Study On Economic Threshold Of Wheat Stripe Rust

Wheat stripe rust is an airborne disease that is more harmful to wheat.The use of chemical pesticides to prevent and control the spread of wheat stripe rust is a basic method for controlling wheat stripe rust.When chemical pesticides are used to prevent and control wheat diseases,unreasonable use will lead to pesticide residues and increase the cost of prevention and control.Therefore,exploring the prevention and control indicators of wheat stripe rust provides a reference for reasonable disease control.In order to clarify the prevention and control indicators of stripe rust in wheat production,the research and test of the prevention and control indicators of wheat stripe rust was carried out in Mianyang,Sichuan and Xiangyang,Hubei in 2018 and 2019.The disease gradient have been caused by inoculation with different densities of stripe rust and different drug gradients.The yield loss model,disease epidemic model,and drug control effect were obtained by analyzing and processing the test data.The economic threshold of wheat stripe rust was derived.The test results:1 In the study of wheat stripe rust yield loss,correlation analysis results show that the correlation between the severity of disease and yield in different wheat growth stages is the highest.Based on the analysis of Mianmai 367 and Xinong 979 random block test results,two yield loss models were established based on the average severity and yield loss rate as reference.The results are as follows:the key period model fitting result of the tested variety Mianmai 367 is y=0.31948*x2（p<0.0001,R-squared=0.8174）;the cumulative disease AUDPC model is y=0.60067*x6（R-squared=0.8773,P<0.0001）.The key stage model of the tested variety Xinong 979 is y4=0.44402*x4（p<.00001,R squared=0.9072）;the AUDPC model is Y=0.93562*x7（R-squered=0.8403,P<0.0001）.2 Observing the scatter plot of the average severity of the top three leaves of wheat and the yield of a single ear,it was found that there was a negative correlation between disease and yield,the higher the average severity was,the smaller the yield per plant wad.In order to establish a linear mixed model of the yield loss of the top three leaves of the tested varieties,a linear mixed model was fitted to the disease severity of six wheat varieties and the weight of a single ear by the Lmer function in Rstudio to determine whether the geographic location as a random effect Partial affected intercept and slope of the fixed effect Partial.Result shows the random effect part has no effect,and the fitted generalized loss rate model is y=0.0006*x.3 In the analysis of disease epidemic research,the dot plots drawn from the survey data of the disease prevalence of wheat varieties Xinong 979 and Mianmai 367 showed that the curve drawn by the disease prevalence and time was similar to the Logistic curve.Therefore,fitting the logistic disease growth model of Xinong 979 and Mianmai 367,the disease growth model of wheat variety Mianmai 367 is y=0.9/[exp（6.10193-0.20127*x）-1]=0.9527,P<0.0001);the disease growth model of wheat variety Xinong 979 is y=0.8/[exp（5.20172-0.21389*x）-1]（R-squered=0.9527,P<0.0001）.4 In the derivation of economic allowable damage level and economic threshold,the investigation result of wheat stripe rust control cost is calculated at 210 yuan/hectare,the pesticide control effect is calculated at 80%,the market price of wheat is 2.2 yuan/kg,and the wheat yield is based on the wheat variety tested The actual yield per hectare is calculated at 6450kg/hectare and 6750kg/hectare.According to the economic allowable damage level formula P*V*L=W and the prevention index derivation formula X_ET=(X_ELT-T*R)*Q,the average severity is used as a reference to obtain the results as follows:The allowable damage level is 0.058 and the economic threshold is 0.036 in Xiangyang area.March 30 was the time for wheat stripe rust prevention and control in 2019.Wheat growth was in the growth period of Zadoks standard value of 10.5,which was the middle of the heading period,and 3/4 of the ears appear.The economic allowable damage level and economic threshold of Mianmai 367 are 0.058 and 0.046 respectively in Mianyang area.The control time was March 19 in 2019.The wheat growth was in the growth period of Zadoks standard value of10.5,that was,the middle and late heading period,and the ears were completely withdrawn.