House flies and stable flies are a problem as their number increases.  Both types of flies lay their eggs in horse manure and horse bedding materials. It is important to maintain a good composting program to avoid the breeding of flies throughout the year.  There are several methods to control flies, ranging from using traps to collect adult flies, insecticides and repellents. Depending on how many horses do you own, you might want to consider using a more aggressive method to control the fly population around your horses. Traps can do a good job with few horses and when bedding and waste is managed properly but those require maintaining them properly.  External insecticides are also often used, and can be also effective. A new generation of fly control program is now available with a new generation of insecticides known as insect growth regulators. Insect Growth Regulators (or IGR’s)  have shown 100% efficacy in inhibiting larvae development. Studies have proven that IGR can be   99.5% effective against stable flies and 100% effective against house flies with no effect on horses, other mammals or beneficial insects. These modern products are licensed for feed-through fly prevention and control of house and stable flies in and around horses, horse barns, stables, paddocks and race tracks. When mixed into a horse's ration daily according to the directions, IGR’s can prevent house and stable fly development. The effects of IGR’s are not immediate. Significant results may be observed within 2 weeks but the full benefit should be realized within 4-6 weeks of administration as the adult populations die off. Insect growth regulator works on the fly's chitin exoskeleton and is very species specific to house and stable flies. As the horse is fed the IGR, it passes through the horse and is excreted in the manure. House flies and stable flies lay their eggs in the manure and the eggs subsequently hatch into the larval or maggot stage. (IGR’s do not effect on the chitin of the adult fly.) As the maturing maggots feed on the manure treated with the component, they become unable to successfully develop into adult flies because the IGR inhibits the proper formation of chitin. The immature stage of the fly dies. Once excreted, IGR’s breaks down to a melamine monomer, a slow release nitrogen fertilizer. IGR’s can reduce the use of neurotoxic pesticide sprays and overhead fly systems creating a healthier environment for horses, staff and riders.  For an effective control, start using the  IGR early in the spring before flies begin to appear and continue feeding throughout the summer and into the fall until cold weather inhibits fly development. In some cases, supplemental fly control measures may be needed in and around paddocks and stables to control adult house flies and stable flies, which can breed not only in manure, but in other decaying vegetable matter or silage on premise.

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