Emerald Ash Borer in MA (2026)

I have been doing tree work in Massachusetts since 1995, and the emerald ash borer is the single worst thing I have seen happen to trees in this state. Worse than the ice storm of 2008. Worse than the winter moth years. Worse than any individual storm. The ash borer has systematically killed every untreated ash tree across our entire service area, and it is still going. Here is everything you need to know as a homeowner.

What Is the Emerald Ash Borer?

The emerald ash borer (EAB) — scientific name Agrilus planipennis — is a metallic green beetle about half an inch long, originally from Asia. It was first detected in Michigan in 2002 and reached Massachusetts by 2012. The adult beetles are not the problem. The larvae are. Female beetles lay eggs on the bark of ash trees. The larvae hatch, bore under the bark, and feed on the cambium layer — the thin band of living tissue just under the bark that transports water and nutrients throughout the tree.

As the larvae feed, they create S-shaped galleries (tunnels) under the bark that sever the tree's vascular system. Think of it like cutting the blood vessels one by one. The tree slowly loses its ability to move water from the roots to the canopy and nutrients from the leaves to the roots. Within 3 to 5 years of initial infestation, the tree is dead.

How to Identify an Infested Ash Tree

Early detection is critical if you want any chance of saving the tree. Here are the signs, roughly in the order they appear:

1. Increased Woodpecker Activity

This is often the very first sign. Woodpeckers feed on EAB larvae under the bark. If you notice heavy woodpecker activity on your ash tree — fresh pecking holes, bark chips at the base — they are likely feeding on larvae. The woodpeckers are actually helping by eating larvae, but they are also telling you the tree is infested. In Billerica, I started noticing woodpeckers hammering ash trees a full year before we saw any other visible signs.

2. Canopy Thinning Starting at the Top

EAB damage typically shows first in the upper canopy. The top third of the tree thins out, produces smaller leaves, or fails to leaf out at all in spring. This is because the upper canopy is farthest from the roots and gets water last — when the vascular system is being severed, the top dries out first. By the time you notice the thinning, the infestation has been active for 1 to 2 years.

3. D-Shaped Exit Holes

When adult beetles emerge from under the bark in June and July, they leave distinctively D-shaped exit holes about 3 to 4 millimeters wide. These are small and can be hard to spot, especially high up on the trunk. Look for them at eye level and on larger branches. The D shape is the telltale — other borers leave round holes.

4. Bark Splitting and S-Shaped Galleries

As the infestation progresses, the bark over larval galleries begins to split and crack. If you peel back a piece of loose bark, you will see the distinctive S-shaped tunnels carved into the wood underneath. These galleries are packed with fine, sawdust-like frass (insect waste). This is definitive confirmation of EAB.

5. Epicormic Sprouting

Stressed trees often push out sprouts from the trunk and major branches — these are called epicormic sprouts or water sprouts. They are the tree's desperate attempt to grow new leaves below the damaged area to keep photosynthesizing. Dense clusters of small shoots growing directly from the trunk are a stress response and a bad sign.

6. Extensive Crown Dieback

By the time 50 percent or more of the crown is dead, the tree is too far gone for treatment. At this stage, the tree is a removal candidate. Dead ash branches become brittle quickly and start breaking off — which is when the safety hazard escalates rapidly.

Can an Infested Ash Tree Be Saved?

Maybe. It depends entirely on how early you catch it.

Treatment: Trunk Injections

The most effective treatment is trunk injection with emamectin benzoate (brand name TREE-age). A certified applicator drills small ports into the base of the trunk and injects the insecticide, which the tree distributes through its vascular system. The insecticide kills larvae feeding under the bark and protects the tree from new infestation.

When treatment works: If the tree has less than 30 percent canopy loss, is otherwise healthy, and has a good trunk structure, treatment can save it. The tree needs to be treated every 2 years indefinitely — the beetles are not going away, so protection needs to be ongoing.

What treatment costs: $200 to $400 per treatment, depending on the tree's diameter. For a large ash, that is $200 to $400 every 2 years for the life of the tree. Over 20 years, that is $2,000 to $4,000 or more. Whether that is worth it depends on the tree's value to your property and your budget.

When treatment does not work: If more than 50 percent of the canopy is dead, the vascular system is too damaged to distribute the treatment effectively. At that point, the tree cannot be saved regardless of how much you spend. In my experience across Tewksbury, Chelmsford, and Billerica, the vast majority of homeowners do not notice the problem until it is well past the treatment window. We have removed far more dead ash trees than we have seen successfully treated.

When Removal Is the Only Option

If the ash tree has lost more than 50 percent of its canopy, has bark falling off the trunk, or has been dead for more than a year, removal is not just recommended — it is urgent. Here is why:

Dead Ash Trees Become Dangerous Fast

This is the part that most homeowners do not realize until it is too late. Ash wood, when it dries out after the tree dies, becomes extremely brittle. Other dead hardwoods like oak remain structurally sound for years after dying. Ash does not. Within 2 to 3 years of death, ash branches snap off with minimal provocation. The wood shatters instead of bending. Climbing a dead ash tree is one of the most dangerous operations in our profession because the limbs you are putting your weight on can break without warning.

I am not exaggerating when I say that dead ash trees are the single most dangerous trees we remove. The unpredictability of the wood makes every cut a risk. That is also why the cost of removing a dead ash goes up the longer you wait. A recently dead ash that still has some structural integrity is easier and cheaper to take down than one that has been dead for three years and crumbles when you touch it.

Falling Branches Are a Real Liability

A dead ash tree dropping a 6-inch-diameter limb from 40 feet onto a car, a fence, a shed, or a person is a serious event. These limbs fall without warning, in calm weather, with no wind at all. They just let go. If a dead ash tree is within striking distance of anything you care about — your house, your driveway, your neighbor's property, a walkway, a play area — it needs to come down before it drops something on someone.

Insurance companies are increasingly aware of the ash borer issue. Some are beginning to ask about dead trees on the property during renewal. If you know about a dead ash tree and do nothing, and it causes damage, you may face a liability argument that the damage was foreseeable. Do not put yourself in that position.

What the Ash Borer Has Done to Our Service Area

Across our 13-town service area in Middlesex County and the Merrimack Valley, the emerald ash borer has fundamentally changed the tree landscape. White ash and green ash were common street trees, yard trees, and forest trees throughout the area. The vast majority are now dead or dying.

In Billerica, I have watched ash trees die on nearly every street over the past decade. In Tewksbury, the ash-heavy neighborhoods around the town center and along the Shawsheen River have lost dozens of large ash trees. Chelmsford, Dracut, Lowell — every town tells the same story. We have removed hundreds of dead ash trees in the last five years, and there are still hundreds more standing dead that have not been addressed yet.

The towns themselves are dealing with dead ash on public property, along roads, and in parks. Municipal budgets for tree removal have been strained across the region. It is an ongoing crisis that will take years to fully resolve.

Other Invasive Pests to Watch

The emerald ash borer is the biggest current threat, but it is not the only invasive pest on the horizon:

Spotted Lanternfly

Originally from Asia, the spotted lanternfly has been devastating trees and agriculture in Pennsylvania and New York and is spreading northward. As of 2026, it has been detected in several Massachusetts locations. It feeds on over 70 plant species, including maples, oaks, walnuts, and fruit trees. It does not usually kill trees directly but weakens them severely and produces a sticky "honeydew" that coats everything underneath with sooty mold. If you see a large, colorful insect with spotted wings and red underwings, report it to the Massachusetts Department of Agricultural Resources.

Asian Longhorned Beetle

The Worcester infestation was declared eradicated in 2024, but this beetle could reappear anywhere through imported wood products. It targets maples — sugar maple, red maple, Norway maple — which are the backbone of the Massachusetts landscape. If you see a large black beetle with white spots and very long antennae, or perfectly round exit holes the size of a dime in maple trunks, report it to USDA APHIS at 1-866-702-9938. Read more in our complete guide to Massachusetts tree pests.

Hemlock Woolly Adelgid

Not new, but still actively killing eastern hemlocks throughout Massachusetts. White, cottony masses on the undersides of hemlock branches are the giveaway. Unlike EAB, hemlock woolly adelgid can be treated effectively with trunk injections, and treatment is worth considering if you have valuable hemlock trees on your property.

What You Should Do Right Now

1. Identify your ash trees. Ash trees have opposite branching (branches grow in pairs directly across from each other) and compound leaves with 5 to 9 leaflets. If you are not sure, we can help identify them during a free property assessment.
2. Check for signs of infestation. Use the checklist above — woodpecker activity, canopy thinning, D-shaped holes, bark splitting.
3. Decide: treat or remove. If the tree has less than 30 percent canopy loss and is in a location where it provides significant value, consult a certified arborist about treatment. If it is past that point, call us for removal.
4. Do not wait on dead ash trees. A dead ash tree near your home, driveway, or any area where people walk or park is a hazard. Every season it stands dead, it gets more brittle and more dangerous — and more expensive and dangerous for us to remove.

McDonald Tree Service has removed more dead ash trees than I can count across Billerica, Chelmsford, Tewksbury, Lowell, Wilmington, Burlington, Bedford, Carlisle, Dracut, Westford, Andover, Woburn, and Lexington. If you have a dead or dying ash tree, call (978) 375-2272 for a free estimate. We will get it down safely before it comes down on its own. For true emergencies — a dead ash tree that is actively dropping limbs or leaning toward your house — we offer 24/7 emergency service.