Okra Root Rot

Disease Identification

• Cotton root rot is also commonly referred to as phymatotrichum root rot or Texas root rot. The fungal disorder is caused by Phymatotrichopsis omnivorum and has more than 2,000 different broadleaf host plants including trees, shrubs, vegetables and ornamental plants. Cotton root rot does not affect grasses and is liable to cause heavy economic losses in peanut, alfalfa, cotton and nut and fruit trees.

Favorable Conditions

• The fungus causing the disease persists for extended periods in the soil, becoming active at soil temperatures of 82 degrees Fahrenheit or more. The disease is frequently seen in okra that is grown in limestone and high pH soil. Disease symptoms are most pronounced between June and September. Cotton root rot is also seen more in okra plants that are not rotated with other crops.

Damage

• The causal fungus enters okra through the roots of the plants, penetrating the woody areas of the roots. Signs of infection include wilting plants with rapid death. Foliage turns brown and dry but is still attached to plants. Inspection of plant taproots reveals severe decay where the affected areas are coated with brown, fuzzy mold referred to as mycelium. Spore mats in the form of circular, white mold are seen around the plants, a distinct trait of cotton root rot.

Control

• There is no effective option for the control of cotton root rot other than avoiding planting susceptible species in areas with previous cases of infection. Once these areas are identified, it is recommended to use only resistant plants in that location. Rotate okra and other susceptible crops for three to four years with grass crops like grain sorghum. Use green manure in soil as this tends to inhibit the growth of the fungus. Use early okra varieties to help minimize chances of infection by harvesting before the heat of summer.