Heavy frost in southern areas of Alberta late last week damaged newly planted canola crops, according to an agronomy specialist with the Canola Council of Canada.
Areas from Vulcan, about 130 km south of Calgary, past the Canada/U.S. border and down to Montana, experienced freezing temperatures for at least eight hours on the night of May 11. Temperatures reached as low as -4 C to a reported -8 C in some areas.
Troy Prosofsky, the Canola Council's agronomy specialist at Lethbridge, said the damage could have been worse, but cooler temperatures in the days leading up to the frost hardened canola crops.
"With canola and frost occurrences it's a function of how hot it was the day before, and then how cold it got, et cetera. So it's those extreme changes that actually cause more damage.
Prosofsky said he scouted over a half a dozen fields a few days after the frost and saw some fields that lost 60 per cent of their plants.
"There was definitely a lot of high mortality rates in some regions. What I did find was no two fields were exactly the same. It was a difference of what stage the crop was, the topography, what their plant counts were, et cetera. However, despite the damage, there weren't any fields that I saw that needed to be reseeded."
Neil Whatley, crop specialist with the provincial Ag-Info Centre at Stettler, recommended farmers wait at least four days to check their crops after a frost before taking action.
"If there's still one or two per square foot, you don't want to reseed. With canola you never want to reseed unless you're down to about three plants per square foot," he said.
Prosofsky said at this point in the season it may not be worth it for farmers to reseed.
Research done by Ross McKenzie, agronomy research specialist for the provincial ag ministry, shows that in southern Alberta, 1.8 bushels are lost for every day crop is planted after May 1, Prosofsky said.
"If we're seeding this late in the game, we'd already be losing 25 bushels of potential yield. So you've got to consider if I'm going for 65-bushel yield, and I only get 40 if I reseed. Or, if I lost 10 per cent, maybe I'm down to 55 bushels."
Prosofsky said it is important for growers affected by the frost to protect their crops from insects and disease.