(David Cappaert)
Toronto has fallen in the latest fight to an invasive species. The victor: the emerald ash borer a small, green insect that is costing Toronto big green — more than $60 million dollars to remove and replace the ash trees it is killing in public spaces across the city.
Councillor Norm Kelly, the chair of the parks and environment committee, represents a ward in Scarborough where removing the ash tree will have a devastating effect on local tree cover.
“The City of Toronto is under attack,” Councillor Kelly told reporters. “And, regrettably, we’re helpless in the face of this invasion.”
The emerald ash borer is a beetle that digs under the bark of the ash tree to lay its eggs; the life cycle of its larvae disrupts the flow of water and nutrients, eventually killing the tree. So many trees have been infected that the city is being advised it needs to remove the ashes and replace them with a variety of other species of trees.
The latest data from the city shows the pest has hit northeast Toronto the hardest, devastating the ash that dominates the Scarborough Bluffs and lines the area’s suburban streets.
The city will not be subsidizing the removal of infected ash trees from private land, but it will waive the need for a tree removal permit. Jason Doyle, Director of Urban Forestry, recommended community groups pool together for bulk rates when removing trees in residential areas.
Beth McEwen, a city manager for urban forest renewal, said some trees will be treated using a pesticide called TreeAzin. However, the treatment is expensive — she says Toronto pays $140 per dose — and must be repeated in the early summer every two years, so the forestry department is trying to get the best bang for its buck.
“The over-mature trees don’t take up the pesticide as well,” McEwen said. “We are choosing not the oldest, stateliest trees, but mid-range size trees.”
Some “high-value” trees include are the ashes that shield Wishing Well Park from the 401 and the trees that line Tam O’Shanter Golf Course in Scarborough.
McEwan explained the emerald ash borer is a particularly devastating invasive species. Ash trees don’t show symptoms until at least a year after infestation, which meant conservationists were playing catch up as soon as they knew there was a problem. By contrast, the Asian long-horned beetle was a slower-spreading, larger bug and therefore easier to detect. City officials say it has been contained since 2007.
The destruction of the 860,000 ash trees across Toronto may remind some of the effects of Dutch elm disease. McEwen says the loss of trees in some neighbourhoods, like Guildwood in Scarborough, will look similar, but the major difference is that some elms actually proved resistant to the disease, while there is no immunity from the emerald ash borer.
In Canada, the first emerald ash borers were found in Windsor, Ont. They were likely brought in wood shipped from Asia. Less than a decade after the first bug was found in 2003, the ash tree has been completely wiped out from Windsor. It’s expected Toronto’s ashes will all be replaced by 2017.
