I've found that DE will keep the flys from anywhere they encounter the DE, but it won't keep them away. They just buzz all around the pullets and the run where the DE is, but won't land. If they do land on occasion, they are gone again in less than a second. They obviously don't like it, but are still buzzing all around.
Perhaps I am not using enough? It also helps with the smell in my new coop. Any suggestions anyone? Thanks. Linda.
The theory is that if the flies lay eggs in the mess that contains DE the larva will eat the DE which tears up their insides and they die before reaching maturity thus sort of stopping the life cycle of the common fly.
I use an old empty 2 liter soda bottle, cut off the top about one third down, add sugar and water until it almost reaches the top and turn the top upside down like a funnel, the flies go in to get the sugar water and drown, I keep one sitting on the rail of our back porch most of the summer, few flies get in the house and those meet the fly swatter real quick.