Biopesticidal Properies of Heliotropium Indicum Leaf Extracts for Controlling Stored Grain Weevils

Abstract The hexane, ethyl acetate, methanol and aqueous leaf extracts of Heliotropium indicum were screened for their biopesticidal activity against the weevils of rice, sorghum and maize grains. Each extract demonstrated promising efficacy in causing mortality at various concentrations (0.01 g/ml, 0.02 g/ml, 0.04 g/ml, and 0.08 g/ml) 24–96 h postexposure. Among the extracts, the methanol extract emerged as the most effective, exhibiting the highest mortality rate of 96.67% at a concentration of 0.08 g/ml, 96 h after exposure, comparable to the standard insecticide (cypermethrin 2.5 E.C). In contrast, the negative control, consisting of untreated grains, showed 1.67% mortality rate for Sitophilus zeamais 72 h post-exposure, which could be attributed to natural death. Additionally, the methanol, ethyl acetate, and aqueous extracts demonstrated mortality rates above 50%, reaching up to 90%, for Sitophilus zeamais. This level of effectiveness is similar to that of cypermethrin, indicating that Heliotropium indicum could be a valuable biopesticide for the postharvest management of stored grains. This study suggests the potential for these plant extracts to serve as natural alternatives to synthetic insecticides, offering a sustainable solution for pest control in stored grain protection. The novelty of this research lies in its comprehensive approach to utilizing multiple solvent extracts from a single plant species, highlighting the untapped potential of Heliotropium indicum in the development of eco-friendly biopesticides. This could pave the way for further investigations into other medicinal plants with similar properties, ultimately contributing to safer and more sustainable agricultural practices.