Aphid-resistant alfalfas help avoid outbreaks associated with chemical control of alfalfa weevil. Consider chemical control if there are more than 10 aphids per stem two weeks before cutting. For more information, see 5.531, Aphids in Alfalfa . Blister Beetles Adult blister beetles are strongly attracted to alfalfa and other blooming hosts. Damage is not important, but the presence of blister beetles, especially the large, striped swarming types, is a concern for producers who sell hay to horse owners.
Blister beetles produce cantharidin, a defense chemical toxic to livestock, particularly horses.
It is the least likely to have blister beetles. Avoid later cuttings, especially from fields near rangeland. Blister beetles are attracted to blooms. Use harvest equipment and practices that give beetles the best chance for survival. Beetles are very active and survivors will quickly leave the field, taking the cantharidin with them.