Detection of rice panicle blast with multispectral radiometer and the potential of using airborne multispectral scanners

Rice reflectance was measured to determine the spectral regions most sensit ive to panicle blast infection. Reflectance increased in the 430- to 530-, 580- to 680-, and 1,480- to 2,000-nm regions at the dough stage both in the laboratory and the field as the percentage of diseased spikelets increased . The wavebands of the greatest sensitivity were in the visible region, loc ated near 485 and 675 nm. After the yellow-ripe growth stage, near-infrared rather than visible reflectance responded to panicle blast infections. Rat ios of rice reflectance were evaluated as indicators of panicle blast. R470 /R570 (reflectance at 470 nm divided by reflectance at 570 nm), R520/R675, and R570/R675 decreased significantly as the incidence of panicle blast inc reased at the dough stage. At the yellow-ripe stage, R550/R970 and R725/R90 0 were used to estimate panicle blast severity as measured in terms of the percentage of diseased spikelets. According to the simulation that uses gro und-based sensor data, airborne multispectral scanners may be effective in detecting the occurrence of panicle blast using a band combination of 530- to 570- and 650- to 700-nm regions at the dough stage.