The City of Toronto is taking decisive action to protect one of its long-standing urban trees, announcing a plan to begin treating 5,300 vulnerable ash along its streets, parks, and natural spaces.
The strategy to safeguard the remaining trees, which will be taking place between June 1 and August 31, comes after the death and devastation of millions of ash in Ontario, caused by the emerald ash borer (EAB).
“The emerald ash borer (Agrilus planipennis) is a highly destructive invasive beetle that attacks and kills all species of ash in the genus fraxinus. It has already killed millions of trees in North America,” according to the Government of Canada.
As a result, EAB is expected to decimate the region’s ash tree population over the next decade, significantly impacting the environment and economy through ecosystem service loss, tree removal costs, and public safety hazards, according to the Toronto and Region Conservation Authority.
To protect the remaining vulnerable ash, the city will be injecting a pesticide named TreeAzin under the tree’s bark using needle-like canisters. The product is absorbed within 15-30 minutes, safeguarding the vascular tissue of the ash against EAB for up to two years, according to the City of Toronto.
The insecticides’ active ingredient, Azadirachtin, works to protect the ash by disrupting the molting, feeding, and growing process of EAB larvae that feed on the tissue of the tree.
“It’s derived from plants, and it’s been modified to be injected, or concentrated and injected into the tree, and it’s relatively safe. I mean, it’s still an insecticide, but because it’s injected, the exposure is very low to humans because it’s a botanical, it’s not as toxic,” Sandy Smith, director of the Daniels Faculty’s forestry program at the University of Toronto, told Now Toronto on Tuesday.
The disruptive process then kills the beetle at what’s known as the most devastating stage of its lifecycle.
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WHERE DID EAB COME FROM?
Since its arrival in 2007, EAB has been responsible for killing more than 800,000 ash across Toronto and more trees across the country. But select, city-owned ash trees have undergone TreeAzin systemic insecticide on a two-year rotation to manage the insects’ progression since 2011.
“It was first detected near Detroit, Michigan and Windsor, Ontario in 2002, but has likely been in North America since the 1990s. EAB is thought to have been originally introduced to Detroit via infected wooden packaging materials or shipping crates imported from Asia. The beetle has been rapidly spreading across North America since its arrival, posing a serious threat to all species of ash,” according to the Invasive Species Centre.
Meanwhile, the vulnerable ash is integral to the environment by recycling nutrients, providing habitat to wildlife, and regulating the flow of streams and rivers.
But other tree types, like the Black ash, are also of concern.
“Because it’s an unusual ash that’s found in wetlands and it’s sort of slowly being lost because of development. I think that’s of concern because it’s highly susceptible,” Smith said.
Ash located in other areas of Canada, including Montreal and parts of Alberta, have also been experiencing devastation resulting from the invasive non-native species, with the U.S. also being impacted, Smith said.
Ash trees have an age-old history in Toronto and were originally planted in place of the elm tree, which had been killed by the highly invasive and infectious fungal infection, Dutch Elm disease.
Despite treatment coordination plans, diversifying the types of trees in the city’s urban forestry landscape may help to combat and reduce the risks posed by invasive pests like EAB, Smith added.
And while the city takes significant strides to prevent further EAB damage to the vulnerable ash, the treatment plan will not completely eliminate the invasive species, Smith said.
“It’s a really comprehensive management to keep ash trees, which are really great trees out there. But the key thing is it’s [EAB] not going to disappear.”
