Mix It Up

There is no simple, one-trick fix when it comes to fly control. In fact, it’s better to think in terms of fly management and IPM rather than control. IPM, or integrated pest management, is key because it allows producers to manage around resistance. It’s not as simple as rotating products, because the same chemical class is used across many types of control methods and product names. It can get confusing fast.

John Cothren, a livestock and field crops specialist with North Carolina State University Extension, wants producers to know: “You will never have 100% fly control, but you can manage them.”

Cothren says in his area, most producers use a combination of fly tags and pour-ons. He stresses the importance of removing those tags at season’s end.

“We are also beginning to see more use of the feedthroughs in minerals,” he adds. “Producers I work with are telling me they are seeing positive effects from those. I think the key there is that you have to start feeding them before fly season and extend it past fly season. If you wait till you have a problem, they aren’t effective. Essentially, you are breaking the life cycle of the fly, so you really need to get ahead of it.”

When To Treat. In beef operations, the horn fly is the pest of most concern economically. The University of Florida reports cattle affected by horn flies can lose 0.3 to 0.5 pounds daily. In a 30-head herd, that adds up to more than $500 each month left unchecked.

Treatment for horn flies, aside from feedthroughs, should be based on economic thresholds established at 200 flies per animal. Rotate chemistries around pyrethroids, organophosphates and feedthroughs. Sometimes, that can become confusing. Different active ingredients aren’t the same as different chemical classes.

For example, the active ingredients permethrin, fenvalerate, resmethrin and flucythrinate are pyrethroids. And, the active ingredients in Rabon, Corathon and the ingredient coumaphos are organophosphates. Diflubenzuron is a larvicide used as an insect growth regulator (IGR) feed additive. So, don’t assume different brands equal different active ingredients. If it’s unclear, check with your county agent or herd veterinarian.

Sprays, Pour-Ons And Rubs. These products give a fast knockdown, but residual is limited. In the case of a pour-on, or drench, the product is poured along the spine. Control lasts about 28 days. Sprays may be more easily washed off. Check labels to see how often a product can be safely applied and note what insecticide class it is in.

Fly Tags. The ease of use for fly tags can make it tempting to not always follow through on the basics. So, while commonly used, they are sometimes left on cattle too long or put in at the wrong time for maximum effectiveness. Tags have a limited period of usefulness and should only be put in when economic thresholds have been reached. Remove fly tags when the season ends. Leaving fly tags in past the point of maximum effectiveness hastens the development of resistance in the fly population.

Feedthroughs And Boluses. IGRs, or larvicides, have been around for decades. They reduce the percentage of horn fly eggs that hatch in manure and are a good fit in herds in isolated areas, and away from other herds where IGR programs are not in place. Feed an IGR 30 days after the first frost in the fall and 30 days before the last frost in the spring.

Biologicals. Parasitic wasps, predaceous mites and beetles, and other biological agents are being used in many operations across the country now. Biologicals need to be applied multiple times throughout the season and are more commonly used around barns and homes. They treat the environment not the animal.

Maintenance. Manure management and good drainage go a long way in helping to limit the development of large populations of both house and stable flies.

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