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Agronomy Update

Stalk Rot in Corn? Time to Prioritize Harvest!

Published on Tuesday, September 20, 2016

Harvest time is finally here and for most of us in the South, this will be the year to forget! Parts of Tennessee encountered the worst drought we’ve seen since 2012. On the other end of the spectrum, parts of Kentucky, southern Indiana, and southern Illinois caught more rain than they could handle for most of the year. The Missouri Bootheel couldn’t make up its mind if it wanted to be too dry or too wet! All of these crazy environmental conditions have led to some serious standability issues in our corn. Just about every corn field I’ve been in recently has shown signs of premature death and stalk rot. This is something we see every year, but some years are worse than others and may require a little more planning before harvest.

In most fields these conditions are only effecting about one to two percent of the plants, but some are closer to 15 to 20 percent. Depending on the severity of the field, you may want to shell some fields first. Fields with a greater occurrence of stalk rot could potentially stalk lodge and cause a major headache at harvest. There are two ways to test the structural integrity of the plant: the pinch test and the push test.

The “pinch test” is pretty simple and it’s just what the name implies. Bend down and pinch the stalk about 6 to 8 in. above the ground. Is it squishy or hard? If the internode is squishy then you most likely have some form of stalk rot in that plant. To get an accurate assessment of the field, you should do this on 20 consecutive plants in a row then multiply that number by five. That will give you a percentage of affected plants. I would also suggest doing this in multiple areas of the field and averaging the numbers to get a feel for the entire field.

The second way to test for stalk rot is the “push test.” If you can push the stalk over enough to touch the adjacent row (assuming this is 30 in. corn) and the plant comes back to its upright position, the stalk is not compromised. If it bends in one of the lower internodes and does not stand back up, you most likely have some form of stalk rot in that plant. Again, you would want to do this to 20 consecutive plants, then multiply by five to gain a percentage of affected plants.

There are several forms of stalk rot that can invade a corn plant, but the two I’ve seen most prevalent this year is Anthracnose stalk rot and Fusarium stalk rot. These pathogens will deteriorate the pith (a major component of structural integrity) in the lower portions of the stalk, which makes that plant vulnerable to late season wind storms.

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Austin Scott
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