Regional epidemic laws of poplar Ice Nucleation Active bacterial canker

Through the methods of correlation analysis and main factor analysis, the relationship between the poplar INA bacterial canker and circumstances was analyzed and 9 main factors for affecting the disease were selected. Based on the comprehensive analysis of main factors and induced factors, the standard for risk grades of this disease was promoted and northeast region of China was divided into 4 districts with different risk grades: seriously occurring district, commonly occurring district, occasionally occurring district, and un-occurring district. Nonlinear regression analysis for six model curves showed that the Richard growth model was suitable for describing the temporal dynamics of poplar INA bacterial canker. By stepwise variable selection method, the multi-variable linear regression forecasting equation was set up to predict the next year’s disease index, and the GM(1,1) model was also set up by grey method to submit middle or long period forecast.