Adulticidal, larvicidal and biochemical properties of essential oils against Culex pipiens L

In this study, the insecticidal properties of sixteen essential oils isolated from Egyptian plants were evaluated against the fourth instar larvae and adults of Culex pipiens L. The inhibitory effects of most active essential oils on the activity of acetylcholinesterase (AChE) and adenosine triphosphatases (ATPases) were also tested. In larvicidal assay against Cx. pipiens, the oils of Artemisia monosperma, S. terebinthifolius and Origanum vulgare showed the highest insecticidal activity with LC50 values of 7.73, 8.14 and 8.40 mg/l after 24 h of treatment and 2.63, 3.46 and 6.74 mg/l after 48 h of treatment. On the contrary, the oils of Schinus molle and Rosmarinus officinalis were the less effective. The results of fumigant toxicity assay against the adults of Cx. pipiens revealed that the tested oils had remarkable toxicity based on their LC50 values which ranged between 0.06 and 12.84 mg/l. The oil of Artemisia judaica was the most active with an estimated LC50 value of 0.06 mg/l air after 24 h of treatment, while the oil of Citrus paradisi was less active. The essential oils of A. monosperma, O. vulgare, S. terebinthifolius and C. paradisi elicited marked enzymatic inhibition towards AChE and ATPases isolated from Cx. pipiens larvae. These results indicated that the essential oils have potential for the development of natural larvicides and fumigants for Cx. pipiens control.