Disease forces longer canola rotations in Manitoba

Widespread blackleg is reducing yields in south-central Manitoba and making producers rethink their crop choices

DAUPHIN, Man. — Farmers in south-central Manitoba are backing away from canola because blackleg is curbing yields and cutting into profits.

Canola yields of 45, 50 or 55 bushels per acre have become normal in many parts of the Prairies, but growers in pockets of southern Manitoba are struggling to achieve those targets.

“They’ve moved from canola-wheat-canola-wheat, probably for the past 15 years, and they’re now increasing their rotations because the blackleg is so bad they are actually having a hard time growing a crop (of canola),” said Anastasia Kubinec, Manitoba Agriculture’s acting manager of crop industry development.

“They’re not able to get 40 bushels an acre anymore…. They’ve hit a (yield) ceiling, just because of disease.”

Kubinec, who spoke at Canolab, an agronomy workshop held in Dauphin March 15-16, attended a grower meeting a couple of weeks ago in a Manitoba town near the U.S. border. Producers in the area have lengthened their canola rotation to cope with the disease pressure.

“It’s representative of numerous areas in Manitoba,” she said.

“They’ve seen what tight rotations have done…. It’s when you get the long- term, really tight rotations that all of sudden things go a little sideways and you have to change something.”

Growing canola every second year is the dominant rotation in many parts of Western Canada. In northeastern Saskatchewan, Statistics Canada data shows that canola was grown on about 45 percent of all acres in 2014.

Blackleg was particularly bad in Alberta last year. A provincial disease survey found that about 90 percent of Alberta canola fields had blackleg, and more than 30 percent of all plants had symptoms of the fungal disease.

At the Canola Council of Canada convention held earlier in the month in Winnipeg, a Bayer executive said tight rotations are compromising the crop’s ability to withstand the pressure of clubroot, blackleg and other pathogens.

“There’s a time now where if we don’t get together and really focus on some of the basics of agronomy, I don’t know if we have canola to be able to be there,” said Garth Hodges, Bayer CropScience’s vice-president of marketing and business development.

“How do we go back to some of the basics like saying we have to go into (good) crop rotation and be better at crop rotation?”

Kubinec said growers in certain parts of Manitoba have learned that lesson. They are putting more crops into their rotation and recognizing the benefits.

“When you get to the longer crop rotations and you’re using the resistant varieties, you probably don’t need a fungicide because your actual concentration of pests in that field … they’re dead or very low,” she said.

“Blackleg, its maximum spore release is 21 to 28 months. So if you’re canola-wheat-canola, you’re getting all those spores.”

However, growing more crops comes with a cost. A producer may need additional labour to manage three, four or five different crops. And most importantly, the non-canola crops in a rotation must be profitable to grow.

“If the producers are making money with a longer, more diverse rotation, they will do it,” Kubinec said. “If they’re not, they will not do it.”

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