This invasive fly could help Kamloops, B.C., fight the invasive Japanese beetle

CBC

a day ago

It may look like your average housefly, but this invasive, parasitic fly species could help stop the spread of invasive Japanese beetles, which were recently found near downtown Kamloops, B.C.
It's called the winsome fly. Like the beetle, it also hails from Japan, and its sole purpose in life is to lay its eggs on those beetles, according to a research scientist with Agriculture and Agri-Food Canada, Paul Abram.
Once the eggs hatch, the larvae get into the beetle, where they develop. They cause the beetle to bury itself in the soil and die, Abram said.
Those flies stay in the soil over winter, and in the spring come back and start looking for new beetles to kill.
Late last year, the Japanese beetles were detected in Kamloops, the first time the pests were detected in B.C. outside the Lower Mainland. The Japanese beetles were spotted just outside the Interior city's downtown core this year.
The beetles feed on grass and plants, and have the potential to cause significant damage. The Canadian Food Inspection Agency (CFIA) recognizes the insect's spread as a threat to commercial crops and native plants, and the Invasive Species Council of B.C. says it "poses a severe threat to ecosystems and industries."
Abram said Japanese beetles invaded northeastern North America in the early 1900s, prompting U.S. officials to go to Japan to collect species that might hunt the insects.
"This winsome fly was one of the species," Abram told CBC's Daybreak Kamloops. "Over the next 100 years, it became naturalized, and it turned out to be very specific to the Japanese beetle."
He said researchers are still collecting data, but they've seen the fly kill up to 75 per cent of invasive Japanese beetles in some areas of Quebec.
While that's promising news, it's unlikely the flies would be able to eradicate the beetles in B.C.
"With any of these invasive pest species, unfortunately, there's seldom or never one sort of single silver bullet solution," Abram said.
But it would certainly help to get to that point, he added.
"The really nice thing about biological control by the winsome fly is … the more that they're doing their job every year, the less you have to do other things."
Climate
However, there is a question as to whether Kamloops' hot, arid climate would be the right place for a fly that's native to the humid, maritime environment of Japan.
Though the flies aren't being introduced to Kamloops just yet, they were established in the Lower Mainland in 2023, Abram said, where the climate is much more similar to Japan's.
However, he said, the fly does seem to like snow cover, which Kamloops certainly does get.
Safety concerns
But what happens to the flies once the beetles are gone?
Most of the research being done around these insects is related to safety, Abram said. The flies need the beetles to procreate, so once the beetles die off, so will the flies.
"There's been some really negative consequences from biological control introduction [of other species]," Abram said. "But those were basically back in the day where there was no safety testing done whatsoever."
He points to the cane toad, native to South and Central America, which is considered one of the worst invasive species in the world. According to the Florida Fish and Wildlife Conservation Commission, they were introduced to the state in the 1930s to control agricultural pests, but the population soon grew out of control.
"Over the last 50 years, biological controls have become a very careful, heavily regulated practice that's informed by lots of careful science," Abram said. "In my lab in Agassiz, that's one of our main focuses is doing that kind of careful safety testing that it takes to make decisions about whether to introduce beneficial species to new areas."
He said there are no big safety concerns around the introduction of winsome flies.
The CFIA is asking Kamloopsians to report Japanese beetles if they find them, and Jason Crandall with the agency said people should trap and freeze the beetles so inspectors can map their spread.