by Kim Adelson
In August of this year, the emerald ash borer officially arrived in Washington state. As someone who lived through this insect’s invasion of Ohio in the early 2000s, I can attest as to what a disaster this could become. Emerald ash borers (EABs) killed literally tens of millions of trees in Michigan and neighboring Ohio during the last decade that I lived in the Midwest: estimates are that 80-99% of all the ash trees in northeast Ohio and southeast Michigan were destroyed; about 1/3 of the ash trees across the entire state of Ohio are now gone. While we are not as ash-heavy here as those Midwestern states, there are areas where they are quite common.
EABs have been slowly moving towards Washington since they arrived in the U.S. in 2002. This first sighting was in Vancouver, WA when two observant individuals spotted one on their car windshield. The EAB has been detected in Oregon since 2022 and in Vancouver BC since 2023.
We have only one native species of ash tree in Washington, the Oregon Ash (Fraxinus latifolia), and it does live in Mason, Lewis, and Thurston counties. It likes damp feet, and so is usually found along riparian corridors, in wetlands, in floodplains, and along lakeshores rather than in more upland forest. Developers and gardeners have also planted numerous Green Ash (for their fast growth) and White Ash (for their beautiful fall color). Fortunately, our beloved Mountain Ash, with its bright red-orange berry clusters, is not a true ash: it is in the rose family, whereas true ashes are in the olive family. So, fortunately, it is not endangered by EABs.
Is there anything each of us can do to slow the spread of this dangerous invasive insect? YES!
First, work to attract bark-foraging birds, which feed on EAB larvae. It is the larvae, not the adults, that directly harm ash trees. Local birds that will eat them include:
- Downy Woodpeckers
- Hairy Woodpeckers
- Pileated Woodpeckers
- Northern Flickers
- Red-breasted Nuthatches
- Brown Creepers
While healthy bird populations will not eradicate EABs or entirely stop their spread, research shows that they can remove up to 40% of EAB larvae. In order to attract these birds to your yard, you can: plant and maintain native conifers such as Douglas firs; leave dead wood (snags) in place; provide suet feeders, especially those with tail props, or peanuts; install appropriate nest boxes (you’ll have more success if you put clean wood shavings inside for woodpeckers to “excavate”); reduce your pesticide use.
Second, report EABs if you see them! This is critical, because early detection greatly helps containment. If you find an EAB, contact the Washington State Department of Agriculture at their EAB hotline, 1-800-443-6684.
Third, don’t transport firewood or deadfall. EABs move very slowly on their own, but they hitch rides (our first sighting was on a car windshield) and this lets them move much faster. They originally came to the U.S. from eastern Asia via a wooden pallet or crate. In February 2026 it became illegal to transport untreated firewood across state lines into Washington, but the confirmed presence of EABs suggests it would be wise to stop relocating untreated wood within the state as well.
Next, if someday you have an infected tree on your property, remove it promptly. Alternatively, if it is a new infestation and the tree is not yet badly damaged, emamectin benzoate injections are 90+% successful at eliminating EAB larvae. These treatments are expensive however – several hundred dollars per individual tree—and they must be repeated every 2 to 3 years.
Finally, do not plant new ash trees, since every new ash is a point from which they can establish themselves and then spread. Instead consider Western service berries, Columbia hawthorns, or mountain ash, all natives.
The emerald ash borer is not a yet a problem in our region. However, taking steps now will reap enormous benefits in the future. Hopefully we will be able to avoid the environmental deterioration that has already occurred in other states. More than 50 local species of animals – butterflies, bees, grosbeaks, Wood Ducks, finches, squirrels, beavers – utilize Oregon Ash trees in some way. They will all benefit from early EAB attenuation efforts. Photo credit: Emerald Ash Borer, APHIS.gov. Public Domain.
