Sheath blight (Rhizoctonia solani)

Affected Part(s):
Lower leaf sheaths, stem

Symptoms:
Dark irregular patches on sheaths and nearby leaves; these spots may join and girdle the stem, causing lodging and wilting

Cause / Type:
Soil fungus (sheath blight).

Management (cultural/biological/chemical):
Plant with wider spacing; remove weeds and stubble; rotate away from rice; maintain field sanitationblog.plantwise.org. Use resistant/tolerant varieties if available (IRRI has some) and only spray fungicide for general disease control if needed.