Fly Predators!

Yes - it's a real thing! 

Parasitic  wasp  

This monthly subscription is cheap and works! 

What works best for Fly control?...

Fly Exterminators are effective against 95% of flies, including houseflies, biting stable flies, garbage flies, and lesser houseflies, and many more Filth Flies. These tiny flying insects are completely biteless, stingless and do not bother humans or animals. Fly Exterminators go virtually unnoticed, only flying inches off the ground. They infect the fly pupae to stop the reproduction of more flies.