Early season pests still an issue in delayed canola crops
By Canola Council of Canada
Early season pests still an issue
in delayed canola crops
Late seeding and weather issues that have delayed the progress of canola may now be negating the benefits of seed treatments in controlling flea beetle and subsequent damage.
By Canola Council of Canada
June 25, 2009 – While normally we would be done talking about early season pests like flea beetles and cutworms by now, with the canola crop behind this year by one to three weeks, growers should continue to be vigilant in scouting their fields," advises Canola Council of Canada (CCC) senior agronomist Jim Bessel.
"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, but 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 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 percent or more of the cotyledons are damaged. "Scout fields regularly to look for cotyledon damage," says Bessel.
Other pests are being detected as well:
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 to 18 mm), they pose the greatest potential for damage, so that is when spraying can be effective. But if larvae are near pupating (30 to 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," says Bessel. "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 percent 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.
For information resources on pests, the CCC recommends that growers check Manitoba, Saskatchewan, and Alberta agriculture websites for pest management information.
Information on pest control appears in the Crop Protection Guide, which is linked to from all the provincial agriculture sites.
Pest information is gathered through the Prairie-Wide Pest Monitoring Program, -a project jointly funded by growers, Agriculture and Agri-Food Canada, and industry stakeholders. With Dr. Owen Olfert as project lead, the Prairie-Wide Pest Monitoring Program monitors existing and emerging pest populations, and provides the information to growers.