Insecticidal properties of essential plant oils against the mosquito Culex pipiens molestus (Diptera: Culicidae)

The insecticidal activities of essential oil extracts from leaves and flowers of aromatic plants against fourth-instar larvae of the mosquito Culex pipiens molestus Forskal were determined. Extracts of Myrtus communis L were found to be the most toxic, followed by those of Origanum syriacum L, Mentha microcorphylla Koch, Pistacia lentiscus L and Lavandula stoechas L with LC50 values of 16, 36, 39, 70 and 89mg litre-1, respectively. Over 20 major components were identified in extracts from each plant species. Eight pure components (1,8-cineole, menthone, linalool, terpineol, carvacrol, thymol, (1S)-(-)-α-pinene and (1R)-(+)-α-pinene) were tested against the larvae. Thymol, carvacrol, (1R)-(+)-α-pinene and (1S)-(-)-α-pinene were the most toxic (LC50=36-49mg litre-1), while menthone, 1,8-cineole, linalool and terpineol (LC50=156-194mg litre-1) were less toxic. © 2002 Society of Chemical Industry.