Characteristics and Management for Red Root Rot in Corn

Red root rot (Phoma terrestris) is a corn pathogen that has had high levels of incidence in corn growing states along the East Coast and has been identified in many Midwestern and Western states. Conditions that favor red root rot infection include high populations, high fertility, irrigation, and moderate temperatures around 75 to 80° F. Infected roots and lower stalk tissue may have a dark red to purple discoloration and can become shredded and deteriorated. In severe cases, yield reductions of up to 20 percent have been reported when premature death occurs.

Red Root Rot Development and Symptoms

As the name implies, red root rot in corn can be identified by reddish to purple discoloration on the roots and lower three nodes of corn stalks. Symptoms typically appear right before corn maturity and can lead to plant death and plant lodging. As root tissue rots, total root mass can be reduced, leading to root systems that are unable to keep plants upright.

Phoma terrestris, the pathogen that causes red root rot, survives in the soil as microsclerotia and can persist in the soil for many years across a wide range of soil types, pH ranges, and temperatures. As is common with other pathogens that weaken plants, P. terrestris often infects corn after plants are weakened by previous Pythium or Fusarium infections.

Management Considerations

Limited management options exist for red root rot. Crop rotation to a non-host crop, such as soybean, can help to reduce inoculum levels over time. While fungicide seed treatments help during early development, they don’t typically provide control late into the season, when red root rot typically infects corn. If your seed provider provides directional ratings on red root rot tolerance levels for their products, it is recommended to use products with higher red root rot tolerance in fields with previous infestations. Alleviating stress throughout the growing season is another management option to help keep corn plants healthy to fend off infections.

Derek Whalen
Agronomist

Sources:

Red Root Rot. Extension & Outreach. University of Illinois Department of Crop Sciences. http://extension.cropsciences.illinois.edu/fieldcrops/diseases/red_root_rot/
Sweets, L.E. and Wright, S. 2008 Corn Diseases – Integrated Pest Management PM 1001. University of Missouri. https://extension.missouri.edu/publications/ipm1001

Websites verified 6/1/23