Sponsored By
indiana Prairie Farmer Logo

Stay alert to detect stalk rot in cornStay alert to detect stalk rot in corn

Corn Watch: Here’s how to identify a common stalk rot.

Tom J. Bechman

August 29, 2023

3 Min Read
A metal blade pointing to a dark spot on a cornstalk
TIP-OFF SYMPTOMS: Black specks or discoloration on the outside of the stalk indicates there could be trouble inside, Dave Nanda says. Photos by Tom J. Bechman

Late-season scouting in cornfields before harvest includes looking for stalk rot. The easiest indicator is to do one of two different tests in the field. Either push stalks to the side and count how many do not snap back crisply, or pinch stalks and see if any are soft vs. hard and firm.

“I recommend doing either the push test or the pinch test on 100 stalks in a row,” says Dave Nanda, director of genetics for Seed Genetics Direct, sponsor of Corn Watch ’23. “Then repeat it on other rows and in other areas of the field. Once you do several different counts, you can determine an average percentage of plants with problems.”

The practical application of doing these tests is to determine if the field could stand later into the season, or if early harvest of that field should be a priority, Nanda says. “If you’re seeing a significant number of stalks ready to lodge early in the fall, mark it for early harvest,” he explains. “Otherwise, stalk lodging could lead to higher field losses when you shell the field.”

Closer look at cornstalks

What you’re determining with the push test or pinch test is how many stalks have already succumbed to stalk rot, or how many are infected and in the early stages of the disease.

“I like to go beyond just knowing how big the problem is, and determine which pathogen is causing it,” Nanda notes. “One of the most common stalk rots in the Midwest is anthracnose. There is also a leaf blight phase, but the stalk rot phase is often most troublesome. Diplodia and fusarium are other common stalk rots.”

Related:Pull tissue samples to check nutrient uptake

Stress of any kind during the growing season helps set plants up for stalk rot. It’s still unclear whether the early-season drought that stressed plants will lead to repercussions this fall. Regardless, it pays to be looking for stalk rots every year, Nanda says.

hand holding cornstalk split in half

Once you identify stalks that don’t rebound in the push test or that are soft in the pinch test, examine them more closely, Nanda says. Anthracnose stalk rot will turn the outside of stalks black, at least in spots. Diplodia can cause discoloration on the outside of the stalk too, usually near a node.

“Cut some stalks open,” Nanda recommends. “A pocketknife is a good scouting tool to keep handy. Split the stalk lengthwise down the middle and look inside.”

Discoloration often happens at the node inside the stem, he says. As the infection worsens, the entire pith can become discolored, depending upon the disease. If you find pinkish, reddish discoloration of pith tissue, it’s more likely caused by the fusarium pathogen, he explains.

“It helps to know which pathogens were in the field and causing issues,” Nanda concludes. “Keep that in mind as you evaluate hybrids for next season. See how resistant different hybrids are to stalk rots.”

Read more about:


About the Author(s)

Tom J. Bechman

Editor, Indiana Prairie Farmer, Farm Progress

Tom J. Bechman is editor of Indiana Prairie Farmer. He joined Farm Progress in 1981 as a field editor, first writing stories to help farmers adjust to a difficult harvest after a tough weather year. His goal today is the same — writing stories that help farmers adjust to a changing environment in a profitable manner.

Bechman knows about Indiana agriculture because he grew up on a small dairy farm and worked with young farmers as a vocational agriculture teacher and FFA advisor before joining Farm Progress. He works closely with Purdue University specialists, Indiana Farm Bureau and commodity groups to cover cutting-edge issues affecting farmers. He specializes in writing crop stories with a focus on obtaining the highest and most economical yields possible.

Tom and his wife, Carla, have four children: Allison, Ashley, Daniel and Kayla, plus eight grandchildren. They raise produce for the food pantry and house 4-H animals for the grandkids on their small acreage near Franklin, Ind.

Subscribe to receive top agriculture news
Be informed daily with these free e-newsletters

You May Also Like