Insecticidal and growth regulating activity of crude leaf extracts of Cassia occidentalis L. (Caesalpinaceae) against the urban malaria vector, Anopheles stephensi Liston (Diptera: Culicidae)

ObjectiveTo investigate insecticidal and growth regulating activity of crude leaf extracts of Cassia occidentalis L. (Caesalpinaceae) against the urban malaria vector, Anopheles stephensi Liston. (Diptera: Culicidae).MethodsLarvicidal activity was studied against third instar larvae for 24 h at concentrations of 62.5, 125.0, 250.0, 500.0, 1 000.0, 2 000.0, 4 000.0 and 8 000.0 mg/L. The effect on development and growth of immature mosquitoes was studied at concentrations of 125.0, 250.0 and 500.0 mg/L and was assessed by growth index. Adulticidal activity on topical application was studied on test dosages of 0.01, 0.05, 0.10, 0.25 and 0.50 μg per newly emerged unfed adult female mosquito.ResultsLarvicidal activity was poor, not proportional to concentration and LC50 values were above the acceptable dose of 10 mg/L. Potential growth regulating activity was observed and the growth index was 277.5, 111.0 and 27.5 times less than control, respectively. Average larval pupal transformation was 5.8, 4.3 and 96.0 times greater than pupal adult transformation in hexane, 5.0, 4.3 and 48.4 in ethyl acetate, and 4.8, 4.2 and 10.2 in methanol extract, respectively. Adulticidal activity was the highest in ethyl acetate, followed by hexane and methanol extract with LD50 values of 0.23, 0.32 and 0.64 μg/female mosquito, respectively.ConclusionsThe crude leaf extracts of Cassia occidentalis studied showed poor larvicidal, potential growth regulating and a moderate level of adulticidal activity.