By Alice McFarlane

Keeping clubroot ‘low’ and ‘local’ key to control

Oct 13, 2021 | 2:30 PM

MELFORT, Sask. – Clubroot is a complicated disease and producers are looking for ways to try and understand it.

Canola Council of Canada agronomy specialist Autumn Barnes said clubroot is the disease caused by soil-borne spores of Plasmodiophora brassicae. Spores spread easily and early infections can be missed for years while clubroot-susceptible canola multiplies spores to very high levels.

Barnes said the infographics that have been created provide a visual explanation on how the disease works. She said higher concentrations of brassicae spores lead to larger clubroot galls, more risk to yield, more resting spores released back to the soil and fewer management options.

“We’re trying to simplify things and make it make a little bit more sense,” Barnes said. “The goal for farmers and for people who support farmers should be to keep the clubroot spores low and to keep them local, so they don’t move them around.”

(submitted photo/Canola Council of Canada)

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Barnes said a new way to control the pest is with patch management.

“What it involves is managing a section of clubroot in the field separately from the rest of the field so that you can reduce spore concentration and then also prevent the spores from spreading,” she said.

The Canola Council also recommends following a crop rotation with a minimum two-year break between canola crops.

“We know that one in three rotation can break down about 90 per cent of clubroot spores,” Barnes said. “If growers stick to that, and they start with a lower spore concentration to begin with, that’s doing a lot of the heavy lifting.”

Barnes said you cannot underestimate the importance of scouting even if you’re in an area that has not had a confirmed clubroot case. She said start pulling up roots in the fall and look for any sort of swelling or growth on the roots paying close attention to the higher traffic and higher moisture areas.

“Clubroot spores get introduced to a field and then a susceptible variety is grown, you’re going to be amplifying and multiplying those spores really fast,” Barnes said.

Other management practices include controlling brassica weeds like volunteer canola, stink weed, flick weed, shepherd’s purse, and mustard. Barnes said these weeds will multiply clubroot spores in a non canola year.

Planting clubroot-resistant (CR) cultivars before the disease gets established will help slow spore reproduction. Barnes said growers who wait until the disease has taken hold in a field could be stuck with challenging levels of clubroot for a long time.

More farmers are growing resistant varieties. Barnes said in 2020 about 40 per cent of canola seeded on the prairies was a CR variety. That number is even higher in Alberta where there is more of a history of the disease.

“Seed companies have agreed to put forward clubroot resistant varieties,” Barnes said. “All varieties will be clubroot resistant in the next few years but we need to make sure growers are building that demand to match the supply because it is such an important practice.”

More information on clubroot and management strategies can be found at clubroot.ca.

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alice.mcfarlane@pattisonmedia.com

On Twitter: @farmnewsNOW