Logistic 模型在植病流行学中应用的有关问题的探讨

On the Application of Logistic Model in Plant Epidemilogy

根据水稻纹枯病流行的研究，观察了病害流行速率（ｒ）与初始病情（ｘ０）的关系，结果表明，病害流行速率与初始病情呈负相关，其回归式为ｒ＝０．１１７７－０．０２２６Ｌｎｘ０１－ｘ０（Ｒ２＝０．３７８８）。在ｘ０不同的情况下，不能直接比较ｒ。对不同环境下的病害最大比率即环境容纳量Ｋ值进行了０．６１８法优化筛选，认为采用０．６１８法拟合病害流行曲线较符合实际。本文还对Ｌｏｇｉｓｔｉｃ模型的应用和存在问题进行了讨论。

The relationship between the amount of initial disease (x 0) and rate of disease progress (r) of rice sheath blight was investigated.A negative corelationship between x 0 and r was found,and could be expressed as r=0 1177—0 0226 lnx 01-x 0(R 2=0 3788).If the x 0 are different,r can not be compared with each other directly.Optimum seeking method (0 618 method) was used to screen k value,i e the carrying capacity and proved to be a practical way to model the epidemical curve.