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Keep an eye open for stalk rots

October 6, 2017
Content Author: Alison Robertson, Rebecca Vittetoe

Over the past couple of weeks we’ve been doing stalk rot assessments at several of the ISU Research Farms including the Southeast Research and Demonstration Farm, the McNay Research Farm, and the Ames Farm. While the plants seemed to be standing well, minus where the raccoons had fun in one of the trials, it was not uncommon to find stalk rots in the plants we sliced open to evaluate.

This is a good reminder that initial symptoms of stalk rots are not easily observed. Unfortunately we typically don’t notice stalk rots until either the exterior stalk tissue is affected or lodging or snapping has occurred.

We encourage you to get out and take some time to evaluate your fields for stalk rots. Check stalk firmness by pinching the lower internodes (“pinch test”). If the stalk crushes easily by hand then the integrity has been reduced by stalk rot and the risk of lodging goes up.

An alternative to the pinch test is the push test. With the push test, push the plant tops approximately 30 degrees from vertical. If the plant fails to snap back to vertical, the stalk has been compromised by stalk rot. Either method works fine.

With both tests randomly select a minimum of 100 plants in the field. We suggest while walking through the field, stop at five different spots and evaluate 20 plants. You want to get a good representation of the field.  If more than 10 percent of plants in a field exhibit stalk rot symptoms, that field should be one of the first or next fields harvested to reduce the potential for plant lodging and for yield loss.

The shiny black blotches on this stalk rind are very characteristic of Anthracnose stalk rot. Photo taken 9/22/17 at the Southeast Research and Demonstration Farm. 
Discoloration and a rotting pith caused by a stalk rot. Photo taken 9/22/17 at the Southeast Research and Demonstration Farm.   


Related article: Towards a Successful Harvest: Stalk Rots and Standability Issues

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on October 6, 2017. The information contained within may not be the most current and accurate depending on when it is accessed.

Authored by
Alison Robertson
Alison Robertson
  • Professor of Plant Pathology and Microbiology
  • Extension Field Crops Pathologist
Dr. Alison Robertson is a professor of plant pathology and microbiology. She provides extension education on the diagnosis and management of corn and soybean diseases. Her research interests include Pythium seedling disease of corn and soybean and Goss's wilt. Dr. Robertson received her bachelor's degree in plant pathology in 1991 from the University of Kwazulu-Natal, Pietermaritzburg, and came to the United States in 1999 to pursue a doctoral degree in plant pathology at Clemson University. She started working at Iowa State University in May 2004.
Photo of Rebecca Vittetoe.
Rebecca Vittetoe
  • Field Agronomist in EC/SE Iowa
Rebecca Vittetoe works with farmers, landowners, and ag retailers to answer agronmy-related questions. Her areas of expertise include general agronomy, crop diseases, corn, soybean, and forage management, cover crops, integrated pest management, and crop scouting. Vittetoe received her B.S. in agronomy along with a journalism and mass communications minor from Iowa State University in 2014. She earn her M.S. in agronomy from Iowa State University in 2019.

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