While there were many great results even after a tough year in 2016, there were some real disappointments too. According to Levi Runkle, a Tri-Ag Products, Inc. agronomist, some of those disappointing corn yields may have been partially the result of a rare issue in Ohio — red root rot. Runkle found the unique challenge for Ohio in a surprising number of fields last year.
“This is a rare late season destructive disease that leads to lodging. As we went into harvest we started seeing problems with hybrids that don’t usually have problems with lodging or ear drop,” he said. “As we got to looking at it, we started to see a lot of purpling or red on the roots that looked like insect damage. That is something we typically don’t see here. You see it more in the Delaware or Maryland area.”
Red root rot needs the right set of conditions to become a problem.
“It is brought on by some type of early stress. For us it could have been from the frost damage last year or an early inoculation of Pythium or Fusarium. As you get into the year, red root rot needs an extended period of stress, which we had with drought stress and higher temperatures,” Runkle said. “Then when we got that large rain event in August, it allowed the inoculant for the red root rot to get in. You can have a really good-looking field and in four or five days it is dead. It completely cannibalizes the stalk and shuts down production and stops packing starch, which really affects grain. We can see 20% yield loss from it. The root mass also decays really fast and your stalk decays fast and it causes a lot of lodging, harvest issues and ear drop. It is really nasty. The higher nighttime temperatures towards the end of August also helped this disease thrive. It is very rare to have all of these things come together in Ohio but it happened last year.”
According to the University of Illinois, symptoms of red root rot include red or pink discoloration of the root system and lower stalk tissue, early death and shriveling showing up just prior to corn maturity. The red color is deeper and darker than that of Gibberella stalk and root rot and the symptoms can vary among different corn hybrids. The rotting of the roots below ground can lead to wilting and grayish green foliage, premature plant death, and lodging in four to five days.
University of Illinois experts said the Phoma terrestris fungus that causes red root rot is associated with Pythium and Fusarium species and can survive in soils with a wide range of temperature and pH conditions. It overwinters as microsclerotia in soil. High yield conditions and moderate temperatures favor the disease.
In many cases Runkle thinks red root rot was a problem in more 2016 fields that people realized because other more common issued were blamed.
“Some people thought it was rootworm but in some cases in Ohio last year it was red root rot,” he said. “Kernels didn’t fill right because the plant died prematurely.”
Runkle does not think red root rot will be a regular problem in Ohio due to the conditions it requires.
“Hopefully we don’t see it again for a long time. It does stay in the soil, but you still have to have those other factors for it to be a problem. You have to have a lot of things line up to get this problem,” he said. “I don’t think it will be a regular problem in Ohio.”