Resistance to Insects in Selective Ecotypes of Cymbopogon pendulus (Nees Ex Steud) Wats

Six insect resistant ecotypes (Pl to P6) of Cymbopogon nendulus obtained through mass selection were screened for their essential oil content and evaluated for their reaction to lepidopteran larvae, Spodop-tera litura and Helicoverpa armigera and d aeteropteran, Dysdercus koenigii nymphs. Phenylpropanoids, elemidn and isoasarone, the major components of these oils, mediated the resistance and could induce growth inhibition and feeding deterrence in these insects. The concentration of these allelochemicals varied in selected ecotypes and the high elemicin content correlated to the resistance. The threshold amount of elemicin required for the deterrence/antibiosis is below the amount present in the elemicin rich C. pendulus ecotypes.