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通过在田间进行人工接种模拟自然发病流行的情况，确定大豆灰斑病发病为２级时是引起大豆减产的病情低限。采用二元多项式逐步回归法，建立了生育期（生长发育天数）和病级单独及联合起来对单株产量、瘪荚率和百粒重影响的优化方程，同时建立了灰斑病对大豆田间群体产量损失估计模型。并且通过相关性分析，确定始粒期病情对大豆产量影响最大，建立了关键点模型
By artificial inoculation in the field to simulate the natural epidemic situation, to determine the incidence of soybean gray spot disease is caused when the second level of soybean low limit of decline. Based on the binary polynomial stepwise regression method, the optimization equation of the effects of single growth period (growth days) and disease stage on the yield of individual plants, the rate of defoliation pod and the weight of 100 kernels was established. At the same time, Population Yield Loss Estimation Model. And through the correlation analysis, it was determined that the disease at the beginning of grain period had the greatest impact on soybean yield, and the key point model