A new weapon is being deployed near Owen Sound in the battle against the tree-killing emerald ash borer.
Natural Resources Canada and Ontario’s Ministry of Natural Resources & Forestry are teaming up with Grey Sauble Conservation to release tiny wasps — they don’t have stingers — that kill the invasive beetles’ eggs and larvae.
Chris MacQuarrie, research scientist with NRCan’s Canadian Forest Service, said Grey Sauble’s West Rock Management Area, just south of Owen Sound District Secondary School, has been chosen as one of the new locations in 2019 for the service’s biological control program, which includes release sites in Ontario, Quebec and New Brunswick.
“What we’re hoping we can do is establish these biological control agents and exert some level of control against the emerald ash borer,” he said Thursday in an interview.
“That’s so we can either protect those ash that are on the landscape now or those ash that might come back after the larger ones that are already infested have died.
“So it’s trying to re-establish the ecological relationship that occurs between these wasps and emerald ash borer in its native range in Asia over here in North America and try to get the same kind of control here that they experience over there.”
Mike Fry, forestry co-ordinator with Grey Sauble Conservation, said MNRF staff oversaw the first release of the parasitoid wasps about two weeks ago and will be returning to the site to release more every few weeks this summer and into the fall. The local project could continue next year as well.
The insects are released by suspending from the trunks of trees blocks of ash wood containing wasp pre-pupae. Wasps will emerge from the wood and fly off in search of emerald ash borers.
Three species of wasp, each native to Asia and approved for release in Canada by the Canadian Food Inspection Agency, are being set free at the West Rocks.
One species lays its eggs inside the borer’s eggs on ash trees’ bark, while the other two drill beneath the bark and deposit their eggs within or on the borer’s larvae. Once the wasps’ eggs hatch, the wasps will eat and kill the borer’s eggs or larvae.
“The overall goal is to get a population (of the wasps) established so they can rear them in Ontario. Right now, they’re being imported from the U.S.,” Fry said.
The emerald ash borer was first discovered in North America in 2002 near Detroit, Mich., and in southern Ontario later that year. However, experts believe the beetle actually arrived about a decade earlier.
Grey and Bruce counties were added to the list of areas infested by the metallic green beetle in 2013.
The invasive bug has been detected within the Grey Sauble watershed, including on the West Rocks property, Fry said.
Since its arrival in North America, the borer has killed tens of millions of ash trees. The Canadian Forest Service estimates the costs for treatment, removal and replacement of affected ash in Canada could hit $2 billion over a 30-year period.
The emerald ash borer kills all species of ash in North America. The adults feed on the tree’s foliage, while the larvae eat the tissue between the bark and wood, girding the trees and cutting off the movement of nutrients and water. Trees typically die within one to four years after the borer becomes established.
Fry said ash make up about five to 10 per cent of the forest trees on Grey Sauble Conservation properties, but some forests are comprised solely of ash.
He said the few known predators of the emerald ash borer in Ontario – like the woodpecker – cannot control the beetle’s population. Individual trees can be protected by injecting an insecticide into the tree’s tissue, he said, but it’s expensive to do so.
He said a biocontrol strategy is needed to control the beetle’s population on a larger, watershed level.
Fry said Natural Resources Canada approached Grey Sauble Conservation about releasing the parasitoid wasps within its watershed area. They decided the West Rocks area would be the best spot.
“It was a perfect combination of good access, had the right species composition and age structure (of ash) and had emerald ash borer present,” he said.
People likely won’t notice the wasps, he said, as they’re about a millimetre in size and don’t fly very far. The insects rarely attack non-target organisms.
The local project will not cost Grey Sauble Conservation, he said, as the Canadian Forest Service is identifying the sites and releasing the wasps.
Along with establishing a local population of the wasps, he said the project will also help the Canadian Forest Service to determine the effectiveness of the insects at controlling the emerald ash borer population.