Invasive insect found in hemlock trees near Churchill Park, Royal Botanical Gardens in Hamilton

A Canadian federal agency has put restrictions on the movement of Hemlock-based firewood, branches and mulch after researchers positively identified an invasive insect infestation in Hamilton, Ont.

The Canadian Food Inspection Agency (CFIA) has confirmed the presence of hemlock woolly adelgid (HWA) in trees on forested areas surrounding Churchill Park in the city and on Royal Botanical Gardens (RBG) property

“Due to the confirmation of the invasive pest, the CFIA has issued a Notice of Prohibition of Movement to both the Royal Botanical Gardens and the City of Hamilton to restrict the movement of hemlock material for this area,” city spokesperson Emily Trotta said in an email.

Hemlock woolly adelgid are aphid-like insects that attack hemlock trees by sucking sap from the base of their needles, draining the trees of their energy and killing them. Their egg sacks look like cotton balls or clumps of snow, making them hard to detect.

HWA pose no threat to humans but are highly destructive to hemlock trees, which are used for firewood, timber and other wood products. Hemlock trees are also indicators of a healthy forest, offer shading for aquatic ecosystems in streams, help deer navigate their trails in the winter by blocking snow and are scenic fixtures in Ontario’s cottage country.

Records estimate hemlocks make up just a small portion of Hamilton’s forest inventory, with only about 320 trees on streets, parks and cemeteries.

“This makes the threat of HWA low for these areas,” Trotta said.

Read more: Invasive insect discovered in southern Ontario could pose risk for hemlock trees

However, city staff say they don’t have any tracking of the tree’s population on publicly and privately owned woodlots, saying that data is not known or available.

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Active populations of the species have also been discovered in the Niagara Region, near Cobourg and Grafton in Northumberland County.

The bugs were likely introduced to North America in the 1950s from Japan through infested nursery stock, according to the Invasive Species Centre.

Chris MacQuarrie, a research scientist with Natural Resources Canada, says the invasive species can be spread by wind, animals and human movement of nursery stock, logs, firewood and other wood products.

He says aside from Ontario, the species was detected in Nova Scotia and likely spread by birds.

“In those places, especially in southern Nova Scotia, it’s killed a fair number of trees,” he said. “It went undetected for a while so it had a chance to build up.”