Dual-mode evaluation of five essential oils for rapid knockdown and seed protection against Acanthoscelides obtectus (Coleoptera: Chrysomelidae)

This study evaluated the chemical composition, fumigant toxicity, and residual efficacy of five commercial essential oils (EOs), Origanum vulgare (L.) (Lamiaceae), Syzygium aromaticum (L.) (Myrtaceae), Eucalyptus globulus Labill. (Myrtaceae), Rosmarinus officinalis (L.) (Lamiaceae), and Lavandula angustifolia Miller (Lamiaceae), against Acanthoscelides obtectus (Say, 1831) (Coleoptera: Chrysomelidae) under laboratory conditions. Gas chromatography–mass spectrometry (GC-MS) analysis identified the dominant compound in each essential oil: carvacrol in O. vulgare, eugenol in S. aromaticum, 1,8-cineole in E. globulus, α-pinene in R. officinalis, and linalool in L. angustifolia. Fumigant bioassays revealed that L. angustifolia exhibited the fastest and most potent adulticidal effect, with 100 % mortality at 1.5 µL within 24 h. In post-infestation trials, R. officinalis provided the highest suppression of adult emergence (99.05 %), followed by O. vulgare and E. globulus. Pre-infestation treatments revealed that O. vulgare completely prevented adult emergence and seed damage across all concentrations, even after 45 days. The results highlight both the acute and long-lasting protective actions of EOs, suggesting their suitability as eco-friendly alternatives for managing A. obtectus in stored beans.