Farm flies, such as the common house fly and the blood-feeding stable fly, present a significant challenge in agricultural environments. These insects act as vectors, transmitting disease-causing organisms, including Salmonella and mastitis, to livestock and humans. The presence of these pests directly impacts animal welfare, causing stress that results in decreased weight gain and lower milk production in dairy herds. Controlling fly populations is an economic necessity, protecting animal productivity and preventing substantial financial losses. A comprehensive management plan must address every stage of the fly’s life cycle to achieve lasting reduction.
Eliminating Breeding Grounds
The most effective long-term strategy for fly control focuses on disrupting the reproductive cycle by eliminating breeding sites. Flies require moist organic matter to breed, making proper management of manure, bedding, and feed paramount. Since the house fly can complete its life cycle in as little as nine to fourteen days under warm, damp conditions, weekly sanitation is necessary to break the cycle.
Manure and bedding should be removed from animal housing frequently, ideally once or twice a week, to prevent the development of larvae into pupae. If immediate removal is not possible, reducing moisture content is highly effective, as dry conditions inhibit maggot survival. Spreading manure thinly in fields allows it to dry quickly under the sun and wind, killing fly eggs and larvae.
Composting is another useful tool, as the heat generated by a properly managed pile reduces the material’s viability as a breeding site. Beyond animal waste, attention must be paid to controlling spilled feed, silage seepage, and wet litter accumulation, as these materials also provide ideal nursery environments. Checking water troughs and repairing leaks to maintain dry flooring and bedding surfaces is important, since uncontrolled moisture contributes to fly outbreaks.
Immediate Removal with Traps and Barriers
While sanitation prevents future generations, existing adult fly populations require immediate, physical methods for removal and exclusion. Physical barriers are highly effective at preventing flies from entering structures like milking parlors and feed rooms. Installing fine-mesh screens on windows and doors blocks access, and high-velocity fans create air movement that disrupts flight patterns, making it difficult for flies to land or enter a building.
Trapping systems are useful for directly reducing the number of adult flies that have escaped sanitation efforts. Sticky traps and ribbons can be hung near windows and other high-activity areas to capture flies seeking light. Baited traps use a strong attractant to lure flies into a container from which they cannot escape, making them effective for monitoring and reducing large populations.
Light traps use ultraviolet light to attract flies into an electrified grid or sticky board, making them an option for indoor areas. Walk-through traps can be positioned where livestock naturally congregate, such as between a pasture and a water source, to passively capture adult flies as animals pass through. These physical methods provide non-chemical control and offer immediate relief from high fly density.
Utilizing Integrated Control Tools
Integrated management combines sanitation and physical controls with targeted biological and chemical interventions. Biological control involves introducing natural enemies to suppress fly populations at the larval and pupal stages. The most common biological agents are parasitic wasps, tiny insects that do not sting people or animals but instead lay their eggs inside fly pupae, killing the developing fly.
These fly parasites should be released early in the fly season and continued on a recurring basis every one to two weeks. The wasps should be scattered around the edges of undisturbed, moist breeding sites, such as compost edges and under feed bunks, so they can find the pupae they need to reproduce. Success depends on consistent, early application before fly numbers escalate.
Chemical controls should be used judiciously and strategically to prevent resistance from developing in the fly population. Larvicides, which contain insect growth regulators, are applied directly to known breeding material like manure to prevent the maggot from maturing into an adult fly. Adulticides are used to kill flying insects and can be applied as residual sprays on resting surfaces or as quick-knockdown space sprays. To protect the beneficial parasitic wasps, residual sprays should be limited to areas where the wasps are not released, and rotation of chemical classes is necessary to maintain effectiveness.