Using Airborne Imagery to Monitor Cotton Root Rot Progression in Fungicide-Treated and Untreated Cotton Fields

Cotton root rot (Phymatotrichopsis omnivora) is a serious and destructive disease that has affected cotton production in the southwestern and south central U.S for over a century. Recent field studies have shown that Topguard fungicide (flutriafol) has considerable potential for controlling this disease. After approval of a section 18 exemption allowing use of Topguard for control cotton root rot in 2012, many Texas cotton growers used this product to treat their fields historically infected with the disease. The objective of this study was to use airborne multispectral imagery to monitor the progression of cotton root rot infection in cotton fields treated or untreated with the fungicide. Airborne multispectral imagery with blue, green, red and near-infrared bands was taken of a number of infected fields in the Coastal Bend near Edroy, TX and the Southern Rolling Plains near San Angelo, TX multiple times during the 2012 growing season. These images were compared with the images taken in previous years to document the consistency and variability of the disease incidence over the years. Images taken from fields with fungicide-treated and untreated areas were used to illustrate the efficacy of Topguard for the control of the disease. Although dry weather conditions in 2012 made it difficult to assess the efficacy of the fungicide in dryland fields, the performance of the fungicide in irrigated fields was generally positive. As another Section 18 has been approved for use of the fungicide in Texas in 2013, the findings from this study, including the historical images, will be useful for identifying infected fields for whole-field and site-specific treatments and for assessing the efficacy of the fungicide in the coming years.