Emerald ash borer (EAB) has become one of the most destructive invasive pests affecting ash trees across Ontario. If you have ash trees on your property, knowing the signs of Emerald Ash Borer infestation can help you act early – and potentially save your tree or prevent further spread.
At CBL Tree Service, we’ve seen firsthand how quickly EAB can damage healthy-looking trees. The challenge is that many of the early symptoms are subtle, which is why regular inspection is so important.
About Emerald Ash Borer
Emerald Ash Borer is a small, metallic green beetle that targets ash trees. While the adult beetles feed on leaves and cause minimal damage, the real threat comes from their larvae. After hatching, the larvae burrow beneath the bark and feed on the inner layers of the tree, where water and nutrients are transported. As they tunnel, they create winding galleries that disrupt this flow, essentially starving the tree from the inside out – one of the earliest and most important signs of Emerald Ash Borer infestation to understand.
Over time, this internal damage weakens the tree, leading to canopy thinning, branch dieback, and eventually death if left untreated. In fact, once an infestation becomes established, many ash trees can decline rapidly within just a few years, making early detection especially important for property owners across Ontario.
6 Signs of Emerald Ash Borer Infestation
Recognizing the early warning signs can make all the difference. Here are the most common indicators to watch for:
1. Thinning or Dying Canopy
One of the first visible symptoms is a thinning canopy, especially at the top of the tree. Leaves may appear sparse, smaller than usual, or begin dying off prematurely.
2. D-Shaped Exit Holes
As adult beetles emerge from the tree, they leave behind small, distinctive D-shaped holes in the bark. These are one of the clearest signs of Emerald Ash Borer infestation and often appear on the trunk or larger branches.
3. Bark Splitting
Vertical cracks or splits in the bark can indicate larval activity beneath the surface. In some cases, you may even see the S-shaped galleries (tunnels) created by larvae if the bark begins to peel away.
4. Increased Woodpecker Activity
Woodpeckers are natural predators of EAB larvae. If you notice increased woodpecker activity or patches of missing bark, it could be a sign they’re feeding on an infestation.
5. Epicormic Shoots (New Growth at the Base)
Trees under stress often produce new shoots at the base of the trunk or along the lower branches. While this might look like new growth, it’s actually a sign the tree is struggling to survive.
6. Premature Leaf Yellowing
Leaves may turn yellow or brown earlier than expected, even outside of the typical fall season. This is often due to disrupted nutrient flow within the tree.
Why Early Detection Matters (and What You Should Do)
Emerald Ash Borer damage progresses quickly, and in many cases, an infested ash tree can decline significantly within just a few years. By the time major symptoms appear, the tree may already be beyond saving. That’s why recognizing the signs of Emerald Ash Borer infestation early is so important. Not just for the health of your tree, but for protecting the surrounding trees in your neighbourhood.
If you suspect your ash tree may be affected, there are a few key steps to take. Avoid removing or transporting firewood, as this is one of the most common ways the pest spreads. Keep an eye on nearby ash trees for similar symptoms, and don’t wait too long to act.
Reaching out to a professional tree service, like CBL, for an assessment can help determine the best course of action. In Ontario, where EAB is already widespread, proactive care and timely removal of heavily infested trees can make a big difference in reducing risks to your property and the surrounding landscape.
Give Your Trees a Fighting Chance with CBL
At CBL Tree Service, we work with property owners across major communities and rural properties across Peterborough County, Northumberland County, and the Kawartha Lakes Region. Our knowledgeable guidance is based on your tree’s condition. From detailed inspections by the owner Joe Corkery to treatment recommendations and safe, efficient removals, our team focuses on protecting your property while helping you make the right long-term decision.
If you’re unsure what you’re dealing with, don’t wait until the damage becomes more severe. Request a quote with us soon!