The experiments of resistance of different super hybrid rice(SHR) combinations to sheath blight(ShB)(Rhizoctonia solani Kühn) and effect of nitrogen fertilizer(NF) dosage and fertilization methods on ShB occurrence were conducted in Hangzhou during 2005-2006.The results indicated that the resistance level of different SHR combinations to ShB were significantly different.For the same combination,the severity of ShB depends on the seeding and transplanting period.The disease index showed a positive correlation with the nitrogen dosage,but depended on resistance level of combination.The ShB severity of susceptible combination showed high positive correlation with NF dosage.At the flowering stage,there were no effect of nitrogen fertilization method on the occurrence of ShB,but the fertilization method showed significantly effect at dough stage.The occurrence of ShB was significantly affected by the supply rate of nitrogen at different rice growing stage.When the total NF supply was 165 kg per hectare,the occurrence of ShB with high NF rate(80%) at early stage(as basal and tillering fertilizer) and low rate(20%) at late stage(as panicle fertilizer) was more serious than that of low NF rate(60%) in early and high NF rate(40%) as panicle fertilizer.The result was the reverse of conventional viewpoint about that high NF supply at rice late growing stage might lead to severe occurrence of ShB.
