Blister beetles are long cylindrical beetles that may be black, gray, yellow and brown striped or black with gray margins on the wing covers.
Three different types on blister beetles can be found in Kentucky but they rarely cause problems in alfalfa. Blister beetle larvae develop in the soil where they feed on grasshopper eggpods. Adults emerge in mid-July and feed on most hay flowering crop or weed. They feed in groups so "clusters" of them may occasionally be found if weeds or alfalfa has bloomed. There is one generation each year.
If small numbers are found, they can be kept out of the harvested hay by avoiding the use of a hay "crimper" when cutting the crop. If the beetles are not crushed during the harvesting process, they will leave the field before the hay is baled. Blister Beetles can be controlled using applications of carbaryl sprays such as Sevin 4F, Sevin 80S, Sevin XLR, or Warrior 1 CS. See the label for the rate to use. Do not apply Sevin or Warrior 1 CS within 7 days of harvest. To protect honey bees, do not make insecticide applications when the crop or weeds are blooming.