Horn flies, stable flies, house flies and face flies can all be a challenge for cattle and cattle producers. The severity of the problem and the species present will vary, depending on several factors including weather conditions, time of year and geographic location. It is important to determine which species are causing problems because treatment strategies will vary for each.
Horn flies are the smallest in size and are generally found on the shoulders and backs of cattle, but will move to the belly on bright sunny days or during windy conditions. Unlike other species, horn flies remain on cattle except when they fly off to lay eggs in fresh manure patties. Another tool to help identify horn flies is that they will almost always be facing toward the ground.
Stable flies are found on the lower legs and are only on cattle when they are taking a blood meal. Both house and face flies are generally found around the head, where they feed on secretions around the eyes, nose and mouth. Face flies are less common in Southern states.
Horn flies are generally responsible for the greatest economic losses. Unfortunately, no control strategies for horn flies are perfect. The best control of horn flies generally results from the use of both a topical insecticide as well as feed-through insecticide. Feed-through insecticides include insect growth regulators (IGR) and organophosphates.
Methoprene and diflubenzuron are IGRs that prevent the development of horn fly larvae and pupae in manure patties. These IGRs are commonly delivered to cattle through self-fed products like loose mineral or mineral tubs. They can also be added to other feed products. To be most effective, cattle need to consume a minimum dose of these products on a regular basis, preferably daily or every other day. If the minimum dose is not consumed regularly, control will be reduced, but these products can still provide some benefit. In these situations, the decision must be made if the cost of the product is worth the partial benefit.
For best results, it is also important to make sure the concentration of the IGR and the targeted intake of the product matches the size of cattle being fed. For example, loose minerals are often formulated for 3 to 4 ounces of intake and may contain 0.01% or 0.014% methoprene. The higher concentration is needed for most cows to achieve a target dose.
