Rice sheath blight evaluation as affected by fertilization rate and planting density

Abstract

Sheath blight, caused by Rhizoctonia solani, is one of the most important rice diseases worldwide, especially in intensive rice cropping systems. However, no rice cultivar has been found to be completely resistant to this fungus. Identifying the effect of crop management on disease intensity is crucial since crop management is a promising strategy to control sheath blight. The objective was to determine the influence of fertilization rate and plant density on disease infection using two different inoculated methods (wooden toothpicks and agar block method). Infection rates near 100% were achieved with the toothpick method. This technique caused lesions 30 h after the inoculation. The lesions from the toothpick method were larger than lesions from the agar block method. High nitrogen (N) rate and dense planting were conducive to sheath blight development. Application of silicon fertilizer under high N rate failed to suppress the disease epidemic, especially when silicon concentration of the soil is high or there is enough plant–available silicon. The present study suggested that appropriate crop management practices, such as the rational use of N rate and optimum planting density can be used as a promising strategy for suppressing sheath blight in rice.