Severe outbreak of leaf blast causes stunting and the
development of small panicles. Early infection of neck nodes
causes white head and yield loss, y, expressed as y = 1.45x
to y =2.55x (where x is the percentage of white head), and
y = 0.31x to y = 0.57x (where x is the percentage of diseased
neck node); x is surveyed on the 30th day after heading. 15
years of data collected in Japan shows that y varies consider-
ably under different circumstances from 1–100%.