An invasive species known to destroy hemlock trees has been discovered in Northumberland County.
The hemlock woolly adelgid (HWA) has been found in several hemlock trees near Grafton, east of Cobourg, according to the Canadian Food Inspection Agency (CFIA).
The insect, which is the size of a grain of pepper, feeds on fluid in hemlock trees, causing needles to drop and a tree to die in as few as four years, the CFIA says.
“The property owner has been notified of restrictions on the movement of hemlock materials (including logs, branches and woodchips) as a result of this confirmation,” the CFIA stated.
“The current regulated area could be expanded once the CFIA has completed its survey work.”
According to researcher Chris MacQuarrie with Natural Resources Canada, the discovery of the pest was found “by chance” by a team of scientists with the National Resource Canada’s Canadian Forest Service, the Great Lakes Forestry Centre (GLFC) and students at the University of Guelph.
“The actual find itself was made by our crew of summer students and the MSc student from Guelph who, whilst measuring trees, noticed the characteristic white fluff,” said MacQuarrie. “They immediately reported this to the crew leader, who notified the CFIA.”
In Ontario, HWA was first detected in Etobicoke and Niagara Falls a decade ago. Most recently, HWA was confirmed in Wainfleet and along the Niagara River in 2019. The pest has ravaged forests in the eastern United States since the 1970s, the Canadian Forest Service notes.
The species relies on being carried by wind, animals or humans to move to different areas. HWA was first found in Canada in British Columbia in the 1920s, believed to have arrived from Japan, the CFIA says.
MacQuarrie says the students conducting tree measurements were “hundreds” of kilometres from the nearest known infestation of HWA.
“They could have just shrugged it off as a mistake, or not trusted themselves to make the ID. But they didn’t,” he said. “And because of that, we know have a way better idea of the threat of HWA to Ontario’s forests.”
According to the CFIA, signs and symptoms of this pest include cottony, white egg sacs at the base of needles on a hemlock tree. As infestations advance, twig tips swell and grey foliage may appear. Defoliation will also occur. HWA poses no risk to human health.
MacQuarrie says the discovery in Northumberland County will help save some trees.
“And not for nothing, this means land managers have a jump on responding to HWA in this part of Ontario,” he said. “It’s likely this population would have continued to go undetected for quite some time. I’m very confident that this work by our GLFC crew will save some trees.”
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