Efficacy of eucalyptus oil as a sustainable biopesticide for population suppression of Sylepta derogata Fab (Lepidoptera: Pyralidae), an okra pest

The extensive use of synthetic pesticides has led to insect resistance and adverse effects on human health and the environment. As a result, farmers increasingly prefer natural pesticides, which degrade easily without leaving harmful residues in soil and water. Eucalyptus oil, an eco-friendly botanical pesticide, serves as a promising alternative for sustainable pest management. This study evaluates the bio-pesticidal efficacy of commercially available eucalyptus essential oil against Sylepta derogata, a major pest of okra in Tamil Nadu. Laboratory experiments were conducted to assess the impact of eucalyptus oil at concentrations of 25, 50, and 100 ppm on different larval instars. A dose-dependent antifeedant effect was observed across all instars, with significant reductions in larval and pupal weight and length, alongside prolonged larval duration. Deformities in pupae and adults were also recorded. When insects in the 1st and 2nd instars were treated with 100 ppm of eucalyptus oil, a significantly high mortality of nearly 95 % was observed. This result suggests that strong larvicidal efficacy of eucalyptus oil at this concentration. Eucalyptus oil at 10 ppm significantly reduced survivorship, with a marked decline in population growth index compared to the untreated control. These findings suggest that eucalyptus oil exhibits potent pesticidal activity against S. derogata larvae and holds potential as a natural alternative for okra pest management.