Toronto’s battle against ash borer beetle not going as well as hoped
Numerous trees treated with synthetic pesticide won’t survive: city report

insidetoronto.com
Feb. 2, 2015
By Mike Adler

Injections of TreeAzin, Toronto’s only defence against an invasive beetle destroying its ash trees, aren’t working as well as hoped.

Facing the destruction of all its ash within a few years, the city started injecting its most significant trees of those species in 2012 with a synthetic pesticide to ward off the fast-spreading emerald ash borer.

But by now there are signs many of those 13,000 injected trees - and another 1,000 ash treated by the city’s public school board - won’t survive.

Trees the city injected in 2012 in parks and along boulevards were studied in 2014 - when it was thought they would need TreeAzin again - and around one quarter were dead or dying, with mortality in some places as high as 60 per cent, Josef Ric, a city forestry supervisor, wrote last week.

“These trees are not necessarily completely dead but have passed a point where efforts to sustain them are no longer worth the effort or money required,” said Ric, adding several reasons why injections in 2012 didn’t work.

One was dry conditions that summer, which may have led to a poor uptake of pesticide, leaving parts of trees unprotected. Higher survival rates are expected for those ash injected during the wetter summer of 2013, Ric said.

Besides that, higher populations of the beetle - and the city concentrated injections in 2012 on ash in the Toronto’s east and north, where ash is particularly common and the infestation was fairly advanced - lead to a higher death rate.

People at a meeting on Thursday, Feb. 12 in Guildwood, a Scarborough neighbourhood dominated by ash, will get a sad message about 300 trees around two local schools: expect almost none of them to survive the pest.

Jack Miner Senior Public School and Wilfred Laurier Collegiate are both school properties hard hit by the beetle, and the board injected 14 mature ash at Laurier and five at Jack Miner.

Unfortunately, the success rate for the injections in southeastern Scarborough was disappointing, Jerry Chadwick, the locak public school trustee, wrote on Thursday. “In other parts of the city where the infestation is not as overwhelming, the injection rates have a much higher rate of success,” he said.

Already, Chadwick added, there are at least 150 trees at Laurier and 109 at Miner that cannot be saved, and at the 6:30 p.m. meeting at Laurier on Guildwood Parkway - planned for Feb. 2 but rescheduled to Feb. 12 due to inclement weather - the board will tell residents of its plan to cut the dying trees down and make use of the wood.

The board, which says it’s removing stricken ash trees across the city “in order to minimize the risk to students, staff, parents and the community,” has also made arrangements for some replanting to be done in the area, Chadwick added.

A culling of dead and dying ash, as well as other trees damaged by the December ice storm, proved controversial when it was done a city contractor over the last winter in nearby Guild Park.

Ric said as many as 300 injected ash across the city “were lost or severely damaged” in last winter’s storm.

Infestations of the beetle are hard to detect, and many trees injected in 2012 may have been infested already. The city has also found white ash responded better to treatments than green ash, and larger-diameter trees did better than smaller ones, said Ric.

TreeAzin’s manufacturers, BioForest, now say ash should be injected every year to ward off the pest, not every two years.

Some 500 ash in Guild Park were injected on a yearly basis to test this theory. “The survival rate is higher among these trees, although the evaluation in the spring, when the trees are in full leaf, will tell us the exact results,” said Ric.

Beth McEwen, the city’s manager of forestry renewal, added some trees the city planned to inject were simply missed by its contractors. She said the city expected to lose 10 per cent of injected trees, though losses among trees treated in 2012 will be higher because of the drought.