1 诊断错误病当虫治,虫当病治。如果树早期落叶,当作红蜘蛛危害;番茄青枯病死苗,错诊为地下害虫咬根等,这样用药再多也不会见效。2 药不对症诊断正确,但药不对症。例如用福美双防治向日葵菌核病,用三氯杀螨防治粘虫,农用链霉素防治白粉虱等等,均没有效果。3 贻误良机防治虫害,应在成虫产卵高峰期或幼虫初卵期施药效果最好。如果幼虫已至三龄以上,作物已受害成灾,此时防治,施药多,效果差。 1 diagnosis error when a worm, insect treatment when the disease. If the early deciduous tree, as a red spider harm; Tomato bacterial wilt dead seedlings, misdiagnosed as underground insect bites, so medication will not be effective again. 2 medicine diagnosis is correct, but medicine is not symptomatic. For example, with the United States and the United States against Sunflower sclerotinia, with trichlorfon mite control armyworms, agricultural streptomycin control whitefly, etc., have no effect. 3 Bungling opportunity to control pests, should be the peak spawning or adult larvae early spawning application of the best. If the larvae have reached the age of more than three, the crop has been victimized, at this time prevention and treatment, spraying more, poor results.