Toxicity of Three Tropical Plants to Mosquito Larvae, Pupae and Adults

The toxicity of the extracts of three common tropical plants; Tobacco plant ( Nicotiana tabacum ), West African Black Pepper ( Piper guineense ) and Jimson weed ( Datura stramonium ) was evaluated on the larvae and pupae of Anopheles gambiae while the fumigation effect of the extracts was investigated on the adult mosquito. The concentrations of the extract used in the study were 0.1%, 0.2%, 0.4%, 0.8% and 1.0%. The extracts of the leaves of N. tabacum and seeds of P. guineense had significant larvicidal and pupaecidal effect on A. gambiae at 1hour and 24hours observation having LC95 values of 0.67mL and 0.1mL for larvae and 0.19mL and 0.1mL for pupae respectively. However, only N. tabacum at 0.8% and 1.0% had significant adulticidal effect on the adult mosquito under 1hour observation. The extract of D. stramonium leaves had LC95 value of 1.07mL for larvae and 0.91mL for the pupae. It was found to be least toxic to the larvae and pupae after 1hour and 24 hours observation period. It also had no lethal effect on the adult A. gambiae at all concentrations. It is inferred from the results obtained that the extracts used had some bioactive constituents, which resulted in the mortality effects.