Normally by now we would be done talking about early-season pests such as flea beetles and cutworms, but with the canola crop behind this year by one to three weeks, growers may need to be vigilant in scouting fields.
“The pest situation was at a bit of a lull due to the cooler weather across the Prairies and the dry conditions, particularly in Alberta,” said Jim Bessel, senior agronomist with the Canola Council of Canada in a release Thursday.
Now, however, “the situation is beginning to change and scouting for flea beetles should still be at the top of farmers’ minds right now, especially for delayed or reseeded fields.”
Bessel, who’s based in Saskatoon, notes that normally most flea beetles would be gone due to pre-seed treatments, but slow emergence may have negated some of that.
Canola is most susceptible to flea beetle damage during the cotyledon to two-leaf stage. The economic threshold for flea beetle control is when 25 per cent or more of the cotyledons are damaged. “Scout fields regularly to look for cotyledon damage,” Bessel said.
Reports of cutworms are most common in Saskatchewan and Alberta fields that were cultivated last summer and had loose soil for the adults to lay eggs. When larvae are small (12-18 mm), they pose the greatest potential for damage, so that’s when spraying can be effective. But if larvae are near pupating (30-35 mm) and when their gullet lacks green material, they are done feeding. That means spraying will be less effective since control is mostly the result of the pests eating treated leaves.
“There have also been isolated reports of other early season pests like red turnip beetle. It has turned up in northwest Manitoba (in a garden area) and there have been some canola fields infested in the southern Peace region of Alberta,” Bessel said. “Because this insect moves into a field by migrating from a neighboring field that was in canola last year, control usually can be achieved with perimeter spraying.”
The cabbage seedpod weevil has started showing up in southern Alberta and has been moving into southwestern Saskatchewan. The optimum time to spray for this pest is early flowering (10 per cent flower). Spraying after this point may not only result in yield loss, but will also impact beneficial insects that have moved into the field, including pollinators.
Grasshoppers were first starting to hatch last week in Saskatchewan. If the warm weather continues, grasshoppers may become a localized problem.