Clubroot inspections by the County of St. Paul are underway as of July 22 and so far, all 50 of the fields checked by agricultural fieldman Keith Kornelsen and his staff are free of the disease.
Clubroot can reduce yields of canola and other cruciferous crops by up to 80 per cent. The disease has been noted in the area over the past few years, with a number of workshops being held to educate local farmers.
Inspections began on the east end of the county, an area the disease has yet to be noted. “We’ve never found it in that area (Division 1) before. Usually we find it in Division 3 and Division 4, there’s more canola grown there,” said Kornelsen.
As part of the county’s clubroot management strategy, Kornelsen and his staff will be inspecting every single canola field in the County of St. Paul over the course of the next month, starting from the most common access road to the field.
“Typically, when a farmer starts seeding his field, they . . . (they) drop the seeder down and then go . . . so if we’re going to find clubroot in a field, it’s typically at the entrance,” said Kornelsen.
He said as part of the inspection, he and his staff walk about 50 to 100 metres in to the field and pull 50 plants along the way to inspect the roots. If they spot any galls on the roots, they send the samples to a lab to confirm what kind of clubroot is present.
“If we find it, we have to go back and do an incidence rating to see how much clubroot you have. And there we pull 100 plants. So typically we’ll pull 50, and then go back and pull 100 more, and then we count them, how many plants we find clubroot on. And based on the number we find we have different ways for the farmer to respond and control the clubroot at that point,” said Kornelsen.
According to Kornelsen, the recommendations include a three-year crop rotation with a clubroot resistant variety of canola and avoiding soil transfer between fields by knocking all the big clumps of soil off equipment before moving to the next location.
“It’s transported in the soil, so at the very least knock the big clumps of soil off. Often that requires going out with a hammer and spending 30 minutes knocking the seeder shoes and the tires and things like that, and make sure you get as much off that as possible,” he said, noting taking the time to pressure wash equipment would do an even better job of reducing soil transfer.
“We’re (county staff) very cautious, we spray our boots with a disinfectant and actually wear rubber booties when we enter the field.”
Kornelsen said another thing that can help reduce the spread is once you know there is clubroot in a field, plan to seed that field last.
The county maintains a list of clubroot positive fields on their website as well as historical data going back to 2014.
Canola Council of Canada recommendations
According to Keith Gabert, an agronomist with the Canola Council of Canada, farmers need to do more than just change the variety of canola they plant if they want to get rid of clubroot in their fields.
“It’s a numbers game, and if it gets away with us, I’m a little concerned we’re not going to win,” said Gabert.
He said knocking all the visible clumps of dirt off of equipment removes about 90 per cent of the risk.
“If you know you’re coming from a known clubroot field or you bought a piece of equipment and you don’t know where it came from, absolutely do the full sanitation . . . We know there can be billions of spores per gram of soil and if you happen to move the wrong lump of dirt from the wrong field, you could have a really aggressive strain of clubroot that would be hard to manage in to the future,” said Gabert.
He also talked about incorporating what he called “patch management” for fields where there are particular areas infested with clubroot. According to Gabert, raising the pH of the soil in a bad clubroot patch can mitigate some of the damage by reducing the number and size of galls on the canola roots, and therefore also reducing the number of spores produced and the speed the disease spreads at.
“If you’ve got a pH of 5.5 or thereabouts, you can probably see about a 25 per cent yield bump on your barley, you’ll see a yield bump on wheat and canola as well. It’s going to cost you,” he said.
Gabert said to raise the pH of an acidic soil requires adding several tonnes of lime per acre, but noted soil conditions are rarely uniform throughout a field, and the practice of adding lime is common in agriculture “everywhere else in the world.”
