Study On Occurrence Regularity And Integrated Control Of Rape Sclerotinia Stem Rot In Main Planting Areas Of Sichuan Province

It investigated and analyzed the basic situation of rape cultivation, occurrence degree of Sclerotinia sclerotiorum, resistance of different rape varieties, amount of Sclerotia in the field, goodness of fit to apothecium breaking through the soil largely and rape florescence, climatic conditions of Chengdu City Xindu District, Deyang City Mianzhu County, Dazhou City Dazhu County, Yibin City, Yibin County, Mianyang City, Santai County, Guangyuan City Jiange County, Nanchong City Yingshan County and Langzhong County in Sichuan province.Combined with experiments such as capture ascospores of S. sclerotiorum in the field and comparison of resistance of different rape varieties after inoculated with different strains, it analyzed the occurrence regularity and the dominant factors of Sclerotinia sclerotiorum in main planting areas of Sichuan province.Through comparison of control effect of different chemicals, different control measures and integrated control, the purpose was to search the control strategies that suitable for Sclerotinia sclerotiorum in the main planting areas of Sichuan province, and to find the simple, economical, effective and safe control methods. The main results are as follows:1 The main series of rape varieties and the basic situation of occurrence of S. sclerotiorum in Sichuan province.The main series of rape varieties were series of Chuan, series of Mian, series of De, series of Rong, series of Yi and series of Shuza. Since 2000, the rape sclerotinia stem rot have never occured seriously in Sichuan province. It may related to the promotion of resistant rape varieties and the addition of the planting area.The difference of occurrence degree of S. sclerotiorum was obvious in different planting areas. The occurrence degree in 2004 to 2006 was higher than that in the other years. The degree in most of places was low in 2007 to 2009, but was relative higher in a few of places such as Santai County and Nanchong City. In 2010, the occurrence degree was low in all the planting areas and the disease index in most of places was under five. The occurrence degree in the eastern, mid and northern Sichuan province was higher than that in the western and southern Sichuan province. 2 Study of factors which affect the occurrence of Sclerotinia sclerotiorum in Sichuan province.Relationship between the occurrence of S. sclerotiorum, amount of apothecium and ascospores released in the field.According to survey in the field, the amount of apothecium was not high, but widespread in Sichuan province, which was bigger in the dry farmland than that in paddy-upland rotation fields. It was important to the occurrence degree of Sclerotinia sclerotiorum that the goodness of fit to apothecium breaking through the soil largely and rape florescence. The rainfall in this period also influenced the occurrence degree. There were two peaks in the period of ascospores released in the field. The first peak was before the rapid increase of the diseased plant rate of leaf. The dynamic change of the amount of ascospores influenced the developing of the disease occurrence.Differences of resistance to disease of rape varieties.15 varieties of rape had been inoculated with 15 strains of S. sclerotiorum which were collected from Nanchong City, Dazhou City and Santai County. It was significant that the differences of resistance to disease between different rape varieties. It was significant that the differences of pathogenicity between different strains. It could be presumed that the differences of resistance to disease of a rape variety in different places were related to the whole level of pathogenicity of S. sclerotiorum in different places. It was a significant positive correlation between the growth speed of mycelium of one strain in the early stage and its pathogenicity. It was found that the resistance performance to S. sclerotiorum in the field of different rape varieties was different. The resistance performance of one rape variety was different when it was planted in different places or in different years.Relationship between meteorological factors and the occurrence of S. sclerotiorum.The occurrence degree was closely related to the total rainfall and the average relative humidity in the period from February to April. The average temperature in the period from February to April could not cause a significant influence to the occurrence of S. sclerotiorum because of the generally warm climate in Sichuan province. The meteorological factors related to the disease occurrence which were selected through stepwise regression analysis were mainly in March and April. Especially, the rainfall and relative humidity in March and April could cause a significant influence to the occurrence of S. sclerotiorum. The accuracy of these regression simulation equations could be above 80%. Using the meteorological forecast data and the regression equation, the occurrence of Sclerotinia sclerotiorum can be forecasted. The result can be an important reference for making prevention strategies of S. sclerotiorum.3. Study of the control of S. sclerotiorumChemical control.Through the test, the chemicals had got significant control effect, such as Carbendazim, Dimethachlon, Procymidone and Thiophanate-methyl. It was found that the resistance of S. sclerotiorum to Carbendazim was not significant in Sichuan province. Chemical control should be taken twice in early stage of rape florescence and seven days latter, and the control effect could be more than 80%.Agricultural control.The control effect of straw mulching or eliminating diseased old yellow leaves was 40% to 50%. Straw mulching could reduce 50% to 70% of the weeds in the field.Biological control.Biological control had an obvious effect, and the control effect was 50% to 80%. The control effect of Trichoderma fertilizer was about 60%, but with significant growth promotion which could make rape yield more than 10%. The control effect of Coniothyrium, bacteria YX7, actinomycetes YJ1 and Trichoderma H6 reached 75%, which has good potential for biological control,and are worth further study.4 Integrated control of S. sclerotiorumThe strategy of integrated control of S. sclerotiorum in Sichuan province should focus on the following points:based on agricultural control, strengthen the cultivation and management; use resistant varieties of rape, pay attention to alternation of varieties; integrated forecasting and prevent and control timely; pay attention to protection of environment and integrated control.According to the light occurrence of S. sclerotiorum in Sichuan province, it is recommended that use Trichoderma fertilizer 25kg/667m2 and mulching straw 300kg/667m2 based on crop rotation, strengthen the management and use resistant varieties of rape. It is better to eliminate diseased old yellow leaves two times at the period of rape florescence if the labor force is sufficient. According to forecast, it is not necessary to take any other control measures in the year of light occurrence degree, but it is necessary to take chemical or biological control timely in the year of high occurrence degree.