Method for evaluation of cotton root rot control practices using airborne high-resolution digital imagery
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Root rot is a common cotton disease in Texas caused by the fungus Phymatotrichum omnivorum. This fungus, that appears to persist indefinitely deep in the soil in the form of resistant propagates (sclerotia), spreads from plant to plant through the soil at rates ranging from 5 to 30 ft per year. Infested areas are generally recurrent, but variable environmental conditions, in particular, variations in soil moisture content, appear to be a most influential factor determining the expression of this disease from year to year. This characteristic plus the normal spatial variability in infestation make difficult the evaluation of cotton root rot control practices within a single season. This paper describes a method to improve the evaluation of such practices using airborne high-resolution digital imagery of two successive cotton seasons combined with ground control points obtained with a sub meter-accuracy global positioning system (GPS) and used for registering and geo-referencing the digital images, and then color-classifying the digital images (pixel classification and pixel counts per class) to discriminate infested and non-infested areas. The effectiveness of cotton root rot practices is then evaluated by comparing levels of infestation normalized with respect to levels of infestation observed in exactly the same location in a previous year.
American Society for Photogrammetry and Remote Sensing - 20th Biennial Workshop on Aerial Photography, Videography, and High Resolution Digital Imagery for Resource Assessment 2005
