By Patrick Wagner
The frequent rain events experienced across much of South Dakota this summer has helped boost forage production. That means alfalfa growers are harvesting second and later cuttings, even in areas that often get only one cutting per season. Although this is great for production, the possibility of encountering blister beetles at harvest increases later in the summer. Adult blister beetles feed on leaves and blossoms and contain a toxic chemical called cantharidin. This chemical poses a health threat to livestock that consume alfalfa bales containing whole or partial blister beetle bodies. Due to increasing blister beetle activity, alfalfa fields should be monitored prior to harvest for the remainder of the growing season.
Identification
Blister beetles have one generation per year. Adults can be up to 1-inch long; have a soft, elongate body; and vary in color and size based on species. The most-common species that is found in early summer is the ashgray blister beetle. Other common species in South Dakota that show up later in the season include the black, immaculate, striped, margined, and spotted blister beetles. A unique characteristic of blister beetles is that their thorax (middle body segment) is narrower than both the head and abdomen.
Source : sdstate.edu