The Temporal Dynamics Model And Economic Threshold Of Grape Downy Mildew

Grape downy mildew occurs in different regions in the world every year,and it is also one of the most serious diseases in china.Now it mainly relies on chemical control,but it has some limitations,because there are many kinds of chemical fungicides in the market and differences in these conditions,such as pathogens,climatic conditions and varieties et al.In order to determine the epidemic period,effective fungicides and the economic threshold of grape downy mildew,aim to guide the appropriate control,this study focus on the temporal dynamic model of epidemic,fungicides control and economic threshold of the grape downy mildew.The results are summarized as follows:1.The occurrence regularity of grape downy mildew was investigated about the Honeydew,Hongru and Zuoyouhong.Using SPSS20.0 to simulate and analyze the time of disease about three varieties,due to the logistic model simulated the temporal dynamic well,the logistic model was established,and it could reflect the temporal dynamic of grape downy mildew.Using the logistic model to deduce epidemic periods of grape downy mildew about three varieties,the results showed that the epidemic periods of different varieties were slightly different.The exponential phase of the disease about Honeydew was from late July to early August,the logistic phase was from early August to late August,and the degenerating phase was from late August to the end of grape growing season.The exponential phase of the disease about the Hongru was from late July to early August,the logistic phase was from early August to late August,and the degenerating phase was from late August to the end of grape growing season.Since downy mildew of Zuoyouhong started relatively early,so the exponential phase was from middle July to late July,the logistic phase was from late July to middle August,and the degenerating phase was from middle August to the end of grape growing season.2.The field experiments were carried out on a total of 28 treatments of 9 fungicides.It showed that 10% Oxathiapiprolin diluted 2500 times and 2000 times had high efficacy,and the control effects were 87.43% and 87.37% respectively.In addition,2% Wuyiencin AS diluted 750 times was worst,the control effect was 48.74%.23.4% Mandipropamid SC diluted 2000 and 1500 times,200g/L Amisulbrom SC diluted 1500 times,10% Oxathiapiprolin OD diluted 3000 times,23.4% Mandipropamid SC diluted 2500 times,50% Dimethomorph WP diluted 1500 times,200g/L Amisulbrom SC diluted 1000 times,50% Dimethomorph WP diluted 2000 times,200g/L Amisulbrom SC diluted 2000 times,50% Dimethomorph WP diluted 2500 times and 80% Bordeaux mixture diluted 500 and 400 times,the control effects of 12 treatments were more than 80%.The control effect of Pythium oligandrum diluted 4000 times was 78.15%,there was a significant difference with other biological fungicides.So it is recommended that chemical fungicides priority to use 10% Oxathiapiprolin OD and 23.4% Mandipropamid SC in the production,and the biological fungicides priority to use Pythium oligandrum.3.According to the calculation of EIL based on the treatment(10% Oxathiapiprolin diluted 2500 times)with the highest control effect.Using SPSS20.0,the linear regression equation(Y=1.553X-6.316)was established about the disease index and loss ratio.Using EIL value to substitute x in the equation(y=0.249x-0.002)about disease index after control and before spraying,the economic threshold of grape downy mildew was obtained.When the disease index was 1.79,it was the best time of the first time spraying control.If the disease continues to rise,spraying control should be carried out every other week.In this way,the disease index can be controlled at the below of the EIL without causing too much economic loss.