EPIDEMIOLOGIC STUDIES OF SHEATH BLIGHT OF RICE CAUSED BY RHIZOCTONIA-SOLANI KUHN

The development of rice sheath blight (ShB) caused by Rhizoctonia solani Kuhn under different cultural conditions was studied. Plants appeared to be most susceptible at panicle initiation-booting stage with more severity in symptoms and extent of damage during the Aus (March-July) season. The rate of lesion length development is high during the three days immediately after initiation of infection and it decreases with time after infection. Varieties differ in lesion length, developing higher in susceptible than in moderately resistant cultivars. The disease is severe under closer planting and the severity increases with increase in the amount of nitrogen applied during both Boro (Nov.-April) and Aus seasons. However, in the boro season high yield is obtained with wider spacing receiving high amount of nitrogen. The disease can be minimized and yield maximized by manipulating spacing and amount of N applied.