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. 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.
The stable fly, Stomoxys calcitrans, is a serious pest that feeds on many livestock animals, especially on bovines and equines. Fly-feeding on grazing hosts has led to reproductive failure and reduction of meat and milk yields, with an estimated annual economic loss of up to two billion dollars for the cattle industry.
Furthermore, stable flies are also capable of transmitting a large variety of pathogens including helminths, protozoans, bacteria, and viruses, some of which are primary agents of mortality in horses and cattle.
Stable fly management involves the use of insecticides and cultural sanitation as primary control methods. The direct application of insecticides results in only marginal control. Cultural control including the removal and dispersal of substrates that could serve as potential breeding sites can be tedious and costly.
Plant derivatives or botanical-based insecticides and repellents have been used against arthropods for at least two millennia in ancient China, Egypt, and India.
Even in Europe and North America, the documented practice of using botanicals extends back more than 150 years, predating the discovery of the major classes of synthetic chemical insecticides. Recent studies have confirmed the repellency effectiveness of plant essential oils against Dipteran blood-sucking insects, particularly in mosquitoes.
Zhu, et al, reported that catnip essential oil acts as an extremely effective antifeedant/repellent against several filth fly species (including stable flies) in laboratory assays. They have further demonstrated that catnip oil is a relatively safe repellent with an extremely low toxicity in rabbits and rats.
The use of repellents could be an effective strategy for reducing the impact of stable flies on horses and other livestock. There is a great deal of interest in developing botanical-based repellent formulations that serve a valuable function in integrated management against stable flies.