Fly Control Principles - Chemical Methods
After maximum effort to suppress fly numbers by proper cultural and biological methods, insecticides are often needed to achieve the desired degree of fly control.
If fly suppression by cultural and biological methods is maximized, then the effectiveness of insecticide treatments will be enhanced, and the rate of development of fly resistance to the insecticide will be reduced.
The most effective insecticide use is as part of an integrated control program, in conjunction with cultural and biological methods.
Insecticides are either adulticides (baits, spray-on, paint-on), or larvicides (spraying breeding sites and using feed additives).
Baits consist of an insecticide mixed with a substance that is attractive to flies, such as sugar.
Fly sex pheromone is added to the formulation to increase the effectiveness of the bait.
Baits may be prepared by the user by mixing an insecticide with molasses, sugar, beer or other attractive substances. However, such mixtures may be hazardous for the user to prepare and their effectiveness may be erratic.
Commercial baits are usually formulated as granules which can be handled easily.
Placement of baits in pans or protected locations where flies are frequent will attract and kill many flies.
Adulticide baits can be used more effectively when placed in a fly trap.
Indiscriminant scattering of bait is wasteful and when it is scattered on manure, there is risk of killing many of the predators.
Traps can be made by cutting four holes in the upper part of plastic containers and placing bait inside (see monitoring section).
Surface sprays applied to the walls, posts, ceilings, etc., of buildings are designed to provide a long-lasting toxic surface where flies rest. It is therefore vital that the insecticide is applied to those surface areas where flies do actually rest for long periods.
Generally, flies rest on higher surfaces inside at night. Evidence of this will be seen in the form of spotting on the surfaces from vomit and feces left by the flies.
House flies resting on a ceiling. Notice spotting left by the flies and their preference for resting on pipes along the edges of cracks.
A coarse spray applied at about 40 psi is sufficient, and application should thoroughly wet the surfaces, although not to the point that runoff occurs.
Surface applications in small facilities can be done with a hand-pumped compressed air sprayer. In larger facilities, power equipment is needed. These may be powered by an electric motor, small gasoline engine, or by the power-takeoff of a tractor.
Paint-on is a very commonly used method of application among all livestock producers.
The main advantages for this method are that it is easy to apply, and that it can be used in all different kinds of areas where flies tend to congregate.
Another advantage of the painting method is that you can paint spots in areas where flies congregate, for example: warm and sunny wall areas, window frames, milk pipes, outside feeding troughs etc.
Paint-on products are normally mixed with lukewarm water until a brushable paint is obtained.
Where there is insufficient surface available for painting or where some light discolouration would be unacceptable, it is possible to paint strips of cardboard, polyethylene, or light boards and hang them from the ceiling.
Paint-on products provide long term residual control of flies.
Another method of adult fly control is with the use of mists. Misting quickly reduces the number of flies in and around a facility.
However, misting gives only temporary control as only the adult flies exposed at the time of application are killed. There is no residual, long-term effect.
Misting may be done with portable or tractor-mounted equipment. For small facilities, electric or gasoline-powered equipment may be hand-carried or mounted on a backpack. For larger facilities there are various larger units available, powered by gasoline engines and mounted on a tractor or truck.
Misting with a fly adulticide is also likely to kill parasites that are active in the area at the time of treatment.
Infrequent misting as an emergency measure during rare occasions of high numbers of flies has only a minor impact on the overall parasite population.
However, frequent regular misting is incompatible with maintaining a high parasite population in a facility.
The Major Pest
The common house fly, Musca domestica, is the major pest species associated with confined livestock production.
Integrated fly control means using a two-pronged attack on flies: larvicides to prevent fly larvae developing into adults, and adulticides to kill adult flies.