Cupressus sempervirens Essential Oil, Nanoemulsion, and Major Terpenes as Sustainable Green Pesticides against the Rice Weevil

In order to find effective, biorational, and eco-friendly pest control tools, Cupressus sempervirens var . horizontalis essential oil (EO) was produced using hydrodistillation, before being analyzed with gas chromatography, specifically, using flame ionization detection. The monoterpene components α -pinene (46.3%), δ -3-carene (22.7%), and α -cedrol, a sesquiterpene hydrocarbon, (5.8%), were the main fractions. An oil-in-water nanoemulsion was obtained following a green protocol. The EO, its nanoemulsion, and its terpenes each exhibited both insecticidal and insect repellent activities against the rice weevil, Sitophilus oryzae . In a contact bioassay, the nanoemulsion induced a 100% adult mortality rate in a concentration of 10.0 µL/cm 2 after 4 days of treatment, whereas 40 µL/cm 2 of EO and α -cedrol was required to kill 100% of weevils. Using fumigation, nanoemulsion and EO at 10 µL/L air caused a 100% adult mortality rate after 4 days of treatment. The LC 50 values of botanicals ranged between 5.8 and 53.4 µL/cm 2 for contact, and between 4.1 and 19.6 µL/L for fumigation. The phytochemicals strongly repelled the weevil at concentrations between 0.11 and 0.88 µL/cm 2 , as well as considerably inhibiting AChE bioactivity. They were found to be safe for earthworms ( Eisenia fetida ) at 200 mg/kg, which also caused no significant alteration in wheat grain viability. This study provides evidence for the potential of using the EO of C. sempervirens and its nanoemulsion as natural, eco-friendly grain protectants against S. oryzae .