Abstract: Based on the data of meteorology and monitoring on Valsa sordida Nits during 2002-2008 in 18 observation stations of Hebei province,the relationship between the occurrence and development of Valsa sordida Nits and meteorological conditions was analyzed applying correlation and regression analysis method.The results showed that the precipitation,rain day,relative humidity and temperature-humidity coefficient were positively related to the incidence of Valsa sordida Nits.It was favorable to the development of Valsa sordida Nits as the precipitation,rain day,relative humidity and temperature-humidity coefficient increased,while it was not favorable to the development of Valsa sordida Nits as the sunshine duration,extreme air temperature increased.The key meteorological factors which affected the occurrence and development of Valsa sordida Nits in Hebei province were temperature-humidity coefficients in March and April,the sunshine hours in the third ten days of March and April,air temperature in the first and third ten days of April,the extremely minimum air temperature in the first ten days of March and April and also last December respectively.The meteorological suitability forecasting model was established based on the normalized key meteorological factors.The validation results by the historical return test showed that forecasting accuracy for meteorological suitability models was 91% by comparing meteorological grade with actual grade.The meteorological grade of the occurrence fastigium during May to June in 2009 was forecasted with forecasting accuracy by 78% by trial forecast.The meteorological conditions in March and April were the key environmental factors affecting the occurrence and development of this disease in North China.The model could be put into the operational application in North China.

Key words: Valsa sordida Nits, Valsa sordida Nits, Normalized, Meteorological suitability, Forecasting model