Researchers have set up 170 traps in Western Canada this summer dedicated to monitoring Swede midge in canola fields, stretching from Elm Creek, Man. to Dawson Creek, B.C.
As of late June, not a single Swede midge had been found.
“They are all just catches of zero and no damage so far. There’s nothing at all,” said Lars Andreassen, an Agriculture Canada research associate in Saskatoon who co-ordinates the Swede midge program.
Provincial government employees, agricultural company representatives and private agronomists are monitoring the traps for Agriculture Canada.
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Andreassen said conditions have been too dry for Swede midge, which prefer to emerge following a rain.
“They just stay in the soil (when it’s dry). They kind of wait it out, in their cocoon.”
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, which is a common pest of crucifer crops in Europe, has devastated canola production in parts of Ontario. This year, many growers around New Liskeard in northern Ontario decided to abandon canola because Swede midge populations had reached unmanageable levels.
Terry Philips, president of the Ontario Canola Growers Association and a producer from New Liskeard, was one of the farmers who stopped growing canola this year.
It was a wise choice because Swede midge pressure was higher than ever this spring.
A field agent for the Ontario association found hundreds of Swede midge flies in pheremone traps during the second week of June near Temiskaming, Ont.
“There were like 800 plus (per trap). The threshold is four,” Phillips said.
The situation in Western Canada isn’t comparable. There has been only one year, 2012, when Swede midge caused economic damage to canola fields in northeastern Saskatchewan.
Based on trap data from this spring and previous years, it seems Swede midge emerges on the Prairies when canola plants are more mature.
“Even last year it wasn’t until June 25 that the first ones were found,” Andreassen said.
“They come out quite a bit later on the Prairies than they do in Ontario.”
Andreassen said the prairie climate partially explains the pest’s delayed emergence, but it may also be attributed to the type of Swede midge found in Western Canada.
“There is a model that works for predicting the emergence of Ontario midges,” he said. “If you run that Ontario midge model with prairie weather data, it (predicts) midge emergence about three or four weeks (earlier) … (before) they actually come out the ground.”
The timing of Swede midge emergence is crucial. The larvae can destroy canola if they get into the growing point when plants are small.
“If it comes before the canola bolts, that’s very bad,” Andreassen said.
“(They) can just make it lie flat on the ground.”
A Swede midge infestation can harm more mature canola plants, but the damage isn’t as extreme.
“By the time it’s flowering and you get the fused, bottle flowers, the plant can compensate for quite a bit of that,” he said.
“If it’s on the primary shoot that (it) gets the fused flowers … the plants probably cut off nutrients to that flower and diverts it to a flower on secondary stems.”
The risk of Swede midge damage might be lower on the Prairies, but the canola industry is taking precautionary action.
For example, Agriculture Canada is developing canola varieties with resistance to Swede midge.
“We’re making good progress on that,” Andreassen said.
“There are very promising things in that area.”
As well, biological help may be available for canola growers in northern Ontario.
Andreassen and his colleagues have discovered two parasitic wasps, native to the Prairies, which attack Swede midge.
Biologists need to study the wasps, but the parasitoids could be introduced into Ontario in a couple of years.
Swede midge risk may be minimal on the Prairies for the moment, but Andreassen said the insect is spreading to new locations and growers should be vigilant.
“Last year when the midge … spread 200 or more kilometres, it was the larvae that were found first,” he said. “So folks could and maybe should have an eye out for the fused, somewhat bottle-shaped flowers, with larvae that jump inside.”
