Comparative Bio-efficacy and Molecular Insights of North-Western Himalayan conifers, Cedrus deodara and Juniperus macropoda Essential Oils against two storage insect Pests

The study, aimed to evaluate fumigation and repellent properties of essential oils (EOs) from Juniperus macropoda leaves and cedarwood, Cedrus deodara against storage pests viz ., Tribolium casteneum and Callosobruchus maculatus . Further, the volatile compounds released from essential oils were collected through headspace extraction and analysed using Gas Chromatography–Mass Spectrometry (GC-MS). The major compounds released from C. deodara EO were α-Cuprenene (15.53%) and α-Himachalene (13.42%) whereas 4-terpineol (22.35%) and Limonene (14.16%) dominated the volatile composition of J. macropoda EO. Fumigation assay showed that C. deodara EO was significantly more toxic than J. macropoda EO against T. casteneum larvae (LC ₅₀  = 103.91 vs. 357.33 µl/l) and adults (LC ₅₀  = 123.10 vs. 724.66 µl/l). Similarly, C. deodara EO exhibited stronger fumigant activity against C. maculatus adult (LC ₅₀  = 16.13 µl/l) compared to J. macropoda EO (LC ₅₀  = 25.68 µl/l). Repellency assay revealed that C. deodara EO significantly repelled C. maculatus adults at 50 and 100 ng, whereas J. macropoda EO showed no significant effect. Against T. casteneum adults, both EOs exhibited significant repellency, except J. macropoda at lowest dose (10 ng). In-silico analysis revealed that in comparison to components from J. macropoda , C. deodara components such as γ -himachalene, α -cuprenene, α -himachalene, and α -(E)-atlantone often showed stronger and more stable binding affinities, consistent with bioassay results indicating the superior insecticidal activity of C. deodara essential oil. Molecular docking also revealed acetylcholinesterase as the primary target, thereby supporting its role in fumigation insecticidal activity of the essential oils.