人工合成的农药,虽然在杀灭害虫中起了很大的作用,但也存在一些缺点:如杀伤自然界中害虫的天敌,造成环境的污染,促使害虫产生抗药性等。但是,如果利用植物体内产生的杀虫物质来防治害虫,可以较好地解决这些问题。在我国目前情况下,因地制宜地发展植物农药,是解决农业用药的一种好办法。我国植物资源丰富,含杀虫素的植物很多,如除虫菊、鱼藤、闹羊花、巴豆、苦楝、榆树、臭椿、烟草、大蒜等都具有杀虫作用。植物体内的杀虫成分非常复杂。一般植物性农药中,有的是一种化合物,有的是几种相类似的化合物,有的是几种不同的化合物。它们的化学成分有生物碱、糖苷类、有毒蛋白质、挥发性香精油、单宁、树脂、有机酸类、酯类及酮类 Synthetic pesticides play a great role in killing pests, but they also have some disadvantages: they kill natural enemies of pests in nature, cause environmental pollution, and promote pest resistance. However, if we use the insecticide produced in plants to control pests, we can solve these problems better. Under the current situation in our country, the development of plant pesticides in accordance with the local conditions is a good way to solve the problem of agricultural drugs. China is rich in plant resources and contains many insecticides, such as pyrethrum, rattan, ragweed, croton, neem, elm, ailanthus, tobacco and garlic. Insecticidal ingredients in plants are very complex. In general plant pesticides, some are a compound, some similar to several compounds, some of several different compounds. Their chemical constituents are alkaloids, glycosides, toxic proteins, volatile essential oils, tannins, resins, organic acids, esters and ketones