1 Faculty of Agriculture, Yamagata University, Tsuruoka 997-8555, Japan
2 Miyagi Prefectural Furukawa Agricultural Experiment Station, Osaki 989-6227, Japan
3 Faculty of Agriculture, Kagoshima University, Kagoshima 890-0065, Japan
4 National Agriculture and Food Research Organization, Tohoku Agricultural Research Center, Morioka 020-0198, Japan
5 College of Bioresource Sciences, Nihon University, Fujisawa 252-0880, Japan
Rice blast disease occurs in rice production areas all over the world and is the most important disease in Japan. Remote sensing techniques may provide a mean for detecting disease intensity for large area without being subjected to raters. This study evaluated the use of airborne hyperspectral imagery to measure the severity of panicle blast in field crops. Hyperspectral remote sensing imagery was acquired at the dough stage of rice grain development in northern Japan. The most consistent relationship, with high R2 and low P, was the simple band ratio R498 to 515/R700 to 717 (i.e., the reflectance at 498 to 515-nm divided by the reflectance at 700- to 717-nm). The band ratio of R498 to 515/R700 to 717 increased significantly (P < 0.001) with increasing visual estimates of disease incidence, defined as the percentage of diseased spikelets (R2 = 0.83). Assessment of disease distribution and severity could provide useful information for making decisions regarding the necessity of fungicide application and estimate potential yield loss due to the disease.
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