Studies On Screening Of Effectual Fungicides And Mixed Preparations For Controlling Soybean Blight

Soybean blight,also called soybean root rot,is one of the most destructive diseases.It is caused by Phytophthora sojae and can infect each growth period of soybean.Soybean blight is found in most soybean-growing regions all over China,has different degrees of influence in there.The occurrence of this disease may reduction of output reached 50%,so millions of dollars are lost each year.In this paper,16 tested strains are from 8 places in Anhui Province,which are Hefei,Bozhou,Fuyang,Guoyang,Guzhen,Huaiyuan,Mengcheng and Taihe.Eight kinds of fungicides,which are metalaxyl,azoxystrobin,dimethomorph,fluorine morpholine,cymoxanil,propamocarb,benzoyl propiconazole,are used to test the toxicities to those strains.The main results are as fellows.The growth rate method was used to determine the growth inhibition rate of 16 strains,which were determined by different test reagents.The EC50 value of soybean blight was calculated by linear regression between the inhibition rate of mycelium growth and the logarithm of the concentration of each agent.Experimental determination of 16 strains of Phytophthora sojae in the EC50 range are as follows:under the action of the fungicides metalaxyl EC50 value in the range of 0.0900～0.1273 pg/ml,the average value is 0.1120g/ml;Dimethomorph EC50 value in the range of 0.0887～0.1579 μg/ml,the average value is 0.1315 μg/ml;Azoxystrobin EC50 value in the range of 0.1506～0.7549 μg/ml and the average value is 0.3147 μg/ml;Fluorine morpholine EC50 value in the range of 0.1513～0.2359 μg/ml,the average value is 0.1928 pg/ml;Cymoxanil EC50 value in the range of 0.1354～0.1732～g/m,the average value is 0.1497 pg/ml;Propamocarb EC50 value in the range of 30.6444～84.4410μg/ml,the average value is 48.6936 μg/ml;Boscalid EC50 the value is in the range of 1.2856～1.7615 μg/ml,the average value is 1.1588 μg/ml;Benzoyl propicondzole EC50 value in the range of 3.7750～5.0863 μg/ml,the average value is 4.3417μg/ml.The growth rate method to detect the toxicity of eight fungicides on Phytophthora,five of those tested fungicides are chosen for pairwise combination,which are metalaxyl,azoxystrobin,dimetho morph,fluorine morpholine,cymoxanil.By compounding experiments to determine the significant synergistic effect of the combination.Among them,the best combination are dimethomorph and cymoxanil.The combination of various proportions of average CTC 290,maximum CTC of 356,which CTCi:3>CTC1:1>CTCi:2>CTC2:1>CTC3:1.