The fly season is approaching. Flies can spread disease from one horse to another, irritate the horse’s mind and his skin, and are a general nuisance. Flies distract your horse from paying attention to you when you are working around him or riding him. The most effective way that I have found to control flies in the barn and in my clinic is to combine a treatment of the manure to kill fly larvae and a fly poison to kill adult flies. We set out fly bait and also hang some fly strips in the barn aisle and in the treatment area of the clinic. I do not care for the automatic spray systems that are installed in many barns. I have been trapped in a stall or barn when these systems come on and spray, and it always leaves me feeling nauseous for hours afterward. I sympathize with a horse that is trapped in a stall with this poison being sprayed down on him day after day. The flower based spray is slightly safer than the chemical based one, however it still makes me feel ill if I get trapped in a stall when it is being sprayed. I believe that many horses have respiratory problems directly associated with breathing these chemicals day after day.

There are two ways to kill the fly larvae before they hatch in the horse manure. You can either place fly predators, which feed on the fly larvae, in the manure in your stalls; or use the “feed through the horse” type of larvicides. I was not a fan of the feed through larvicide’s until Solitude™ came on the market, as the older products are stored in the fat of the horse, and there is no long term research to determine if this product will build up in the fat and be detrimental to the horse’s health over time. Solitude™ goes through the horse’s digestive system untouched. It is approved for use in chickens that are used for human consumption. Solitude™ has been extensively tested for safety and efficacy. It is safe for pregnant mares, breeding stallions, and foals. It takes about three weeks of feeding the product before it can catch up with the adult fly population. It is easy to make sure the larvicide is in all of the manure since it is fed to the horse.

We have also used fly predators. Fly predators are a type of wasp that eats fly larvae. They are purchased from companies such as Arbico and Spalding Laboratories. The wasps are mailed to the consumer every two weeks from February until late fall. When they arrive, you keep them in a warm place until they hatch out. It takes about seven to ten days for this to occur, depending on the batch of predators and the company that sends them out. I have had much better luck with the predators from California than the ones from Arizona. Once the fly predators hatch out, they are placed in horse manure. This means a little manure must be left in the stalls, to place the fly predators in. Care must be taken not to throw the fly predators out when the stalls are cleaned. You have to make sure the fly predators are placed everywhere that the horses pass manure. One problem that arises with both the fly predators and the Solitude™ is if the neighbors have horses that are close to your property and do not treat their manure, the flies will hatch out next door and fly over to your property and get on your horses. The distance necessary to prevent flies hatched in the neighbors manure from reaching your barn depends on which direction the wind blows in the summer in your area. Flies will travel up to a quarter mile, and will be aided by the wind.

The fly poisons, such as Golden Malrin® help to control the adult flies until the larvacide has time to catch up. The flies are attracted to the poison by a sugar base, so care must be taken to place the poison in area where chickens, pets, and children cannot get into it. The fly strips offer a poison that is less likely to be hazardous. We have had good luck with Starbar fly strips called Quick Strike™. Fly sprays do not seem to last for more than a few hours. They will repel the flies for a few minutes while I am working with a horse, but not long enough to be of great value. Read the ingredients on the fly spray bottle and realize that they are not very strong. The first ingredient is usually water. Citronella based fly sprays are less toxic than the chemical sprays, and I like to use them in areas where killer bees are not an issue. The citronella has been known to attract the bees. Equi-Mist™, by Chamisa Ridge, was named the “best buy” natural fly spray by the horse journal a few years ago. Other plant-based, non-chemical sprays that are available are: I particularly like Flick’s, by Animal Legends. It is all natural essential oils. I use these natural sprays on horses that I am working on in the clinic.