Bertha armyworm

Bertha armyworms prefer canola but also feed on other crops including flax, rapeseed, mustard, alfalfa, field peas, and potatoes. The highest risk of economic damage is in canola and flax.  During hot, dry weather, young larvae may be found feeding on the lower leaves or hiding under debris at the soil surface.   Larvae migrate from an infested field only when the food supply is short or when the crop is over-ripe.