The emerald ash borer (Agrilus planipennis) is a species of metallic wood-boring beetle native to East Asia, including China and the Russian Far East.
Most species of North American ash trees are very vulnerable to this beetle, which has killed millions of trees in Canada in forested and urban areas.
No North American natural predators, such as woodpeckers, other insects or parasites have been able to slow the spread of the emerald ash borer or keep trees from being killed by it. Up to 99% of all ash trees are killed within 8-10 years once the beetle arrives in an area.
It can fly several kilometres, however, the transport of firewood is the main factor of propagation. It is therefore essential not to transport firewood from a region to another to avoid spreading the infestation to areas that are not yet affected.
Emerald ash borer infestations cause significant ecological and economic impacts in forested and urban habitats:
- In forest habitats, losing the majority of ash trees can affect tree species composition, natural forest succession, and nutrient cycling. Habitats also become more vulnerable to invasion by exotic plants.
- After an infestation remaining beetles can kill new growth, jeopardizing forest recovery.
- In urban areas, infestations have killed tens of thousands of ash trees planted in parks and along streets.
- Municipal governments are responsible for removing dead ash trees on urban land. Infested trees should be chemically treated or removed and replaced, which can be a significant economic burden.
- Losing urban canopy can increase homeowner heating/cooling costs and can affect people with health issues such as respiratory illnesses.
Signs become visible 3 or 4 years after the onset of infestation. The most striking signs are a general decline of the tree, indicated by:
- premature yellowing of foliage
- dead branches
- thinning-out at the top
- "S" shaped larval galleries under the bark
- "D" shaped exit holes on the bark
- Peak holes and bark removed by squirrels
- Feeding notches on foliage
- Presence of the apple comma mealybug
The tree generally dies in under 7 years.
In 2015, the City adopted by-law number 775 pertaining to the fight against the spread of emerald ash borer. The purpose of this by-law is to control the spread of emerald ash borer on the territory of the City by introducing measures aimed at counteracting the spread of outbreaks.
During the summer 2019, inspectors have conducted an inventory of all ash trees located on the City's territory in order to assess the emerald ash borer situation and put in place infestation management measures. They had the mandate to list all ash trees, including those on private property. The results of the inventory will be presented in the fall.