Fungus the last stand against insects wiping out ash trees
The city is betting on an experimental program to control emerald ash borers before the destructive bugs kill off what’s left of our ash trees.
Before the invasive species of Asian insect started making its way up the Highway 401 corridor from the U.S. about 10 years ago, Toronto was home to an estimated 860,000 ash trees.
Since then, the emerald ash borer infestation has killed or resulted in the removal of all but about10,000 ash trees in the city, with the rest likely headed for the same fate unless a solution is found.
The answer — hopefully — is blowing in the wind and dangling from the high branches of ash trees in the Guild Park and Gardens, where the final battle is underway.
My regular walking route includes the Guild Park, where signs were recently attached to ash trees asking people not to fool around with ropes that lead to two types of traps suspended far above the ground. Josh McMeekin, a forest health care inspector with urban forestry, said the Guild area is “a unique place, very ash dominant,” and home to a lot of the remaining local ash trees, making it the right place to take the fight to them.
The city has been using a tree injection program to kill the bugs, but results have been mixed and the treatment is expensive, averaging upwards of $150 a tree, said McMeekin. So it teamed up with GDG Environment from Montreal a couple of years ago in a research trial to fight emerald ash borers with a bio-control program that uses a natural fungus to kill them.
The fungus, called Beauvaria bassiana, is dished out to the insects in a long green “funnel trap.” They then take off and spread the fungus to their friends, which kills a lot of them, he said. Triangle-shaped “prism traps” are then used to catch the ash borers, which are then tested to see how many have been infected with the fungus, he said, adding that “it’s not realistic to expect eradication.”
The prism traps are lowered once a week to remove the accumulated ash borers, which are sent to the GDG lab in Montreal for analysis to determine fungus infection levels, he said.
The goal is to save as many ash trees as possible, and results so far have been encouraging, but it’s a long-term project that requires time, McMeekin said.
If it works, ash trees could make a local comeback. Let’s keep our fingers crossed.