Description
This plant disease, also known as Texas root rot, is caused by a fungus (Phymatotrichum omnivorum) that lives in soils throughout much of the Southwest. This fungus infects more than 1,700 species of plants, eventually killing them by rotting their roots. Infected plants wilt and may die within a few days if they are suffering from drought or heat stress. When pulled out of the ground, the roots are covered with yellow or tan fungal growth. The fungus thrives in warm, poorly aerated, alkaline (pH 8.0 and up) soils that are low in organic matter. In many areas, the fungal strands and spores are concentrated 1 to 3 feet below the soil surface. Cotton root rot can survive in the soil for 5 years after plants have died. It is spread from plant to plant by brown fungal strands that grow through the soil, and by the movement of contaminated soil and transplants. Cotton root rot is most active from midsummer to frost.
Control
Creating a soil environment unfavorable to its development can reduce the severity of cotton root rot. Improve soil aeration by digging or tilling your soil. To improve the drainage and increase the number of competing beneficial microorganisms, incorporate lots of mulch, compost, or other organic matter into the soil. Reducing the alkalinity of the soil also helps. Fumigating the soil will kill the fungus (see Soil Fumigation and Solarization). For a list of plants resistant to cotton root rot that may be used to replace infected plants, see Plants Resistant to Cotton Root Rot.
