I purchased some food grade DE at Tractor Supply, and I have been spreading it around our chicken run, but it isn't helping the fly problem at all. There must be hundreds of flies out there. I have started putting it in the chickens food also. Our run is just dirt,and we usually keep straw or hay down to cover the dirt. When we spread the DE we just sprinkled it on top of the hay. The first time I did a thin layer, but when that didnt have any effect I went back and put a thicker layer, and it still hasnt helped. Should I be spreading it a certain way, or is there something I should be doing that I am not? Thanks!