Feed thru fly control works wonders. I used to work at the SPCA and we took in neglected horses in addition to the other animals. Flies were awful when I started, in all the buildings etc. I used the feed thru at my house and flies were almost non existent after I started using it. I got them to try the product (11 cents per day per horse) and within 2-3 weeks flies were almost totally gone. I know the neighbors loved it! When the horse manager went on vacation for 3 weeks the staff quit feeding the product and within about 10 days we were back to flies everywhere. When Kaycie returned and put everyone back on feed thru, within 2 weeks we were back to almost fly free. The product we used contained dimilin, which halts the development of the larvae in the manure. It also does not affect earthworms as they do not have the hard body shell. Just a thought.