Insecticidal activity and repellency of Salvia rosmarinus Spenn. (Lamiales: Lamiaceae) essential oil against two major stored-product beetles

This study, conducted in 2025 at the laboratory of sustainable management of natural resources in arid and semi-arid areas, Naâma, Algeria, aimed to evaluate the chemical composition, contact toxicity, and repellency of Salvia rosmarinus Spenn. (Lamiales: Lamiaceae) essential oil (SREO) from Algeria against two major stored-grain pests, Lesser grain borer, Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae) and Red flour beetle, Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae). GC/MS analysis identified 1,8-cineole (43.63%), camphor (23.13%), α-pinene (8.75%), and β-pinene (6.43%) as the dominant compounds. In contact bioassays, SREO induced concentration-dependent mortality, with LC50 values of 16.2 µL/mL for R. dominica and 28.5 µL/mL for T. castaneum. Repellency assays showed strong concentration- and time-dependent avoidance, reaching 76.5% and 74.5% repellency at 16 µL/mL for R. dominica and T. castaneum, respectively classifying SREO as Class IV repellent. The higher susceptibility of R. dominica underscores species-specific responses. These results highlight SREO as a promising botanical agent for eco-friendly management of stored-product insects.