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Blister Beetles in Soybeans (06/28/18)

Several calls have come into the office on blister beetles feeding on soybeans causing defoliation on leaves from Crosby in Divide County, and Upham in Bottineau County.

Blister Beetles in Soybeans

Several calls have come into the office on blister beetles feeding on soybeans causing defoliation on leaves from Crosby in Divide County, and Upham in Bottineau County. Blister beetles are uncommon pests of field crops, but are known to feed on alfalfa, sweet clover, canola, potatoes, dry beans, soybeans, sugar beets and weeds. They are ravenous feeders devouring leaves, stems, flowers, and pods. Use defoliation thresholds in crops; for example, the action threshold for vegetative soybeans is 35% defoliation.

Blister beetles are mobile and gregarious, and often congregate in certain spots in a field due to an aggregation pheromone (insect attractant). In some instances, blister beetles feed for a short time and then move to other areas of field or move out of the field. Alfalfa is a preferred host of blister beetles and they often move into other fields after alfalfa is cut for hay. Blister beetles produce a toxin called cantharidin and any livestock, especially horses, which ingest blister beetles while eating forages can become sick or even die.

There are several species of blister beetle in ND, including Lytta nuttalli, a large purplish green beetle; Epicauta fabricii or the ash-gray blister beetle; and Epicauta ferruginea, a smaller rusty-colored, pubescent beetle.

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Janet J. Knodel

Extension Entomologist

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