Efficacy of Bacillus sphaericus in different breeding habitats of Culex quinquefasciatus.

ABSTRACT

'Spherifix', an alginate based slow release formulation of Bacillus sphaericus was field tested in different types of breeding habitats of Culex quinquefasciatus at the dose of 15 kg ai/ha at bimonthly interval. The efficacy of the formulation was higher in most of the months except in rainy and post-rainy months. The mean percentage reduction +/-SD during the treatment phase of one year was 31.2 +/- 17.9, 50 +/- 29.4, 28.3 +/- 17.6, 30.3 +/- 21.1, 66 +/- 22.5 and 53 +/- 20.4 in larval density and 49 +/- 20.8, 65.1 +/- 26.1, 30.3 +/- 21.9, 59.8 +/- 22.6, 63.1 +/- 21.9 and 47.7 +/- 24.2 in pupal density respectively in cement tanks, cesspools, cesspits, disused wells, unlined drains and cement lined drains. The reduction in immature density was relatively higher in undisturbed, debris free and shallow habitats such as cesspools, unlined drains and cement lined drains. After withdrawal of treatment, the effect of the formulation could be seen for a period of four months.