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New Mexico State University

New Mexico State University

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Early Detection of Blister Beetles Can Prevent Livestock Poisoning

LAS CRUCES - Livestock owners and hay producers should take precautions following the deaths of several horses from blister beetle poisoning in southern New Mexico, a New Mexico State University specialist said.


Carol Sutherland, entomologist with NMSU's Cooperative Extension Service, said blister beetle precautions should begin with inspecting alfalfa fields and hay for traces of the toxic beetle before harvest.

Blister beetles have cylindrical bodies about a half-inch long. Some of the most common species are blue-gray in color with small black spots on the wing covers. They also have black legs and antennae.

"When the beetles are active, they feed on the flowers and buds of plants. A very sharp grower should be out there immediately prior to harvesting any of his hay and fields looking for evidence of these beetles," said Sutherland. "If they find blister beetles or suspect that they are there, they can take a sample of them to their county agent for identification or look in the field"guide. If it is confirmed that they are blister beetles, appropriate insecticides can be used."

Sutherland said the insecticides for treating blister beetle infestation have a short residual period, and the alfalfa can be harvested on schedule.

If infested alfalfa is left untreated, blister beetles can be crushed during the harvesting process, releasing cantharidin, the blistering agent in the beetles' blood, into the alfalfa, Sutherland said. Cantharidin creates blisters in the gastrointestinal tract of animals, which can be fatal. She said livestock poisoned by the beetles often stick out their tongues, bury their faces in water or roll on the ground in agitation.

Sutherland added that hay buyers should be aware of the beetles to protect the health of their livestock.

"Alfalfa buyers will probably want to check with the grower before purchasing hay to find out what kind of management tools were used to ensure that the crop is free of these pests," Sutherland said. "Ask some questions because you're the consumer and you want your animal to be well fed as well as safe."

Harvested alfalfa infested with blister beetles should be burned and should not to be fed to other animals. County Extension offices statewide can provide information on insecticide treatments as well as a publication about blister beetles in alfalfa.