How to Fight Against the Devastating Emerald Ash Borer
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How to Fight Against the Devastating Emerald Ash Borer

The tiny green insect will devour 850,000 Toronto ash trees, but the City and local non-profits hope to limit the damage.

It might look innocuous, but the tiny emerald ash borer has had a profound effect on Toronto’s tree canopy.

The emerald ash borer is an invasive species of beetles first spotted in North America in 2002. Since then the metallic-green insect has destroyed tens of millions of ash trees across the continent. When it was detected in Toronto in 2007, its devastating effects were widely known. Simply put, once the emerald ash borer takes root in a locale, it is nearly impossible to stop its spread, and the subsequent destruction of the entire ash tree population.

According to a study undertaken by the City of Toronto’s Urban Forestry department, there were 860,000 ash trees at the time of the infestation, with approximately 40 per cent located on public land. The City implemented a mitigation and replacement strategy to limit the damage, including planting new trees and using an injection to protect existing ash trees. The injections, which use the insecticide TreeAzin, manage to protect the trees from the emerald ash borer, but must be reapplied on an annual basis. As of the end of 2015, there were 11,479 trees located on public lands that had received these life-sustaining injections, while 48,400 ash trees have been removed by Urban Forestry. Although there are no firm figures available for ash trees located on private property, Sarah Doucette (Ward 13, Parkdale-High Park), Council’s tree advocate, estimates that just 300,000 remain in the city. This number will continue to dwindle, with all but the injected ash expected to be dead by 2020.

While Torontonians have responded by removing ash trees from their properties, they are being encouraged to plant replacement trees from different genera. According to LEAF’s Melissa Williams, many Torontonians are participating in their Backyard Tree Planting Program. For a subsidized rate of $150–220 per tree, the organization sets up a consultation with an arborist, who recommends and plants a five to eight foot tall tree. This program is open to local residents, even if they haven’t lost a tree to the emerald ash borer.

Despite the negative impact of the emerald ash borer, there have been some positive outcomes. According to Williams, the plight of the ash has highlighted the benefits of the tree canopy, what it means to neighbourhoods across the city, and how best to achieve those goals. “The emerald ash borer infestation has underscored the importance of planting for biodiversity,” she told Torontoist. “When we see entire streets that were planted with trees of a single genus–ash–and now all of those trees are gone, it really hits home how important it is to plant a wide variety of trees in every neighbourhood.”