I’ve got blister beetles (see attached photos) on several plants around my barn and I’m worried for my horses. I heard they can get sick from ingesting this insect so I want to spray something that won’t hurt them. These bugs are pretty heavily infested on several plants around the house and yard too and they’re nasty. My fly spray is a little too strong I’m thinking so I was hoping you had something organic that won’t hurt the horses. Thnks.
Blister beetles are unique in that they can cause all kinds of reactions on people and pets. They readily feed on plants and insects and their body contains cantharadin, a known toxin, which is the real culprit. When handled, the beetles will release cantharadin which can cause nasty blisters to form on the skin. The exact reaction can range in look from poison sumac to a real “blister burn” one would get from something hot. Blister beetles readily infest vegetables and fruits and organic gardeners commonly come in direct contact with them while unknowingly removing them by hand from infested plants. Be careful not to handle or touch them; reactions vary from person to person.
Horses seem to be extra vulnerable to this toxin so I understand your concern. Horse feed laced with even trace amounts of cantharadin can cause illness and even death. Be sure the infestation doesn’t spread to feed bins or grazing locations. Blister beetles will many times leave their excretion trails unknowingly over foodstuff so contamination can be discreet and subtle so the rule is to be wary where they have been seen and known to be active.
Treatments can be done with several products some of which are certified organic. In the garden, a good choice is the MULTI PURPOSE INSECT KILLER. It’s strong enough to handle any garden pest and food crops can be harvested in one day following the treatment. People and horses can eat sprayed food crops safely so if you need to treat anything you believe may be used for food, this would be good choice. HOUSEPLANT INSECT KILLER is an aerosol option that might be good to keep around in case you need to do a small “spot treatment” in between regular spraying. It’s ready to spray, safe for use on edible plants and again, certified organic.
Out in the yard, a good option for large areas would be the CYONARA RTS. Labeled for used on plants and gardens, Cyonara uses an active which is strong enough to control blister beetles but safe enough to be used on food crops. It’s not organic so it’s definitely a “stronger” option but it can be used safely if the area being treated won’t be used for food immediately. The big difference with Cyonara compared to the organic options is that the days to harvest much longer. Allow for at least 7 and maybe even 14 days depending on the strength and amount being used.