Synergistic activity of Bacillus consortia combined with botanical oils and low-dose clothianidin against larval and adult Anopheles mosquitoes

Background Increasing insecticide resistance in malaria vectors and growing ecological concerns necessitate the development of effective, environmentally sustainable alternative control strategies. This study evaluated the larvicidal and adulticidal efficacy of a Bacillus consortium alone and in combination with Azadirachta indica (Neem) oil, Jatropha curcas (Jatropha) oil, and low-dose Clothianidin against Anopheles mosquitoes. Methods Eight compatible Bacillus strains, confirmed to have no antagonistic interactions, were formulated and tested individually and in combination with botanical oils and Clothianidin. Larvicidal and adulticidal bioassays were conducted under laboratory conditions across multiple concentrations and exposure times. Lethal concentrations (LC₅₀ and LC₉₅) were estimated using Probit regression analysis. Results All treatments exhibited concentration- and time-dependent activity. Combined formulations showed greater efficacy than individual treatments. Bacillus + Clothianidin achieved an LC₅₀ of 0.0006 mg/mL, while Bacillus + Neem + Jatropha achieved an LC₅₀ of 0.0007 mg/mL, substantially lower than those of the individual plant oils (LC₅₀ = 0.031–0.087 mg/mL). The triple combination produced rapid and complete larval mortality and 100% adult mortality. Conclusion Integrating a Bacillus consortium with botanical oils or low-dose Clothianidin enhanced larvicidal and adulticidal efficacy against Anopheles mosquitoes. These findings indicate that combined microbial-botanical-chemical formulations provides a promising and more sustainable approach to mosquito control while potentially reducing reliance on conventional insecticides.