A viral disease caused by the rice necrotic mosaic virus (RNMV). Polymyxa graminis is considered to be the vector of the RNMV. The disease occurs in central and southern Japan. Infected plants have elongate or spindle-shaped, yellow flecks and streaks on the basal portions of stems and sheaths. Plants may be moderately stunted with reduced tiller number and spreading growth habit. It can be transmitted by mechanical means and through the soil. There has been no evidence that insects or seeds transmit the disease.