Check to Protect Your Trees

Invasive hemlock woolly adelgid

Invasive Hemlock Woolly Adelgid is Slowly Making Its Way

In 2003, the invasive Asian long-horned beetle (ALHB) was first detected in Ontario. Its appetite for hardwood trees, like maple, threatened to put Ontario’s forests and forestry industry at risk.

The Canadian Food Inspection Agency (CFIA) responded rapidly, removing all host trees within a 400-metre radius. A second outbreak, this time in Mississauga, received the same treatment. A quarantine was established and all the host trees within an 800-metre radius were removed. By 2020, ALHB was an invasive species success story: the beetle was deemed eradicated. 

But success didn’t come without its costs: Over 30,000 trees were removed and $35 million was spent to manage an infestation limited to two and a half square kilometers of urban neighbourhood.

Had the beetle gone undetected or spread more quickly across the landscape, the situation could have been much worse, like what we’ve seen with the invasive emerald ash borer (EAB). Efforts to control EAB have been ongoing since it was first detected in 2002. Estimates suggest it will cost approximately two billion dollars over 30 years to manage the infestation.

August is Tree Check Month

Early detection and rapid response are critical to protecting our trees, woodlands and livelihoods from the environmental and economic impacts caused by invasive species infestations. In 2021, the CFIA declared August Tree Check Month to encourage everyone to take an active role in protecting our tree and forest communities. They’ve provided helpful resources on what to look fortree check tips and general plant health.

Report any suspicious sightings of new invasive species activity to EDDMapSCVC or the CFIA

Plantations are at greater risk

Plantation landowners need to be extra vigilant. Plantations are more susceptible to pests and disease because they contain fewer tree species. A single pest can rapidly impact an entire plantation forest. Connect with us to learn more about how to care for your plantation.

Species to Watch For

Here are four species to watch for when conducting your tree check or even when out in your neighbourhood or other natural areas. See CVC’s priority forest pest list for other pests and diseases to look out for in the Credit River Watershed or visit the CFIA website for the complete list.

Spotted Lanternfly

Spotted lanternfly
Spotted Lanternfly

First detected in Pennsylvania in 2014, this hard-to-miss invasive insect has not yet been seen in Canada but has continued to spread across the United States. It feeds on a range of tree species, including apple, grape and stone fruit trees, and poses a threat to Canada’s fruit, wine and forestry industries. Read more.

Oak wilt

Leaves with disease
Photo: D. W. French, University of Minnesota,

This fungal disease has not yet been found in Canada, but is present in many regions of the United States. Some trees can withstand the disease, but others can die within a year. Oak wilt is of special concern as many oaks have recently been affected and likely weakened by spongy moths. Oaks provide essential habitat and food for birds and small mammals. Read more.

Hemlock Woolly Adelgid

Photo: Chris Evans, University of Illinois,

This aphid-like insect feeds on eastern hemlock, producing woolly sacs at the base of the tree’s needles. It can destroy trees within four years and makes them susceptible to blowdowns. It has been seen in Etobicoke, Niagara Gorge, Wainfleet and Fort Erie. Hemlock are ecologically important. They provide essential habitat and dense shade that moderates water temperature. Read more.

Asian Long-horned Beetle

Photo: Kenneth R. Law, USDA APHIS PPQ,

Although considered eradicated, it’s important to stay vigilant when it comes to highly destructive species like ALHB. Adults are about 20-35 mm in length and are distinguished by their irregular white spots and long, segmented antennae. Look for shallow, chewed pits in the bark of hardwood trees, large, round exit holes, leaking sap and yellowing leaves. Read more.

Learn more about invasive species in the Credit River Watershed by visiting

Your Countryside Stewardship Team

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