Feeding injury can result in plant death and significant stand loss, especially during hot, dry weather. Flea beetles overwinter as adults. The beetles fly to canola, rapeseed, and other mustards, moving into fields just as the seedlings emerge. The feeding injury appears as holes or small pits in the cotyledons and leaves. Injury can range from a few shot holes to destruction of the entire plant.
Flea beetles feed most actively when the weather is sunny, warm, and dry.
Beetle activity is less when weather conditions are cool and damp. When warm, dry conditions exist and feeding injury is occurring, the plant can be stressed quickly. Cool, damp conditions can reduce the feeding intensity of the beetles and aid plant growth to the point where they can withstand the feeding damage. Once the crop is beyond the seedling stage and the first true leaves are fully expanded, serious damage usually does not occur. By mid June, adult beetles decrease in number.