Glebe Ash Trees Succumbing to Emerald Ash Borer


Now that the trees have leafed out, the devastation being wrought by the Emerald Ash Borer is there for all to see. While our foresters have been sounding the alarm bells for several years, seeing the incontrovertible evidence in our front and backyards is still shocking.

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After the demise of the Elm due to Dutch Elm disease, Ash trees became the tree of choice for many. Growing tall and stately, it became the next ‘signature tree’ and was overplanted. 25% of Ottawa’s urban canopy is ash (approximately 10-15% in the Glebe).

The Ottawa Carleton School Board reckons it has approximately 7,000 ash trees spread across 150 schools. Emerald Ash borer damage is far worse than expected this spring in the trees in our schoolyards in the Glebe. While the school board administration will try to save ash trees that are still strong enough – it is clear that only a few will make it. Arborists generally will not treat trees that have lost more than 30% of their canopy.

Without treatment, virtually all ash trees will die. Treatment needs to happen during the summer months (June-August) while the trees are still strong. A product called TreeAzin, whose main component is derived from Neem tree seeds, a natural pesticide, can be injected into ash trees and is effective in killing the larvae of the emerald Ash borer which burrow just under the bark. An increasing number of the city’s tree companies are offering this treatment (see The treatment costs about $250.00 per tree. The city has been treating 2-3% of its trees.

Mature trees can add 10 to 15% to the value of a property. Most Glebe homeowners are losing their ash trees – only few have been treated with the biocide so far. The challenge now is to identify which ash trees are still healthy enough to be saved.

Many landmarks will lose the ash trees which give grace, verdancy, shade and health to our neighbourhood. Dr. Curtis Lavoie at the Children’s Hospital of Eastern Ontario has been pointing out that trees not only produce oxygen, but also remove pollutants from the air. That in turn helps asthmatics and asthma, emphysema and pneumonia are leading causes of hospital admissions.

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