Study On The Sensitivity Baseline Of Rhizoctonia Cerealis To Modern Fungicides And The Principle Of Chemical Control

The paper studied the sensitivity baselines of Rhizoctonia cereatis which caused the sharp eyespot of wheat to 15 fungicides, the selection of fungicides for controlling the disease and principle of tebuconazole combating the sharp eyespot of wheat. The results of the sensitivity research of Rhizoctonia cerealis to 1 5 fungicides showed that the sensitivity of Rhizoctonia cerealis to different types of fungicides was significantly different. To all fungicides, hexaconazole, tebuconazole, fiudioxonil, diniconazole, tolclofos-methyl appeared very high activity in vitro with their average EC50 at O.Ol2lpg/ml, O.0384iig/ml, O.0138L抔/ml, O.0707pg/ml and O.1231~x g/m I respectively, while the activity of isoprothiolane against the pathogen was the lowest with EC50 63.1783 ~t g/ml. All isolates of the fungous were much more sensitive to diisothiocyanatonethane, cultar, dimethachlon, seedvax and other DIMs than to prochloraz. The result of sensitivity meseauring of 50 isolates to 15 fungicides pointed that the sensitivity of Rhizoctonia cerealis population appeared normal distribution. The sensitivity distribution of population of Rhizoctonia cerealis to triadimonol revealed that the fungicides resistance has developed in the field. Sensitivity among anastomosis groups to tebuconazole was obviously different. The study of field experiment appeared that the rate of incidence and disease severity index were reduced through seed treatment by four fungicides. Diisothicyanatomethane and tebuconazole appeared better controlling effect on sharp eyespot of wheat. The result of experiment in vitro showed that the mixture of diisothicyanatomethane and diniconazole appeared synergistic or independent action depending on different proportion of both fungicides. The electrolyte of mycelium treated by the mixture with synergistic biological response showed more obvious leakage than that by the single fungicide at the same concentration 3 Tebuconazole had the high antifungal activity and inhibited mycelia growth rather than sclerotiuni germination. The pathogenicity and physiology of mycelia treated by tebuconazole changed obviously, and the electrolyte of mycelia leaked distinctly in 1 ----32 hour. The results of experiment by way of pot showed that the controlling effect on sharp eyespot of wheat reached more than 70% in a month after emerge of seeding through seed treatment with 2% Raxil WS at the dosage of 0.125% seed weight, while the controlling effect descend to 17% at 70 day after emerge. The paper studied also thc biological characters of Rhizoctonia cerealis.