Insecticidal, antifeedant, and repellent effect of Lavandula mairei var. antiatlantica essential oil and its major component carvacrol against Sitophilus oryzae

The genus Lavandula encompasses plants commonly known for their bioactivities and applications as insecticides. Despite this recognition, certain species such as Lavandula mairei Humbert have received no attention. For this reason, our study offers a close insight into the chemical profile, insecticidal (i.e. fumigant and contact toxicity), repellent, and antifeedant effect of Lavandula mairei var. antiatlantica (Maire) Maire essential oil (LMEO) against Sitophilus oryzae (L.), a major stored product insect. Additionally, the major compound of LMEO, i.e. carvacrol, was also tested for the aforementioned bioactivities. In the fumigant bioassays LMEO and carvacrol showed LC₅₀ values of 69.5 and 69.3 μL/L of air, respectively, after 72 h while in the contact bioassays LC₅₀ values of 0.14 and 0.117 μL/insect, respectively, after 24 h. In terms of antifeedant effect, carvacrol and LMEO significantly influenced the Feeding Deterrent Index (FDI) recording 83.2 and 55.0%, respectively, at a concentration of 3.2%. Furthermore, a notable reduction of 5.5 and 2.1-fold in Relative Consumption Rate (RCR) was observed for carvacrol and LMEO, respectively, compared to the control. Regarding the repellent effect, carvacrol and LMEO exhibited percentages of repellency (PR) of 94 and 82%, respectively, at 0.312 μL/cm² after 24 h. In conclusion, our study underscores the significant insecticidal, feeding deterrent, and repellent effects of LMEO and its major compound against the rice weevil. Its cultivable potential and bioactivities confirmed through this study promote its use as sustainable pest control solution.