害虫不但为害农作物、损害贮备粮食,也传播病菌危害人畜健康。第二次世界大战以来人们用DDT等化学药剂来防治,在一定时期内起到了一定的疗效,但随着时间的推移、害虫的抗药性逐渐增加,人们不得不生产另一种新的药物来代替原来有效的药物。长此以往,药物越来越复杂、环境也渐受污染,保护健康的药物反而成了污染环境、有碍健康的因素。除虫菊花早已为人们用来提炼对人畜无毒的杀虫剂、但这种除虫菊剂造价很高,暴露在空气和阳光下化学分解太快、容易失效。40年代后期,科学家们对除虫菊剂的分子结构与杀伤昆虫力之间的关系进行 Pests not only harm crops, damage to stored food, but also spread germs harmful to human and animal health. Since the Second World War, people used DDT and other chemical agents to prevent and cure them, and they have achieved some effect over a certain period of time. However, as time goes on, pest resistance gradually increases and people have to produce another new drug Instead of the original effective drugs. Over time, drugs become more and more complex, the environment is getting contaminated, and the protection of healthy drugs has become a factor that pollutes the environment and hinders health. Pyrethrum has long been used for people to extract non-toxic insecticides to humans and animals, but this pyrethrins costly, exposure to air and sunlight chemical decomposition too fast, easy to failure. In the late 1940s, scientists conducted a study on the relationship between the molecular structure of pyrethrin and the killing insect force