By Jay Whetter, Canola Council of Canada
Canola damage thought to be from swede midge is likely caused by two separate midge species. Swede midge has been found in the past, and sparked our current research. The other species, a close relative to swede midge that produces similar larvae and symptoms, is new to science.
Scientists were suspicious that two midge species were present in canola in Western Canada when pheromone traps specific to swede midge were not catching any even though midge were present at relatively high numbers in fields and in emergence traps.
Either the pheromone traps weren’t working or two species were present. As a test, midge researchers sent the pheromone traps to Ontario, where swede midge are fairly common, and the traps lured lots of midge. Ruling out trap malfunction, adults from the suspect species were sent to midge experts in Ontario, who confirmed it as a separate species.
“The good news is that neither species has caused significant damage in the Prairies yet, but the potential is there,” says Keith Gabert, agronomy specialist with the Canola Council of Canada. “Damage from swede midge in some counties in Ontario has stopped farmers from growing canola.”
Boyd Mori, research scientist with Agriculture and Agri-Food Canada in Saskatoon, says when swede midge lay eggs early – at the five- to seven-leaf stage of canola – the plant may yield next to nothing.
The new species has been found in the northern canola-growing belt in Saskatchewan and into east central Alberta. Researchers will more intensely study distribution of both species, and focus on the biology of the new species, Mori says. This includes analysis of how many generations it can produce per season and its potential impact on yield.
When scouting, look for galled bottled flowers as an indicator of the new species. These malformed flowers result from larvae feeding inside. Damaged flowers do not produce pods or seeds.
“If either midge became a real issue, we don’t have great control options,” Gabert says. “Larvae develop while sheltered and enclosed inside the plant and adults are not around long, so efficacy and timing of a spray, if it is to work at all, become essential.” Researchers have identified two beneficial parasitoid wasps that attack at least one and perhaps both species. Mori is also looking at plant traits that could provide resistance.
“For producers’ sake, I hope we don’t see any increase in populations or damage, but at the moment we don’t know what their population levels will be like in the future,” Mori says.
For more information on the new midge and on canola midge in general, go to canolawatch.org.
The latest Canola Watch podcast, available through iTunes and Google Play, features Mori and Gabert discussing the new midge. You can listen here.