Chemical composition and larvicidal activity of <i>Zanthoxylum armatum</i> against diamondback moth, <i>Plutella xylostella</i>

<div><p>The diamondback moth, <i>Plutella xylostella</i> (L.) (Lepidoptera: Yponomeutidae) is the most serious pest of cruciferous crops grown in the world causing economic yield loss. Several synthetic insecticides have been used against <i>P. xylostella</i> but satisfactory control was not achieved due to development of resistance to insecticides. Therefore, the present study was carried out to screen different fractions of <i>Zanthoxylum armatum</i> for their insecticidal activities against second instar larvae of <i>P. xylostella</i>. Results indicate, all the fractions showed activity to <i>P. xylostella.</i> However, <i>n</i>-hexane fraction of <i>Z. armatum</i> showed maximum larvicidal activity with minimum LC<sub>50</sub> value of 2988.6 ppm followed by ethanol (LC<sub>50</sub> = 12779.7 ppm) and methanol fraction (LC<sub>50</sub> = 12908.8 ppm) whereas chloroform fraction was least toxic (LC<sub>50</sub> = 16750.6 ppm). The GC–MS analysis of <i>n</i>-hexane fraction of leaf extract showed maximum larvicidal activity, which may be due to two major compounds i.e. 2-undecanone (19.75%) and 2-tridecanone (11.76%).</p></div>