Laboratory Evaluation of Crude Leaf Extracts of Cassia occidentalis Linneaus (Caesalpinaceae) as an Oviposition Determinant and Ovicide against Vector Mosquitoes Anopheles stephensi Liston, Culex quinquefasciatus Say and Aedes aegypti Linneaus (Diptera: Culicidae)

The oviposition determinant and ovicidal activity of hexane, ethyl acetate and methanol crude leaf extracts of Cassia occidentalis against Anopheles stephensi , Culex quinquefasciatus and Aedes aegypti were studied in laboratory. The ovipositional determinant nature of the test solutions was studied at 0.1% by choice based oviposition of gravid vector mosquitoes. In hexane, ethyl acetate and methanol crude leaf extracts, the effective deterrence was 97.0%, 92.5% and 93.7% in Anopheles stephensi ; 87.8%, 90.4% and 73.0% in Culex quinquefasciatus ; 94.0%, 96.2% and 99.0% in Aedes aegypti respectively. The ovipositional active index was -0.9, -0.9 and -0.9; -0.8, -0.8 and -0.5; -0.8, -0.8 and -0.9 respectively indicating the deterrent property of the crude leaf extracts. The ovicidal activity was studied at 0.25%, 0.50%, 1.00% and 2.00%. Gravid vector mosquitoes were constrained in an ovitrap to lay eggs directly on to the test solutions. Egg mortality rate (per cent of eggs unhatched) was determined for assessment. At the lowest concentration, among the extracts, no absolute mortality was obtained and the hexane extract caused maximum egg mortality in both Anopheles stephensi (74.5%) and Culex quinquefasciatus (66.5%) and methanol extract in Aedes aegypti (92.5%) indicating poor ovicidal activity.