Cotton Root Rot (fungus - Phymatotrichum omnivorum): Root rot appears suddenly, starting in early summer. It causes rapid wilting, followed by death of the plants within a few days (Figure 3). Usually, the leaves of the plant are not shed, but remain attached. The disease kills plants in circular areas ranging from a few square yards to an acre or more in size. The root system of affected plants decay. Scraping the taproot reveals a darkened, reddish to wine-colored stain. If examined soon after death, the stems will be near normal color internally. Vascular streaking is not present as in the wilt disease. Fine, light brown strands of fungal threads (rhizomorphs) are usually found on the roots. Under moist conditions spore mats may appear on the soil surface near diseased plants. These are 2-12 inches in diameter, first snow-white and cottony, later tan and powdery. Controls include management and cultural practices as no chemical treatment has been found that economically controls cotton root rot. Deep plowing approximately 12 inches with mold board plow, planting early maturing varieties to escape disease, addition of organic matter or green manure and crop rotation have proven to be the most effective control methods. To achieve maximum control, an integrated program involving all practices is recommended.
