It is that time of year when most need to start thinking about horn and stable fly control strategies. There are no magic bullets for controlling either of these flies, but there are strategies that can be used to reduce their impact.
First, it is important to distinguish between the two and understand their life cycle (eggs, larvae, pupae, adults) and reproduction. One of the easiest ways to help identify which of these species is causing a problem is knowing what parts of the animal they tend to attack. Horn flies are primarily found on the back and shoulders. When it is windy or hot, they will move to the belly. Also, horn flies always stay on the animal except when they fly off to lay eggs in fresh manure patties.
Stable flies, on the other hand, primarily attack the legs and are only found on the animal when they take a blood meal. Another indicator of stable flies is seeing cattle bunched up in a circle in the pasture. The flies bite the legs of the cattle on the edge, so those animals move to the middle of the group trying to get relief.
Control of horn flies is best accomplished with the use of both topical and oral insecticides. Topical insecticides can be applied with eartags, pour-ons, sprays, dust bags, rubs or gel cap applicators to kill adult flies. If using eartags, it is often beneficial to also apply a pour-on or spray when the fly tags are applied. Oral insecticides can be included in loose minerals, tubs or other self-fed products. Insect growth regulators (IGRs) like methoprene and diflubenzuron work by inhibiting the molting process during the larvae or pupae stages. When using IGRs, it is important that cattle consume the targeted dose daily or at least every other day. If using a loose mineral with methoprene, check the concentration; for cattle weighing over 1,000 pounds, the 0.014% concentration is needed.
Treatment strategies for stable flies normally involve practices to reduce breeding sites or applying residual wall sprays to barns and other structures. Stable flies like to lay eggs in decomposing vegetation like old feeding sites. To reduce problems, spread out any wasted hay so it can dry out or treat those sites with diflubenzuron or another appropriate insecticide. If stable flies are really bad, spraying the animals – especially their lower legs – is justified to provide some relief.
