With Summer Comes Blister Beetles

The presence of blister beetles is always a cause for concern but even more so as a horse owner. Blister beetles contain a chemical, cantharidin, that when consumed by horses and other livestock, can cause illness and sometimes death.

Blister beetles are known to feed on flowers and foliage of a wide variety of crops including alfalfa, ornamental plants, potatoes, soybeans, garden vegetables and other plants. Immature stages feed on grasshopper eggs, live in solitary bee hives or are predaceous, depending on species. 

Adults can be found on flowers or infested crops. Blister beetles in alfalfa fields at harvest can be killed by the harvest machinery and incorporated into the baled hay. Cantharidin is a very stable compound and remains toxic even in the dead and dried blister beetles that may contaminate alfalfa hay. Since blister beetles often occur in large groups, or swarms, within a field, dead beetles can be concentrated in a small portion of the bales.

 

Care should be taken to not handle them. Never handle blister beetles preserved in alcohol because the cantharadin dissolves in alcohol and will cause blisters on the skin.

Cantharidin causes irritation of the lining of the digestive and urinary system in horses. The number of beetles that result in illness is variable and depends on the sex and species of blister beetle and on the age, weight, bred and general health of the horse. The estimated number of ingested beetles that would be lethal to a horse ranges from 50-545.

For more information visit:

https://texasinsects.tamu.edu/hemiptera/blister-beetle/#:~:text=The%20wing%20%28elytra%29%20covers%20are%20usually%20soft%20and,mostly%20orangish-yellow%20with%20three%20black%20stripes%20on%20each

http://entnemdept.ufl.edu/creatures/urban/medical/blister_beetles.htm