It is a hard work to deal with the problem above, firstly we must understand the reason , occurence rule and traits of various harms , and secondiy establish correspond control strategy and methods.

• 解决以上问题是一项艰巨的任务，首先我们必须理解各种病害发生的原因，规律和特点，其次建立对应的控制策略和方法。