Effective fly control for horses requires a lot of attention in the suburbs as opposed to a farm or agricultural community.
Because of the many neighbors, who are likely to be bothered by the flies.
There are many different ways you can control this particular problem.
I'll just share with you a few.
Flies will be attracted to your stable even if you keep it clean.
But the cleaner it is the fewer flies you will have.
You can hang old fashioned fly paper or fly traps, where your horses can't get to them.
You can also use fly baits but be careful to keep them out of reach of horses and children.
If you have can afford it, it would be a good idea to invest in a fly insecticide misting system for your barn or stable.
It's harmless to your horses and will keep the fly problem down significantly.
There are also bags and water traps that work pretty good I like to place a mixture of water and vinegar in them with a lil vegetable oil.
Another good ides is t feed your horses a fly feed larvicide.
It's a feed supplement that contains a larvicide & can be fed to your horses daily, to prevent development of flies in manure.
For best results start feeding it to your horse early in the spring before the flies appear and continue feeding until the beginning of winter.
Also use fly sprays and repellents on your horses.
You can even make your own fly spray and repellent and save a lil money, because buying fly spray can be costly depending on your situation, area and how many horses you have.
I usually mix a lil apple vinegar, baby oil, and fabric softener in a spray bottle.
I've been doing this for years and it has worked great.
Just be sure that if you are going to ride your horse don't spray it on your horse until after you have saddled him or else you may find your saddle sliding if you have sprayed his back, due to the baby oil.
There are many other natural remedies to making a horse fly repellent just look around the internet.
Do forget to use a good fly blanket & a fly mask to keep your horse from being irritated.