How to Manage Fly Pests in the Cattle Herd

Fly Pests

Have flies been bothering your livestock? Fly management can help support cattle health, welfare, and productivity.

Fly Identification

To put fly management steps in place, identifying the type of fly or flies affecting your livestock is an important first step. 

The environment in which cattle are managed can help indicate which fly pests are most likely to be present. Two common settings are barns and pasture systems.

In barns, two of the most common fly pests are house flies and sometimes stable flies. House flies (Figure 1) breed in manure, animal droppings, decaying silage, spilled feed, bedding, and other moist organic matter. Under warm, favorable conditions, development from egg to adult can occur in about a week to 10 days. Adult females may live for several weeks and can lay multiple batches of eggs during their lifetime. House flies do not bite, but they can mechanically transport a wide range of microorganisms, including pathogens associated with livestock disease. When populations are high, house flies may irritate cattle and can also create nuisance and sanitation concerns around animal facilities.

Stable flies (Figure 2) develop in wet straw, manure mixed with bedding, spilled feed, decaying silage, grass clippings, and other moist, decomposing vegetation. Development time varies with temperature and substrate quality and may take about 2 to 4 weeks under favorable conditions. Male and female stable flies take blood meals, often feeding several times per day. Their painful bites commonly occur on the legs and lower body, and cattle may respond by stomping their feet, switching tails, bunching, or other defensive behaviors. High stable fly pressure can reduce weight gain, feed efficiency, and productivity. Stable flies are important biting pests during warmer months and may affect both confined and pastured cattle, but they do not prefer larger barns. Calves raised in confinement may experience high stable fly pressure, particularly where moist organic material provides suitable breeding habitat.

In pasture systems, common fly pests include horn flies, face flies, horse flies, and deer flies. Horn flies (Figure 3) remain on cattle for most of the day, and both males and females take numerous blood meals each day, most often from the shoulders, sides, and back. On hot or rainy days, horn flies will move to the underside of the belly. Females leave the host briefly to lay eggs in very fresh cattle manure. Under favorable conditions, development from egg to adult can occur in about 10 to 20 days. In colder climates, horn flies overwinter primarily as diapausing pupae beneath or within cattle manure pats. High horn fly populations can reduce weight gain and milk production and increase blood loss and defensive behavior. When horn fly populations exceed treatment thresholds, chemical and nonchemical management options can be considered as part of an integrated pest management program.

Face flies (Figure 4) are non-biting but can vector pathogens that cause disease. As the name indicates, face flies are most active around the face and eyes.  Face flies can contribute to the mechanical transmission of pathogens associated with infectious bovine keratoconjunctivitis (pinkeye) and can serve as intermediate hosts for Thelazia eyeworms. Face flies primarily feed on ocular and nasal secretions but may also consume blood and fluids from existing wounds. Development from egg to adult commonly takes about 2 to 3 weeks, and adults can travel several miles to find hosts. Face flies generally remain outdoors during summer, but adults may enter buildings or other protected sites in the fall to overwinter. Females lay eggs in fresh cattle manure.

Horse (Figures 5 and 6) and deer flies (Figure 7) consist of over 300 individual species and belong to the family Tabanidae, which includes hundreds of species in North America. Adult females cut the skin with blade-like mouthparts and feed from the resulting pool of blood; males do not blood-feed. Their bites are painful and can result in pronounced defensive and avoidance behaviors. Large populations can disrupt grazing, contribute to blood loss, and reduce productivity. Horse and deer flies have been implicated in the mechanical transmission of several pathogens, although their epidemiologic importance varies among pathogens and production systems. Females typically lay eggs on vegetation near marshes, ponds, streams, wet soils, or poorly drained areas, and development may take several months to 2 years, depending on the species. These flies are strong fliers and are difficult to manage with insecticides alone. Where practical, reducing cattle exposure to areas with high tabanid activity, providing access to shaded refuges, or changing pasture use during periods of peak activity may reduce biting pressure. Traps designed for horse and deer flies may also reduce local activity in some settings.

Integrated Pest Management

Use an integrated pest management (IPM) plan to sustainably reduce fly populations below the economic threshold. Integrated pest management combines monitoring, prevention, and complementary control tactics to maintain pest populations at acceptable levels while minimizing risks to animals, people, beneficial organisms, and the environment. For livestock flies, an effective IPM program may include cultural, biological, mechanical or physical, and chemical approaches. The most appropriate combination depends on the fly species, production system, season, pest pressure, and management goals.

Cultural

Cultural forms of pest management alter the environment where pests would normally thrive. For house flies and stable flies, sanitation and moisture management are especially important because immature stages develop in moist organic material. Frequently removing manure, spoiled feed, wet bedding, and other organic debris can reduce breeding habitat. Repairing water leaks, improving drainage, and preventing feed accumulation around bunks can also help. If composting manure fits into your operation, proper compost management can generate temperatures that reduce the survival of fly eggs and larvae. Manage manure storage areas to limit excess moisture and prevent suitable sites for fly development. Cultural control is often the foundation of a successful filth-fly IPM program.

Biological

Biological control uses natural enemies of pest flies, including predators, parasitoids, and pathogens. Commercially available parasitoid wasps are commonly used against house flies and stable flies that develop in accumulated organic material. These wasps do not control all cattle fly species and primarily attack the pupal stage of susceptible filth flies. Releases are often made on a recurring schedule during fly season near manure, bedding, or other fly development sites. Match release rates, parasitoid species, timing, and placement to the production system and fly pressure. Biological control works best when combined with sanitation and other IPM tactics rather than used as a stand-alone treatment.

Mechanical and Physical Control

Although not normally listed in fly IPM, a mechanical method for fly removal is pulling every fly off the animal. A vacuum is used to suck flies into a vacuum system that collects the flies in a removable bag for disposal. This method requires a high initial investment and takes time to get cattle used to running through the chute, but it may reduce reliance on insecticides and, therefore, reduce selection pressure for insecticide resistance. High-velocity fans used during summer heat also help keep flies off cattle in feedlots; however, coverage in most buildings is not uniform, so other methods are needed. Walk-through vacuum systems can mechanically remove substantial numbers of flies from cattle. High-velocity fans can also reduce fly activity around cattle in some confined settings. Traps, screens, air curtains, and other physical barriers may also be useful in appropriate settings.

Chemical

The last IPM method is chemical control, or using chemicals to kill pests. This can include ear tags, feed additives, larvicides, baits, rubs, bags, residual premises, whole animal (pour-on), space sprays, and building treatments. Insecticides should be used strategically and in combination with cultural, biological, and mechanical approaches when appropriate. Some insecticides can adversely affect beneficial insects, including dung beetles and parasitoid wasps, so product selection, formulation, timing, and application method should be considered carefully. Always follow the product label, including use restrictions, retreatment intervals, and animal-use directions.

A common chemical used for fly control is pyrethrin because it kills insects immediately upon contact.  Pyrethroids are synthetic, or non-naturally occurring, compounds created to imitate pyrethrin. An example of a pyrethroid would be permethrin. Unfortunate naming has made these chemicals easy to confuse. Pyrethrins are naturally derived insecticides obtained from chrysanthemum flowers, while pyrethroids are synthetic compounds modeled after pyrethrins. Permethrin is one example of a pyrethroid.  Organic operations should use products that are allowed under their certification program and should verify current status through the Organic Materials Review Institute (OMRI) or their certifier. Product eligibility can vary by formulation and use pattern.

Feed additive insecticides pass through the animal and remain in the manure. When fly larvae develop, they consume the larvicide and die. Cattle consume feed-through products, which pass into the manure and can interfere with the development or survival of immature flies. Some products are conventional insecticides, while others act as insect growth regulators. These products are most useful against fly species whose larvae develop in cattle manure, such as horn flies and face flies. Immigration of flies from untreated neighboring animals can reduce the apparent effectiveness of feed-through products.

Rotate feed troughs and other chemical control methods based on the active ingredient's mode of action. This rotation can prevent or delay pest resistance to chemical treatments over time. When appropriate and consistent with label directions, rotate among products with different modes of action and integrate nonchemical control tactics. Appropriate rotation and other resistance-management practices can help delay the development of insecticide resistance, but they cannot guarantee that resistance will be prevented.

Some products can negatively affect beneficial organisms, such as Figure 8, that break down manure patties naturally, which reduces fly populations due to manure patties spreading out and drying quicker. Some insecticides or feed-through products may also affect beneficial organisms associated with manure. Dung beetles and other beneficial insects contribute to manure breakdown, nutrient cycling, and reduction of some fly development sites. When these organisms are an important part of the production system, consider their potential exposure when selecting a product.

Conclusion

In conclusion, identify flies that are pests to cattle and understand their life cycles to best manage fly populations. The best control method combines strategies known as integrated pest management. Combine cultural, biological, and chemical methods to have the most effective fly control strategy. Whether your operation is organic or conventional, one control method is seldom a sustainable option. Each livestock owner needs to chart an IPM strategy that controls fly populations and is cost-effective for their operation. An IPM program should also include monitoring, sanitation, and habitat management, mechanical or physical control, and targeted insecticide use when needed.

References

Brewer, G. J., Boxler, D. J., Domingues, L. N., Trout Fryxell, R. T., Holderman, C., Loftin, K. M., Machtinger, E., Smythe, B., Talley, J. L., & Watson, W. (2021). Horn fly (Diptera: Muscidae)—Biology, management, and future research directions. Journal of Integrated Pest Management, 12(1), Article 42. doi.org/10.1093/jipm/pmab019 [ OUP Academic ]

Cornell and Penn State Cooperative Extension. Pest Management Recommendations for Dairy Cattle. D.A. Rutz, et al., 2010.

Cornell Cooperative Extension. Integrated Management of Flies in and around Dairy and Livestock Barns. D.W. Watson, et al., 1994.

Cornell Cooperative Extension. Pest Flies of Pastured Cattle and Horses. P.E. Kaufman, et al., 2001

Geden, C. J., Nayduch, D., Scott, J. G., Burgess, E. R. IV, Gerry, A. C., Kaufman, P. E., Thomson, J., Pickens, V., & Machtinger, E. T. (2021). House fly (Diptera: Muscidae): Biology, pest status, current management prospects, and research needs. Journal of Integrated Pest Management, 12(1), Article 39. doi.org/10.1093/jipm/pmaa021 [ OUP Academic ]

Rochon, K., Hogsette, J. A., Kaufman, P. E., Olafson, P. U., Swiger, S. L., & Taylor, D. B. (2021).  Stable fly (Diptera: Muscidae)—Biology, management, and research needs. Journal of Integrated Pest Management, 12(1), Article 38. doi.org/10.1093/jipm/pmab029 [ OUP Academic ]

Trout Fryxell, R. T., Moon, R. D., Boxler, D. J., & Watson, D. W. (2021). Face fly (Diptera: Muscidae)—Biology, pest status, current management prospects, and research needs. Journal of Integrated Pest Management, 12(1), Article 5. doi.org/10.1093/jipm/pmaa020 [ OUP Academic ]

Machtinger, E. T., Gerry, A. C., Murillo, A. C., & Talley, J. L. (2021).  Filth fly impacts to animal production in the United States and associated research and Extension needs. Journal of Integrated Pest Management, 12(1), Article 41. doi.org/10.1093/jipm/pmab026