Invasive tree-killing insect found in 3 more Oregon counties

PORTLAND, Ore. (KOIN) -- Invasive emerald ash borer beetles were discovered in three more Oregon counties this summer, officials said.

Emerald ash borers are small metallic-green beetles native to eastern Asia; however, they have begun showing up in the United States, and according to the Oregon Department of Forestry, they have killed millions of trees across the eastern United States.

Over the course of the summer, officials said that the emerald ash borers were found in Yamhill, Clackamas and Marion counties.

Officials said that the emerald ash borer larvae burrow inside the bark of ash trees, which can result in canopy dieback and eventually tree death. Signs of infestation include thinning and yellowing leaves, bark splitting, D-shaped holes and basal shoots.

The Yamhill County beetle was found in a trap near Gaston, just seven miles away from where Oregon's first emerald ash borer was found in Forest Grove in Washington County in 2022.

The Marion County beetles were first noticed by a Portland General Electric employee who reported seeing ash trees in the Elliot Prairie area showing canopy decline, one of the symptoms of the emerald ash borer.

Upon investigation by ODF Invasive Species Specialist Wyatt Williams, he said he found several Oregon ash trees that showed a marked decline.

Williams also investigated an area near Butte Creek which forms the border between Clackamas and Marion counties and he said he saw evidence of the borers on both sides of the creek.

“The extent of dieback suggests that EAB may have been present for a number of years at the site but went unnoticed given the difficult access and dense vegetation, which includes a mix of oak and conifers,” said Williams.

In late July, Williams found five adult emerald ash borers in traps along the Pudding River, which he said indicates a significant population in the area.

“Given the trees did not show any signs of damage, we would not have known about this site for some time if not for the traps,” Williams said.

Cody Holthouse with the Oregon Department of Agriculture shared that the department will be thoroughly searching the surrounding areas for more emerald ash borers to discover if they have spread further away.

"No state has been able to eradicate EAB, so since its first detection in Forest Grove, we have expected it to eventually show up in new parts of Oregon,” said Holthouse. “That’s why folks from collaborating agencies have been methodically surveying for the insect, setting out traps beyond the known infestation area and training people to know the signs and symptoms of infestation. That definitely helps us learn where the insect is spreading.”

According to officials, it is still unknown if the recent discoveries are offshoots of the original Forest Grove discovery or if these beetles came from different sources.

Emerald ash borers often travel in loads of firewood that are being transported by people, so it's very possible they aren't connected to Forest Grove.

“We want to protect the rest of Oregon for as long as possible to give communities more time to prepare,” said Holthouse.

To help prevent the spread, officials are asking Oregonians to buy firewood near where they intend to burn it and to not take firewood more than 10 miles from where it was cut.