EVALUATING THE EFFECTIVENESS OF OCIMUM GRATISSIMUM (L) AS AN INSECTICIDE AGAINST ADULT ANOPHELES MOSQUITOES

The insecticidal effect of Ocimum gratissimum (Lamiaceae) on wild-caught adult Anopheles (WAA) mosquitoes was investigated. The aim of this investigation was to find an eco friendly, affordable and available means of physically combating mosquitoes near our homes. Sixty (60) wild - caught adult mosquitoes were exposed to three concentrations, 1%, 2% and 3% , of the aqueous extract of the leaves of Ocimum gratissimum in an insect box. Investigations were based on the World Health Organization (WHO) susceptibility test for adult mosquitoe bioassay procedure which involves exposing the mosquitoes at different time intervals to different concentrations of the suspected insecticidal extract. 0.75% of 2, 2-dichlorovinyl di methyl phosphate (DDVP), was used as a reference insecticide. Results obtained showed a time dependent insecticidal effect of the extract on WAA mosquitoes, such that a t 60 minutes there was 100% mortality of mosquitoes at all concentrations of exposure, indicating the insecticidal potentials of the aqueous extract of O. gratissimum against malaria – causing mosquitoes. Further investigations to ascertain and isolate the active ingredient with this potentiality in the herb extract, is being recommended as an initial step in the formulation of a cost effective and eco- friendly bio-insecticide