I can’t think of a single person or animal I have ever had anything do with (with the exception of a spider)– who liked flies. Flies irritate us all whether we are equine or human. Flies bite and create sores on horses and can cause them to hurt themselves or cause damage to their surroundings trying to escape their constant assault- whether they are tiny gnats or full sized horse flies. Flies are not only annoying to you and your neighbors but also carry diseases.
The best way to reduce flies in your barn is to keep the area clean. This means not only picking up manure daily in stalls and small paddocks but dragging fields weekly (more often if possible). Something many people don’t realize is it is equally important to make sure you remove wet areas because flies look for warm moist areas to breed and lay eggs. By removing all the wet bedding from the urine spot in a stall and also any wet hay or combination of materials under water buckets the fly population can be drastically reduced.
Fans in a barn can also help to discourage flies who are not partial to a strong breeze. And don’t forget to cover garbage cans and limit the amount of exposed sugary surfaces (sugar cubes and peppermints, open soda cans) that can also attract flies. Storing cleaning equipment, wheelbarrows, buckets away from horses in stalls.
As the saying goes it’s location, location, location at least as far as a manure pile goes. Find a spot that is well away from streams and neighboring property lines. The pile should be covered until it can be spread or hauled away. An even better all-around solution is to compost – the heat created in the pile will help to kill the fly larvae. If you are careful to continuously turn the pile so the heat is evenly distributed, flies will become less and less of a problem.
You can always use an insecticide to help eliminate flies but there are several other natural solutions. Tiny parasitic wasps are widely available, and work by destroying the fly larvae before it can hatch. Harmless to humans and so small you can barely see them; the wasps are shipped (usually on a monthly basis) still in the egg stage. Once a few of the wasps hatch in the plastic bag after delivery, you sprinkle the contents in and around your horse’s living area.
Traps can also be effective available in a variety of different types, fly traps work by attracting flies, either through color or scent. Once the fly lands on or enters the trap, it can’t escape and eventually dies. The same is true of fly paper or sticky tape -not pretty but it can be helpful.
Many owners report having success with using vinegar as a fly breeding ground deterrent. Most recommend spraying it on the manure as you take each load out to your manure pile. My father was of the generation that used vinegar for everything. We always put a cap full in each horse’s water bucket because it prevented the aversion to strange water many show horses seem to have and kept them drinking no matter where we were. And now I think of it we didn’t have much of a fly problem. He also used to make us all drink it every day on the belief it helped your digestion and my mother used it to clean the calcification from her tea kettles.
Here are a couple of helpful fly abatement articles: