I usually experience an excessive amount of flies in my coop and run only after it rains, or if I leave table scraps laying around. (primarily, sweet corn on the cob) I have been harvesting our sweet corn from the garden, and there are partiuclar ears that go to the chickens. Sweet corn attracts flies in a bad way!
But, if I keep the run raked, and keep the un-eaten food picked up, I can't really complain.
But, if I keep the run raked, and keep the un-eaten food picked up, I can't really complain.