Chemical Control Of Rice Sheath Blight And Effect Evaluation Of Several Pharmaceutical Compounds

The plant-pathogenic fungus Rhizoctonia solani was the causative agent of the Sheath blight on rice, which is a main disease in our rice and widely distributed all over the world. In the past decades, jinggangmycin, triadimefon and carbendazim have been used to control this disease. However, with these fungicides have been used continually for long time, the fungicide resistance has developed in the pathogen population. Thus screening more effective and lower costy new fungicides is exigent to be solved.110Rhizoctonia solani strains were collected from Nanjing, Yangzhou, Zhenjiang, Suqian, Yancheng and Suzhou of Jiangsu Province. Their sensitivity to difenoconazole was determined on PSA. The EC50values in inhibiting mycelial growth of the110R. solani isolates were0.0065-0.4924μg/ml, with an average EC50value of0.2495μg/ml, and the MIC was4μg/mL. The unimodal baseline sensitivity curve could be used for disease control by difenoconazole. The mixture of difenoconazole and propiconazole which posed a protective and curative activity by ratio of2:1or1:1had an effective control against rice sheath blight with synergism.In this study,25%propiconazole EC,125g/L epoxiconazole SC,250g/L tebuconazole WE,20%azoxystrobin WG,50%hexaconazole WDG and70%thiophanate-methyl WP were screened by field trials on rice that the control effect reached60%to90%, and the rational use of time and dose was also analyzed.Field trials showed that the control effect of30%difenoconazole·propiconazole WE against rice sheath blight by45g/hm2,67.5g/hm2and90g/hm2reached77.61%,83.62%,89.04%, respectively. Among them,30%difenoconazole·propiconazole WE with45g/hm2active ingredient had a considerably control effect compared with60g/hm2of10%difenoconazole WG; while30%difenoconazole·propiconazole WE with90g/hm2active ingredient had a considerably control effect compared with67.5g/hm2of30%difenoconazole·propiconazole EC or150g/hm2of25%propiconazole EC. Control effect of30%difenoconazole·propiconazole SC against rice sheath blight by90g/hm2,78.75g/hm2 and67.5/hm2reached80.09%,75.87%and71.43%, respectively. Among them,30%difenoconazole·propiconazole SC with90g/hm2active ingredient had a considerably control effect compared with150g/acre of25%propiconazole EC. Results showed that field efficiency of30%difenoconazole·propiconazole WE, EC or SC on rice sheath blight was better than10%difenoconazole azole WG or25%propiconazole EC at an equivalent dose.