Red Root Rot (Corn)

Phoma terrestris

Corn roots showing symptoms of Red Root Rot infection
Corn roots showing symptoms of Red Root Rot infection. Photo courtesy of William M. Brown Jr. Licensed under CC BY 3.0.
Red root rot is a late season corn disease that turns roots a reddish color and is known to reduce yield up to 20 percent in some areas. Infection causes premature death of corn plants.
Red root rot is first caused by a variety of soilborne pathogens that weaken the root system, allowing for easy access by the true red root rot pathogen. This pathogen is able to adapt to a wide range of temperatures and soil conditions where it can last for many years before infecting its host. Infection usually begins no earlier than midsilking in corn, or early August.
Symptoms of red root rot are generally not apparent until the fungus has significantly reduced the health of the plant. The base of the stalk as well as the roots are usually changed to a pinkish red color. If compared to healthy plants, the infected root bundle is visibly reduced in total mass. The symptoms in foliage are very similar to other stalk rot diseases: grayish and wilted leavees. Foliar effects are noticed 4-5 days after infection, and the plant death along with lodging occur 2 to 5 days after foliage symptoms appear. Not to be confused with Gibberella stalk rot, the red root rot discoloration is a much deeper red.
Red root rot is dangerous due to its late infection and rapid death of corn plants.The dead root ball may be pulled up during harvesting, causing difficulties during harvest. Yield loss has been reported to be 15 to 20 percent in some areas.
Discovering and developing resistant corn hybrids has proved to be difficult. Therefore they are few if any truly resistant strains. One way that many growers combat this disease is to rotate in a non-host such as soybeans.
Please contact your local plant pathologist to learn what is most effective in your area and how to use it best. Always read and follow all label instructions.