Last summer Todd, a farmer near Red Deer, Alta. called with a problem in his canola crop.
In late July, large patches of yellowed plants had him worried about sclerotinia. I went out to visit him at his field with a colleague. Various visual clues on the affected plants allowed us to eliminate sclerotinia, along with a number of other common diseases such as fusarium wilt, blackleg and alternaria.
We quickly realized we were probably looking at a solution that none of us wanted to find. We pulled a few plants to inspect the damage below the soil surface. Sure enough, large whitish galls were attached to Todd’s canola roots. It was clubroot.
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Clubroot was first diagnosed in Alberta in 2003. It is insidiously making its way through the province and is listed on the Agriculture Pest Act in Alberta. We can only assume it will spread beyond provincial borders.
At this point, there are no fungicides in Canada that effectively combat the disease. With a 50 per cent yield loss typical in a field with a 100 per cent infestation rate, and with resting clubroot spores living up to 20 years in the soil, clubroot is a menace producers have to avoid at all costs.
When I told Todd that canola is susceptible because it belongs to the Crucifer family, he immediately identified a possible source. A large market gardener that produces cabbage, broccoli, turnips, radish and mustard borders his land. It’s certainly possible that the clubroot has transferred to his field via contaminated soil on equipment, footwear and vehicles.
At this point, long rotations out of canola for at least four years are the only proven way to avoid clubroot infestation. Now that we’ve diagnosed Todd’s problem as clubroot, Todd is advised to play on the side of caution.
With no fungicide solutions at present, he should probably implement a rotation of five to seven years. Because the pathogen can survive for so long in the soil, this rotation won’t completely eliminate his clubroot but it will keep things manageable. And when we suggest to Todd that he stay away from canola for the next five years, that includes being especially wary of weeds in the mustard family, dock, hoary cress, orchardgrass, red clover, red-top and perennial ryegrass.
Todd should immediately implement a zero-tillage plan. Clubroot is a soil-borne disease, which means it is happy to use water or wind as its mode of transport, if it can’t find willing equipment or vehicles.
Todd might also consider talking to his agronomist about liming his soil. There is new research that suggests a pH of 7 or higher could reduce the incredible longevity of clubroot spores, along with the damage they cause.
Make sure you learn from Todd’s bad luck. Be fussy about keeping your vehicles, equipment and even clothing clean of all dirt when you’re entering a new field. We’ve all got to do our part to keep clubroot at bay.
Brian Hellegards is the manager of Richardson International’s Kelburn Farm
