Emerald Ash Borer in Simcoe County: Is Your Ash Tree at Risk?

How EAB Kills Ash Trees

EAB larvae feed on the inner bark (cambium) of ash trees, creating serpentine galleries that disrupt the tree's ability to transport water and nutrients between roots and canopy. A healthy ash tree can typically survive one or two years of infestation before symptoms become visible — but by that point, the damage is often extensive. Without treatment, virtually every untreated ash tree in an EAB-infested area will die within 3–5 years of initial infestation. The Canadian Forest Service confirms that EAB has a near-100% mortality rate in untreated ash populations.

Signs of EAB Infestation

Early detection is critical because treatment is only effective when the tree still has enough healthy canopy to recover. Watch for these signs:

• Crown thinning and dieback: The canopy starts thinning from the top down. You'll notice fewer leaves, smaller leaves, and dead branches in the upper crown — often while the lower canopy still looks relatively healthy.
• D-shaped exit holes: Adult EAB beetles emerge through distinctive D-shaped holes approximately 3–4 mm wide in the bark. These are a definitive sign of infestation.
• Bark splitting and serpentine galleries: As larvae feed beneath the bark, vertical splits may appear. Peeling back loose bark reveals the characteristic S-shaped feeding galleries packed with frass (sawdust-like waste).
• Epicormic sprouting: The tree produces desperate clusters of new shoots along the trunk and major branches — a stress response indicating the canopy is failing and the tree is attempting to generate new foliage closer to the root system.
• Increased woodpecker activity: Woodpeckers feed on EAB larvae. Heavy woodpecker damage — flaking bark, pecking holes — on an ash tree is a strong indicator of infestation.

When Treatment Is Still Viable

Trunk injection with emamectin benzoate (marketed as TreeAzin in Canada) is the most effective treatment against EAB. The active ingredient is injected directly into the tree's vascular system, where it kills feeding larvae and provides protection for up to two years per treatment. However, treatment is only viable when the tree meets certain criteria:

• The tree retains at least 50–60% of its original canopy
• The trunk shows no signs of significant structural decay
• The tree is worth preserving — positioned to provide shade, privacy, or aesthetic value

Treatment must be repeated every two years for the life of the tree. At current Simcoe County rates, trunk injection costs approximately $8–$15 per centimetre of trunk diameter per treatment cycle. For a 40 cm diameter ash, that's approximately $320–$600 every two years. Our pest and disease treatment service includes full assessment and trunk injection for ash trees that are good candidates for preservation.

When Removal Is the Better Option

If an ash tree has lost more than 50% of its canopy, removal is almost always the better investment. A heavily infested tree will not recover even with treatment, and continuing to treat a declining tree is a sunk cost. Dead and dying ash trees also become extremely hazardous very quickly — EAB-killed ash trees lose structural integrity faster than almost any other species. The wood becomes brittle within 1–2 years of death, and branches and trunks can snap without warning. Insurance companies and municipalities across Ontario have flagged dead ash trees as a priority hazard. Delaying removal of a dead or severely declining ash tree increases both the risk and the eventual cost — dead ash trees are more dangerous and more expensive to remove than living ones because the brittle wood is unpredictable during dismantling. Our tree removal and hazard removal crews handle EAB-killed ash removals across Simcoe County daily.

The Cost Question: Treatment vs. Removal

Here's a realistic comparison for a mature ash tree (40–50 cm trunk diameter) in Simcoe County:

• Trunk injection treatment: $320–$750 every two years, ongoing for the life of the tree
• Removal: $1,500–$4,000 one-time cost (depending on size and access), plus $150–$400 for stump grinding

Over 10 years, treatment costs $1,600–$3,750. Removal is a one-time expense. For a healthy, well-positioned tree that provides significant value to your property, treatment makes financial sense. For a tree that's already in decline, in a poor location, or one of several ash trees on the property, removal is typically the more practical choice.

What Axe & Wedge Recommends

We assess every ash tree individually. Our qualified arborists will evaluate canopy health, trunk condition, structural integrity, and the tree's value to your property before recommending treatment or removal. We don't push treatment on trees that won't respond, and we don't push removal on trees that can be saved. With 583 five-star Google reviews, $5 million in liability insurance, and crews working across Simcoe County every day, we're equipped to handle whatever your ash trees need. Call 705-540-0760 for a free on-site assessment.