Blackleg reduces Man. canola yield


Disease incidence higher in 2012 | Hot summer, dry conditions add to poor yields

Canola growers in Manitoba have been extremely disappointed by yields this harvest season, as record temperatures and arid conditions hindered pod development in July.


Yet, the extreme heat may not be the only factor behind poor canola returns, which ranged from 20 to 25 bushels per acre on many farms, because blackleg also robbed canola growers of yield in 2012, says a provincial oilseed specialist.


As a case in point, when Ed Rempel harvested the northern portion of one of his canola fields in August, the yield meter on his combine dropped dramatically. 


The remainder of the field produced 40 bushels per acre or higher, but in his 80 acres of lower lying land the yield sank to nearly 25 bu. an acre. 


“I saw a substantial 12 to 15 bushel decrease in the blackleg area of the field,” said Rempel, who farms near Starbuck and is president of the Manitoba Canola Growers Association. “Fifteen bushels an acre is $200 an acre.”


Manitoba Agriculture’s annual canola disease survey, done in late July and early August, showed that blackleg was present in 70 to 75 percent of canola fields, said Anastasia Kubinec, provincial oilseed specialist.


While that’s higher than previous years, the bigger story is the severity of blackleg in the 2012 canola crop.


“We’re seeing more plants within each field that are affected,” Kubinec said. “Normally, we’re usually seeing that 10 percent (of plants) in a field have blackleg. We’ve had a lot more cases this year where we have seen 60, 70 or 80 percent (of plants) had blackleg.”


It’s only a rough estimate, but Kubinec guessed that blackleg reduced canola yields in Manitoba by 10 percent this year.


Blackleg acts like an elastic around a plant’s stem, restricting its ability to draw moisture and pull nutrients, Kubinec explained.


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Most fields developed blackleg later in the growing season, which hindered plant development during the final stages of pod filling.


“Instead of having the seed…off those top pods, it has completely dried out and they’ve blown out the back of the combine, or you have really small seeds in your sample,” she noted.


Manitoba Agriculture surveyed 150 canola fields throughout the province for disease this summer.


As part of the process, they send a letter to the grower with information on the level of disease in the crop.


Normally the letter goes out in October, but this year it was sent in the fourth week of August because growers will soon be making seeding plans for 2013.


In the letter, Manitoba Agriculture recommended that growers rotate away from canola.


“If you have high incidence of blackleg you should maybe think twice about putting canola on that field next year. Or even two years from now,” Kubinec said.


Rempel is one grower who is taking the recommendation to heart.


“No canola in this (blackleg) field… until 2016,” Rempel said, unless he divides the field and plants canola on the portion without blackleg prior to 2016.


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Overall, canola yields on Rempel’s farm this year were well below average. Most of his 600 acres yielded less than 25 bu./acre because of the extreme heat in July.


Looking beyond his farm, Rempel said canola acres in Manitoba’s Red River Valley are bound to decline in 2013 and beyond, because disease and climate pressure will push growers toward other crops. 


“Looking out at the cropping landscape for the next year, I’m seeing that in the (Red River) valley we will lose canola acres to soybeans in a very real way,” said Rempel, who plans to cut his canola acreage next year.


“I think everyone in Western Canada has been pushing their rotations…. In the (Red River) valley, maybe some of those chickens are coming home to roost.”


Besides blackleg, Rempel is also concerned about the extreme weather that has become a normal part of the growing season in North America.


Assuming record hot spells, 100 millimetre rainfalls and periods of drought are part of a new climate reality, Rempel said the canola industry might need to respond accordingly.


“For canola growers, in the valley for sure, what we need are varieties that are more robust, that maybe aren’t the yield prima donnas, but can hang onto a good average yield through times of crop stress,” he said.


“The geneticists have been trying to give us about two percent yield increase per year… and God bless them for it. But from where I’m sitting, it looks like we need more robust varieties.”

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