Canola growers pondering their next steps after heavy frost hit some regions of the Prairies over the weekend will need to wait a few days for some of the answers, the Canola Council of Canada suggests.
Some canola-growing areas of southern Alberta logged temperatures as low as -8 C over the weekend, the council said, leaving growers wondering whether the crop could survive, whether they need to reseed and when or if they should resume weed control.
It may take a few days to accurately gauge a frost-touched crop’s survival rate, the council said.
Where the risk of crop damage would be "minimal" through a light frost of 0 C to -2 C, it would take time for new leaves to start emerging from the growing point between the plant’s cotyledons.
"If no growth occurs within this time, the plant is likely dead," the council said. "Also, if the stem is pinched off or the plant flops over, the plant will likely die. The pinched-off or broken stem cannot provide nutrients to the growing point."
Check the whole crop the day after a frost and three to four days after a frost to assess the situation, the council recommended.
If many plants have been killed, it takes a few days to determine the kill rate, which would inform a grower’s decision on whether to reseed a field.
"If one or two plants per square foot have survived and if that stand is fairly consistent throughout the field, the best choice is probably to leave it alone," the council said.
"A thin stand is not optimal for yield but a thin stand in mid-May may have better yield and quality potential than a reseeded field, particularly in southern Alberta."
If large parts of a field are lost, reseeding or fallow may be the only alternative for those areas, the council said.
After a light frost, spraying could resume after at least one night with minimum temperatures of 5 C — the minimum for biological activity to occur — and at least one day of warm and sunny growing conditions have passed. Warm and sunny conditions must also be present at spraying.
Growers also need to see no evidence of frost damage (such as blackening and water-soaked appearance) on the crop or the weeds before resuming spraying.
The crop’s condition must also be considered, because even a herbicide-tolerant canola requires that a plant’s metabolism work at full capacity to be able to effectively process the herbicide and prevent injury, the council said.
Growers will also want to consult their local product reps to see how or if a company will support the use of its product following a frost or cool temperatures.