Question

My neighbor says it is a common practice to sort through hay before feeding it to horses in order to check for blister beetles (extremely toxic insects). Do we have anything like that in the Northwest?

Answer

Blister beetles contain a poison (cantharidin) that is extremely toxic to horses. Unfortunately, there is not a specific antidote for cantharidin poisoning. Ingestion of even a few beetles results in severe colic and, many times, in death. The death of horses from blister beetle ingestion has been reported from Florida to Arizona and as far north as Illinois. The states known to have the biggest problems with blister beetles are Texas and Oklahoma.

To date, blister beetle poisoning is not a problem for hay grown in the Treasure Valley region of Idaho, one reason hay for the 1996 Summer Olympic Games was purchased from Idaho hay growers. I agree with your neighbor, however, that regardless of your location or the incidence of blister beetle poisoning there a quick inspection of the hay you are providing to your horse is always a good idea.

There are many things that can be baled into hay that may not be good for your horses, including small, dead rodents that can potentially cause botulism, and aluminum cans that may cause digestive tissue damage.