Two formulations, VectoBac® 12 AS and VectoBac® WDG, of Bacillus thuringiensis israelensis (Bti) and one formulation, VectoLex® WDG, of Bacillus sphaericus were tested against Anopheles maculipennis, Culex pipiens, Culex theileri, Aedes caspius, and Aedes dorsalis larvae in drainage canals, a flooded plain, and a drainage well in the Igdir Plain of Arafat Valley, Turkey. VectoBac 12 AS applied at 0.5 and 1 liter/ha to a drainage canal provided complete control of Cx. theileri and 80% to 98% control of An. maculipennis. VectoLex WDG at 400 g/ha provided 100% larval control of Cx. pipiens and Cx. theileri in polluted drainage canals. High larval density of Ae. caspius decreased the efficacy of VectoBac 12 AS and VectoBac WDG in the flooded plain. Residual effects of Bti formulations lasted only a few days in the breeding areas. Residual activity of VectoLex WDG was negatively influenced by water depth, organic pollution, and sunlight and positively influenced by low water velocity and emergent vegetation.