Repellent, antifeedant, and insecticidal effects of Pinus halepensis Mill. (Pinaceae) extract against two stored-product insects

This study aims to investigate, and for the first time, the toxic, repellent, and antifeedant effects of the methanolic extract of Pinus halepensis Mill. (Pinaceae) leaves against Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae) and Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae). The major components of this extract, identified by HPLC-DAD-ESI-MS analysis were vitexin (21.36 %), cirsiliol (15.11 %), and syringetin rutinoside (9.29 %). The different doses of extract (19, 23.75, 47.5 and 95 mg/mL) showed a repellent effect against T. castaneum ranging from 50.25 to 87.25 % and 57.25–93.75 % against R. dominica at different exposure times from 10 min to 5 h of exposure. For T. castaneum, the highest repellency was observed at the highest dose of 95 mg/mL after 5 h of exposure. Similarly, for R. dominica, the greatest repellency was achieved at 47.5 mg/mL after 4 h of exposure, also showing a 100 % repulsion rate. In terms of its antifeedant effect, the highest antifeeding index was observed after 3 days of exposure. At the highest dose (95 mg/mL), the extract reached 84 % for R. dominica, classified as strongly deterrent, and 57 % for T. castaneum, classified as moderately deterrent. Not only that, this extract showed a toxicity against T. castaneum (LD₅₀ = 16.38 mg/mL, LD₉₀ = 47.48 mg/mL) and R. dominica (LD₅₀ = 12.84 mg/mL, LD₉₀ = 31.56 mg/mL) after 7 days of exposure. This study highlights the potential of P. halepensis acting as a strong repellent, antifeedant, and toxic agent against both pests. Its wide distribution and availability promote its use as a novel botanical insecticide to control pests as an alternative to chemical insecticides.