When Your Ash Tree Starts Thinning Out: What It Usually Means in Kalamazoo?
A homeowner in the Westwood neighborhood called me out a few springs ago. She had a big green ash in her backyard, probably 60 years old, and she noticed the canopy looked thin. Not dead. Just lighter than she remembered.
She had watered it. She had not hit it with the mower. She could not figure it out. When I walked around the base and looked up through the branches, I already had a good idea of what we were dealing with.
That thinning canopy on a mature ash tree in Kalamazoo almost always points to one thing: emerald ash borer.
What Most People Assume First?
The most common assumption I hear is that the tree is stressed from weather or drought. And that is understandable. We had a dry stretch, the canopy looks sparse, and drought stress does show up that way.
But ash trees in Kalamazoo County have been under pressure from emerald ash borer for well over a decade now. This beetle does not make a dramatic entrance. It works quietly inside the bark while the tree slowly loses its ability to move water and nutrients from the ground up to the branches.
By the time the canopy looks thin, the damage underneath is usually significant.
What a Crew Actually Looks At?
The Exit Holes
Emerald ash borer larvae chew S-shaped galleries under the bark, then exit as adults through small D-shaped holes in the outer bark. They are easy to miss if you are not looking for them, and easy to confuse with other bark damage.
A crew checks the lower and mid-trunk for these holes closely, often on the south and west-facing sides where adults tend to emerge first in warmer spots. On a green ash or white ash here in Kalamazoo, finding even a handful of these holes tells us the infestation has been active for at least a full season.
How Much of the Canopy Is Gone
Arborists use canopy loss as a rough guide to how far the infestation has progressed. A tree that has lost less than 30 percent of its canopy still has a chance with treatment. One that has lost more than half is usually past the point where treatment makes sense.
We also look at the upper canopy specifically, because that is where ash trees show decline first. Deadwood near the top of the tree, before the lower branches are affected, is a reliable indicator that the vascular system has been disrupted for a while.
The Structural Condition of the Tree
This matters even if treatment is the plan. If the tree has co-dominant stems, existing decay pockets, or large sections of deadwood throughout the canopy, the structural integrity of the tree becomes a separate concern.
A treated ash that survives EAB but has significant internal decay or weak branch unions can still become a hazard. Part of our hazard assessment is asking whether this tree, even if it recovers from the borer, is one we would be comfortable leaving near a house or a play area.
A Brief Word About Me
I'm Noah Perkins, owner of Perkins Lawn Care, based in Kalamazoo. We work on trees and lawns across the Kalamazoo area, including Portage, Mattawan, and the surrounding parts of Kalamazoo County. Homeowners who want to understand how this kind of evaluation works before making a decision can find out more here.
What You Can Watch for Yourself?
You do not need any special tools to spot early signs. Here is what to look for on an ash tree on your property:
Thinning or sparse canopy, starting at the top: Healthy ash trees fill out fully. When the upper branches start looking see-through in summer, something is interfering with water movement.
S-shaped grooves visible under loose or peeling bark: If a section of bark has loosened or fallen away, look at the wood beneath for winding channels. These are the feeding galleries left by larvae.
Small D-shaped holes in the bark: They are about the size of a capital D on this page. Look low on the trunk and on the main scaffold branches.
Woodpecker activity on the trunk: Woodpeckers feed heavily on EAB larvae. Unusual pecking patterns or stripped bark patches on an ash are a reliable secondary sign.
Epicormic sprouts low on the trunk: These are small sprouts that shoot out from the lower trunk or base. Trees produce them when the upper canopy is failing and they are trying to maintain leaf area.
If you notice two or more of these together on the same tree, it is worth having someone take a closer look. Homeowners across Kalamazoo County can check details here to learn more about our work before reaching out.
The Decision Is Not Always Obvious
There are ash trees in this area worth treating and ash trees that are too far gone to make treatment worthwhile. The tree species, its size, its location, and how far along the damage is all factor into that call.
What I tell people is this: the sooner you catch it, the more options you have. A tree that is 20 percent gone is a different situation than one that is 60 percent gone.
Closing Thought
Ash trees are a significant part of the canopy in Kalamazoo. The older ones especially have been shading yards and lining streets for generations. Losing them is real, and making a thoughtful decision about each one matters. The ones worth saving usually are saveable, if someone looks at them soon enough.
Noah Perkins Owner, Perkins Lawn Care 155 Haymac Dr, Kalamazoo MI 49004 269-716-3332 https://perkinslawnandtree.com/
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