High Blister Beetle Numbers Reported in Texas

High Blister Beetle Numbers Reported in Texas

Blister beetles come in a variety of colors and patterns. Contact your local extension agent or veterinarian to find out what beetles, colors, and patterns to look for in your area.

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Texas horse owners might want to take a second look at the hay their horses consume: County Extension agents from Texas AgriLife Extension Service are reporting higher than usual numbers of blister beetles, which are toxic to horses, in many areas of Texas this summer.

Wayne Becker, MS, PhD, extension agent in Cooke County, located in North Texas, speculates that high populations of both weeds and grasshoppers might have contributed to the surge in blister beetles. Blister beetle larvae feed on grasshopper eggs, while adult blister beetles are pollen feeders. Adult beetles are attracted to flowering weeds and plants such as pigweed, clover, goldenrod, peanuts, soybeans, thistle, and--of most concern to horse owners--alfalfa cut in late stages of bloom.

Blister beetles travel in swarms, causing a large number of beetles to populate a small area of a field at a given time. Adult beetles range in size from one-half to 1 ¼ inches in length and come in a variety of colors and patterns, including striped or spotted. Blister beetles differ from other kinds of beetles because of the thin segment between their head and thorax. Local extension agents, university entomologists, and veterinarians can help horse owners identify blister beetles.

Blister beetles produce cantharidin, a toxic agent which can cause blistering when it comes into contact with tissue, including horse and human skin. Blister beetles can also be toxic when ingested, which is often horse owners' main concern. Depending on the type and number of beetles ingested, blister beetle poisoning can cause severe illness and/or death. Clinical signs of poisoning in horses include blistering of the mouth and tongue, reduced feed intake, frequent drinking, splashing of water, colic, diarrhea, bloody stool, frequent urination, or bloody urine.

If you suspect blister beetle poisoning, contact a veterinarian immediately. Veterinarians will generally analyze a blood sample for low blood calcium and magnesium levels to differentiate from other causes of acute colic before beginning treatment.

Becker said the best measures horse owners can take to protect their animals is to control weeds by mowing fields and maintaining fencelines or use herbicides judiciously to reduce the flowering weeds that attract the beetles.

Additionally, extension agents and veterinarians advise horse owners to inspect alfalfa hay closely for dead or dried blister beetles, as even these can cause blistering or poisoning if ingested.

Horse owners seeking additional information about blister beetles in their geographic area should contact their veterinarian or local agricultural extension agent.

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About the Author

Jon Padgham

Jon Padgham is a freelance writer and works as an equine nutritionist for D&L Farm and Home in Aubrey, Texas. He obtained his master’s degree in horse nutrition from Kansas State University in 2001.

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