Chemical Identification Of Volatiles From Suaeda Salsa Plant And Biological Acitivity Measurement Of These Volatiles To Spodoptera Exigua Moths

The beet armyworm,Spodoptera exigua(H(u|¨)bner),is a key pest in many crops around the world.This insect now is becoming extremely difficult to control by application of synthetic insecticides,due to its development of high resistance to many classes of insecticides,so alternative control techniques are urgently needed to develop.Many field investigations showed that some chenopodiaceous weeds including Suaeda salsa are hosts of oviposition and feeding by S.exigua.In order to develop a pest control technology by regulating the moth behavior,we aimed to find some effective volatiles from S.salsa plants that is an abundant biological resource along the costal area in Jiangsu province.The present study dealt with chemical identification and bioassay of the volatiles from the S. salsa plants.The results were summarized as follows:1.Using GC-MS,six components includingβ-caryophyllene were chemically identified from volatiles of live S.salsa plants collected by dynamic pumping absorption method.2.EAG measurement showed that crude extract prepared by dynamic pumping absorption method elicited remarkable responses to male and female moth,which meant that there were active components in the crude extract.Further electroantennogram response measurement with 3 of those six identified components showed thatβ-caryophyllene and 2,6-bis(1,1-dimethylethyl)-phenol elicited remarkable responses to female S.exigua,and thatβ-caryophyllene elicited remarkable responses to male moth, with highest responses elicited by the component at the dose of 50μg.However,EAG responses of binary and ternary mixtures were not significantly higher than that ofβ-caryophyllene alone.EAG responses of males to blends of plant volatile components and female sex pheromone components were significantly higher than that of sex pheromone alone.3.In the oviposition preference experiments,female moths preferred ternary mixtures andβ-caryophyllene to the hexane control.Olfaction experiments showed that ternary mixtures elicited remarkable preference to female moth at the dose of 250μg.For male moths,EAG responses were not significantly increased by adding the tertiary mixture of plant volatiles to the female sex pheromone components at any tested dose.Olfaction experiments of male and female moth to single volatile component showed thatβ-caryophyllene elicited remarkable preference to female moth at the dose of 100μg,while there was no effect ofβ-caryophyllene on the attractiveness to male moths at any dose.In conclusion,total 6 components were identified from the volatile extract from S. salsa plants.Among the 6 identified components,3 were tested in terms of biological activity to the beet armyworm moths.It is concluded thatβ-caryophyllene was the only component with the biological activity to female moth but not male moth.The results might provide some theoretical basis for development of the behavioral control method against S. exigua.