The volatile oil of Ageratum conyzoides had siqnificant biological actirities on fungi,insects and plants,particalarly on plant diseases and insect pests.The volatile oil and its major component precocene Ⅱ not only had insecticidal efficacy,but also anti\|feeding effect and delayed molting of insects.The chemical constituents of the volatile oil from A.conyzoides were analyzed in detail by means of GC/MS.Twenty\|seven compounds were identified,and ageratochromene with its derivatives as well as monoterpene...