From oak wilt to jumping worms: A look at the invasive species threatening Canada

New invasive species are ruffling feathers in Canada and climate change could speed up their spread across the country, experts warn.

Canada is no stranger to invasive species – flora and fauna that are detrimental to agriculture, forests and the overall ecosystem – but the growing discoveries of new non-native pests that have recently crept into the country are raising concern.

“As our seasons get longer and hotter, we risk having more pest life cycles in the summer, therefore allowing them to potentially do more damage,” said Patricia McAllister, national manager of the horticulture section with the Canadian Food Inspection Agency (CFIA).

“I think the challenge that we’re facing is that sometimes you don’t know the impact until later on,” she added.

Increasing international travel and trade presents new species with more opportunities to “hitchhike,” said Michael McTavish, a post-doctoral researcher in forestry at the University of Toronto.

“We have more non-native invasive species because the ones we had before are often still present, so it is a cumulative additive kind of effect.”

Here is a look at some of the pesky invaders that are keeping Canadians on their toes this summer:

Last month, the CFIA detected oak wilt in Niagara Falls, Ont. – the country’s first confirmed discovery of the invasive fungal disease which affects oak trees.

It has since also been found in the township of Springwater, Ont.

The affected trees will be removed to prevent further spread, the CFIA said, and they’re also monitoring neighbouring oak trees for potential infection.

Jason Griffin, a plant program supervisor with the CFIA, said at this time, the agency does not anticipate any impact on the oak product trade as the detections have been isolated to residential areas.

However, if oak wilt becomes established in the country, it could have “significant impacts on Canada’s natural resources and forest industries,” Griffin said.

There is no known risk of oak wilt on the health of humans and animals, according to the CFIA.

A 2020 study published in the scientific journal Nature estimated that the potential costs for the removal and replacement of urban oak trees could cost Canada up to $420 million.

Oak wilt spreads through the vascular system of oak trees, and red oaks are at highest risk, said Madison Sturba, a program development coordinator at the Invasive Species Centre.

“(Trees) can die in a single season, sometimes in as little as two to six weeks,” she said.

Some signs of this pathogen include cracks in the trunk, early and sudden leaf drop, white, grey or black fungus and dull green, brown or yellow leaves.

The fungus can spread from tree to tree via below-ground transmission as root systems collide. Insects such as beetles play a role in transmission, as does human transport of contaminated logs.

The box tree moth is a pesky invader that is making its way across Canada.

It’s a green caterpillar that was first detected in Toronto in 2018 but has recently been found at several retail locations in Quebec and Atlantic provinces due to the transport of greenhouse and nursery stock.

It was added to Canada’s list of regulated pests in November 2022.

The box tree moth, which is native to Asia, can invade boxwood shrubs, which are planted in gardens as ornamentals and typically used as hedges.

“This one is of great interest to our nursery sector because boxwood is a very important shrub and in addition to that, it also is a shrub that we have traditionally exported to the United States,” McAllister said.

“For homeowners, the pest is very devastating because if left uncontrolled, it will eat your hedge down to nothing more than sticks.”

Jumping worms are also wreaking havoc in gardens, backyards, and parks across Ontario.

After the first detection near Windsor in 2014, the province has seen a run of observations of these glossy grey or brown-coloured slimy creatures.

So far, at least five types of jumping worms have been discovered in Canada and they are becoming more common, McTavish said.

“They are certainly a concern,” he said, adding that there aren’t any good and effective tools available to remove them.

These earthworms are native to Asia and have the ability to twitch or thrash violently side to side to fend off predators, which is why they are called “jumping” worms, McTavish explained.

They live close to the surface of the ground and alter the soil layer by eating up organic matter.

“These alterations in soil structure make it difficult for many plants to grow and negatively impact other organisms in the ecosystem like birds, millipedes and salamanders,” according to the Canadian Council on Invasive Species.

And once they make their way into a location, it’s tough to boot them out, said McTavish, which is why it is important to slow their human-mediated spread as much as possible.

He advised against sharing plants and to knock off any mud or dirt from shoes and bikes if they have been in an area infested with jumping worms.

The spotted lanternfly has not been detected in Canada as of yet, but researchers are keeping a close eye on it as this small destructive insect could hit the country’s grape and wine industry.

The closest infestations to Canada are in Buffalo, N.Y., and Pontiac, Mich.

“It’s getting closer and so therefore we’re watching and paying very close attention to it,” said McAllister.

“It’s our grapevine sector that we are really concerned about based on the experiences with this pest in the United States since it was first detected in Pennsylvania in 2014,” she said.

The spotted lanternfly, which is also native to Asia, has already spread and wreaked havoc in at least 14 different eastern U.S. states since it was first detected in North America almost a decade ago.

The pathway of spread can vary between invasive species, but a big part of it is human-mediated spread, especially through international travel, experts say.

Whether that is wood packaging, firewood movement or international shipments, pests can find a number of ways to hitchhike.

More frequent severe weather events due to climate change can also play a role by stressing native species and creating more opportunities for pests or pathogens to move, Sturba said.

Warmer climates can affect the life cycles of species and change the way they move as well as the timing of movement, she said.

“Generally, in forests, for example, warmer climates could stress native trees and just make them more vulnerable to invasive insect and pathogen attacks.”

With climate change acting as a disruptor and creating disturbances in the ecosystem, problematic species are likely to have better success of invasions when they do arrive in a non-native environment, McTavish added.

“Changing conditions” create space for competitive species to move in, take advantage of underutilized resources, compete with organisms that might be stressed and then have a better chance of establishing themselves, he explained.

Public awareness and reporting are going to be crucial in the fight against invasive species, experts say, which is why the Canadian Food Inspection Agency is urging people to remain on the lookout and flag any sightings.

“When you see something that doesn’t look right, telling us can really make a difference because early detection is really our best tool when something’s here,” said McAllister.