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Blister Beetles in Field Crops (07/11/19)

Ash gray blister beetles, Epicauta fabricii, have been reported in canola, soybean and alfalfa fields in central, northwest and north central areas of ND.

Ash gray blister beetles, Epicauta fabricii, have been reported in canola, soybean and alfalfa fields in central, northwest and north central areas of ND. Adult blister beetles can be an occasional pest causing defoliation to the leaves and clipping flowers or pods. In canola, they are attracted to blooming canola fields for its nectar and pollen, but they also devour leaves, flowers and pods. Blister beetles are a major problem in alfalfa / hay fields or in bales, since they produce a toxic chemical (cantharidin), which is toxic to livestock, especially horses. Larvae of Epicauta species actively prey on grasshopper egg pods.

Blister beetles are mobile and gregarious, and often congregate in certain spots in a field (edges). In some instances, blister beetles only feed for a short period and then migrate to other fields. Alfalfa and forage are preferred hosts of blister beetles and they often move into canola or other field crops after the alfalfa is cut. If treatment is necessary to avoid yield loss, producers can ‘spot treat’ with a foliar insecticide. Please avoid spraying flowering crops for bee/pollinator safety.

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Janet J. Knodel

Extension Entomologist

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