Sustained release pellets for control of Culex larvae with Bacillus sphaericus.

Bacillus sphaericus was formulated in pellets with partially hydrogenated vegetable oil, talc and a starch-based superabsorbent polymer. This formulation increased the residual activity against Culex spp. larvae in large and small plots, including polluted water. When the pellets were applied to dry artificial larval habitats 5 days prior to flooding, the Psorophora columbiae that hatched at the time of flooding were eliminated. After the pools were dried and reflooded, 611 Bacillus colony-forming units/ml were present in the surface water. An equivalent amount of primary powder suspension was ineffective as a preflood treatment, apparently due to solar inactivation of the toxin.