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Take to Fields Now to Look for Stalk Rot

Here’s how to test corn to see if it needs to be harvested first.

Increasing reports of stalk rot from across the Midwest are serious enough that you need to take to your fields now to investigate stalks. Doing so will dictate which fields need to be harvested immediately.

There are two ways to check for the presence of rot.

With the tipping test you grab the stalk at your height and push it at about a 45° angle. “If it snaps back when released, that stalk is healthy,” explains Doug Jardine of Kansas State University (jardine@ksu.edu). “But if it kinks or breaks near the bottom, you have a stalk that has been weakened by rot. If you look at 100 plants, and 50 of them kink with the tipping test, then you have a 50% lodging problem. That field should be harvested early.”

Another stalk rot test is to pinch stalks 1 to 2 nodes up from the ground on 10 consecutive plants. If the pinching causes the stalk to collapse, it likely has some sort of stalk rot.

Take time to split the stalk of the collapsed plants open and examine the internal stalk contents. If the pithy area of the stalk has shrunk or become discolored, stalk rot is evident.

Jardine points out that stalk rot is the No. 1 cause of crop loss at harvest. “In some years it’s worse than others. And in 2019 stalk rot is bad in some areas,” he adds. 

What makes this year worse than others for stalk rot? Weather conditions have been very conducive to stalk rot, especially Fusarium stalk rot (the most common stalk rot). “It likes a weather pattern where it is fairly wet in the beginning of the season, then turns hot and dry in the middle followed by wet, cold weather,” Jardine explains.

There are other issues that can lead to a high incidence of stalk rot.  “One important one is nitrogen deficiency,” Jardine points out. “There were a lot of problems with denitrification this year, and that has compromised stalk health.”

Another cause of stalk rot is leaf health. If you have a healthy plant that is photosynthesizing properly, you are going to get good grain fill. If you start to lose photosynthetic leaf area for whatever reason, the plant is not photosynthesizing enough to fill grain. What the plant will do is mobilize carbohydrates and nutrients from its roots and crowns to ensure ear fill.

This, in turns, weakens the stalk and makes it more susceptible to diseases such as those that cause stalk rot.

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