选用农药把四关农药防治是植物保护的主要方法，在具体运用上应本着经济有效安全的原则，重点把握好“四关”。１把对症下药关选择、购买、使用农药之前首先要弄清楚对植物造成危害是病害、虫害、螨害、草害、鼠害中的哪一类哪一种，再区别主要防治对象和兼治对象，结合农... The use of pesticides to control the four pesticides is the main method of plant protection in the specific application should be based on the principle of cost-effective and safe, focusing on a good grasp of the “four.” 1 the right remedy Before choosing, buying, using pesticides, we must first figure out what is harmful to plants is the disease, pest, mite damage, grass damage, rodent in which one, and then distinguish the main control targets and treating both the object, Combine farming ...