Colorado State University measured the cantharidin levels in several blister beetle species and estimated their relative risk to horses of different body weights. Based on average cantharidin content, and assuming the presence of equal numbers of male and female beetles, the lethal dose of three species is shown in Table 2. Clearly, different blister beetles species pose different risks to horses. Take these differences into account in management decisions. See 5.524, Blister Beetle in Forage Crops .
Cultural practices involve timing of cutting and modification of harvest equipment.
Because blister beetles are attracted to flowers, cut the crop before bloom to reduce their presence in hay. It also is important to control flowering weeds and choose harvest equipment that gives the beetles the best chance of survival. Research at Kansas State University has shown that self-propelled swathers, without conditioning rollers but with windrowing attachments, are safer than mower conditioners and sicklebar mowers. Even with the conditionerless swather, avoid hay from the ends of the fields where the machine is turned around and beetles may be crushed by the tires. Chemical control treats the crop just prior to harvest to eliminate beetle activity during harvest.