Ontario's top 5 invasive species of summer 2023 - Action News
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Ontario's top 5 invasive species of summer 2023

They're here. From oak wilt to asexual crayfish, meet some of the province's main invaders.

Oak wilt, grass carp and asexual crayfish on the list

A leaf with fungus on it.
Oak wilt can kill a red oak tree in only two to six weeks and has been found in the Niagara Region. (Submitted by Lauren Rogers)

From a carp that can reach 45 kilogramsto a femalecrayfish that reproduces without a male, the summer of 2023 saw new invasive species spottingsin Ontario.

With the climate crisis expected to accelerate their introduction and spread, CBC London asked anexpert to share his list of the province's top invaders.

#1Oak Wilt

"That's the primary concern of mine," said BrookSchryer, assistant coordinator with theinvading species awareness program for Ontario Federation of Anglers and Hunters.

The vascular diseaseshowed up in the city of Niagara Falls in June, making itthe first confirmed detection in Canada. It's since been found in the Township of Springwaterin Simcoe County, and the town of Niagara-on-the-Lake.

Fungus on a tree.
Oak wilt disease was discovered in Belle Isle in 2016. (Michigan Department of Natural Resources)

"This is aninvasive pathogen that is known to occur in the United States, particularly in places like Minnesota, but it hasjumped over the border," said Schryer.

Oak wilt impacts what Schryer calls the "pipeline" of thetree, making it hard to send water and nutrients up and down. "The tree is not able to provide its canopy with water and nutrients," he said, adding that some species with oak wilt can die within two weeks.

The Canadian Food Inspection Agencyhasrestrictionson the movement offirewood totry to prevent the spread of oak wilt to the rest of the province.

#2 Grass Carp

A large carp
"They're massive fish," said Schryer. A grass carp typically weighs two to four kilograms, but can weigh up to 40 kilograms. (Toronto and Region Conservation)

"The grass carp is the most imminent threat to the Great Lakes today," said Schryer, adding that it's been found in Lake Ontario, Erie and Huron.

He said three grass carp were counted this year in Ontario. The first one was on the Grand River, which feeds into Lake Erie,and was found by the Department of Fisheries and Oceans.

Grass carp have arrived in Great Lakes, study concludes

Otherreports of grass carp have been in Fort Erie, a town on the Niagara River. The other was on the Bay of Quinte, on Lake Ontario's north shore, he said.

A man in a baseball cap, standing on a boat, holding up two large fish.
Brook Schryer with silver carp captured in Illinois River. (Submitted by Brook Schryer )

This invader is known for a few things: growing so quickly in its first year of life that it outgrows the mouth size of possible predators, consuming large amounts of aquatic vegetation, and the potential forfemales to lay up to a million eggs in a single spawning.

Grass carp is unable to fully digest the plants, so they expel a nutrient-rich waste that can contribute to algal blooms,Schryersaid.

#3 Marbled Crayfish

A green-grey crayfish
The marbled crayfish is a highly invasive species that reproduces by cloning itself. (Submitted by Wolfgang Stein)

A crayfish that can reproduce asexuallyhas been spotted in Burlington.

"This crayfish in particular is a prohibited species in Ontario," said Schryer. Of even more concern: female marbled crayfish can reproduce without a male mate.

"We do not want it spreading," said Schryer.

'They're coming!': Mutant all-female crayfish are cloning themselves at an incredible rate

"It's not the biggest crayfish, it's not the most aggressive, but it would still be competing for resources and space against our native crayfish species."

It's against the lawin Ontario to move crayfish over land for any reason, alive or dead, he said.

#4White River Crayfish

A hand extended with a large, brown crayfish.
Schryer says the white river crayfish is larger than the marbled crayfish, with larger claws and an aggressive streak. (Submitted Brook Schryer)

This crayfish can contribute to shoreline erosion when itburrows.

"When you have hundreds of those dug into an embankment every year, you're going to see shoreline erosion," said Schryer, who described this crayfish's burrows as "massive."

The white river crayfishisnative to the U.S., but popped up in the Six Mile Lake area, in the Township of Georgian Bay, Muskoka, and alsoon Pelee Island in Lake Erie.

Schryerbelieves the crayfish was introduced by a human who possibly used it as bait. "I just want to reiterate to all anglers that you should never dump your bait," he said. "And, in this case, they shouldn't have been transporting crayfish in the first place."

Compared to the marbled crayfish, the white river variety has larger claws andseems to be more aggressive.

#5Spotted Lanternfly

An insect with spotted wings.
Spotted lanternfly (Submitted by Brook Schryer)

Unlike the other species, the spotted lanternfly is a news makerfornot showing up this summer.

"I think it'sone of the good stories from this year," Schryer said. "It's now spread to various locations in the U.S., and it's close to the border."

He's asking people to stay on the lookout. As a fruit-feeding species, the fly could have serious environmental and economic impacts, for industries like grapes and wines.

Spotted lanterflies
Spotted lanternflies often cluster together, especially on its preferred nesting plant, the also invasive Tree of Heaven. (Courtesy of the Invasive Species Centre)

Spotted aninvasive species? Try to capture a photo and note your location. You can report it two ways:
callthe toll-free hotlineat1-800-563-7711
report it online or with your mobile device here.