Screening Of Effective Fungicides For Controlling Barley Powdery Mildew And Evaluation Of Their Field Efficacy

In this study,control agents were screened for sowing period,early onset period and prevalence period of barley,to discuss the staging control of upper powdery mildew of barley,and to determine the safety of three seed coating agents for barley emergence and efficacy against powdery mildew.The fungicides with high activity against barley powdery mildew were selected by pot experiment to evaluate whether the insecticides were safe for barley.Field experiments were conducted to verify the effect of the insecticides on field control.The main research results are as follows:（1）Safety evaluation of three seed coating agents on barley and efficacy test on powdery mildewAccording to the data of seed emergence test and indoor pot experiment,the seed emergence rate of 50%carbendazol,60 g/L pentazolol（Ricoxo）seed treatment suspension and 25 g/L fluoxonil（xylase）seed mixing treatment was above 78%,and the seed emergence rate of 50%carbendazol concentration was equal to or higher than that of water control group.The seed emergence rate of 25 g/L fluoxonil was better than that of water control group at low concentration,but slightly lower than that of water control group at high concentration.The seedling emergence rate of 60 g/L tezolol（Rickeshow）was slightly lower than that of water control group.There was no significant difference in the emergence rate between the treated group and the clean control group,indicating that the three seed coating agents had certain safety for barley emergence.The control effect of the three seed coating agents on barley powdery mildew was significantly stronger than that of the water control group and the other two agents.The three seed coating agents significantly promoted the agronomic characters of barley plants at the optimal concentration.（2）Toxicity test of six agents to barley powdery mildewThe synergistic effects of several agents on barley powdery mildew were calculated.Compared with the clean water control group,all the 6agents used in the experiment had certain control effect on barley powdery mildew,and the control effect reached the best when the concentration was the highest in the recommended dosage range.The control effect of chemical agents was significantly higher than that of biological pesticides.The results showed that the control effect of pyrazoline spray was the most significant(EC₅₀=0.161x+0.3844 mg/L).The toxicity of each agent from the highest to the lowest was 250 g/L pyrazoline>125 g/L flucyclozole>10%phenoxymethyclozole>10%linnanamycin>1×10¹⁰CFU/g Bacillus subtilis>3×10⁸CFU/g Trichoderma hartsz.The EC₉₅value of fluocyclozole showed the most significant control effect(EC₉₅=0.1863x+0.331 mg/L),125 g/L fluocyclozole>250 g/L pyrazole>10%phenyclozole>10%linnanamycin>3×10⁸CFU/g Trichoderma harzia>1×10¹⁰CFU/g Bacillus subtilis.125 g/L flucyclozole had the best control effect,followed by 250g/L pyrazolium.（3）Field experiment on control effect of four agents against barley powdery mildewAccording to the field test data,the best control effect was 250 g/L pyrazolate,and the control effect reached 74.35%after 7 days,72.10%after 14 days,followed by 125 g/L flucyclozole,and the control effect reached 68.76%after 7 days,and 62.78%after 14 days.The control effect of biological agent 10%Ningnanmycin was 52.32%and 46.40%on 7 d after application,and the control effect of 1×10¹⁰CFU/g Bacillus subtilis was 50.83%and 44.33%on 14 d after application.According to the test data,the control effect of chemical pesticides 10%pyrazole and125 g/L flucyclozole was significantly stronger than that of 10%Ningnanmycin and 1×10¹⁰CFU/g Bacillus subtilis.