The Canola Council of Canada (CCC) is advising growers whose fields have been or could be hit by frost to take the time before acting to fully assess damage.
“With the lateness of this year’s crop as well the multiple stages of maturity in the fields, many producers are delaying swathing so the crop can properly mature,” says CCC agronomist Doug Moisey. “Of course, that increases the potential for exposing the crop to a fall frost. I would advise any grower whose canola crop has experienced frost in the mid to late pod fill stage, to not react too quickly, and to carefully evaluate the extent of the damage.”
Research suggests that the main effect of mild frost is to cause an accelerated desiccation, which forces a premature transition from grain-filling to dry down. However, if the frost is light, there can still be some curing of damaged seed to minimize yield and grade losses, given enough time and adequate moisture conditions.
Frost in excess of -5˚ C at high seed moisture contents is generally lethal, resulting in non-viable seed. Pods of immature canola crops frozen at lethal temperatures tend to turn black, whereas mild frost turns pods white or white-speckled.
“Before producers decide on a plan of action, they should undertake a general overall assessment of the fields to determine the level of damage,” says Moisey. “Once they’ve determined that, they can decide whether to swath or leave the crop standing.”
Moisey suggests producers assess affected fields within 1-3 days after the frost, though more than one assessment may be required. “One option would be to inspect the day of the frost then again 1-2 days later to examine seed damage that may not be apparent immediately after the frost.”
The decision to either leave the crop standing and follow through to proper stages for swathing, or to start swathing immediately after a frost should be based on the level of damage in each field, says Moisey. “Ultimately, the decision will boil down to a comparison of the risk of yield loss from shattering versus the potential for further curing and improved grade in the remaining intact seed.”
He adds that the weather after the frost event will play a large role in determining how much shattering or curing will occur.
