A new idea concerning economical threshold of energy flow(EET)was advanced.EETis meant by that the energy flowed out of the crop to the subsystem of pest amounts to suchan extent of allowable threshold,as a result that the economic gains should be the maximum.The EET,relating only to standing-corp of producer,shows a dynamic curve.In this paper,regarding the cotton field without appling insecticides as an object of system,a program wasput foward for researching EET:to construct the models of energy flow in th...