在花木病虫害的防治中,常会出现这样的现象:一种农药在同一病虫上连续反复地使用,一段时间以后药效会明显减退,甚至无效。例如:一六○五是有机磷杀虫剂中最早推广的品种,开始用来防治红蜘蛛、蚜虫等害虫时,稀释倍数在5000倍以上,但现在用1000倍都常常控制不住。再如:六六六是五六十年代农业生产中普遍使用的一种农药。那时农药品种比较单一,日常生 In the pest control of flowers and trees, there often occurs such a phenomenon: a pesticide on the same pests and repeatedly used, after a period of time efficacy will be significantly reduced, or even invalid. For example, one six five five is the earliest promoted organophosphate insecticide. When it was used to control pests such as red spider, aphid and other pests, the dilution factor was more than 5000 times, but it is often uncontrollable with 1000 times now. Another example: 666 is a commonly used pesticide in agricultural production in the 1950s and 1960s. At that time, a single species of pesticides, daily life