The stable fly, Stomoxys calcitrans, is about the size of a house fly but is dark gray. Its abdomen has seven rounded dark spots on the upper surface. The adult’s piercing mouthparts protrude spearlike from under the head. Stable flies breed in wet straw and manure, spilled feeds, silage, grass clippings, and in various other types of decaying vegetation. Each female fly lives about 20 to 30 days and lays 200 to 400 eggs during her lifetime. Under optimum conditions, an egg develops to an adult in about 3 weeks.
Horses are most irritated by these pests during the warm summer months. Both male and female stable flies feed on blood several times each day, taking one or two drops at each meal. Stomping of feet is a good indication that stable flies are present, since they normally attack legs and bellies.
A variety of cultural control practices can be used effectively to manage house flies and stable flies.
The fly life cycle requires that immature flies (eggs, larvae, pupae) live in manure, moist hay, spilled silage, wet grain, etc., for 10 to 21 days. Removing and spreading fly breeding materials weekly helps to break the cycle. Waste management is therefore the first line of defense in developing an effective fly management program. It is much easier and less costly to prevent a heavy fly buildup than to attempt to control large fly populations once they have become established.
The main fly sources in confinement areas are animal pens. The pack of manure and bedding under horses should be cleaned out at least once a week. In barns, the next most important fly breeding areas are the stalls, which should be properly drained and designed to encourage complete manure removal. Wet feed remaining in the ends of troughs breeds flies and should be cleaned out at least weekly.
Spreading manure and bedding as thinly as possible will help ensure that it dries out quickly. Eliminate drainage problems that allow manure to mix with mud and accumulate along fence lines in exercise yards. Seal gaps under feed bunks where moist feed can accumulate.
Use sticky tapes/ribbons
Sticky ribbons, especially the giant ones, are very effective for managing small to moderate fly populations. Their only disadvantage is that they need to be changed every 1 to 2 weeks because they dry out, get coated with dust, or get "saturated" with flies.
Insecticides can play an important role in integrated fly management programs. Chemical control options include space sprays, baits, larvicides, residual premise sprays, and whole-animal sprays. Space sprays, mist foggers, and baits are compatible with naturally occurring fly biological control organisms such as predators and parasitoids.
Space sprays and mist foggers provide a quick knockdown of adult flies in an enclosed air space. Because space sprays have very little residual activity, resistance to these insecticides is still relatively low.
Fly baits containing an insecticide are also very useful for managing low to moderate fly populations. Commercial traps are available, but a baited-jug trap can be made easily from a gallon plastic milk jug. Cut four access holes, each 2 to 2.5 inches in diameter, equidistant around the upper part of the jug, and attach a wire to the screwtop for hanging. Place about 1 oz of a commercial fly bait on the inside bottom of the jug; a bait containing the fly pheromone muscalure (Muscamone, Z-9-tricosene) is most effective. Hang the traps above animals, since scattering bait will destroy beneficial insects. Ensure that baits will not accidentally be eaten by animals or mixed into their feed.
Avoid directly applying insecticides to manure and bedding because of harmful effects on beneficial insects. The only exception is occasional spot treatment of breeding sites that are heavily infested with fly larvae that cannot be cleaned out.
Treatment of building surfaces with residual sprays has been one of the most popular fly control strategies over the years. As a result, high levels of resistance to these insecticides are now very common. These materials should be used sparingly and only as a last resort to control fly outbreaks that cannot be managed using the previously mentioned tactics.
Whole-animal sprays can be made directly on the animals to manage stable fly problems. Although this approach can provide needed relief from biting fly pressure, the control is rather short-lived.