Chemical composition and insecticidal activity of lemon verbena essential oil

Essential oil extracted from the leaves of lemon verbena, Lippia citriodora Kunth (Verbenaceae) was tested for fumigant toxicity in the laboratory against two stored-product insects Tribolium confusum Jacquelin du Val and Callosobruchus maculatus (F.). The chemical composition of the isolated oil was examined by GC-MS. The major compounds were citral (11.3%), limonene (10.6%), neral (7.9%), 4-phenyl undecan-4-ol (7.7%), ?-curcumene (6.5%), ?-cedrol (4.5%) and caryophyllene oxide (4.5%). Furthermore, lesser amounts of other components i.e. carveol (3.7%), linalool (3.5%), ?-pinene (3.2%), caryophyllene (2.8%) and geranyl acetate (1.8%) existed in the essential oil. The fumigant toxicity of essential oil at 27 ± 1 °C and 65 ± 5% R. H., darkness condition and 24 h exposure time, showed considerable differences in mortality of insects. C. maculatus (LC50 = 10.2 µl/l air) was significantly more susceptible than T. confusum (LC50 = 497.8 µl/l air). These results suggested that essential oil of L. citriodora could be used as a potential control agent against stored-product insects.