Fly-control strategies can keep the buzz at bay

If you have horses, you’ll deal with flies. Typically, stable and house flies are the biggest nuisances. Stable flies bite and aggravate horses, causing them to stomp their feet, swish their tails and twitch their bodies to reduce fly pressure. This behavior takes energy. House flies don’t draw blood, but they spread diseases. House flies feed on fresh manure as well as at the horse’s body orifices and eyes, spreading fecal bacteria.

Stable and house flies are considered “filth” flies. Understanding how these pests live and breed can help horse owners control them. Filth flies complete their lifecycle using moist organic material. Old feces, rotting feed waste and used animal bedding are ideal fly development locations. Managing such debris is an effective way to prevent filth flies.

Appropriate debris management impacts all areas of your operation. Keep feed dry, and avoid ground feeding. Disk, spread or compost waste feed. Place waterers in well-drained areas, and keep them separate from where you place feed. Make sure waterers are kept in good repair. Replace bedding weekly. Straw is more prone to fly problems than wood shavings or sawdust, so consider those materials if flies are a big concern. Plan to remove manure at least twice a week, and spread or compost it to reduce fly growth. Insecticides are also a popular option, but even the best product in the world won’t be enough if the manure, feed and bedding materials aren’t kept clean and controlled.

If you choose to use an insecticide, be sure to read the label, and follow its instructions. Insecticides have different applications. Space sprays and pyrethrum fogs kill adult flies indoors but don’t last long. Longer-lived pyrethroid and organophosphate residual sprays that can be used inside or outside last for up to three weeks. The effective length of time varies by how the product is used. These sprays are most effective when applied to fly-perching areas, which are solid spaces often above eye level. You can locate them by noticing the “fly specks,” small brown spots of fly waste.

Fly traps can provide some control. Baited traps work for house flies but do not attract stable flies. Sticky traps and ultraviolet electric traps can be effective as part of a solid fly-control plan.

Biological control is another option that has merit. Stingless parasitic wasps are small insects that look almost like ants. They don’t hurt people or livestock but do help control flies. I see more wasps in feedlots every year. The wasps are “parasitoid” insects that lay their eggs in or on another insect. Juveniles of the parasitoid develop inside the other insect, eventually killing them.

Natural populations of parasitic wasps often occur near barns, but owners usually purchase and release additional parasitic wasps to augment native populations. Most wasps have a specific host. For example, the parasitoids used to control soybean gall midge are not the same species as the wasps for control of flies.\

“Understanding how these pests live and breed can help horse owners control them.”

Success with this method varies. For some situations, the wasps can really help. Australian research reports a third of the flies in feedlots being killed by wasps. The Aussies have also used mites to control flies. This Australian website provides useful information on control of livestock flies: flyboss.com.au. I have looked for similar U.S. or North American resources but have not been successful.

For horses, citronella sprays, leggings and leg bands reduce the amount of tail switches, shoulder twitches, head backs and hoof stomps. However, treatment with sprays and leg bands are not able to stop all of these behaviors and provide the horse complete relief.

Hanging bags of water around buildings is a commonly used but ineffective fly-control method. I know of no controlled studies that show the practice reduces flies. Similarly, barn lime, also known as “hydrated lime”, “slaked lime” or “builders’ lime,” has been used for fly control, but it is more effective in reducing moisture and ammonia odor.

For more information on effective fly-control solutions for your farm, visit with your local MFA solutions provider. 

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