Activity of Rosmarinus officinalis (Lamiales: Lamiaceae) Essential Oil and Its Main Constituent, 1,8-Cineole, against Tribolium castaneum (Coleoptera: Tenebrionidae)1

Abstract

Abstract Rosemary essential oil (EO), from Rosmarinus officinalis L. (Lamiales: Lamiaceae), has potent properties against stored insect pests. This study aimed to evaluate the efficacy of EOs from both manually extracted and commercially produced R. officinalis, as well as the main compound 1,8-cineole, against adults of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Chemical analysis of the R. officinalis EOs was conducted using a gas chromatograph–mass spectrometer. Toxicity and repellent effects were assessed through contact and fumigation bioassays in a factorial experimental design with five replicates. Each R. officinalis EO type showed nine major compounds (>90%), with 1,8-cineol as the predominant component (>52%). Contact toxicity bioassays showed 1,8-cineole had a median lethal concentration of 1.12% at 48 h, 1.54% for manually extracted EOs, and 1.64% for commercially produced R. officinalis EOs. Furthermore, 0.5% of 1,8-cineole displayed strong contact efficacy against T. castaneum. Fumigant toxicity was observed at 140.07, 127.28, and 121.52 μl/L air, respectively. Manually extracted EO at 160 μl/L air demonstrated strong fumigant efficacy against T. castaneum, acting as a contact (66–94%) and fumigant (82–69%) repellent within 8 h, outperforming commercially produced EO and 1,8-cineole. These findings highlight the potential of manually extracted EO from R. officinalis as a natural insecticide, effective in both contact and fumigation against T. castaneum. This offers a promising avenue for using plant extracts in storage pest prevention, potentially leading to the development of insecticide products.