Even one poorly performing plant is enough to ask questions, Dave Nanda says. While it may have zero effect on yield if the rest of the field is healthy, it’s worth figuring out what made even one plant sick. It’s part of the scouting process, he adds.

Nanda is an independent crop consultant based in Indianapolis. He scouts the Corn Watch ’18 field regularly during the growing season. The Corn Watch ’18 project is sponsored by Seed Genetics-Direct.

This year’s field was planted April 28. (Earlier reports may have said April 30, but actual planting date was April 28.) A historically warm May resulted in fast emergence and growth. Freak storms with hail twice in the same day tattered leaves before the corn reached the five-collar leaf stage. There was also ample rainfall at that point.

Nanda inspected the field after the hail and found tattered leaves, but an overall fast-growing, otherwise healthy corn crop. Thirteen days later he visited again and found seven-collar leaf corn, with the primary visages of any hail damage confined to a few tattered leaves near the bottom of some plants. Overall, new growth was healthy and vigorous.

However, there was an occasional very short, sickly plant, sometimes two or three in a row, stuck in between healthy plants in a few places. He found them primarily on the edges of the field and in a spot where water ran during a rain after planting. Overall, though, the field was very healthy.

Track cause
Nanda was curious about the sickly plants. The farmer wanted to know what their problem was, as well. So Nanda went to work. Here is what he observed:

• Healthy roots. The first step was to dig up a couple of the sick plants. For the most part, roots were healthy. He found no evidence of a seedling disease that would have affected rooting.

• Healthy inner tissue. When Nanda split stalks open, they were healthy, as well. He saw no discoloration that would indicate a seedling disease. The growing point appeared healthy too. Nanda ruled out disease as a cause.

• Twisted leaves. A few of the sickly plants, but not all, had leaves still twisted together and not unfurled. Was it possible the hail damage impacted these plants so much that they never unfurled and recovered properly? It’s possible, Nanda says, but there is no way to prove it.

• Location where water ran. Some of the poor plants were growing where water ran after planting. Others were on ends where water might not drain as easily. Was it possible that herbicides concentrated where water ran or sat, and a few plants got more herbicide than they could tolerate? Again, it’s possible, Nanda says, but there is no way to prove it. Chemical injury can look like many other things.

• Nitrogen factor. The farmer applied nitrogen in the spring before planting. After planting he suspected some injury where plants germinated over knife rows. However, there wasn’t an overall pattern evident in the field. From what Nanda observed, he couldn’t rule in or out injury from nitrogen application.

Inconclusive evidence
Sometimes you don’t wind up with a definite cause for a plant’s poor condition, Nanda says. The best thing you can do is rule things out. He eliminated disease as a possible cause. Several other possible factors at play — hail damage, chemical damage and nitrogen injury — could alone, or in combination, produce symptoms that are hard to distinguish from each other.

The good news in this situation is that whatever the cause of the plants’ injury, there should be no effect on yield.    

Click through the slideshow to see photos of the sickly plants.