Chemical composition and effects of four essential oils on mortality, development and physiology of the West Nile virus vector, Culex pipiens

The search for new natural insecticides to control the West Nile virus vector, Culex pipiens, and other mosquito species has gained importance in the past two decades. Therefore, the current study aimed to evaluate the insecticidal and developmental effects of essential oils from Artemisia judaica, Cupressus macrocarpa, Callistemon viminals and Citrus aurantifolia on Cx. pipiens. The essential oils were extracted by hydrodistillation and their chemical compositions were characterized by gas chromatography/mass spectrometry (GC/MS). The oils were mainly composed of monoterpene hydrocarbons and oxygenated monoterpenes. β–Thujone (49.83%), terpinen-4-ol (20.29%), 1,8-cineole (71.77%) and limonene (40.19%) were the most dominant compounds in A. judaica, Cu. macrocarpa, Ca. viminals and C. aurantifolia oils, respectively. The essential oils exhibited larvicidal activity against Cx. pipiens and their activity improved with increasing the concentration and exposure time. The oils of C. aurantifolia and Cu. macrocarpa were most effective and produced 73.3 and 52.0% mortality at 100 mg/L by the end of larval stage. Meanwhile, the oils induced pupal and adult mortality ranged between 3.33 and 25%. Based on the LC50 values of the total stages mortality, C. aurantifolia oil (LC50 = 13.49 mg/L) was the most active, followed by Cu. macrocarpa (LC50 = 22.93 mg/L) and Ca. viminals (LC50 = 38.69 mg/L). Furthermore, the oils of Cu. macrocarpa and Ca.viminals significantly increased the longevity of larva and pupae, while drastically decreased adult longevity of Cx. pipiens. Additionally, the four essential oils caused pupal and adult malformation and induced abnormalities of stomach and great inhibition in reproduction tracts. This is the first report on developmental and malformative effects of tested essential oils. The results showed that the essential oils demonstrated various bioactivities against Cx. pipiens, suggesting their potential use in insect control programs.