Sustained-release biopolymer based formulations for Bacillus sphaericus Neide ISPC-8

Abstract

Sustained-release biopolymer based formulations for an indigenous Bacillus sphaericus Neide ISPC-8 strain were developed and evaluated under laboratory conditions. These formulations were assessed for residual activity, response to UV-B radiation and shelf-life. The mosquitocidal activity of tested formulations showed a varied residual activity pattern against Culex quinquefasciatus Say larvae. The residual activity of unformulated spore-crystal suspension drastically decreased after 4 days whereas the formulated preparations persisted until 28 days. All the formulations except sodium alginate-based formulation showed more than 95% mortality within 48 h. Although the sodium alginate-based formulation showed delayed initial mortality, it persisted for a longer period of time (42 days). Based on the persistence studies, promising formulations based on sodium alginate, gelatin and acacia gum were selected for further evaluation. The respective LC 50 values of these three formulations were 0.085, 0.117, and 0.196 mg/l against C. quinquefasciatus after 48 h. The biopolymers combined with Congo red protected the sporecrystal moiety from UV-B radiation. These formulations were found to be stable up to 18 months when stored at room temperature. Thus, these biopolymers could serve as suitable ingredients for development of biopesticide based on B. sphaericus ISPC-8.