Toxicity of β-citronellol, geraniol and linalool from Pelargonium roseum essential oil against the West Nile and filariasis vector Culex pipiens (Diptera: Culicidae)

•Culex pipiens vectors key pathogens and parasites, e.g. West Nile and filariasis•We evaluated the toxicity of Pelargonium roseum and its major constituents on Cx. pipiens•The oil major constituents were β-citronellol, geraniol, and linalool•The oil tested on larvae and egg rafts of Cx. pipiens showed LC50 of 5.49 and 0.45 μg/ml•Geraniol, β-citronellol and linalool had LC of 6.86, 7.64 and 14.87 μg/ml on larvae

Insect vectors are responsible for spreading devastating parasites and pathogens. A large number of botanicals have been suggested for eco-friendly control programs against mosquito vectors, and some of them are aromatic plants. Pelargonium roseum, a species belonging to the Geraniaceae family, due to its pleasant rose-like odor may represent a suitable candidate as mosquito repellent and/or larvicide. In this research, we evaluated the toxicity of the essential oil from P. roseum and its major constituents against the West Nile and filariasis vector Culex pipiens. The chemical composition of P. roseum essential oil was analyzed by gas chromatography-mass spectroscopy. Major constituents were citronellol (35.9%), geraniol (18.5%), and linalool (5.72%). The bioactivity of P. roseum essential oil and its three major compounds on larvae and egg rafts of Cx. pipiens was evaluated. The essential oil had a significant toxic effect on larvae and egg rafts of Cx. pipiens, with 50% lethal concentration (LC50) values of 5.49 and 0.45 μg/mL, respectively. Major constituents, geraniol, citronellol and linalool resulted in LC50 values of 6.86, 7.64 and 14.87 μg/mL on larvae, and 0.8, 0.67 and 1.27 μg/mL on egg rafts. Essential oil and two of its constituents, citronellol and geraniol showed moderate knock-down on Cx. pipiens adults. Overall, the present investigation revealed that the major components of P. roseum and specially the whole essential oil could be helpful in developing novel and safe mosquito control tools and also offer an environmentally safe and cheap tool for reducing Cx. pipiens mosquito populations.