The study was conducted to evaluate effects of varied concentrations of methanol extract of lemongrass, Andropogon nardus L. (10.5%, 9.5%, 8.5%, 7,5%, 6.5%, and 0% as control) on mortality andfeeding activity of the third-instars of P.xylostella larvae. It was used a randomized complete designwith three replicates. The results showed that the leaf extract of Andropogon nardus at 8.5 % wasthe best treatment as it could caused high mortality of P. xylostella (66.67 %) and it was able todeter the feeding activity up to 82.66 %. The data suggested that extracts of Andropogon narduscontains toxic oil and feeding activity repellant.Key words: Diamondback moth, insecticidal activity, lemon grass
