The “Queen of Herb”, Tulsi is an important herb with greater medicinal value used in Ayurveda, Siddha, Unani, Greek and Roman medicine for prevention and cure of many illness. Fifth instar larvae inoculated with Beauveria bassiana were fed with mulberry leaves enriched with different concentrations (1 %, 2%, 3% and 4% ) of ethanolic extract of Ocimum sanctum leaves and its effect on cocoon weight, pupal weight, shell weight, shell ratio and silk characteristics were studied. Among the different concentrations, 3%ethanolic extract of O. sanctum has been found to be most effective against B. bassiana infection as compared to others. Inoculated control group recorded very low economic values as compared to normal control and other treated groups.