Essential oils from underexplored Moroccan species Deverra scoparia and Ruta montana exhibit multifaceted insecticidal and behavioral effects against Sitophilus oryzae

This study aims to evaluate the chemical profile, insecticidal, repellent, and antifeedant effects of the essential oils (EOs) obtained from Deverra scoparia (stems and grains) and Ruta montana (aerial parts) against Sitophilus oryzae. The GC-MS analysis revealed a significant variability in the chemical composition of EOs of D. scoparia, where stems were dominated by geranyl acetate (41.3%), while myristicin (46.2%) was the predominant compound in grains. As for R. montana, 2-undecanone (40.9%) was detected as the major compound. In terms of the fumigant toxicity, R. montana EO displayed the most potent toxicity after 48h, with an LC50 value of 114.61 μL/L of air. Similarly, R. montana EO displayed the most potent toxicity in the topical application bioassay, where 0.143 and 0.100μL/insect were the LC50 obtained after 24 and 72 h, respectively. Regarding the antifeedant effect, D. scoparia grain EO displayed the most pronounced disruption in the four nutritional indices. This EO exhibited the highest feeding deterrence index (FDI) (91%) and significant reduction in RGR (2-fold), RCR (7-fold), and ECI (19-fold) compared to the control at the highest concentration used (1.96μL/pellet). As for the repellent activity, all EOs exhibited a potent effect, where the percentage of repellency ranged between 98.0 and 90.0% at 0.156μL/cm2 after 24 h. Hence, this study highlights the chemical richness and diversity in both EOs, showing distinct levels of insecticidal, feeding deterrence, and repellent properties. Future research is required to domesticate these plants and incorporate their EOs into sustainable and eco-friendly uses in integrated pest management.