Emerald ash borer is a small metallic-green beetle that arrived in North America in shipping material and has since killed ash trees across the Midwest on a scale that is genuinely hard to overstate. Indiana has been in the middle of it. Every county in the state has been affected, and if you drive through older Indianapolis neighbourhoods you can still pick out the grey, bare-topped skeletons standing in yards and along fence lines. Ash was a wildly popular street and yard tree for decades — fast, tough, tolerant of clay soil and road salt — which is exactly why the loss has been so visible.
The beetle itself does not do the killing. The larvae do. An adult female lays eggs in bark crevices, the larvae hatch and bore in, and they spend their lives feeding in the phloem — the thin living layer just under the bark that carries sugars from the leaves down to the roots. They chew serpentine, S-shaped galleries through that layer, and as the population builds those galleries multiply until they have effectively girdled the tree. The roots starve. Water and nutrients cannot move. The tree dies from the top down, and there is nothing it can do about it because ash has no natural defence against an insect it never evolved alongside.
The signs, in rough order of appearance: thinning in the upper canopy, because the top is furthest from the roots and starves first. Then epicormic sprouting — leafy shoots pushing straight out of the trunk and the base of the tree, which is the ash making a desperate attempt to grow foliage below the damage. Then heavy woodpecker activity, patches of pale, flecked bark where birds have chipped it away to get at the larvae underneath; that flecking is one of the most reliable field indicators there is. Then bark splitting vertically, and underneath those splits you will find the S-shaped galleries. Finally the exit holes: distinctly D-shaped, about an eighth of an inch across, flat on one side. Nothing else leaves that mark.
By the time you can see thinning from the ground, the tree has typically been infested for two or three years. That is the cruel part of the timeline — the damage is well advanced before it is visible. Treatment with a systemic insecticide, applied properly by a professional, does genuinely work and can protect a healthy ash indefinitely with repeat applications. But it is preventive, not curative. The rule of thumb across the industry is that if a tree has already lost more than a third to a half of its canopy, treatment is throwing good money after bad, because the vascular tissue needed to move the insecticide up the tree is already too damaged to carry it.
So the practical decision for most Indiana homeowners now comes down to this: if you have a healthy, structurally sound, well-placed ash that you value, treatment is a legitimate and reasonably economical choice, and it needs to be maintained on a cycle for the life of the tree. If you have an ash that is already visibly declining, the money is better spent on removal and replanting with something else. And if you have an ash you have never treated and never really thought about, it needs looking at now, not next year.
This is where it gets serious, and it is the part we most want people in Indianapolis to understand. A dead ash is not like other dead trees. Ash wood loses its structural integrity extraordinarily quickly after the tree dies — far faster than oak or maple. It goes brittle. Limbs that look solid snap under load with no warning at all, and the wood does not bend or creak first the way most species do; it simply lets go. A dead ash cannot safely be climbed with spikes and rope after a certain point, and no competent crew will try. It has to come down from a bucket truck or with a crane, working from outside the tree rather than inside it, which costs more and is exactly why waiting is a false economy. The longer a dead ash stands, the more dangerous and the more expensive it becomes to remove, and eventually it comes down by itself, at a time and in a direction of its own choosing.
Every summer in Central Indiana we get storm calls that turn out to be dead ash that finally let go in a straight-line wind, and the owner almost always says they had been meaning to get to it. If you have an ash anywhere on your property — treated, untreated, dead, or you are not even certain it is an ash — we will come out and tell you honestly what you are dealing with. The assessment is free, and this is one problem where the honest answer really does depend on doing something before the next storm rather than after it.