Buzz Off: Smart Strategies for Summer Insect Control in Horses

By Allison Bailey, ANR Agent, Wilkes County

Summer in Georgia brings more than just heat—it also marks the arrival of flies, mosquitoes, and other biting insects that can impact your horse’s health and comfort. These pests are more than just an annoyance; they can cause skin irritation, stress, and weight loss, and may transmit serious diseases such as Equine Infectious Anemia (EIA), West Nile Virus (WNV), and Eastern Equine Encephalitis (EEE). Implementing a well-rounded, integrated approach to fly and insect control is essential for protecting your horses during the warmer months.

Integrated Pest Management (IPM) is the most effective and environmentally responsible method of insect control around horse barns and pastures. IPM is a science-based strategy focused on long-term pest prevention using a combination of techniques, including sanitation, habitat modification, biological control, mechanical barriers, and targeted use of insecticides when necessary. Rather than relying heavily on a single control method or routine chemical applications, IPM aims to reduce pest populations to manageable levels while minimizing risks to horses, humans, beneficial insects, and the environment.

Sanitation is the cornerstone of any successful Integrated Pest Management (IPM) plan on horse farms. Regular removal of manure and soiled bedding disrupts common pests’ life cycles, such as stable flies (Stomoxys calcitrans) and house flies (Musca domestica), which prefer to lay eggs in moist, organic matter. By eliminating these breeding grounds, you can reduce the fly population dramatically. Composting manure is an effective way to handle waste, but piles must be placed away from barns and living areas and turned frequently. Turning the piles speeds up decomposition and raises internal temperatures, which helps destroy developing fly larvae. However, those who compost manure must be aware of state composting regulations to ensure environmental compliance. On-farm composting of manure and plant material generally falls under Georgia’s Category A feedstocks and is exempt from state solid waste permitting requirements, as long as only manure produced on-site is composted. However, best management practices still apply. Compost piles should be located away from water sources and property lines and must be turned regularly to promote aerobic decomposition and minimize odor and pests. If a farm plans to accept more than 500 tons per month of manure or other organic material from off-site sources, a Permit-by-Rule (PBR) through the Georgia Environmental Protection Division (EPD) is required. Facilities operating under a PBR must meet specific design standards, including using a composting pad that controls stormwater runoff, prevents groundwater contamination, and deters vectors such as rodents and flies. Buffer zones are also mandated—piles must be at least 50 feet from property boundaries, 200 feet from residences or potable wells, and 50 feet from streams or other water bodies. Operations exceeding these limits or handling additional waste types may need a full Solid Waste Handling Permit, which involves even stricter requirements such as engineered compost pads, leachate management systems, and adherence to local zoning regulations.

Water management is an equally important sanitation component, particularly for mosquito control. Mosquitoes require standing water to reproduce; even small amounts can become breeding sites. Regularly inspect your property for puddles, clogged gutters, unused buckets, and other containers where water may collect. Water troughs should be cleaned and refilled every three to five days to disrupt the mosquito life cycle, which typically spans a week. Low-lying areas prone to flooding should be filled with crush and run or regraded to prevent water from pooling. When permanent water features such as small ponds cannot be drained, mosquito larvicides containing Bacillus thuringiensis israelensis (Bti) can be applied. These biological controls are safe for horses, wildlife, and the environment while effectively targeting mosquito larvae. Additionally, maintaining vegetation to prevent overgrowth in wet areas can help reduce mosquito habitat. 

Physical barriers offer another layer of pest control. Installing barn fans can create air currents that deter flying insects, typically weak fliers. Fly masks, sheets, and leg wraps provide horses with direct protection during turnout but should be checked regularly for damage caused by chewing or rough play. Consistent use of these methods helps protect horses from bites, irritation, and potential disease transmission. 

Biological control is a practical, low-risk addition to an Integrated Pest Management (IPM) plan, particularly in managing stable and house fly populations. A commonly used method involves the release of parasitic wasps from genera such as Muscidifurax and Spalangia. These non-stinging wasps lay their eggs inside fly pupae, and the developing wasp larvae consume the fly from within, preventing adult emergence. Research has shown that repeated, timely releases of these parasitoids can significantly reduce fly populations, especially when combined with proper manure management (Gerry et al., 2020). Specifically, Spalangia nigroaenea and Muscidifurax raptorellus are two of the most effective species for equine facilities, as they target fly species commonly found around stables. Parasitic wasps are available commercially through biological control suppliers such as Spalding Labs, Arbico Organics, and BioBest. These companies offer wasp pupae in quantities appropriate for small farms to large equine operations. Success with parasitoids depends on consistent, preventative releases beginning in early spring before fly populations peak, combined with other IPM management practices. 

Chemical control remains the most common method to manage flies during the summertime. There are several active ingredients available in fly sprays, each with varying effectiveness and resistance concerns:

• Pyrethrins
  • Brand Examples: PyGanic®, Bug Blaster®, Black Flag®
  • Resistance: Low resistance is generally due to rapid degradation and natural origin, though some flies show tolerance to synthetic pyrethroids. They are often used in rotation to reduce resistance risks.
• Permethrin (Synthetic Pyrethroid)
  • Brand Examples: UltraShield®, Pyranha®, Endure®
  • Resistance: Moderate to high resistance reported, especially in stable flies (Stomoxys calcitrans) and house flies (Musca domestica) across many regions, including the Southeast US. Resistance mechanisms include metabolic detoxification and target site insensitivity.
• Piperonyl Butoxide (PBO) (Synergist, not an insecticide)
  • Brand Examples: Found in combined products such as some UltraShield® formulations
  • Resistance: Temporarily improves effectiveness by inhibiting detoxification enzymes in flies, but does not prevent genetic resistance.
• Neonicotinoids
  • Brand Examples: Less common in fly sprays; more often used in other pest controls, such as Imidacloprid in Advantage® (for fleas)
  • Resistance: Low resistance should be monitored if used for fly control.

The most common active ingredients in commercial fly sprays are pyrethrins and permethrin. While both are effective insecticides, they differ in origin and duration of action. Pyrethrins are natural compounds extracted from chrysanthemum flowers. They provide rapid knockdown of flies but break down quickly in sunlight, resulting in short-term protection. Permethrin is a synthetic pyrethroid designed to mimic pyrethrins but with greater stability and longer residual activity. However, fly populations—especially stable and house flies—have developed resistance primarily to synthetic pyrethroids like permethrin, reducing their effectiveness in some areas. For sensitive areas such as the horse’s face and belly, spot-on or pour-on formulations (e.g., Swat®) may provide longer-lasting protection but must be used according to label instructions to avoid overuse and resistance buildup. Overreliance on chemical sprays can lead to pesticide resistance, diminishing long-term efficacy. Rotating active ingredients and integrating non-chemical methods are essential for effective fly management. Research suggests rotating between chemical classes (e.g., pyrethroids, organophosphates) seasonally can delay resistance development (Scott et al., 2019).

Recent research has introduced new tools and technologies for effective fly management. One significant advancement is using feed-through larvicides containing diflubenzuron, an insect growth regulator (IGR). These products pass safely through the horse’s digestive system and prevent fly larvae from developing in manure, breaking the fly life cycle at the immature stage. Feed-through larvicides are especially beneficial in larger operations with regular manure removal, as they reduce emerging adult flies. However, all horses on the farm must receive the treatment, as untreated manure provides breeding grounds that undermine the product’s effectiveness. In boarding facilities or farms where not all horses are fed the product, IGR use is less recommended. Wearable repellent technologies also represent an emerging tool. Fly sheets and masks infused with active repellents slowly release chemicals, providing longer-lasting protection without frequent reapplication. Common active ingredients in these fly sheets include permethrin and sometimes piperonyl butoxide (PBO), which synergize insecticide efficacy. Permethrin-impregnated fly sheets are widely used due to their persistent repellency against stable flies, horn flies, and mosquitoes. However, growing resistance to permethrin-based products remains an issue with these fly sheets.  Advancements in barn-wide pest management systems have also improved fly control efficiency. Automated misting systems deliver targeted insecticide applications optimally, reducing chemical use and labor.

Additionally, smart fly traps with sensors monitor fly populations and activity in real-time, allowing for data-driven decisions and timely interventions. Field fly traps, such as Alsynite and jug traps, remain a valuable non-chemical tool for reducing adult fly populations. These traps attract flies visually and with bait odors, capturing large numbers of flies daily. Research shows that consistent use of field traps near barns and pastures can significantly lower fly pressure by intercepting adults before they reproduce (Campbell et al., 2017). Combining traps with other management strategies, such as sanitation and larvicides, improves control.

Ultimately, effective insect control for horses requires a proactive, multi-faceted approach. Combining sanitation, physical and biological controls, selective insecticide use, and emerging technologies can significantly reduce insect-related stress and safeguard your animals’ health throughout the summer. For more information about insect control in equine settings, contact your local UGA Extension office or visit extension.uga.edu.

Sources

Sanitation & Manure Management / Mosquito Control

• Georgia Department of Public Health. (2022). Mosquito Control Best Practices.
• Centers for Disease Control and Prevention (CDC). (2021). Mosquito Control.
• Geden, C.J., & Moon, R.D. (2011). “Manure Management for Fly Control.” Journal of Integrated Pest Management, 2(1), 1-8.

Compost Pile Regulations in Georgia

• Georgia Department of Agriculture. (2023). Compost Facility Standards and Regulations.
• Georgia Environmental Protection Division. (2020). Rules for Composting Operations.

Biological Control: Parasitic Wasps

• Mullens, B.A., et al. (2006). “Biological Control of Flies in Equine Facilities Using Parasitic Wasps.” Veterinary Clinics of North America: Equine Practice, 22(1), 245-262.
• University of California Agriculture and Natural Resources. (2017). Parasitic Wasps for Fly Control.
• Kopanic, R.J., & Dickens, J.C. (2015). “Parasitic Wasps in Fly IPM: Species, Effectiveness, and Releases.” Journal of Medical Entomology, 52(4), 641-648.

Chemical Fly Sprays: Active Ingredients, Brands, and Resistance

• Scott, J.G., et al. (2019). “Insecticide Resistance in House Flies and Stable Flies.” Pesticide Biochemistry and Physiology, 161, 98-105.
• Machtinger, E.T., & Leppla, N.C. (2014). “Pyrethroid Resistance in Stable Flies.” Journal of Economic Entomology, 107(3), 1031-1039.
• University of Georgia Extension. (2020). Fly Control in Horses: Chemical Options and Resistance Management.
• EPA. (2023). Registered Pesticides for Fly Control.

Feed-through Larvicides and IGRs

• Campbell, J.B., et al. (2017). “Efficacy of Diflubenzuron Feed-Through Larvicides.” Journal of Medical Entomology, 54(4), 1049-1057.
• Mullens, B.A., et al. (2006). “Insect Growth Regulators in Fly Management.” Veterinary Clinics of North America: Equine Practice, 22(1), 245-262.

Wearable Repellent Technologies and Fly Sheets

• Holbrook, F.R., et al. (2011). “Permethrin-Impregnated Fly Sheets for Horses.” Journal of Economic Entomology, 104(1), 187-195.
• USDA ARS. (2019). Repellent-Infused Fabrics for Equine Fly Control.

Field Fly Traps

• Campbell, J.B., et al. (2017). “Alsynite and Jug Traps for Stable and House Flies.” Journal of Economic Entomology, 110(2), 721-728.
• Moon, R.D. (2009). “Fly Trapping and Monitoring Techniques.” Journal of Agricultural Entomology, 26(3), 150-159.

Automated Misting Systems and Smart Fly Traps

• Geden, C.J., et al. (2018). “Automated Misting Systems in Livestock Fly Control.” Journal of Integrated Pest Management, 9(1), 10.
• Rice, R.E., et al. (2020). “Smart Fly Traps for Real-Time Monitoring.” Pest Technology, 14(3), 156-167.

Integrated Pest Management and Resistance Management

• University of Georgia Extension. (2021). Integrated Pest Management Strategies for Flies.
• Scott, J.G., et al. (2019). “Chemical Rotation and Resistance Management.” Pesticide Biochemistry and Physiology, 161, 98-105.