Chemical Composition, Repellency, and Insecticidal Activity of Pinus halenpenssis Leaf Essential Oil from Morocco on Adults of Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Rhyzopertha dominica and Tribolium castaneum are two significant insect pests that affect the quality, quantity, and commercial value of stored products. The aim of this study was to assess the chemical composition, repellency, and insecticidal activity of Pinus halepensis leaf EO on adults of Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). The EO of P. halepensis Mill. was extracted using hydrodistillation and analyzed for its chemical composition by GC-MS. The major components identified were 1-nonadecene (25.51%), 1-hexadecene (20.79%), pimaric acid (16.71%), and palmitic acid (12.47%). The repellency test was determined by the area-preference method. P. halepensis EO exhibited significant repellent activity against T. castaneum and R. dominica. It showed high class IV repulsion rates, reaching 63.60% against T. castaneum and 66.50% against R. dominica. The repellent effect was most potent at the highest concentration tested (16 µL/mL), achieving a 100% efficacy against T. castaneum after 4 h and after 3 h against R. dominica. The contact toxicity test was carried out by impregnating filter paper disks with increasing doses of the EO studied. P. halepensis EO was the most toxic against R. dominica (LC50 = 17.11 µL/mL, LC90 = 30.02 µL/mL) and T. castaneum (LC50 = 20.92 µL/mL, LC90 = 32.18 µL/mL) after 96 h of exposure. The ability of P. halepensis EO to repel and eliminate insects suggests that it could be used as a new treatment to prevent insect infestations of R. dominica and T. castaneum.