Effects of non-alkaloid extracts from tropical yam, Dioscorea hispida against the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae)

Abstract

A non-alkaloidal extract obtained from rhizomes of Dioscorea hispida was isolated and purified by thin layer chromatography. Each fraction was examined to evaluate feeding deterrent activity, developmental effects and toxicity against larvae of the diamondback moth (DBM), Plutella xylostella. Activity was shown in the benzene fraction, which was further fractionated into 5 fractions (Frs. 9 to 13). All fractions showed feeding deterrent activity at higher concentrations, however, Frs. 11, 12 and 13 exhibited feeding deterrent activity at lower concentrations of 10, 25, 100 μg/ml, respectively. These fractions significantly reduced larval weight and caused higher larval and pupal mortalities at 40% (Fr. 11), 37% (Fr. 12), and 27% (Fr. 13). No delay in larval development was observed in any of the fractions.