Tree-ravaging beetle threatens Oregon ecosystems
The trees are dying, and the fish could be next.
An invasive beetle — the emerald ash borer — has arrived in Forest Grove with a lethal reputation, at least as it concerns native ash trees.
While local entomologists and foresters have anticipated this day, there is little to do to prevent a loss of tree canopy and habitat that could have devastating consequences for broader ecosystems.
Last month's discovery of the ash borer in Forest Grove was the first time the invasive insect has been found in Oregon.
To say that experts are concerned would be an understatement.
"It kills trees very quickly. It's not from here. We don't have any natural controls," Oregon Department of Forestry entomologist Christine Buhl said. "Our trees don't have defenses. This beetle can cause 100% mortality in ash trees wherever it goes, and there is no way to eradicate it."
Biologist Dominic Maze arrived early to pick his kids up June 30 from summer camp at Joseph Gale Elementary School in Forest Grove when the dying treeline caught his eye.
"I noticed they were ash, and the whole line of them was dying. I was still 15 feet away and felt a sinking pit in my stomach, because ash is really hardy. Nothing bugs ash, other than beavers and EAB," Maze said, using an abbreviation for the emerald ash borer. "My little girl could see my face and that I was kind of upset. She asked what was wrong."
Maze called the Department of Forestry, and Buhl responded to take samples and confirm the sighting.
Forest Grove, as its name suggests, has always prided itself on its trees. Daniel Riordan, a senior planner in Forest Grove's community development division, said around 800 ash trees make up about 3% of street trees in the city.
Residents with dead or dying trees can apply for free removal online.
Even at the local level, Riordan said, the emerald ash borer has been on officials' radar.
"Anticipating that this day would come, the city has been proactively working toward diversifying the street tree canopy," Riordan said. "The city will work with property owners to allow removal of ash trees in poor health and replant with other tree species."
Ash trees grow in wetland environments and in heavy clay soil where other trees struggle to root.
Trees are an important part of the ecosystem, and a die-off could have serious ramifications for other species, including some of Oregon's most iconic fish, like salmon and trout.
Maze, who runs the invasive species program in Portland, said he led a study of local waterways that determined river temperatures could rise 5% to 10% in some areas without the current shade provided by ash trees. He said ecosystems along the Tualatin River and remote tributaries to the Willamette River are most reliant on ash trees for shade and shelter.
"That's a big deal. Five to 10% is a nail in the coffin for steelhead," Maze said. "The upper Tualatin is probably 95% ash, and tributaries of the Willamette that go through low, slow farmland areas, 90% of those trees are Oregon ash. Salmon, elk, deer, snakes, lizard — they're all reliant on these trees."
Maze added, "I don't want to sound all doom and gloom, but everybody is going to be affected by this. Trying to boat on the river, everything is going to be choked down with wood. Heat is going to increase in urban areas. Everybody."
Like Forest Grove, Portland has been planning for the arrival of the emerald ash borer in Oregon. Maze said the city government has had preparedness plans for the ash borer for at least 12 years, and it stopped using Oregon ash in restoration projects in 2016.
"While I have to give ourselves credit for seeing this coming, we were just listening to scientists elsewhere and the feds saying, 'Don't plant that stuff,'" Maze said.
The ash borer's larvae feed on the ash tree's cambium layer, the growing part of the trunk.
Elsewhere in the United States, the emerald ash borer — which is indigenous to Asia — has devastated tree populations.
A study by the National Park Service of parks around Washington, D.C., found 334,820 ash trees in 2010 had been reduced to 80,460 in 2021 following the arrival of the borer.
At the Oregon Department of Forestry, officials like Scott Altenhoff are working to plan a response.
Altenoff manages the department's urban and community forestry assistance program. He said he is hoping soil, mulch and other use can be made of all the fallen trees. He added that there is a pesticide that has proven effective at holding off infection that could be used for valuable residential and community trees, but it is not practical on a larger landscape scale.
"Based on what I'm hearing from folks in other states, our hopes of eradicating it or stamping it out completely are slim," Altenhoff said. "Hopefully we can slow things down, and if we can flatten the curve and make the infestation occur on our timeline rather than the bug's timeline, we can budget, we can adapt, we can pivot as needed, and you replant in stages rather than have to do it all at once."
The Department of Forestry is asking Oregonians to report sighting of the emerald ash bore to the state's invasive species hotline at oregoninvasiveshotline.org.
Buhl said there are a variety of native, non-pest beetles with similar green sheens that could be confused for the invasive species, particularly the golden buprestid.
Altenhoff said dead trees are more difficult and expensive to remove than dying trees.
"Once it starts, it's kind of like a train wreck in slow motion," Altenhoff said. "My hope is that we can use what we've learned to get people to take it seriously. It might be painful and expensive and hard work, but we'll make it through it."
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