https://doi.org/10.37229/fsa.fja.2026.08.01

The present study evaluated the insecticidal efficiency of selected essential oils (clove, peppermint, eucalyptus, and ginger) and their nano-emulsions against the lesser grain borer, Rhyzopertha dominica, under laboratory conditions. Nano-emulsions were successfully prepared using an ultrasonic method, producing stable formulations with droplet sizes ranging from 106.48 to 146.73 nm. Toxicity bioassays revealed a clear concentration- and time-dependent mortality across all treatments, with nano-emulsions consistently outperforming their crude counterparts. Clove oil exhibited the highest toxicity, where nano-emulsification reduced the $\text{LC}_{50}$ value from 1.110% to 0.701% after 24 h and from 0.534% to 0.262% after 72 h. After 72 h of exposure, the $\text{LC}_{50}$ values for peppermint, eucalyptus, and ginger nano-emulsions reached 0.519%, 0.574%, and 1.446%, respectively, compared to 1.178%, 1.151%, and 2.144% for their bulk forms. Furthermore, long-term evaluation over 90 days showed that nano-emulsions caused a significant reduction in $F_1$ progeny production, reaching up to 93.48% for clove, 93.27% for eucalyptus, 87.55% for peppermint, and 82.63% for ginger nano-emulsions at a 2% concentration, thereby effectively preventing grain weight loss. Despite these strong insecticidal effects, seed germination percentages remained high (>90%) in most treatments, confirming low phytotoxicity and safety for stored grain protection. Overall, essential oil nano-emulsions represent highly effective and eco-friendly alternatives for R. dominica management.