Three different methods (steam distillation,Soxhlet extraction,decompress steam distillation) were used to extract plant
volatiles.The percentage of getting
volatiles by the three methods were analyzed.The results showed that the percentage of getting volatiles using Soxhlet extraction was the highest.Four Chinese herbal medical plant,Zanthoxylum piperitum,Ipomoea nil Roth,Azadirachta indica Adr.Juss,Allium sativum L.and aloe were studied. The effect of the five plant volatiles on population inhibiting and killing by touch to three insects,Rhizopertha dominica Fbricius,Tribolium confusum(Herbst)and Troctes divinatorius Muller,was studied.The results showed that the effect of Allirm sativum L. on the three insects was the best.Aloe extract has the good effect against R.dominica,but the effect against T.castaneum and Liposcelis was not compared with Zanthaxylum piperitum and Azadirachta indice
extracts.Column chromatography was used to primarily separate the volatile of Allium sativum L.,and five crude extracts were gotten.The five crude extracts were analyzed by gas chromatography(GC-112A)with capillary column(SE-54 30m×0.25um×0.2um) and FID.The result showed that there were more than three chemical components in each crude extract.The killing effect of No.2 was the best.The result of analysis by GC-MS showed that there were five chemical sulphur components