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Prepare for Horn Flies This Spring Horn flies are a yearly parasite concern on cattle operations. Flies can cause calves, stockers and feeder cattle to lose weight, but they can be easily controlled if the cattle are treated at the right time and with the right product, according to James Hawkins, D.V.M., Ph.D., manager, veterinary professional services, Merial. "Compared to other external parasites, horn flies are easy to control because they spend all their time on the host animal," he says. "If you treat the herd several times throughout the horn fly season, you can keep fly numbers below economically damaging levels." Hawkins warns producers that they can not get absolute control of horn flies. Realistic goals for producers are to lower fly numbers below the economic threshold (one to two hundred flies per side of the animal) and kill flies resistant to commonly-used fly control products. Horn fly treatment options include dusting powders, sprays, ear tags, backrubbers and pour-ons, many of which use pyrethroids or organophosphates as the active ingredient. Both of these compounds are highly effective against flies, but also have documented fly resistance. To prevent resistance, producers should rotate products that have different modes of action. Pyrethroid ear tags should be removed when they are no longer killing flies. "Pyrethroid-resistent flies are common in the Southern United States, as well as on most large cattle farms, depending on their treatment history," Hawkins says. "Not pulling tags is a big problem because as the level of pyrethrin wears off, flies develop resistance." Producers should consult their local Extension agent or animal health supplier to implement a horn fly control program best suited for their operation. |
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