Screening Of Effective Fungicdes For Corn Stalk Rot And Sheath Blight And Field Control Experiment

Corn stalk rot and corn sheath blight are two major soil-borne diseases that harm corn.Corn stalk rot is mainly caused by single or combined infection of Pythium spp and Fusarium spp.Corn sheath blight is caused by Rhizoctonia solani infection.Now,the use of chemical fungicides is still the main method to control corn stalk rot and sheath blight.In order to screen out effective fungicides for controlling corn stalk rot and sheath blight,the indoor toxicity of commont fungicides to Pythium aphanidermatum?Fusarium graminearum and Rhizoctonia solani was determined by mycelium growth rate method.Three fungicides of fludioxonil,hymexazol and difenoconazole are selected to be compounded in pairs,the combined toxicity of different combinations to Fusarium graminearum and Rhizoctonia solani was determined.According to the co-toxicity coefficient and the performance of single fungicide,the best compound combination was screened out,and the suspended seed coating agent was prepared by the laboratory,and the indoor safety test,pot test and field control effect test were carried out.In order to provide basis for reasonable selection and comprehensive control of fungicides for controlling corn stalk rot and sheath blight in the field.Toxicity test results showd that,eight fungicides,metalaxyl-M,pyraclostrobin,oxine-copper and bromothalonil,octylamine acetate,cymoxanil,captan and hymexazol,have good indoor activities against Pythium aphanidermatum,EC₅₀0 value was between 0.4410 and53.3533 mg/L.The 15 fungicides of metconazole,difenoconazole,prochloraz,flusilazole,myclobutanil,epoxiconazole,tebuconazole,fludioxonil,prothioconazole,pyraclostrobin,bromothalonil,captan,hymexazol,trifloxystrobin and azoxystrobin have good indoor activities against Fusarium graminearum,EC₅₀0 value was between 0.2018 and 12.9433 mg/L.The 15 fungicides of fludioxonil thifluzamide prothioconazole epoxiconazole metconazole tebuconazole pyraclostrobin myclobutanil bromothalonil iprodione hymexazol captan prochloraz difenoconazole have good indoor activities against Rhizoctonia solani,EC₅₀0 value was between 0.2432 and 39.3771 mg/L.The combined toxicity test results showed that,when three fungicides of difenoconazole,fludioxonil and hymexazol were compounded in pairs according to the ratios of 20?1,10?1,5?1,1?1,1?5,1?10 and 1?20 respectively,when difenoconazole and hymexazol,difenoconazole and fludioxonil,fludioxonil and hymexazol were mixed at 20?1,20?1 and 1?1 respectively,the toxicity coefficient?CTC?of Fusarium graminearum was the highest and the synergistic effect was the best,when the ratios of 10?1,5?1 and 1?5 were used,the toxicity coefficient?CTC?of Rhizoctonia solani was the highest and the synergistic effect was the best.The safety of 6%hymexazol fludioxonil suspension seed coating agent?5?1?and 6%thifluzamide fludioxonil suspension seed coating agent?2?1?on corn after seed dressing was evaluated.The safety results showed that,the dosage of 6%hymexazol·fludioxonil suspension seed coating agent was 18,27,36 and 45 g/100 kg seeds according to the active ingredients,and the dosage of 6%thifluzamide·fludioxonil suspension seed coating agent was12,18,24 and 30 g/100 kg seeds according to the active ingredients,the germination rate and emergence rate of maize were not affected by dressing the three tested maize varieties respectively,but the root length,root number and plant height were promoted to different degrees?p<0.05?.The results of pot experiment and field control experiments in two places a year showd that,the effective components of 6%hymexazol fludioxonil suspension seed coating agent were 15 and 18 g/100 kg of seeds,and the effective components of 6%thifluzamide fludioxonil suspension seed coating agent were 9 and 12 g/100 kg of seeds,after seed dressing corn,it had better indoor and field control effects on corn stalk rot and sheath blight,and did not affect the emergence of corn.