author(s)
Zineb Dahchar, Fatiha Bendali-Saoudi, Noureddine Soltani

abstract
The larvicidal potential of aqueous extracts from leaves of three plants (Ricinus communis L., Daphne gnidium L. and Thymus vulgaris L.) was evaluated against the different larval instars of Culex pipiens Linné 1758 and Culiseta longiareolata Aitken 1954 mosquitoes. Mortality counts were made after 24, 48 and 72 hours exposure, respectively. The extracts exhibit insecticidal activity against larvae of the two tested mosquito species. Lethal concentrations (LC) values gradually decreased with increased exposure times. The LC₅₀ values of the tested plant extracts recorded after 72h of exposure were determined: D. gnidium (0.05, 0.03, 0.06, 0.07g/l), R. communis (0.03, 0.04, 0.04, 0.06 g/l) and T. vulgaris (0.02, 0.03, 0.03, 0.02 g/l) respectively against 1, 2, 3 and 4th instar larvae of Cx. pipiens. Concerning Cs. longiareolata, the LC50-72h found against 1, 2, 3 and 4th instar larvae were respectively for D. gnidium (0.09, 0.07, 0.12, 0.13 g/l), R. communis (0.02, 0.06, 0.09, 0.08 g/l) and T.vulgaris (0.02, 0.02, 0.03, 0.03 g/l). Plant extracts tested were found more effective against Cx. pipiens and the highest activity was found for T. vulgaris extracts.