Authors : S. S. Keita, B.A.Umoetok and J.G.Smith
Abstract: A laboratory experiment was conducted to investigate the insecticidal activities of petroleum ether extract of H. suaveolens seeds on second instar larvae of the Diamond back moth, Plutella xylostella (L.). Four concentrations (1.25, 2.5, 5.0, and 10.0% v/v) of the seed extract diluted in 70:30 v/v petroleum ether: olive oil mixture, were prepared. Spraying was done using the Potter tower. Two millilitres of the spray solution was pipetted into the reservoir of the Potter tower and sprayed onto fresh Chinese cabbage leaves, which, were placed at the base of the Potter tower. An unsprayed Chinese cabbage leaves were included as control. Ten second instar larvae of Plutella xylostella were released into each container. Mortality was observed after 24 and 48h. The seed extract showed high toxicity against P. xylostella. LC50 values of 6.49 and 4.39 % were recorded after 24 h and 48 h exposure, respectively. At 24 and 48 h of exposure, mortality was significantly (p=0.05) higher (63 and 82%) at 10% concentration than at other concentrations. The regression analysis of percent concentrations of the extracts against percent mortality of P. xylostella indicated a high coefficient of determination (r2 = 0.9216 and 0.9369), which indicated that 92.16 and 93.69% of the mortality was accounted for by the concentrations of the extracts.
Keita, S. S. , B.A.Umoetok and J.G.Smith , 2006. The Insecticidal Activity of Petroleum Ether Extract of Hyptis suaveolens Poit (Labiatae) Seeds on Plutella xylostella (L.) (Lepidoptera:Y ponomeutidae). Agricultural Journal, 1: 11-13.