Emerald Ash Borer in Connecticut: Is Your Ash Tree Already Infected?

For years, it felt like every other phone call we received was about an ash tree.

Since emerald ash borer (EAB) was first discovered in Connecticut in 2012, it has killed millions of ash trees across the state. At its peak, it seemed impossible to keep up with the number of declining ash trees we were evaluating and removing.

The good news is that I believe we’re finally seeing a shift.

Like many invasive species, emerald ash borer populations exploded when food was abundant. After more than a decade of widespread ash mortality, mature ash trees have become far less common across Connecticut. With fewer host trees available, EAB populations appear to have declined significantly over the past couple of years. Another encouraging development is the release of tiny parasitic wasps by entomologists throughout Connecticut. These wasps feed exclusively on emerald ash borers and are helping provide long-term biological control.

Unfortunately, while the worst of the outbreak may be behind us, the danger isn’t.

Many properties still have ash trees that are declining or were infected years ago and are now becoming hazardous. We continue to evaluate ash trees every week, and homeowners are often surprised to learn that a tree that still has some green leaves can already be structurally compromised.

The question today isn’t whether emerald ash borer has reached Connecticut.

The question is whether your ash tree has already been affected.

How to Tell if Your Ash Tree Is Infected

By the time most homeowners notice symptoms, emerald ash borer has usually been in the tree for multiple seasons. The larvae feed beneath the bark, destroying the tissues that move water and nutrients throughout the tree.

Some of the most common signs include:

• Thinning or dead branches in the upper canopy. EAB typically attacks the top of the tree first, causing the crown to thin before symptoms appear lower down.
• Distinctive D-shaped exit holes. Adult beetles leave small D-shaped holes, about 1/8 inch wide, as they emerge from the tree.
• S-shaped galleries beneath the bark. If bark has begun to split or peel away, winding tunnels are one of the clearest indicators of emerald ash borer.
• Sprouts growing from the trunk or base of the tree. Stressed ash trees often produce numerous shoots in an attempt to replace their failing canopy.
• Vertical bark cracks. Heavy larval feeding frequently causes the bark to split, sometimes exposing the galleries underneath.
• Heavy woodpecker activity. Woodpeckers quickly learn where EAB larvae are hiding. Large patches of missing outer bark—often called “blonding”—are a common sign.

One symptom alone doesn’t necessarily mean emerald ash borer is present. However, if you notice several of these signs together, it’s worth having the tree evaluated.

Why Ash Trees Become So Dangerous

One of the biggest misconceptions is that a tree has to be completely dead before it becomes hazardous.

Ash trees are different.

Once emerald ash borer has killed the tree, the wood dries quickly and becomes extremely brittle. Branches can fail unexpectedly, and the trunk itself becomes increasingly difficult—and dangerous—to remove as decay progresses.

In many cases, an ash tree with scattered green leaves can already have significant structural weakness.

That’s why we generally recommend evaluating ash trees before they become completely dead, especially if they’re near a home, driveway, play area, or neighboring property.

Can an Ash Tree Still Be Saved?

Sometimes.

Healthy, valuable ash trees that are only lightly infested can often be protected with systemic insecticide treatments. These treatments work best before the tree has suffered significant canopy loss.

However, treatments require ongoing applications every one to three years for the life of the tree. Once a tree is heavily infested or has declined substantially, treatment is usually no longer effective, and removal becomes the safest option.

Looking Beyond Emerald Ash Borer

While emerald ash borer dominated the conversation for well over a decade, we’re beginning to see another invasive pest take center stage.

If you’ve walked through Connecticut’s forests recently, you’ve probably noticed beech trees with dark, scorched-looking leaves. Beech Leaf Disease is spreading rapidly across the state, and we’re already receiving an increasing number of calls from concerned homeowners.

It reminds me of where we were with emerald ash borer years ago.

There’s still much researchers are learning about this disease, but it appears likely to become the next major challenge for Connecticut’s forests.

(We’ll be covering Beech Leaf Disease in much more detail in an upcoming article.)

Concerned About an Ash Tree?

If you have an ash tree on your property and aren’t sure whether it’s been affected, we’d be happy to take a look.

At Arbortech Tree Inc., we’ve been helping homeowners throughout Hartford, Tolland, and Windham Counties evaluate hazardous trees for more than 20 years. Whether the tree can be treated or should be removed, we’ll walk you through your options and help you make an informed decision. Contact us today to get started.