Tree pests and diseases in Washington and Oregon

The quarantine pest pages

• Emerald ash borer in Oregon: first West Coast find in Forest Grove on June 30, 2022; permanent quarantine under OAR 603-052-1075 covering Washington, Yamhill, Marion, Clackamas and Multnomah counties; 2026 detections in Salem, Beaverton, Silverton, Hillsboro and East Portland; the signs, the treat-or-remove thresholds, and the October-to-March removal window.
• Emerald ash borer in Washington: the first state detection in Hazel Dell, Clark County, confirmed by USDA on August 19, 2026; what WSDA, DNR and the Invasive Species Council ask ash owners to do; the firewood exterior quarantine in chapter 16-476 WAC; and how to report a suspect beetle.
• Sudden oak death in Oregon: Phytophthora ramorum in Curry County, the OAR 603-052-1230 quarantine and its 2024 emergency expansion of about 148 square miles, the tanoak, rhododendron and bay laurel hosts, and why the nursery trade makes it a statewide question.

Native beetles that kill yard trees

These are not quarantine pests, but they kill more yard trees in some parts of the region than the regulated ones do, and the removal timing matters.

• Pine bark beetles in eastern Washington and central Oregon: western pine beetle, mountain pine beetle and the pine engraver; western pine beetle mortality on about 32,800 acres of Washington ponderosa pine in 2024 (DNR/USFS); the signs, the October-to-February removal window and how to handle pine slash and firewood.
• Bronze birch borer in Washington and Oregon: first found in Portland in 2003 and Klamath Falls in 2017 (OSU); why European white and Jacquemontii birches die from the top down; the 40 percent canopy line for treat-or-remove; and resistant replacements.

What the rules have in common

Both quarantines regulate the wood, not just the tree. Inside Oregon’s EAB counties, hardwood firewood of any species stays put unless it is chipped to 1 inch or heat-treated to 160°F for 60 minutes, with civil penalties up to $10,000 (ORS 570.995). Inside the sudden oak death boundary, infected material cannot leave at all and host material needs disease-free certification. Either way, the removal crew’s disposal plan is part of the job; ask before the chipper starts.

Other problems covered on this site are not quarantine pests but behave like them. Portland’s Dutch elm disease rule bans elm pruning from April 15 to October 15 and bars storing elm wood as firewood (PCC 11.60.060); it is covered in best time to trim trees. Western redcedar dieback, bigleaf maple decline and laminated root rot are on the trees pages. When a diseased tree has to come down, the service pages are tree removal and dead tree removal, with a certified arborist’s role explained under arborist services.