Red root rot is a late season disease characterized by the pink to red discoloration of the root and crown tissue, usually not apparent until just prior to senescence. Above ground symptoms develop quickly in a 4 to 5 day interval during late ear fill. Stalks and foliage turn a green to gray color and the plant will die prematurely. Depending on weather conditions, severe lodging can occur following infection. Symptoms of this disease are most frequently seen where corn is grown in high population, fertility, and irrigated environments.
The causal agents of red root rot are complex of fungi that includes Phoma terrestris as the primary pathogen in association with Pythium and Fusarium species. P. terrestris is widespread saprophytic organism that colonizes the underground parts of a variety of hosts. It is very resilient, being able to survive for years in the soil under a wide range of temperature and pH conditions through the use of fungal structures called, microsclerotia. Recent research indicates that early infection of Pythium and other fungal species weakens the root system allowing P. terrestris to invade earlier and more effectively. Further research is needed to provide more details on this disease. (Blog and pictures provided by Nick Prudhomme, U of I Plant Clinic Student.)
Multicellular microsclerotia of Phoma terrestris