Site-Specific Relationships between Cotton Root Rot and Soil Properties

Cotton Root Rot (CRR), caused by Phymatotrichopsis omnivora, is a problem across the southwestern United States and northern Mexico, commonly killing plants in infected portions of fields and greatly reducing overall yields. Over several decades a few studies have attempted to determine how soil properties influence the incidence of CRR, but no consistent associations have been found. Recent technological improvements allow for rapid collection of high-resolution disease damage estimates from aerial photography and of soil-property data, most notably with devices that measure apparent electrical conductivity (ECa). These technologies provide another avenue for evaluation of possible relationships between disease damage and soil properties. Data were collected from three geographically separated fields in Texas known to exhibit CRR: (1) aerial imagery to document CRR infection, (2) ECa data of soils with an electromagnetic induction device, and (3) several physical and chemical soil properties measured on soil cores sampled from the sites. Images were analyzed for incidence of CRR, and all other data were geographically overlaid for comparison among data sets. A significant relationship was found between ECa and CRR at one site but was not found at the others. The relationship between ECa and other soil properties tended to involve hydrologic factors such as clay and sand contents, which affect soil water holding capacity, and depth to soil matrix effervescence and inorganic carbon content, which indicate relative water movement through the soil profile. Soil properties that were significantly related to CRR incidence included soil pH (two of three locations) and clay and sand contents (at one site only).