Tiny invasive fruit flies causing major problems for Manitoba farmers

An invasive fruit fly called the spotted wing drosophila is festering in Manitoba crops. 

Conditions have been ideal for the rapid population growth of the tiny pest, to economically-damaging levels, the province said in its July 16 crop report. It has been seen in all fruit crops currently being harvested, including strawberries, saskatoons, sour cherries and is just starting in raspberries, according to the report.

"This year was an invasion," said Edith Smith, owns the cherry and raspberry orchard Prairie Adventure Farm along with her husband Wayne, in Carman, Man.

"We had a mild winter and a cooler spring — they like cool, they don't like heat — and then [there was] kind of a domino effect with all the rain. It was too wet for us to get out and spray, which we normally would do beginning of July," she said.

"This year we couldn't do that so they ended up coming en masse and there is a lot of them out there." 

Spotted winged drosophila are a vinegar fly of East Asian origin that can cause damage to many softs-skinned fruit crops. 

A Manitoba government fact sheet said the insect pierces seemingly healthy fruit and lays its eggs, which hatch in about three days. Early detection is important because symptoms often don't appear until after the fruit is harvested.

SWD differs from the common fruit fly because the common ones feed on overripe and rotting fruit. 

"It can actually cut into the fruit and lay its egg before the fruit is ripe," said Smith. "Therefore, when the fruit is ripe, eggs have already hatched. It's a very big problem if they're en masse the way they are this year."

Manitoba Agriculture fruit crop specialist Anthony Mintenko told CBC News the species has been in the province since about 2012 or 2013 and are now becoming an annual pest for fruit crops in Manitoba.

Mintenko also said the insect's population growth depends on weather conditions. The cool weather and rain have helped the species to thrive in fruit crops this year, he said. 

"Most of May [and] June into July, the conditions have been perfect," he said. "Essentially, the more favourable the conditions, the faster you can get a life cycle. So it goes from egg to larvae to adult in a faster time."

Mintenko also said the fruit fly has been seen more in southern than northern Manitoba so far. 

A weekly application of approved insecticides is quite effective at controlling the insects, according to the province's fact sheet.

But regardless of the preparations taken for the future, Smith said the flies have already caused a "big commercial hit" in taking out about two thirds of her orchard. 

"We're asking people to come and pick what is ripe out there before it gets infected," she said. "We expect that not to last much longer because the fruit fly population will rebuild and it won't matter.

"So we're trying to get the next four or five days of picking off and that'll be it."

Farmers dealing with invasion of fruit flies in Manitoba berry crops

5 months ago

Duration 1:34

An invasive fruit fly has been causing problems for farmers in the province. The spotted wing drosophila has been found in everything from strawberries to saskatoons and sour cherries as they are being harvested. The cooler start to summer and moist conditions were a perfect storm for the pests.