Update : May 18, 2017.
The emerald ash borer (Agrilus planipennis) constitutes a serious threat for the thousands of ash trees in our city, including the roughly 800 specimens at the Botanical Garden. Unfortunately, at present there are no means of eradicating this exotic pest, but research aimed at finding new methods of fighting it is under way. The strategy adopted by the City of Montréal is designed to check the progress of the insect and the mortality rate of ash trees. Here’s a summary of the actions that have been implemented so far at the Botanical Garden.
A major element in the struggle against the emerald ash borer, tracking makes it possible to paint a picture of the infestation, to trace its evolution, to decide on which actions to take and to evaluate the effectiveness of the measures employed. Two tracking methods are used: debarking the branches at the top of the tree, and installation of sticky traps equipped with an attractant.
Felling and safe disposal of the residue
Infested ash trees are felled in order to reduce ash borer populations and the dispersal of the insect. The smaller branches are chipped at the site, while the larger residue is transported to a processing site to be neutralized.
Injection of low-impact pesticide
Ash trees deemed essential for conservation – including those in the historical alignment bordering the gardens along Pie-IX Boulevard, in the Arboretum collection, and certain subjects in the theme gardens – are treated with TreeAzin. This pesticide, minimally toxic for the environment and human health, is injected directly into the tree. It stops larval development and reduces fecundity and fertility in females.
Biological control through the use of natural enemies is a long-term management tool aimed at reducing pest populations to an acceptable level. Since 2015 the Ville de Montréal environment department has been running a research project with the parasitic wasps Tetrastichus planipennisi and Oobius agrili in the Ash Woodland at the Botanical Garden. This project is being carried out in collaboration with Natural Resources Canada and the United States Department of Agriculture. Other tests with the entomopathogenic fungus Beauveria bassiana have been conducted for a few years at the Botanical Garden. Advances in that area are promising.
Replacing ash trees
To ensure the regeneration of the Ash Woodland, tree species well suited to the site conditions (red oak, bur oak, bitternut hickory and so on) are introduced there. In the historical alignment, as ash dieback continues, a diversity of North American species will be planted.
To learn more about the fight against the emerald ash borer in Montréal: