INSECTICIDAL ACTIVITY OF METHANOLIC EXTRACT OF THE LEAVES OF HYPTIS SUAVEOLENS (L.) POIT AGAINST ADULT CULICINE MOSQUITOES

This study determined the evaluation of insecticidal activity of methanolic extract of the leaves of Hyptis suaveolens (L.) Poit against adult culicine mosquitoes.The Agilent gas chromatography/mass spectrometry analysis of the methanol extract of Hyptis suaveolens leaves revealed the presence of 63 chemical compounds. Dehydroabietinol (23.6%), Bis(2-ethylhexyl) phthalate (6.8%), and Eucalyptol (6.8%) are the three most abundant chemical compounds found in the plant extract with the retention time (RT) of 21.5, 23.2 and 6.1 minutes respectively. The methanol extracts of H. suaveolens leaves showed a varying number of mosquitoes knocked down for all replications after different periods of exposure, with the 100.0 mg/ml treated group having the most knock downs and the control group replicates showing no knock down. A one-hour exposure to the plant extract resulted in a 62.7 - 85.3% dose-dependent increase in the number of mosquito knockdowns. After 24 hours of exposure, all treatment groups had 100% mortality, with the exception of the control group, which had 6.7% mortality. Following 6 hours of exposure, there were 0.0, 72.0, 82.7, and 100.0% deaths in the control, 25.0, 50.0, and 100.0 mg/ml treatment groups, respectively. The three concentration yield LC50 of 24.9mg/ml and LC90 of 48.5mg/ml in culicine mosquito.