Here’s a list of treatment options to consider as the cattle flies wars heat up:

Ear tags

Insecticide ear tags are one of the best devices for deterring cattle flies. If you use insecticide ear tags, Boxler suggests these management tips:

  • Apply the tags when horn fly numbers approach the economic injury level of 200 cattle flies per animal.
  • Tag all adult animals in the herd at the recommended label rate.
  • Rotate insecticide classes. Don’t use the same insecticide class year after year.
  • Remove the tags when they no longer provide effective control, or in the fall after first fros

    2. Waste management

Remove the places where flies breed, and you will start to notice a significant decrease in the number of flying foes circling your herd. “Buildup of organic matter is the biggest breeding grounds for flies,” says Mike Peacock, Southern States Cooperative ruminant nutritionist. With the average 1,250-pound beef cow generating 75 pounds of manure a day, this leaves many areas for flies to reproduce.

On average, the fly life cycle lasts anywhere from 10 to 21 days. To break the fly cycle, you need to remove fly-breeding material on a regular basis. Manure, wet grain, spilled silage, moist hay — focus on these areas first.

“You can eliminate a large portion of flies by simply cleaning the hay rings where cattle were fed all winter,” Peacock says.

To further eliminate breeding areas, start by removing manure from livestock pens as frequently as possible. Take the manure and spread it thinly on fields or other large outdoor areas to facilitate drying. Flies cannot develop in dry environments, therefore they cannot develop in dry manure. Drag your fields to more evenly distribute manure. The key is to dry out the manure.

Remember, it’s easier and more cost-effective to prevent fly breeding than to try and control adult flies already born. The quicker you can remove their habitat and breeding grounds, the better off you’ll be.

Dust bags

Dust bags can be a low-maintenance and effective way to combat flies. “This fly control technique requires fencing around a water tank or mineral feeder and suspending dust bags at the entrance-exit gate,” Boxler says. “Dust bags placed in a forced-use situation will usually reduce fly numbers by 80-90% throughout the season if properly maintained. Dust bags in a free-choice design (like a loafing area) will provide 25-50% less control than a forced-use dust bag design,” he says.

Back rubbers

Back rubbers are used much in the same way as a dust bag. A small amount of oil or insecticide gets on the animal as it rubs under the device. “When charging a back rubber, use a quality grade mineral oil or fuel oil (not motor oil) to mix with the insecticide to avoid irritation,” Boxler says. Back rubbers and oilers are most effective when used in a forced-use design, he adds.


Pour-ons are ready-to-use formulations poured along the backline of cattle. “As a rule, they provide several weeks of fly reduction, so they must be re-applied throughout the fly season,” Boxler says.


Animal sprays can be effective in controlling horn fly populations, Boxler says, but it’s important to get complete coverage of the animals. High pressure sprays may provide better coverage, but it’s necessary to gather and corral the cattle, which may make this application method unpractical.

Sprays can also be delivered using a mist blower or low pressure sprayer mounted on an ATV. With this method, you can drive to where the cattle are and apply the insecticide by driving around and amongst the cattle.

Oral larvicides

Oral larvicides, such as feed additives and boluses, are products that are incorporated into minerals or other feed products. The insecticide passes through the animal’s digestive tract into the manure, where it prevents fly larvae from developing into adults. “To be effective, cattle must consume a label-specified amount on a daily basis,” Boxler says.

Fly predators

Not all cattle flies are bad. Fly predators, nature’s own self-inflicted enemy, can be your ally in the fight against pest flies. These are tiny, non-stinging, non-biting wasps that feed on fly larvae and interrupt the breeding cycle of flies, destroying the next generation of flies before they hatch into disease-carrying adults, Peacock says.

Fly predators work by both laying eggs in the fly pupa (or cocoon) and feeding on fly larvae while it’s in the manure on your farm. The wasps “bug” the bugs but never disturb the cattle, pasture plants, or humans for that matter.

Although a natural method of controlling flies, fly predators aren’t typically found in large enough amounts to control the entire fly population on your farm. However, many companies sell fly predators and can ship them straight to your farm. Once they arrive, all you have to do is sprinkle the predators on manure piles at dusk. And watch them go to work.

As a rule of thumb, replenish your fly predator supply once a month from April to September. It’s important to use them during the entire fly season; otherwise the fly life cycle will only be broken for a few weeks.

Don’t get frustrated if you don’t see an immediate reduction in fly populations. Both face flies and horn flies can travel several miles in search of cattle. If you’re managing your fly population, but your neighbor isn’t. You may be getting “cattle flies without borders” as they travel in search of a meal. With an ongoing fly management program, however, both you and your cattle should rest a little easier.