Canola School: Four insects you need to know
There are few things as frustrating as spending untold hours of preparation and seeding (and finally some rain!) only to have a host of insects crawl or fly in and eat the crop’s yield potential.
In this episode of the Canola School, provincial entomologist for Saskatchewan’s Ministry of Agriculture, James Tansey, gets outside to talk about four of the most common (and sometimes most devastating) insects to feed on or impact the canola crop. In the video below, you’ll learn about diamondback moth, bertha armyworm, aster leafhoppers, and flea beetles; which overwinter, which insect is on the rise, and which is getting tougher to control. (Summary included below the video).
Diamondback moth: This insect can feed from the seedling to pod stage, depending on when the wind carries it to Canada. It can be a big yield robber depending on when the damage to flowers, pods, or seedlings occurs. This insect is relatively well controlled by parasitic wasps, but in high numbers it can be devastating.
Bertha armyworm: Native to the Prairies, this insect overwinters here and usually runs in an eight to 10 year cycle. Right now, we might be on the upswing with populations, Tansey says. This pest emerges in the spring and needs to be monitored to find hot spots. Keep tabs on the flight of the adults. The economic thresholds are quite advanced for this insect. Watch for defoliation in July and even into August.
Aster leafhopper: The insect itself doesn’t feed on canola, but it does carry a phytoplasm that causes aster yellows, leading to stunted growth and bladder-like pods. This insect is also carried to Canada by wind and very attracted to yellow. It’s more of a mid-grade pest, as far as economic damage risk goes, but it is already showing up on the Prairies this season.
Flea beetles: What most call flea beetles are actually several species of the same insect, but unless you look closely they all look similar. The two main pest types are crucifer and striped flea beetles. They can co-occur in the same field, but the striped seems to be increasing in dominance. That’s an issue as it seems that insecticide options are slightly less effective on this type of flea beetle. Both are early pests, but the striped species is usually one to four weeks sooner, depending on the temperature. Flea beetles can emerge as early as mid-April from shelterbelts and grassy areas and feed on flixweed, wild mustard, and volunteer canola. Flea beetles can fly up to a mile, but usually spread by walking or hopping (like fleas!). Feeding has to happen for seed treatments to work, which still causes damage, and heavy pressure can also require a foliar insecticide in addition to seed treatments.