Assessment of Rice Panicle Blast Disease Using Airborne Hyperspectral Imagery

Takashi Kobayashi,Shu Hase,Masashi Sasahara,Kiyoshi Ishiguro,Eiji Kanda,Yoichi Torigoe

doi:10.2174/1874331501610010028

Abstract

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.

Highlights

Rice blast disease, caused by the ascomycete Magnaporthe oryzae B
Panicle blast occurred in all fields selected for assessment, and its incidence ranged from 0.4% to 84.4% of diseased incidence
Reflectance differences among disease incidences in the VIS region were smaller than the differences observed in NIR region

Summary

Introduction

Rice blast disease, caused by the ascomycete Magnaporthe oryzae B. Couch, is considered to be the most important fungal disease in rice (Oryza sativa L.) because of its worldwide distribution and its destruction [1, 2]. Rice blast causes severe damage under cool summer conditions in northern Japan. The blast fungus affects the leaves, on which it causes diamond-shaped white to gray lesions with dark green to brown borders surrounded by a yellowish halo. Neck blast is usually the most destructive symptom of the disease [2]. Spores formed in the upper leaf blast lesions are the inoculum responsible for panicle blast. The grain-filling process is remarkably obstructed in these affected panicles and grain quality and quantity are drastically reduced [2]

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