The emerald ash borer, an invasive tree-killing beetle, was confirmed in three more Willamette Valley cities this month, the Oregon Department of Forestry announced Tuesday.

According to the agency, private residents in Silverton, Tualatin and Newberg recently reported seeing signs of emerald ash borer infestation in ash trees to the Oregon Invasive Species Hotline. State officials have now confirmed those reports.

Two trees in Newberg were heavily infested, ODF reported, and they are located about a mile from the ash-shaded banks of the Tualatin River.

The infestations were all found within an emerald ash borer quarantine zone spanning Clackamas, Marion, Multnomah, Washington and Yamhill counties. The state agriculture department has ordered tree material from ash, olive and white fringe trees — including firewood from any hardwood tree — to stay within that quarantine zone to prevent spreading the invasive beetle.

The emerald ash borer was previously confirmed in Multnomah County when an infestation was discovered in Northeast Portland last year. The first infestation in Oregon — and the first confirmed case on the West Coast — was discovered in 2022 in Forest Grove.

Invasive emerald ash borer has reached Portland, dooming ash trees

Kat Bethea, an emerald ash borer support specialist with ODF, said the spread of the infestation across the region isn’t a question of “if” but of “when.”

“We also know that there has not been a case of it being ever successfully eradicated from the landscape, so we are aiming at suppression,” she said.

Forestry officials have said Oregon could eventually lose almost all of its ash trees to the invasive pest.

Bethea said not transporting firewood long distances “is actually one of the largest things that everyone in Oregon can do” to help manage the spread of the invasive beetle.

Signs of infestation include D-shaped holes in tree bark that beetles leave when they exit the trunk and S-shaped galleries created by beetle larvae feeding. Symptoms of beetle infestation in a tree also include outer bark flecking, shoots growing at the base of the trunk, woodpecker holes, bark splits and canopy decline.

Not all infested trees need to be removed immediately. Until a tree has lost 30% of its crown, Bethea said, emerald ash borer infestation can be treated with pesticides, potentially saving the tree.

Bethea recommends exploring treatment options for the tree early on, as removal can become more dangerous — and thus more expensive — as the health of the tree worsens. After a tree has lost more than 30% of its crown, the tree should be removed quickly, she said, as fully dead ash trees can become a public safety hazard.

“Removing an ash tree before it’s fully dead is the safer option. It is best practice to work with that [International Society of Arboriculture] certified arborist to do so,” she said. “This is not typically a good DIY project because ash trees, as they die, become very brittle, and they’re prone to fragmenting, shattering.”

The emerald ash borer beetle arrived in the Midwest from Asia and has decimated more than 100 million ash trees across the country since it arrived in 2002.

“I’ve talked to arborists from the Midwest who have dealt with this, and the word they use is: Ash trees ‘explode’ when they’re dead,” Bethea said.

However, ODF advises waiting until autumn to remove infested trees, if possible. Matt Mills, who’s also an ODF emerald ash borer support specialist, said preemptive removal could cause beetles to move from an infested tree to other trees that might otherwise avoid infestation.

Bethea recommends residents visit www.OregonEAB.org to learn the signs of infestation and which infestation management options are available.

News Source : https://www.opb.org/article/2026/06/23/emerald-ash-borer-invasive-pest-silverton-tualatin-newberg-oregon/