Using Mosaicked Airborne Imagery to Assess Cotton Root Rot Infection on a Regional Basis

Cotton root rot is a serious and destructive disease in many of the cotton production areas in Texas. Since 2012, many cotton growers in Texas have used the Topguard fungicide to control this disease in their fields under Section 18 emergency exemptions. Airborne images have been used to monitor the progression of this disease and the performance of fungicide treatments in south and central Texas in the last few years. The objective of this study was to develop methods and procedures to mosaic individual airborne images taken over a cotton growing area as one single image to assess the extent and severity of cotton root rot infection in fungicide-treated and nontreated fields on a regional basis. Airborne RGB and near-infrared (NIR) images taken from a 13 km by 32 km (8 mi by 20 mi) area in San Angelo, TX near the end of the 2013 growing season were used for this study. The images were taken at 3050 m (10000 ft) above ground level and each image had a pixel array of 5616 x 3744 covering a ground area of 5.5 km by 3.6 km (3.4 mi by 2.3 mi) with a pixel size of 1.0 m. Images were taken along three flight lines with 30% sidelap and 30-60% forward overlap. Procedures were developed to create a mosaicked four-band image from individual RGB and NIR images. The mosaicked image clearly showed the distribution and severity of root rot-infected fields within the imaging area. The image will be useful for both growers and county agents to assess the effectiveness of the fungicide control program and make management decisions for more effective control of the disease on a regional basis.