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Flea Beetles in Canola
Flea beetles are the most serious pest of canola in North Dakota. The small, black beetles feed on the emerging cotyledon and first true leaves of the young plant. Feeding injury can result in plant death and significant stand loss, especially during hot, dry weather.
Flea beetles overwinter as adults. They become active when temperatures reach 68 F. 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.
Flea Beetle Management:
Early Planting . . . The early planting and establishment of canola can prevent significant injury to young plants by flea beetles migrating to fields after the first true leaves are fully expanded.
Seed Treatment . . . Seed treatments are available and should be strongly considered for use in areas with substantial canola acreage.
Foliar Treatment . . . Fields should be checked daily for the presence of flea beetles while canola plants are at risk. The treatment threshold is when injury is approaching 25% and beetles are present. Foliar treatments must be made quickly. The weakness of foliar control strategies is the inability to cover large numbers of acres quickly when feeding pressure is high, and residual protection by the insecticides is short, allowing for re-infestation to occur.
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