Evaluation of larvicidal potency of Bacillus subtilis SPB1 biosurfactant against Ephestia kuehniella (Lepidoptera: Pyralidae) larvae and influence of abiotic factors on its insecticidal activity

Microbial-derived biosurfactants are amphipathic surface active molecules produced by diverse bacterial genera. A well-known class of such compounds includes the lipopeptides. Many strains of Bacillus are known to produce broad spectrum lipopeptides including surfactin, iturin, bacillomycin, fengycin, lichenysin, etc. In this study, lepidopteran larvicidal potency of the biosurfactant secreted by Bacillus subtilis SPB1 strain was determined. The LC50 of the biosurfactant against third instar larvae of Ephestia kuehniella (Lepidoptera: Pyralidae) was 257.0 μg/g six days post treatment. Interestingly, this insecticide could withstand environmental stresses such as extreme pH and temperature and sunlight/UV radiation. Its larvicidal potency was also resistant to proteases action. These properties of B. subtilis biosurfactant could be exploited for the formulation of a novel biopesticide for effective control of lepidopteran larvae.

► Bacillus subtilis SPB1 biosurfactant was active against Ephestia kuheniella. ► The LC50 was of about 257 ng/g. ► B. subtilis biosurfactant exhibits high stability to varied environmental conditions. ► Its larvicidal potency was also resistant to proteases action.