If you own ash trees anywhere in Jefferson County, emerald ash borer isn’t a distant regional threat — it’s already here, and it has been since 2019. This guide covers what EAB is, what it does to an ash tree, what the timeline actually looks like, and how to decide between treatment and removal before the wood turns dangerous to bring down.
EAB Is Confirmed in Jefferson County
The New York State Department of Environmental Conservation confirmed emerald ash borer in Jefferson County starting in the fall of 2019. The first positive sample came from a street tree in the City of Watertown, on South Massey Street, identified by the Cornell University Insect Diagnostic Lab. A second infestation location was confirmed the same year in the village of Clayton, on the St. Lawrence River. Watertown has been a Tree City USA every year since 2000, with an active Urban Forestry Program overseeing the city’s public trees — EAB is exactly the kind of threat that program was built to respond to, and it’s just as real a concern for the ash trees on private residential property throughout the county.
By now, several years past those initial confirmations, infestation has almost certainly spread more broadly across the county’s ash population — EAB moves both on its own and via infested firewood, and it doesn’t stay contained to two points on a map for long. If you own an ash tree anywhere in Jefferson County, the safe assumption is that EAB risk applies to it, not that your specific tree has somehow been spared.
What EAB Actually Does
Emerald ash borer is a wood-boring beetle, roughly 3/8 to 5/8 of an inch long, with metallic green wing covers and a coppery red or purple abdomen. It’s the larval stage that does the damage: after adult females lay eggs on the bark, larvae chew their way in and feed on the living tissue just beneath the bark, creating S-shaped tunnels called galleries. That layer is exactly where a tree transports water and nutrients up to its crown, so as the galleries multiply, the tree is effectively being girdled from the inside, cut off from its own water supply a little more each season.
Signs to watch for: thinning or dying canopy starting at the top of the tree and working down, bark splitting or falling away in patches (sometimes from woodpeckers feeding on larvae underneath, a phenomenon called “blonding” for the lighter wood it exposes), and small 1/8-inch, D-shaped exit holes in the bark where adult beetles emerged. Epicormic sprouting — a burst of small new shoots low on the trunk — is also common as a stressed tree tries to compensate.
Adults typically emerge and are most active in late spring through summer, which is when D-shaped exit holes from the previous year’s generation are easiest to spot on the bark. By the time canopy thinning becomes obvious from the ground, the tree has usually already been infested for a year or more — the visible symptoms lag behind the actual internal damage, which is part of why an assessment from someone trained to spot early signs matters more than waiting for a tree to look obviously sick.
Why Standing-Dead Ash Is a Different Kind of Dangerous
An ash killed by EAB doesn’t fail the way most dead trees do. Because the beetle attacks the layer just under the bark, the wood loses structural integrity from the top down and from the inside out, and it happens fast — often within a couple of years of the tree’s decline becoming visible. The wood turns brittle well before the tree looks obviously dead from the ground, and dead ash is notorious in the tree care industry for shedding limbs and snapping without much warning, which is part of why removing a standing-dead ash costs more than removing a healthy tree of the same size — see our Cost Guide for how that premium breaks down. It also means waiting rarely makes a dead ash safer or cheaper to deal with; the opposite is closer to true.
Treat or Remove?
For an ash tree that’s still healthy or only lightly affected, preventive insecticide treatment is a real option, and it can meaningfully extend a valuable specimen tree’s life — but it’s an ongoing commitment, typically reapplied on a regular cycle, not a one-time fix. Treatment makes the most sense for a tree with genuine landscape or shade value that you’re prepared to keep treating for years, not for every ash on a property indiscriminately.
Once a tree has significant canopy dieback — commonly cited around the 30 to 50% range of crown loss — treatment success rates drop considerably, and removal becomes the more honest recommendation. We’ll tell you plainly which side of that line your tree is on rather than upselling treatment for a tree that’s past the point where it reliably works. A free hazard assessment is the right way to get that answer for your specific tree.
A Note on Firewood
One of the ways EAB spreads to new areas is firewood, since larvae and eggs can travel inside cut wood well before any visible symptoms appear. If you have an ash removed, DEC guidance is to use the wood on site or chip it down to less than an inch in at least two dimensions rather than transporting it — and firewood generally shouldn’t move more than about 50 miles from where it was cut. If you’re keeping wood from an ash removal as firewood, plan to burn it locally rather than taking it to a camp, a relative’s house, or anywhere outside the immediate area.
If You Think You Have EAB
A hazard assessment from us is a free, direct way to get an answer specific to your tree, including whether it’s actually an ash in the first place — not every declining tree is EAB, and treating the wrong cause doesn’t help. If you want to report a sighting directly to the state, DEC’s Forest Health Diagnostic Laboratory accepts photos and location details by email, and regional DEC Private Lands Staff are available for landowners with broader questions about managing an infestation across a larger property. We’ve also put together a printable identification and decision checklist if you’d rather work through this on paper, tree by tree.
What This Means If You’re Planning Ahead
The honest long-term picture is this: if you own ash trees in Jefferson County, you’re not choosing whether EAB affects you, only when and how you respond to it. Getting ahead of it — a hazard assessment this season, a removal scheduled on your own timeline rather than after a limb comes down — is consistently the cheaper and safer path compared to waiting for the tree to force the decision.
What to Plant Instead
If you’re removing an ash and want to replant, it’s worth choosing something that isn’t vulnerable to the same threat. Native species that handle this region’s winters well and aren’t currently facing a comparable pest pressure include red maple, hackberry, and swamp white oak for wetter sites. A replacement tree planted now has decades to establish before it reaches anywhere near the size of the ash it’s replacing, so there’s real value in not waiting until every ash on a property has already failed.
Ash Trees on Rental and Managed Properties
If you manage rental units or a larger portfolio — a common situation around Fort Drum given the area’s PCS turnover — ash trees deserve specific attention during routine property inspections rather than being lumped in with general landscaping. A tenant or a home inspector finding a declining ash during a walkthrough is a worse outcome, and a more expensive one to resolve on short notice, than catching it during a scheduled seasonal check.
The same logic applies to anyone selling a property with ash trees on it — a buyer’s inspector flagging a declining ash can stall a closing while the two sides negotiate who handles it. Addressing it before listing, or at minimum having a documented recent assessment in hand, tends to make that conversation much shorter.
Frequently Asked Questions
How do I know if my tree is actually an ash tree?
Ash trees have opposite branching (branches grow in pairs directly across from each other, one of the few common trees that does this) and compound leaves with 5 to 9 leaflets. A hazard assessment can confirm it along with the tree’s condition.
Is it too late to treat my ash tree?
It depends on how much canopy has already been lost. Trees with significant dieback — commonly past 30 to 50% crown loss — have much lower treatment success rates, at which point removal is usually the more realistic recommendation.
Can I still use wood from an EAB-killed ash?
Yes, but keep it local — DEC guidance is to use it on site or chip it small rather than transporting it any real distance, since moving infested wood is one of the main ways EAB spreads to new areas.
Does every ash tree in Jefferson County have EAB?
Not necessarily every individual tree, but EAB has been confirmed in the county since 2019 and has almost certainly spread further since. The safe assumption for any ash tree here is that EAB risk applies.