Sheath blight is a major disease of rice in Arkansas. It is caused by a soil pathogen and the fungus has several hosts including soybean and corn among others. It prevails in any rice field if conditions are right for the fungus to develop. Prolonged periods of high humidity and high temperatures favor the sheath blight disease to start and progress.
The fungus mostly survives as “sclerotia” (tiny masses of fungal structure called “mycelia”) which are capable of floating on flooded rice fields. The floating fungal structures coming in contact with the growing rice and infect the sheath at or just above the waterline and spread throughout the plant tissue. The infection progresses upward through the canopy and to adjacent plants.
Read the full report at: http://www.arkansas-crops.com/2015/07/15/rice-sheath-blight/