ANTIFEEDANT AND GROWTH-INHIBITORY EFFECTS OF THE LIMONOID TOOSENDANINAND MELIA-TOOSENDAN EXTRACTS ON THE VARIEGATED CUTWORM, PERIDROMA-SAUCIA (LEP, NOCTUIDAE)

Antifeedant and growth inhibitory effects of toosendanin, a limonoid a llelochemical from the bark of the trees Melia toosendan and M. azedar ach, were determined for the variegated cutworm, Peridroma saucia, usi ng different bioassays. Toosendanin significantly deterred feeding of 2nd and 4th instar larvae in diet choice and leaf disc choice bioassay s, respectively. Refined bark extracts containing 60-75% toosendanin w ere less deterrent than the pure compound in both bioassays. However, the 60% extract significantly inhibited growth of neonate larvae in a dose-dependent manner when incorporated into an artificial diet, with an EC(50) (concentration reducing growth by 50% relative to controls) of 42.3 ppm at 7 days. Extracts containing 60% and 75% toosendanin wer e more inhibitory than equivalent amounts of pure toosendanin in this chronic growth bioassay, suggesting the presence of other minor consti tuents which must be significantly more inhibitory, though less deterr ent to feeding, than toosendanin itself. Nutritional analyses of 4th i nstar larvae following both oral and topical administration of toosend anin or the 75% extract confirm that both materials possess a combinat ion of antifeedant and growth inhibitory properties.