House flies, Musca domestica, are nonbiting insects that breed in animal droppings, manure piles, decaying silage, spilled feed, bedding, and other moist, warm decaying organic matter. Adult house flies are about 1/4 inch long and mostly dull gray in color, with four black stripes on the thorax. Their mouthparts are spongelike and are used for ingesting liquid foods. Each female can produce up to six batches of 75 to 200 eggs at 3- to 4-day intervals, laying the eggs in cracks and crevices under the surface of the breeding material. Larvae (maggots) hatch from the eggs in 12 to 24 hours. They are white and cylindrical, tapering at the front. Maggots complete their development in 4 to 7 days, passing through three growth stages, or instars, as they grow larger. Mature larvae form a dark reddish-brown hardened case, called a puparium, from the larval skin, and then pupate. The pupal stage usually lasts 3 to 4 days, after which an adult fly emerges to complete the cycle. Generations overlap; all stages are present at the same time. The life cycle is temperature-dependent, requiring 10 days at 85°F, 21 days at 70°F, and 45 days at 60°F.
Adult flies live an average of 3 to 4 weeks, but they can live twice as long. They are most active during the day at temperatures of 80°F to 90°F and become inactive at night and at temperatures below 45°F. Resting adults can be seen inside facilities on ceilings, walls, posts, and other surfaces. Outside, they can be seen beneath roof overhangs and on walls, fences, and vegetation. Preferred resting places can be detected by the accumulation of "fly specks," light-colored spots formed from regurgitated fluid and darker fecal spots. Even though flies appear to have no direct effect on production, they are a concern to producers because they can cause public health and nuisance problems resulting in poor community relations and legal action. House fly dispersal range is 1/2 to 2 miles, but distances as great as 10 to 20 miles have been reported. Generally, flies disperse either across or into the wind, with nuisance densities highest closest to the source.
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.