Efficacy of Bacillus sphaericus against larvae of malaria and filarial vectors: an analysis of early resistance detection

We are reporting in this paper the control of Anopheles stephensi Liston and Culex quinquefasciatus Say using Bacillus sphaericus. These have been now considered with a practical solution because of its specific and prolonged killing action against mosquito larvae. The efficacy of B. sphaericus were assessed against all instars of A. stephensi and C. quinquefasciatus separately. During the experiments, the mortalities were not found highly effective in dose concentration of LC₉₀ 0.01 mg/l. It is recommended by the World Health Organizations in all instars of larvae of A. stephensi and C. quinquefasciatus. Thereafter, six different concentrations were used in laboratory bioassays (05, 10, 20, 30, 40, and 50 mg/l) for A. stephensi. Similarly, in the case of C. quinquefasciatus, six statistically significant different concentrations were used (0.01, 0.04, 0.05, 0.10, 5.0, and 10.0 mg/l) of B. sphaericus. It was recorded after exposure of 24 h. The percentages of mortalities were different for the different instars of C. quinquefasciatus and A. stephensi. The probit equations were drawn by the probit method. The result of the study distinctly showed that B. sphaericus is not effective on selected defined doses against A. stephensi and C. quinquefasciatus. This probably indicates an initiation of resistance. This efficacy study can be useful while detecting early resistance phenomena in environment specific zones.