How is Portland preparing for an emerald ash borer infestation?

Published 4:55 am Friday, August 1, 2025

A pesky, yet pretty, invasive beetle are making their way into Portland’s neighboring regions, so the city is gearing up for the arrival of this highly destructive tree pest.

The emerald ash borer attacks and kills all species of ash trees and have been spotted in Clackamas, Marion, Yamhill and Washington counties, with Columbia County being at “very high risk” of infestation.

Portland Parks and Recreation’s Urban Forestry Division has created an emerald ash borer response plan to address the potential arrival of the invasive beetle. The city has approximately 95,000 ash trees located in parks, neighborhoods, natural areas and yards.

Officials confirmed the first case of emerald ash borers on the West Coast occurred in Forest Grove in June 2022.

If emerald ash borers arrive in Portland, this could lead to major canopy loss, according to the parks department, threatening wildlife, stream health and neighborhood shade.

“This is why we actively push for diverse species when we plant and promote tree planting,” City Forester Jenn Cairo said in a statement. “So that when a disease or pest attacks one species, it causes less harm to the canopy as a whole.”

Because these insects, which are smaller than a dime, cannot be eradicated, preventative measures are critical in slowing the spread of the pest and lessening its impact.

What is the city doing?

The response plan outlines how Portland will slow the spread of emerald ash borers, protect public safety, preserve ash trees where possible and spread costs and actions over time.

Current measures underway include:

• Treating healthy ash trees in city parks with insecticide to prevent infestation.
• New permit rules allow residents to treat street trees or remove and replace small ash trees with free permits.
• Mapping and keeping inventories of ash and other trees across the city.
• In 2019, ash tree species from Portland’s Approve Street Tree Planting List were removed.
• Requiring species diversity in regulated tree planting.
• Avoiding ash trees in tree giveaways and planting programs.

PP&R’s Urban Forestry Team is continuing to work with the Oregon Department of Forestry, Oregon Department of Agriculture and community partners to help limit the beetle’s impact.

“By diversifying tree species, using data-driven tools, and planning ahead, we’re better prepared to face threats like EAB and build a resilient, healthy canopy,” Deputy City Administrator for Public Works Priya Dhanapal said in a news release.

How can you help?

Stop moving firewood.

Emerald ash borers spread mainly when humans move or transport infested wood, particularly firewood, according to PP&R.

These are the best ways to help:

• Buy firewood locally and don’t move it from other areas.
• Learn to identify ash trees and signs of emerald ash borers.
• Report suspected sightings or unhealthy ash trees to the Oregon Invasive Species Hotline at 1-866-INVADER.
• Manage your ash trees. Small trees should be replaced with other species. Healthy trees can be treated with a permit.

To stay updated on emerald ash borer updates in the city, visit portland.gov/trees/eab.