Variety selection key to disease control

Crop rotation also important | Scientist says canola-cereal rotation is not long enough

LACOMBE, Alta. — Neil Olstad used to buy his seed based on its yield potential.

In the future, he plans to take a closer look at disease resistance.

“I have a serious interest in leaf disease,” Olstad, who farms near Millet, Alta., said after spending a day in Lacombe listening to cereal disease specialists.

“Every year it seems like it is getting worse. I suffered a fair loss two years ago because I didn’t spray enough. I am for sure going to spray every acre of cereals this year and the wheat maybe twice.”

Spraying for leaf disease wasn’t the only recommendation discussed at the cereal disease workshop.

Kelly Turkington, a research scientists with Agriculture Canada, said breaking the canola-wheat cycle and adding more variety will allow Mother Nature to help control disease.

He said research at Agriculture Canada has discovered that the shift from conventional tillage to conservation tillage has not affected the amount of scald or net blotch in field.

Crop rotation is the factor most consistently associated with increased levels of scald and net blotch, he added, particularly growing barley on barley and a wheat-canola-wheat rotation.

“Ideally you want to see at least two years of a non-host crop,” he said.

Whether a variety is susceptible or resistant is the next most common factor in cereal disease.

“Variety and crop rotation were the key factors,” he told the workshop.

Turkington said the most common rotation of canola-cereal is not long enough to allow for the decomposition of infected barley and wheat residue and blackleg infested canola residue and clubroot resting spores.

“What we’re looking at is a lack of diversity and time,” he said.

“It’s one of our major risk factors as far as disease. Really, what’s happening is you’re allowing for build up for infested crop reissues and pathogen structures.

“With a tight rotation of continuous cereal or cereal every second year, it’s not long enough for Mother Nature to take care of that resting body for you and decompose it.”

Turkington said switching varieties can cut disease in half, comparable to spraying the crop, although a better option may be to grow another crop to break the disease cycle.

In Europe, researchers found that growing a mixture of barley, oats and triticale in the same field as feed can also reduce disease by 50 percent.

Fungicides have the biggest impact on disease, but Turkington said the choice of fungicide is the least important decision.

If they’re registered for disease, they will all work reasonably well.

He said timing is the more important factor, with the most significant disease reduction achieved when the fungicide is applied at the flag leaf stage.

There are exceptions, especially in years of high levels of infection, he added.

Not all varieties have the same response to fungicide applications. A susceptible variety will respond better to a fungicide while a resistant variety will have little benefit.

Turkington said there are no silver bullets to controlling diseases in crops. An integrated approach to crop, insect or weed control works best.

Olstad said he plans to add more crops to his canola-wheat rotation now that the price of grain has increased.

“I want to do more barley, some oats and peas, perhaps fababeans,” he said. “I will also select the different varieties of barleys for resistance. The ones I picked were the worst.”

Bryan Adam of Stony Plain, Alta., said he attended the workshop to learn more about disease.

“It’s obvious more management is needed and scouting is getting more important all the time,” he said.

“Everybody knows our rotations have been short. Rotation is the biggest effort we need to put in now, and rotating varieties as well.”

Adam said he also plans to focus more on disease resistance when choosing varieties.

“I didn’t realize there was quite as much difference between varieties as there is. I know I’m going to pay more attention in the future.”

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