Check Horses’ Alfalfa Hay for Blister Beetles

Blister beetles in alfalfa can be deadly. Here’s what to watch for and how to keep your horses healthy.
Share
Favorite
Close

No account yet? Register

ADVERTISEMENT

Blister beetle
A blister beetle’s diet is mainly composed of pollen, blossoms, and leaves of flowering plants, making alfalfa the perfect meal for them. | Photo: Photo: Clemson University/USDA Cooperative Extension Slide Series/Wikimedia Commons

It might be hard to imagine that an essential part of the horse’s diet could contain potentially deadly hidden toxins. But it’s a hard truth that horse owners must be aware of: Alfalfa hay can harbor blister beetles (Epicauta spp), which can contain a harmful toxic substance called cantharidin.

A member of the Meloidae family, blister beetles live throughout the United States and Canada. Their average body length is about 0.3 to 1.3 inches. A blister beetle’s diet is mainly composed of pollen, blossoms, and leaves of flowering plants, making alfalfa the perfect meal for them. Most alfalfa infestation occurs during late summer and early fall, when the adult blister beetle population also peaks.

Male blister beetles produce a natural defense toxin called cantharidin. This irritant can cause blisters on skin (of both horses and humans) within a few hours of contact, hence the insect’s name. When ingested, cantharidin is lethal in horses with as little as half a milligram per kilogram of body weight, equivalent to consumption of around 125 beetles for an average-sized horse. And it’s not just the live insects that are harmful: The toxin is still effective long after the beetle dies

Create a free account with TheHorse.com to view this content.

TheHorse.com is home to thousands of free articles about horse health care. In order to access some of our exclusive free content, you must be signed into TheHorse.com.

Start your free account today!

Already have an account?
and continue reading.

Share

Written by:

Kristen M. Janicki, a lifelong horsewoman, was born and raised in the suburbs of Chicago. She received her Bachelor of Science degree in Animal Sciences from the University of Illinois at Urbana-Champaign and later attended graduate school at the University of Kentucky, studying under Dr. Laurie Lawrence in the area of Equine Nutrition. Kristen has been a performance horse nutritionist for an industry feed manufacturer for more than a decade. Her job entails evaluating and improving the performance of the sport horse through proper nutrition.

Related Articles

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from TheHorse.com

Sponsored Content

Weekly Poll

sponsored by:

Where do you primarily feed your horse?
300 votes · 300 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form

Create a free account with TheHorse.com!