Abate works quite well. Also you can mix DE (
http://internet-grocer.com/diatome.htm )with water and spray it everywhere and that will help.
Abate-
http://www.agritectx.com/frame.html
Fly Control
ABATE (XP) is extremely effective in eliminating fly production. The following points outline how this is accomplished.
1. Ordinary fly and odor control products typically work by contact and/or residual, and is directed on the fly itself. ABATE (XP) is quite different because it is active in the organic matter which is the host bed for fly larvae and is the point where odors arise due to natural organic decay.
2. The addition of ABATE (XP) in the manner recommended, in the treatment information, alters the organic material as no natural decomposition can do and thus creates an all new environment which cannot create mal-odors and in which the fly larvae cannot survive.
3. In the process, ABATE (XP) converts ammoniacal nitrogen to nitrites so that odors typical of urine do not develop. There is little or no "gassing off" with ABATE (XP). The gasses produced are odorless. The action of ABATE (XP) also causes a small amount of Urease Oxygen to be produced, which soon hydrolyzes Urea (from the urine) to form Ammonium Carbonate. The use of ABATE (XP) impedes the formation of fatty acid ammonium carbonate, indole, scatole and sulfurated hydrogen, thus completely altering the mal-odor, fly attraction, and fly supporting organic material into an entirely incongruous material.
4. Manure, so treated, makes excellent fertilizer because while it contains valuable plant nutrients, it cannot burn grass or other plant life, even when used in large quantities.
http://www.agritectx.com/abatefrm.html
