Prediction Model,Pathogen Differentiation And Integrated Management Of Rice Sheath Blight

Rice sheath blight(ShB), caused by Rhizotonia solani, is one of the most widespread and destructive fungal diseases. This disease can greatly decrease the level of rice yield and quality because of the long period of disease. Especially in recent years, diseases of ShB is more and more serious in southern China,due to the promotion of the two-line hybrid rice cultivars, new modes of cultivations and enhancement of chemical fertilizers. Therefore, it is very important that draw up a scientific integrated control strategy of rice sheath blight, based on an early warning for degree of ShB severity, pathogenicity of ShB fungus, resistance of rice cultivars and the effects pesticides. The results of these studies are as follow.For early warning for degree of ShB morbidity, it is the key that build precise rice sheath blight occurrence prediction model based on the induced factor. A variety of sheath blight popular prediction models have been build based on meteorological factors and linear model. However, the data of sheath blight popular, with nonlinear characteristic, belongs to typical multidimensional time series data which is caused by meteorological factors as well as variables of order for time series such as bacterium source number. So, it is necessary that building a nonlinear prediction model based on variables of order for time series. In this study, a high precision nonlinear prediction model of rice ShB was proposed, according to the dataset of Hengyang in 1995-2013. Firstly, the dataset was analyzed by geostatistics and the variables of order for time series were extracted. Secondly, nonlinear prediction model of support vector regression was constructed based on the order of time series and meteorological factors. Lastly,13 variables out of 23 were selected. The rice sheath blight disease indexes for 2014 were predicted used this new prediction model, the results showed that the model could accurately forecast the occurrence of ShB.The identification of rice ShB anastomosis group, pathogenicity identification of sheath blight, identification of rice resistance and field test of pesticide effectiveness for five bactericides were implemented. The results showed that 35 strains can fuse with AG-1IA, moreover,4 out of the 35 strains can fuse with AG-1IC. So the major anastomosis group of rice ShB in Hengyang is AG-1IA. The pathogenicity identification of 35 ShB fungus isolates showed that HY04?HY32?HY25 have the strongest pathogenicity, and HY28?HY12? HY30?HY03?HY29?HY02 with the most weak pathogenicity.The results of resistant identification of rice cultivars to sheath blight indicated that Shen liang you 5814?Y you 159?Cyou liang 34156 have high susceptible to rice sheath blight. Lastly, the results of the five fungicides in controlling ShB in paddy field demonstrated that two kinds of fungicides,75% trifloxystrobin· tebuconazole and 30% difenoconazole propiconazole hold efficacy of 86.03% and 84.80%, respectively, and the 2 fungicides can be used as the main control agent in Hengyang.