So let's say you've tried the other four steps on our list, and you're still finding your home and yard inundated with flies. That means it's time to fight dirty. There's a variety of pesticide sprays available specifically designed to treat a yard for flies, as well as other insects like fleas and ticks. A thorough and proper application of these sprays should be enough to put down the flies living in your lawn.
To apply these chemicals, you'll need a pump sprayer, some sort of misting system or a device that attaches to your garden hose. But if hosing your lawn down with harsh chemicals doesn't sound ideal, a growing number of organic insect sprays are available as well. The blog Organic Gardening.com recommends a spray you can make yourself using onions, garlic and cayenne peppers. In other words, you have options available -- it just depends how aggressive you want to be when you finally go after the flying pests in your lawn.