Reference
Emerald Ash Borer: Treat or Remove?
The short answer
Emerald ash borer (EAB) is an invasive beetle whose larvae tunnel under the bark and kill ash trees. If you own an ash tree in or near an infested area, the key decision is whether to treat it with insecticide or remove it, and that depends on the tree's location, value, health, and the cost of treatment versus removal.
As a rule of thumb, treatments are far more effective on trees with less than about 50% canopy thinning; trees with more than 50% canopy loss are generally not worth treating and should be removed. Homeowner soil-drench products struggle to protect large trees, so trees roughly 15 inches in diameter or more are best handled by a professional arborist, who can use more effective trunk-injection products. Because this is a costly, long-term decision, use your local Extension office or a certified arborist to evaluate the specific tree before you commit.
Why EAB matters
EAB larvae feed in the tissue that moves water and nutrients, and untreated ash trees typically die once infested. Canopy thinning and dieback, usually starting at the top, are common signs. Because the beetle spreads, early decisions protect both your tree and your budget.
The treat-or-remove decision
- Consider the tree's location, value, and health, plus the cost of treatment versus removal
- Treatments are significantly more effective on trees with less than 50% canopy thinning
- Trees with more than 50% canopy thinning are generally not worth treating and should be removed
- Homeowner soil-drench products struggle to protect large trees
- Large ash trees (roughly 15 inches diameter and up) should be evaluated by a professional arborist
Get a professional assessment
Because effective treatment of larger or valued trees usually requires professional trunk-injection products and repeat applications, and because removal of a large tree is costly, have a certified arborist or your local Extension office assess the tree's health and your options before deciding. Follow the label on any insecticide.
⚠ A declining ash near a house or walkway becomes brittle and hazardous; if you are leaning toward removal, plan it before the wood becomes dangerous to fell.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Wisconsin Horticulture — Is My Ash Tree Worth Treating for Emerald Ash Borer? — Decision factors: location, value, health, cost; treatments effective on trees with <50% canopy thinning; >50% thinning not recommended, remove; large trees need professional; homeowner soil drenches struggle on large trees.
- UMN Extension — Emerald ash borer in Minnesota — EAB biology, signs of infestation, and treat-or-remove considerations for homeowners.
- MSU Extension — Emerald ash borer treatments for homeowners — Homeowner treatment products, size thresholds, and when to consult a professional arborist.