Evaluation of Bacillus sphaericus formulations against the vector of bancroftian filariasis.

Three different formulations of Bacillus sphaericus viz, Spherimos, Vectobac and Spherifix, were evaluated for their efficacy and residual activity against Culex quinquefasciatus breeding in polluted disused wells. Spherimos, a flowable concentrate formulation, exerted 96-100% control when treated at the dosage of 10 l/ha for 17 days, whereas the effective residual activity lasted up to 67 days at 15 l/ha. In the case of Vectolex, a granular formulation, the residual activity lasted up to 56 days with the dosage of 30 l/ha and up to 66-77 days with higher dosages of 45 and 60 l/ha. The residual activity of Spherifix, a floating controlled release formulation, lasted up to 67 days with a dosage of 10 kg/ha.