Tests conducted over a three-year period show that a dust made from Diazinon 50% wettable powder and agricultural gypsum will successfully kill domestic flies on poultry ranches. Best results were obtained when the dust was applied at weekly intervals to droppings beneath the poultry cages of commercial layer houses. These treatments gave good control of the little house fly (Fannia canicularis) and the false stable fly (Muscina stabulans), but failed to control the house fly (Musca domestica).

Valuable assistance was obtained through the cooperation of H. E. Grimm, R. W. Bell, and M. G. Andersen, poultry ranchers, Orange, California.