There are about 860,000 ash trees in Toronto. In a briefing this afternoon, City staff told reporters that almost every single one of those trees will be gone by 2017, because no power on Earth can stand in the way of the tiny insects that are eating them to death.
The insects in question are known as emerald ash borers, and they’re nice-looking little bugs, metallic green in colour. The problem is that they’re an invasive species, originally from Asia, that have developed a taste for the tissues beneath the bark of North American ash trees. From first infestation, a tree has just two to three years to live.
The City confirmed the first ash borers in Toronto in 2007, at Sheppard and the 401, by which point it was already too late. An insecticide called TreeAzin can save trees that aren’t already heavily infested, but staff consider it too expensive to use on any but the largest and most prominent among the 40 per cent of Toronto’s ash tree population that grows on public land. Other methods of stopping the ash borer are still experimental, and likely won’t be ready in time to be of any help here.
“Control of the spread is no longer feasible,” said Beth McEwen, manager of urban forest renewal for the City. Her department is concentrating on damage control, with the expectation that nearly all of Toronto’s ash trees will be dead and in need of removal by 2017.
Costs associated with cutting down and replacing just the ash trees on public land are expected to amount to more than $60 million over the next decade. The City will spend an additional $8 million to plant new trees, a combination of different varieties to avoid similar problems when and if the next invasive insect comes along.
At its last meeting, city council responded by asking the federal and provincial governments for financial help with the problem.
Trees on private property will need to be removed or treated with TreeAzin at the expense of private owners. McEwen recommended that anyone concerned about an ash tree on their property call 311 to find out whether or not the tree is on public land.
The City will begin issuing removal notices for infested City-owned trees on public boulevards this month, starting in Scarborough (where the infestations are the furthest advanced). Many suburban neighborhoods in Toronto were planted almost exclusively with ash trees, and staff expect the effect on streetscapes to be dramatic.
McEwen agreed that the the epidemic could be compared to Dutch elm disease, except in one respect: it’s worse. Dutch elm disease came in waves over decades, and many elm trees survived.
“The difference with the ash,” said McEwen, “is that they’ll all be killed.”
Find out more about the emerald ash borer on the City’s website. The City will be holding three public meetings about ash tree treatment and removal this week and next. Details are here.