Bacillus sphaericus strain 2362 was evaluated for the control of Culex larvae in dairy wastewater lagoons. Both initial and long-term efficacy were studied. Two primary powder preparations of ABG-6184 yielded mediocre and short-term control at the rates of 0.25 and 0.5 lb/acre (0.26 and 0.56 kg/ha), while level of control and persistence greatly increased as the dosages were increased to 1.0, 2.0 and 4.0 lb/acre (1.12, 2.24 and 4.48 kg/ha). The 1.0 and 2.0 lb/acre rates yielded almost 100% control for 4 weeks and the 4.0 lb/acre rate yielded control (99%) for 49 days or longer. A flowable concentrate preparation (BSP-2) yielded complete initial and persistent control of larvae for 14-21 days at 2.0, 4.0 and 5.0 lb/acre (2.24, 4.49 and 5.6 kg/ha). Granular formulations of B. sphaericus 2362 (ABG-6185) were also evaluated at 2.5, 5.0, 7.5, 10.0 and 20.0 lb/acre (2.8, 5.6, 8.4, 11.2 and 22.4 kg/ha) of the granules. Some of the formulations were more active than the others, yielding excellent initial and persistent control (80% +) for 14-21 days with one treatment.