Catnip, the plant that attracts domestic cats like an irresistible force, has proven 99 percent effective in repelling the blood-sucking flies that attack horses and cows, causing $2 billion in annual loses to the cattle industry. That’s the word from a report published in ACS’ biweekly Journal of Agricultural and Food Chemistry.

Junwei Zhu and colleagues note that stable flies not only inflict painful bites, but also transmit multiple diseases. Cattle harried by these bloodsuckers may produce less meat and milk, have trouble reproducing, and develop diseases that can be fatal. All traditional methods for controlling stable flies — even heavy applications of powerful insecticides — have proven less than effective. The scientists thus turned to catnip oil, already known to repel more than a dozen families of insects, including house flies, mosquitoes and cockroaches.

They made pellets of catnip oil, soy, and paraffin wax, and spread them in a cattle feedlot. Within minutes, the pellets shooed the flies away, with the repellent action lasting for about three hours. Pellets without catnip oil, in contrast, had no effect. The scientists now are working on making the repellent action last longer, which they say is the key to putting catnip to use in protecting livestock both in feedlots and pastures.