Fall Frost in Canola

By Samantha Marcino, PAg. CCA, Crops Extension Specialist, Yorkton

Challenging spring weather or imperfect growing conditions can be a few reasons why canola maturity may be delayed and therefore, susceptible to fall frost. Although not an ideal situation, there are options for producers to manage the outcome of their canola crop.

Green canola seeds are caused by chlorophyll not being cleared from the seed. This causes issues with both the quality and colour of canola oil. Chlorophyll is the green pigment in plants that allows them to photosynthesize. When plants are still green and above 20 per cent moisture, frost can cause this chlorophyll to be trapped in the seed. When a canola plant matures naturally, there are enzymes that help clear out the chlorophyll from the seed. Frost in immature canola damages these enzymes and locks the green colour within the seed. No amount of time, moisture or heat will take the green out of these seeds.

Swathing early can be used as a frost management tool, but it is not always effective. Canola must be swathed at least 72 hours before a frost so the moisture can get below 20 per cent. If your canola crop is very immature, swathing early can result in very small seeds and yield loss.

Symptoms of frost on canola plants include, white flecks on the pods, shrunken seeds, wilted plants, split pods or dropped pods. The pods can also sweat and release juices because the ice crystals have destroyed the cell walls. There is no specific temperature where frost damage can occur as it depends on factors such as acclimatization, dew, crop stage and temperature.

If a frost does occur on standing canola, it is best to wait a minimum of four to six hours before assessing. If the field does not look like it was damaged producers are advised to go back in a few days to confirm that there is no injury. If pods are severely damaged swathing may be required to reduce pod shelling and pod drop.

While Mother Nature is ultimately in control of fall temperatures, there are management strategies that can help you make the best out of a bad situation. For more information contact your local crop extension specialist or the Agriculture Knowledge Centre at 1-866-457-2377 for more information.;