Watch Alfalfa for Blister Beetles
Blister beetles are an occasional late-summer problem in Iowa alfalfa fields. The beetles feed on alfalfa and soybean foliage, but leaf loss is not of economic importance. The bigger concern with blister beetles is their toxicity to livestock when accidentally consumed in feed. The beetles produce cantharidin, an irritant that causes painful blistering when the insects are handled. The cantharidin remains in the beetle’s body even after it dies and can cause health issues in livestock when dead blister beetles are consumed with hay.