Asarones fromAcorus calamus L. Oil : Their effect on feeding behavior and dietary utilization inPeridroma saucia

Asarones (2, 4, 5-trimethoxypropenylbenzenes) isolated from the essential oil ofAcorus calamus L. rhizomes, are potent growth inhibitors and antifeedants to the variegated cutworm,Peridroma saucia Hubner.cis-Asarone added to artificial diet significantly inhibited growth and feeding by first-, third-, and fourth-instar larvae, whereas thetrans isomer produced an antifeedant effect alone. Gross dietary utilization (efficiency of conversion of ingested food, ECI) was decreased when the diet was supplemented withcis-asarone or when this compound was topically applied to fourth-instar larvae. Inhibition of growth occurred even at a moderate topical dose (5 μg/larva) primarily as a result of decreased efficiency of conversion of digested food (ECD), even though the approximate digestibility (AD) of the food was unchanged. Oral or topical treatment withtrans-asarone also significantly inhibited larval growth, but in this case the effect can be strictly attributed to decreased consumption, as dietary utilization (ECI) was not affected. Both isomers displayed a direct antifeedant effect based on leaf disk choice tests. Thecis isomer was 7.0 and 5.5 times more potent thant thetrans isomer against fourth- and fifth-instar larvae, respectively. Our data suggest that the two asarone isomers have different modes of action.cis-Asarone is toxic in addition to having strong antifeedant activity, whereas thetrans isomer acts only as an antifeedant with no appreciable toxicity.