle.
It has no natural U.S. predators.
Portland estimates it has 26,000 ash trees on public and private property and another 68,000 in natural areas. Oregon could lose up to 99% of its ash trees over time, OPB reported Aug. 6, citing state forestry officials. The beetle has now spread to five Willamette Valley counties, including Multnomah, according to KOIN.
The threat is personal for Jill Punches, a Multnomah County contract specialist who has lived near Laurelhurst Park since the 1990s. Her street-side ash is a city-designated Heritage Tree with a canopy roughly 100 feet wide. When a large bough collapsed onto her house in June 2021, the thinner canopy changed her summers. She had to buy four air-conditioning units, she told Willamette Week, which first reported on the beetle's local impact Oct. 15.
"People tend to think of trees more as liabilities, but they are also assets," Punches said.
Anya Moucha, forest pest and pathogen coordinator for Portland's Urban Forestry division, told Willamette Week the situation is manageable. She said homeowners can either treat trees chemically or remove and replace them, but warned that once more than 20% of a tree's canopy dies, insecticide can no longer spread effectively through the trunk.
The city issued a response plan in 2025 combining chemical treatment of healthy park trees, underplanting new species and proactive removal of ash trees in poor condition. A seasonal pruning and removal moratorium runs April 1 through Sept. 30 each year, when adult beetles are active. That moratorium lifted Oct. 1, and the city is encouraging residents to hire a certified arborist to assess any ash trees on their property before spring.
Mark Ragozzino, a biological control entomologist with the Oregon Department of Agriculture, is also testing a tiny parasitic wasp called the oob. Brought from Asia after a decade of safety testing, the wasp lays eggs next to emerald ash borer eggs on bark.
Hatched oobs consume the beetle larvae before they emerge. Ragozzino helped introduce the wasps in Cottage Grove near Eugene, where they slowed the beetle's spread, Willamette Week reported.
Residents who suspect an infestation should call the Oregon Invasive Species Hotline at 1-866-INVADER. The city's EAB identification guides and full response plan are posted on its Urban Forestry page.
Portland Parks & Recreation is giving away 4,500 free trees at events running through Oct. 31, as we reported Oct. 15. Upcoming giveaways include Saturday, Oct. 17, at Harrison Park, Saturday, Oct. 24, at Gabriel Park and Saturday, Oct. 31, next to Mt. Tabor Community Garden.
