Canola School: Controlling grasshoppers, an atypical pest
It’s been dry, windy, and hot across most of the Prairies this year, and an insect pest that you don’t typically see attacking canola is thriving in these conditions.
Lyle Jensen, agronomist at AgroPlus, joins Kara Oosterhuis for this Canola School episode where they discuss grasshopper pressures and options for control.
“As we’ve basically been in drought conditions here with the heat, grasshoppers have been pretty rapidly expanding their territory out of the ditches and some of the grazing land,” says Jensen. Now that the pest has finished off the more lush grass in the ditches, they’re moving into canola, which isn’t a preferred food source for grasshoppers.
In the video below, you can see that a grasshopper will strip a canola plant entirely — leaves, lateral stems, and all:
Feeding will mostly be on tender, green parts of the plant like the leaves. As the leaves are decimated, grasshoppers will go after the pods, causing a direct yield loss.
The two-striped grasshopper will typically feed by taking strips off the pods, in a line, while the migratory grasshopper will take a chunk.
“The end result is basically the same, it’ll compromise pod integrity and if they’re hungry they’ll eat the seeds right out of the pod,” says Jensen.
The threshold to take action will vary depending on the condition of the crop, says Jensen, and if the damage is severe along edges, it can be worth spraying just the edges.
If the population is throughout the field, at seven to ten grasshoppers per square metre, it’s worth spraying the whole field, depending on the yield potential.
Jensen says that a Group 28 insecticide applied to field edges has been effective at controlling the grasshoppers so far, and is a little more effective at the nymph stage. A Group 1 or Group 3 insecticide is a bit faster in terms of spraying ditches, but doesn’t have a meaningful residual at controlling adult grasshoppers that are flushing off of nearby grass. A grasshopper bait, such as EcoBran, is another control option, says Jensen.