Resistance to insecticides varies with diferent fly species, areas, and materials used, but flies have been able to survive and eventually build up resistant populations despite any insecticide used to date. Resistance to new compounds appears to develop even more rapidly where flies are already resistant to an earlier used compound. Well known fly control methods including good manure management and general farm sanitation in essential as a means of reducing the need for frequent insecticide applications and thus delaying the development of resistance.

Photo by Kenneth L. Middleham, U.C., Riverside