When you’re dealing with armies of clubroot spores, use your shotgun.
That was the advice from two Canola Council of Canada agronomists who urged Manitoba farmers to start suppressing now, before they face an Alberta-like situation.
Looking for any silver bullet to kill the quickly spreading disease is probably futile. It has multiple means of spreading, including by wind and along watercourses.
“It’s not going to be always in your control. It could just be blowing in the wind,” said Dan Orchard, who has followed the clubroot outbreak since the early 2000s.
“That’s why this shotgun approach of doing everything you can to keep it from becoming a problem on your farm is important.”
Orchard and Manitoba-based Justine Cornelson said there’s no reason clubroot can’t become just as big of a problem on the eastern Prairies as in central Alberta.
“It’s a matter of time before we all have clubroot,” said Cornelson.
The agronomists said farmers need to keep spore loads low so canola crops don’t suffer. The spores can be found everywhere, but usually symptoms can’t be spotted above ground until there are about 100,000 spores per gram of soil. In the Edmonton area there are often millions per gram.
Canola crops can manage if spore loads are kept low.
The “shotgun approach” means employing multiple ways to suppress the spread of clubroot.
The three-year rotation is vital because the two-year rotation allowed clubroot to get out of control around Edmonton. However, adding an extra year of canola absence causes most clubroot spores to die. Adding more years than that doesn’t help much, so growing canola once-in-three-years is a primary way to stop spore loads from surging out of control.
Using resistant varieties is also important, as well as knowing which resistant varieties are being grown and which strains of clubroot are active in the area.
Reducing tillage is important because much clubroot spread comes when field machinery drags soil around the field.
Cleaning equipment between fields does much to reduce spore transfer, as does restricting the places where machines can enter and exit fields.
Scouting is vital in catching clubroot outbreaks before they spread widely.
“I highly encourage you to go scouting,” said Orchard.
“I think you’ll start to find it at the low levels.”
If patches are found, they need to be managed. That can mean pulling and burning infected plants, grassing, liming and other physical alterations to the patch.