If you own an ash tree in Clark County, this is worth a calm read, because a little preparation now saves trouble later. The emerald ash borer is a small green beetle that kills ash trees, and it has been steadily working its way toward us. As of mid-2026, it has not been confirmed anywhere in Washington state. But it is close, and the people who watch this for a living have stopped asking if and started planning for when.
How close it actually is
The beetle turned up in the Portland area in the summer of 2022, the first sighting in the Pacific Northwest. Since then it has spread to five Oregon counties, including Multnomah and Clackamas just across the river, and in June 2026 inspectors found it in three new spots in the northern Willamette Valley, near Tualatin, Newberg, and Silverton. It has been in Vancouver, BC, since 2024. Oregon lays out the latest Willamette Valley detections in detail.
It is not here yet, but it is nearby. Local foresters put it plainly, that with the beetle already in Portland, our turn feels like a matter of time. No alarm bells, but no reason to assume it will skip us. The City of Vancouver, WA urban forestry page tracks the local status.
Do you even have an ash tree?
A lot of folks are not sure, and that is fine. Ash is not our most famous yard tree, but our native Oregon ash is all over Clark County, especially in the wet spots. It loves floodplains, creek edges, and the low corners of a yard that stay soggy in winter. A big tree down by Burnt Bridge Creek or in a low, damp part of your yard is very likely one. Here is how to check without a botany degree:
- Opposite branching. The fastest gut-check. Twigs, buds, and leaves grow directly across from each other in matched pairs, not staggered. Very few trees around here do this.
- Compound leaves. Each leaf is a stalk with several leaflets, usually five to nine. Native Oregon ash runs toward the lower end, five to seven.
- Diamond bark. Mature ash bark has a tight, ridged pattern of little diamonds.
- Paddle-shaped seeds. Single canoe-paddle shapes hanging in droopy clusters, not a maple's paired helicopters.
Two or three of these together, and it is an ash.
What the damage looks like when it comes
The frustrating part is that by the time a tree looks obviously sick, it has usually been infested for years. The larvae feed under the bark and cut off the tree's water and food, and it hides that well at first. So learn the signs, but do not wait for them:
- D-shaped exit holes. Tiny, about an eighth of an inch, with one flat side. The most definitive sign, left by adult beetles on their way out.
- Thinning from the top down. The canopy goes sparse up high and works its way down. Easy to mistake for ordinary stress, which is why it gets missed.
- Sprouts from the trunk. Tender shoots erupting from the trunk or big limbs, the tree trying to make up for a failing canopy.
- Heavy woodpecker activity. Woodpeckers strip patches of bark going after the larvae, sometimes noticed before the D-holes are.
Peel back loose bark and find winding, S-shaped tunnels, and that is the larvae too.
Treat it, or plan to replace it?
This is the real decision, and the honest answer is that it depends on the tree. There is an effective preventive treatment: a licensed applicator injects the trunk with an insecticide that protects the tree for a couple of years, then repeats every two to three years. It works, but it is a recurring cost for the life of the tree, so weigh it against what the tree is worth.
Treatment makes sense for a healthy, high-value ash in a good spot: solid structure, good shade, not crowding a house or power line, no existing disease. WSU's guidance is to start once the beetle is confirmed within about 30 miles. A young, declining, or awkwardly placed ash is usually not worth the ongoing expense. And there is a point of no return: as a rule of thumb among arborists, once a tree has lost roughly a third to half its canopy, treatment stops being reliable and removal is the sensible path. A certified arborist can give you a straight read on which of your trees fall where, which is what our arborist reports are for.
Why a dead ash is its own kind of problem
Ash wood goes brittle fast once the tree dies, and brittle limbs snap without warning. That makes a dead ash more dangerous to be around, and more technical and expensive to take down, than a tree that is still sound. The longer it stands, the worse that math gets. So if you end up with an ash you cannot save, the safest and usually cheapest move is to deal with it while the wood is still solid, not years later. Our tree removal crew handles exactly this, and if you are unsure whether a tree has reached that point, our post on signs a tree needs to come down walks through it.
Do not move firewood
One of the main ways this beetle jumps long distances is inside firewood. On its own it flies only about half a mile a year, but a truckload of infested wood can carry it across a state. Buy firewood where you burn it rather than hauling it from home.
What to do this year
A few sensible steps put you well ahead of most people:
- Figure out whether you have an ash tree, using the traits above.
- If you do, get a baseline read on its health now, so any change later is easy to spot.
- Decide ahead of time whether yours is a tree you would treat or one you would eventually replace. That call is easier made calmly now than under pressure.
- If you think you have spotted the beetle, report it through invasivespecies.wa.gov rather than diagnosing off a single photo. Several harmless native insects get mistaken for it.
These trees line a lot of our creeks and wetlands, and they are worth a little forethought. Being prepared beats scrambling later. We are a family-run, ISA Certified Arborist company in Vancouver, WA, and we are glad to come identify your ash or take an honest look at its health. And if your tree is perfectly fine and needs nothing, we will tell you that too.
