author(s)
Khedidja Amira, Touahria Chouaib, Nour El-Houda Djeghader and Hamid Boudjelida

abstract
Mosquitoes are vectors of several diseases affecting humans and domestic animals worldwide. Plants seem to be alternative sources, instead of conventional pesticides, for mosquito control agents. Essential oils are used fumigants and have low toxicity to non target animals and toxicity to insect pests. The purpose of the present study was to assess the larvicidal activity of a medicinal plant, Hertia cheirifolia, against Culex pipiens mosquito, under laboratory conditions. The toxicological assays were carried out using a powder formulation of Hertia cheirifolia, with different concentrations (8, 16 and 48g/l), on the fourth instar larvae of Culex pipiens, for 24 hours as recommended by World Health Organization (WHO), to determine the two lethal concentration LC₅₀ and LC90. The obtained results showed a highly significant effect of this plant with all tested concentrations, with dose response relation-ship mortality, for all treated larval stages. Using the highest concentration of 48g/l of the plant extract the mortality increased throughout the stages; when it was 98.66% for the L1, 93.33% for L2, 86.66% for L3 and 82.66% for the oldest stage L4. The lethal concentrations LC₅₀ and LC₉₀ were estimated with confidence limits, and their values increased inversely to the larval stages.