Swede midge threat remains small out West

Ontario canola growers are seeing the worst of insect pest

Swede midge is not a serious threat to prairie canola crops, at least for now, says an Agriculture Canada entomologist.

The pest has been in northeastern Saskatchewan for years and is spreading to other parts of the Prairies, but research suggests the type of Swede midge found on the Prairies isn’t as damaging as the genotypes in Ontario.

Lars Andreassen, an Agriculture Canada research associate in Sask-atoon, said Swede midge in Ontario emerge from the soil earlier in the growing season and threaten developing canola plants.

“They can build up and have a generation already going by the … two and four leaf stage,” Andreassen told Manitoba Ag Days in January.

“So they can have a huge flush when the canola plants are just young and really susceptible.”

As noted on the Canola Council of Canada website, Swede midge females lay eggs in the meristems, or growing points, of canola plants. The larvae from those eggs feed on the plant and can cause:

  • Twisted or distorted young shoots.
  • Misshapen buds in bud cluster.
  • Abnormal flower development.

Swede midge populations are entrenched in parts of Ontario, particularly the Temiskaming district around New Liskeard.

The Ontario Canola Growers Association said in its January newsletter that farmers in the region should cease growing canola until 2018 because Swede midge is overwhelming the crop.

“Currently, huge numbers of adult Swede midge emerge from soil pupae in the spring … (and) overwhelm young canola plants in neighbouring fields throughout Temiskaming,” the association said.

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“Considering the disappointing average yields of well below one tonne per acre in 2013 and 2014 (and) the overwhelming number of pupae now present in soils … the strategy being encouraged by OCGA… is a moratorium on canola production in Temiskaming for three years.”

The Swede midge is a widespread pest of crucifer crops in Europe and is rife in parts of Ontario, but Agriculture Canada studies in Melfort, Sask., and on farms in northeastern Sask-atchewan tell a different story.

Andreassen and Agriculture Canada entomologist Julie Soroka have observed that Saskatchewan Swede midge emerged later in the growing season than Ontario midges.

“What we found was … there weren’t any Swede midge coming out of the ground until the canola plants were in already in the first flowering stage,” Andreassen said.

“In Ontario, the overwintering cocoons would come out in three different groups: an early group, a middle group a couple of weeks later and a couple weeks later, a third group…. It seems like that first early group, we don’t have it here (on the Prairies).”

The early versus late emergence is significant because Swede midge in Ontario can produce four or five generations of offspring during the spring and summer.

“There seems to be only time in northeastern Saskatchewan for only two generations to occur,” Andreassen said. “There’s more to it than different climates. We also have different (Swede midge) genetics in Sask-atchewan.”

Fewer replications reduce the likelihood of a population explosion over a summer and limit the number of eggs laid in the soil before winter, which come out the following spring.

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The late emergence is positive, but there are several concerns surrounding Swede midge:

  • The tiny flies are spreading rapidly across Saskatchewan and other parts of the Prairies. Last year they were detected near North Battle-ford, Sask., Meadow Lake, Sask. and Swan River, Man.
  • Swede midge prefer a warm, humid climate. Eastern Manitoba and the region between Edmonton and Red Deer have a favourable climate for it.

“If it’s dry, the adults will only live for a day or less,” Andreassen said.

“If it’s humid air, then they’ll live for up to five days. It’s on the second day that their egg laying takes off.”

  • Insecticides aren’t effective against Swede midge because the larvae deform the plants and it’s difficult to achieve insecticide contact when the pest hides in the folds.

Killing adults is also challenging.

“With the adult stage, the peak of emergence is a three week peak,” Andreassen said.

“Even if you sprayed for the adults and killed them (one day) … there’s still more coming out the next day and the next day.”

On the positive side, he said pheromone trap counts are low in Western Canada. Many traps snared one or two Swede midge over the entire summer, while Ontario traps have caught dozens in a day.

As well, Andreassen has discovered two parasitoids in Saskatchewan that don’t exist in Ontario, which attack the Swede midge and could be harnessed to kill the pest.

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robert.arnason@producer.com

  • 1996: Ontario crucifer vegetable crop suffers high production losses. Researchers not sure why.
  • 2000: Guelph scientist identifies presence of Swede midge in Ontario.
  • 2003: Jumping larvae observed in canola pods in northeastern Saskatchewan.
  • 2004: Swede midge detected in New York state.
  • 2006: Swede midge spreads throughout southern Ontario and parts of Quebec.
  • 2007: Confirmed in one location in Nova Scotia, three locations in Saskatchewan.
  • 2008: Found at two Manitoba locations.
  • 2012: First noticeable damage to canola in Saskatchewan.
  • 2013: Swede midge damage more prevalent in northeastern Saskatchewan.
  • 2015: Swede midge is endemic in area around New Liskeard, Ont. Ontario Canola Growers Association recommends a three-year moratorium on canola production in the region.