13 Facts About Fly Control For Horses and Cattle  

Flies can be more than an annoyance – they can even be dangerous, whether impacting a ride with your horse in a single, painful bite, or transmitting diseases to horses and cattle.  

“Flies are pesky, they're hard to control. And a lot of times, we can't really control them adequately with only one modality. We need to use a variety of options for optimal control,” says Tony Hawkins, DVM, Valley Vet Supply Technical Service Veterinarian. “The good news is that we have many options available to control these pesky little critters.”  

Read on, as Dr. Hawkins shares 13 facts about controlling flies.  

1.    Flies don’t stop at the fence line. “If neighboring properties are not doing a good job of keeping flies under control, even a couple of miles down the road, flies can soon make their way to the next farm.” 

2.    Many fly control methods are available. “We have fly sprays and feed-through insecticides that inhibit growth of immature fly stages, as well as fly traps, pour-on insecticides and for cattle, there’s also insecticide tags, dust and cattle rubs.” 

3.    For the best fly control, multiple methods are needed. “We're not going to control the flies adequately with only one modality. Attacking these flies from multiple directions will give us our best protection. That's going to be our best bet.” 

4.    Many fly control options are cross-species; check labels. “Some products may also be formulated for smaller animals, like goats, sheep, and some can even be used on dogs. Be sure to check the labels and adhere to the manufacturers’ recommendations.” 

5.    For cattle, flies are less annoying, but still risky. “Because cattle have a much thicker hide, flies don’t bother them quite as much. However, cattle are still at risk for fly-transmitted diseases, like pinkeye and anaplasmosis.”  

6.    Painful and annoying, flies also impact horse health. “Flies contribute to significant equine diseases and conditions, including pigeon fever, strangles, influenza, Salmonella, eye worms and summer sores, which are chronic, fleshy and non-healing wounds that can require months off from riding and training as the horse heals. Horses are also more sensitive to a fly’s painful bite.” 

7.    Fly attractants attract flies. “I see a lot of people put fly traps inside of their barns, which is counterproductive in the long-term. Just as the name suggests, having them in the barn will draw flies indoors. Be sure to place them around the exterior perimeter of paddocks and pens.” 

8.    Stable flies are tricky to control. “Persistent stable flies can best be controlled using sticky fly trap products that feature a series of colors in a multi-dimensional pattern. This design is an insect attractant, and they work well.”  

9.    There are different insecticide options for cattle. “There are concentrated pour-ons, where we pour a small volume down the top line. Pour on fly control for cattle is absorbed and distributed across the whole surface of the animal. They're usually formulated to be longer lasting. There are also concentrates that we can mix and spray onto horses and cattle (a higher-volume administration). For horses, who are often easier to bring up than a herd of cattle, either option works great. But for cattle, I recommend producers consider their preferences – if they're applying insecticide out at pasture, a pour-on down the top line is likely going to be more challenging, so misting from a distance could work better. But if you've got cattle in an alleyway, then those pour-ons are a good choice.”  

10.    Fly sprays can be long-lasting. “Many factors determine how long a horse fly spray lasts – one, being the specific formulation from the company, another being the carrier. Typically, oil-based products last longer than water-based, providing a longer-term control solution. This is because they are not lost to evaporation, nor wash off as easily with a heavy rain or dew, when compared with a water-based fly spray (however, there are longer-lasting, water-based sprays available, too). The most common ingredients are going to be permethrins. Other ingredients are also commonly combined with permethrins to help those fly sprays work better. Typically, as a rule, the higher the percentage of ingredient, the more effective it's going to be.” 

11.    Expect brief delay, but effectiveness, when using Insect Growth Regulators (IGR). “When consumed by the animal, IGR ingredients pass through the animal into the feces, and as the flies lay their eggs and larvae in those feces, the same ingredients inhibit development of immature fly stages, significantly decreasing fly numbers. Because you are attacking from the larval fly stages, you will continue to temporarily see adult flies. It takes a generation or two (eliminating larvae), then you will really see a difference.”  

12.    Good management is key, in addition to effective fly control products. “The importance of environmental management to minimize fly breeding areas cannot be overstated, especially for confinement operations and horse stables. In the pasture setting, encourage water drainage and minimize decaying plant matter with cutting or burning. In confinement areas like pens, stalls or paddocks, remove manure, damp and soiled hay, uneaten grain, and any other source of decaying organic matter weekly at a minimum, and scatter to dry. Proper cleaning and addressing damp areas will reduce fly breeding sites, disrupting the fly life cycle, and will have a significant impact on fly numbers.”  

13.    Fly control requires a multi-faceted approach, but it’s worth it. “Like I mentioned at the very beginning, we're not going to adequately control flies with only one modality. Sometimes, it can be difficult to tell if your control efforts are having a positive impact. But, I can assure you that they are.”