Abstract
Synthetic pesticides have shown important limitations in the control of stored-products pests. The investigation of plant essential oils as an ecofriendly alternative has attracted the attention of many researchers. This study focuses on the chemical composition of Laurus nobilis L essential oil and its insecticidal potential against the larval, pupal, and adult stages of Tribolium castaneum (Herbst) following topical and dietary exposure. GC–FID and GC–MS analyses showed that the essential oil contained 47.18% identified terpenes, including 36.10% oxygenated monoterpenes. The major constituents were 1,8-cineole (13.52%) and α-terpinyl acetate (12.34%). The obtained results following topical application at concentrations of 1%, 10% and 20% highlight a significant (p < 0.05) mortality after 7 days of exposure, where the highest concentration (20%) caused 100%, 88%, and 72% mortality in larvae, adults, and pupae, respectively. The toxicity increases with exposure time, as reflected by the decrease of LC₅₀ values, where larvae are the most susceptible developmental stage (LC50 = 2.83% after 7 days). However, the ingestion assays showed moderate toxicity at all tested concentrations, the highest mortality was registered for larvae (40%) after 21 days with a gradual reduction in LC₅₀ values from 54.16% to 22.54%. Nutritional analyses revealed a significant increase in the relative consumption rate (RCR), with a negative feeding deterrence index (FDI) recorded at all tested concentrations, especially at 1% (−131.85 ± 51.81%), indicating a phagostimulant effect. The obtained results highlighted that L. nobilis essential oil is more toxic against T. castaneum through contact than through ingestion. This study supports the potential of L. nobilis essential oil as a promising botanical insecticide for the management of stored-product pests.
| Keywords: | Nutritional index Median lethal concentration Median lethal time Larva Pupa Adult |