Emerald Ash Borer in Michigan: What to Do With the Ash You Still Have

Emerald ash borer was first identified in North America near Detroit in 2002. It almost certainly arrived years earlier in wood packing material, and by the time anyone knew what it was, it was already established across southeast Michigan.

What followed is the largest tree die-off in the region's modern history. Tens of millions of ash trees across the state. And two decades on, we still find standing dead ash on properties in Wayne, Redford and across Downriver — trees people have been putting off for fifteen years because they have not fallen on anything yet.

What the insect actually does

The adult beetle is small, metallic green and does very little damage — it nibbles leaves. The problem is the larvae. Adults lay eggs in bark crevices, larvae hatch and bore into the layer just under the bark, and they feed on the phloem, the tissue that carries sugars from the leaves down to the roots.

They carve S-shaped galleries as they feed. Enough larvae and those galleries girdle the tree completely, cutting the canopy off from the roots. The tree starves. Untreated, an infested ash typically dies within two to four years.

How to identify an infested ash

First: is it actually an ash?

Ash have opposite branching — buds and branches directly across from each other rather than staggered. Compound leaves with five to eleven leaflets. Mature bark forms a distinctive diamond-shaped interlacing pattern. Only a handful of common Michigan trees have opposite branching: maple, ash, dogwood and horse chestnut. If the leaves are compound and the branching is opposite, it is almost certainly ash.

Then: the signs

• D-shaped exit holes about an eighth of an inch across. The flat side of the D is the giveaway — other borers leave round or oval holes.
• Bark blonding. Woodpeckers strip the outer bark to reach larvae, leaving pale yellow patches. This is often the first thing visible from the ground and it is a strong indicator.
• Canopy thinning from the top down. Ash die from the crown downward.
• Epicormic sprouts — clusters of shoots coming directly out of the trunk and large limbs. That is a stress response, the tree trying to make leaves anywhere it still can.
• S-shaped galleries packed with sawdust-like frass, visible if a piece of bark comes off.
• Vertical bark splits over the galleries.

Treat or remove?

Treatment is real and it works, on the right tree. Systemic insecticides applied as trunk injections protect ash effectively, but they are a permanent commitment — the treatment has to be repeated on a cycle, typically every one to three years depending on the product, for as long as you want the tree.

Treatment makes sense when

• The tree is healthy with less than about a third canopy loss.
• It is a significant landscape tree — large, well-placed, hard to replace.
• You are prepared to keep paying for repeat treatments indefinitely.
• The tree is otherwise structurally sound.

Removal makes sense when

• Canopy loss is already past a third, or the tree is dead.
• The tree is small, poorly placed, or one of several ash on the property.
• You do not want an open-ended treatment commitment.
• It is near a house, garage, driveway or anywhere people spend time.

Why waiting on a dead ash costs money

This is the part that matters most practically. Dead ash does not just stand there — it deteriorates fast. Within a couple of years the wood becomes brittle enough that a climber cannot safely tie into it. At that point the job needs a bucket truck or a crane, and the price goes up accordingly.

Dead ash also shed limbs without warning and can shatter unpredictably when cut, which is why some companies simply will not touch them. Our hazardous tree removal crew handles standing dead ash regularly, and the honest advice is always the same: the cheapest time to take one out was two years ago, and the second cheapest is now.

What to do with the wood

Ash is excellent firewood — it burns clean and hot and seasons faster than most hardwoods. The important rule is not to move it. Michigan and federal quarantine restrictions on ash wood movement have relaxed as the beetle spread across the region, but the underlying principle still holds: do not haul ash firewood to a cabin up north or across state lines. Burn it where it fell.

What to plant instead

Diversity is the lesson of this whole episode. Communities that planted ash on every street lost every street tree at once. If you are replacing an ash, choose something different from whatever else dominates your block — hackberry, Kentucky coffeetree, swamp white oak, tulip poplar, hornbeam, serviceberry and Ohio buckeye all do well in southeast Michigan and none of them are what your neighbors planted.

Not sure whether your ash is worth saving? Our free assessments will give you a straight answer either way.

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