Monitoring Cotton Root Rot Infection in Fungicide-Treated Cotton Fields Using Airborne Imagery

With authorization to use Topguard® fungicide on cotton in Texas in 2012 and 2013 through section 18 exemptions from registration, many growers used this product to treat their fields that had been historically infected with cotton root rot, caused by the soilborne fungus Phymatotrichopsis omnivora. The objectives of this study were to use airborne multispectral imagery to monitor the progression of cotton root rot infection in cotton fields treated with the fungicide and to assess the efficacy and performance of the fungicide treatments. Airborne multispectral imagery was taken from a number of treated cotton fields in the Coastal Bend near Edroy, TX and the Southern Rolling Plains near San Angelo, TX multiple times during the 2013 growing seasons. Temporal images revealed that the fungicide either completely controlled the disease within the season or delayed the initiation of the disease until near the end of the season. Comparison of images taken in 2013 with those under natural infection conditions in previous years showed that the fungicide with a rate of 2.34 L/ha (32 oz/acre) performed well in irrigated fields. The results from this study will be useful for assessing the efficacy of the fungicide and refining application methods and rates for optimal control of the disease.