Not long ago, ash trees were among the most widespread native species in Quebec. Their wood was highly valued for furniture, hardwood flooring, and tool handles. Thanks to their elegant form, strong branch structure, and tolerance to pollution and road salt, ash trees were widely planted in both urban and rural landscapes. But that was before the arrival of the emerald ash borer… What has changed since then?
What Is the Emerald Ash Borer?
The emerald ash borer is a beetle, part of the Coleoptera order, like lady beetles and scarabs. Native to Asia, it was first detected in 2002 near Windsor, Ontario, and Detroit, Michigan. In Quebec, it was first identified in Carignan in 2008 and later confirmed in Montreal in 2011. Since then, it has spread across many regions of the province.
This highly destructive insect attacks all ash species. In late spring, adults feed on leaves in the canopy before mating, causing minimal visible damage at this stage. Females then lay eggs in bark crevices along branches and trunks.
Once the larvae hatch, they feed beneath the bark in the phloem and cambium—the tissues responsible for transporting sap. As larvae create extensive galleries, sap flow becomes restricted, eventually leading to tree death. In just a few years, an infestation can wipe out ash populations across entire regions, and its rapid spread makes it very difficult to control.
How to Identify the Emerald Ash Borer?
Adult beetles are difficult to spot due to their small size and discreet behaviour. They are usually found in the upper canopy. Their metallic emerald-green colour and small size (about 1.5 cm long) are distinctive.
The larva looks very different from the adult. It is white and measures between 1 and 30 mm depending on its development stage. Its body is composed of 10 distinct segments.
Because early detection is difficult, infestations are often only noticed after several years.
Typical symptoms include thinning canopy, yellowing leaves, branch dieback, and the appearance of numerous suckers at the base of the trunk. Bark may crack and peel, revealing distinctive S-shaped galleries underneath.
Once approximately 30% of the canopy shows decline, the tree cannot recover.
For a visual overview, watch this short animation produced by the Montreal Metropolitan Community: Emerald Ash Borer Situation in Quebec.
Current Status of the Emerald Ash Borer in Quebec
Since 2008, the emerald ash borer has continued to spread, while ash trees have steadily disappeared from Quebec landscapes.
The pest is now present in all southern and central regions of Quebec, as well as Bas-Saint-Laurent. Since 2022, it has also been detected in Gaspésie, and in November 2023, its presence was confirmed in Témiscamingue.
How Can We Limit Its Spread?
Emerald ash borers can fly up to 10 kilometres, but human activities—especially transporting firewood—allow them to spread much farther.
To reduce this risk, the Canadian government regulates the movement of potentially infested wood. Learn more from the Canadian Food Inspection Agency about the risks of moving firewood.
Additional best practices include:
- Always buy firewood locally and verify its origin;
- Avoid planting ash trees—many municipalities now prohibit them;
- Replace dead ash trees with recommended alternative species;
- If more than 30% of the canopy is dead, remove the tree during dormancy (October 1 to March 31).
Susceptible Ash Species
In North America, all ash species are vulnerable to emerald ash borer. In Eastern Canada, the most common species include:
| Common Name | Latin Name |
| White Ash / American Ash | Fraxinus americana |
| European Ash | Fraxinus excelsior |
| Black Ash | Fraxinus nigra |
| Green Ash / Red Ash | Fraxinus pennsylvanica |
Is There Hope for Ash Trees?
The emerald ash borer has destroyed millions of trees, and its spread has been rapid. Will ash disappear completely? Not necessarily—research offers some hope.
Genetic Resistance
Some ash trees in Ohio have shown natural resistance, where larval development is interrupted. This trait may be inherited. Research is ongoing to identify these traits and develop resistant varieties.
In Quebec, efforts focus on hybridizing native black ash with Manchurian ash, a more resistant species.
Seed Banks
Natural Resources Canada is collecting seeds from unaffected areas to preserve genetic diversity for future restoration.
Biological Control
In its native habitat, the emerald ash borer is regulated by natural predators. Research is underway in Canada to introduce parasitoid wasps that could help control populations.
Fungal Traps
Innovations such as FraxiProtect traps use a natural fungus (Beauveria bassiana) to infect adult beetles, reducing populations locally by up to 40%.
Insecticide Treatments
Preventative trunk injections (such as IMA-jet or TreeAzin) are used by municipalities and certified arborists. These treatments must be repeated annually and are not always fully effective.
Which Trees Can Replace Ash?
Planting ash trees is now discouraged or prohibited. Here are recommended alternatives adapted to Eastern Canada conditions:
| Common Name | Latin Name | Zone | Key Characteristics |
| Yellow Birch | Betula alleghaniensis | 3b | Height: 20–25 m Sun: full sun to partial shade Soil: rich, moist |
| American Hornbeam | Carpinus caroliniana | 3b | Height: 15–20 m Sun: full sun to partial shade Soil: moist, fertile |
| Swamp White Oak | Quercus bicolor | 4b | Height: 18–24 m Sun: full sun to partial shade Soil: moist, slightly acidic |
| Common Hackberry | Celtis occidentalis | 3a | Height: 9–15 m Sun: full sun to partial shade Soil: well-drained |
| Eastern Hemlock | Tsuga canadensis | 4a | Height: 25 m+ Sun: shade to partial shade Soil: moist, acidic |
Once a dominant feature of Eastern Canada landscapes, ash trees have left a significant ecological and visual gap.
Filling this gap is essential—trees play a key role in improving air and water quality, capturing carbon (CO₂), regulating temperatures, and enhancing biodiversity.
Planting the right trees today helps build resilient landscapes for tomorrow.
If you’re unsure where to start, see also How to Plant a Tree or Shrub.
