Canola School: Plant stand counts and post-harvest disease scouting

If the weather was in your favour this fall, and the canola is off, now is a great opportunity to review what went wrong or what went right with the crop. One way to get some insight is to do plant stand counts and some post-harvest scouting.

“Despite the challenges that 2020 threw at us, it is nice to have trials off early,” says Jeanette Gaultier, service specialist with BASF, out of western Manitoba. “Something that we do for our own trials is go in right after harvest and do some plant stand counts.”

Optimal canola plant stand is around five to seven plants per square foot. The Canola Council of Canada is a great resource for a how-to on counting plant stands. If the plant stand is under that range, and the yields weren’t as expected, then that could be the first reason.

On the other hand, late seeding into warm soils, and good survivability perhaps wasn’t accounted in the seeding rate, so the plant stand count maybe exceeded that five to seven plants per square foot. A denser plant stand can contribute to lodging, which many farmers might have seen in their crop this year. Seeding rate and equipment can be adjusted for next year if this is the case.

Watch the full conversation between Gaultier and RealAg’s Kara Oosterhuis below: 

If you were within the optimal plant stand range, and the crop still lodged, that’s an indicator that something else was going on — probably disease. Both blackleg and sclerotinia are easy to look for once harvest is over. Post-harvest is the perfect time to scout for those two diseases by clipping stems, but they need to be identified properly to know for sure. Alternaria and fusarium are also possible diseases that can impact the canola crop, and may be confused for the more common ones.

“Just because there’s discolouration on your stem clippings or on your outer stem, doesn’t mean you have blackleg,” says Gaultier. Knowing what the other diseases look like is important. Alternaria and fusarium are also possibilities — verticillium stripe also causes grey discolouration, with accompanying sclerotia.

Wondering what you are looking at? Take advantage of diagnostic labs in the province or the Canola Council resources, and, when in doubt, send a sample in for testing. It might also be a good time to think about switching varieties. Not all varieties will be tolerant to the various diseases, but at least knowing what’s present in the field can mean managing it for the future canola crop further along in the rotation.

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