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Why are some corn leaves purple?

Corn Commentary: Early-season discoloration due to deficiencies should clear up with better weather.

Tom J. Bechman, Midwest Crops Editor

June 11, 2024

3 Min Read
Green corn leaves with purple spots
MANY COLORS: You want to see corn leaves that are green. Why did some leaves turn purple or show some browning along edges? Purdue’s Dan Quinn says plants may be deficient, but the problem should correct itself. Tom J. Bechman

One week corn plants were all green. Then the next week, a month after planting, lower leaves on some plants turned purple. On other plants, edges of some lower leaves turned brown or yellowish-brown. Are these signs of problems that need to be fixed?

Dan Quinn, Purdue Extension corn specialist, examined photos of these plants from the Corn Commentary field. It’s a cornfield in central Indiana that he will follow all season, using observations to help address issues that could show up across the Corn Belt.

“Purpling could be due to a variety of issues,” Quinn says. “It can be caused by phosphorus deficiency, cool temperatures, restricted root development, or a pattern of bright sunny days and cool nights. Often, most plants come out of these symptoms once the weather, especially the temperature pattern, improves.”

Browning or yellowish-brownish discoloration along leaf edges often signifies potassium deficiency in older plants. Again, Quinn suspects that in this case, it’s a temporary situation caused by weather conditions.

Deeper dive

Because the primary symptom observed was purpling, here’s a closer look at why it occurs.

“Purple corn symptoms are caused by accumulation of anthocyanin, a purple pigment, in corn leaves,” Quinn says. “Corn leaves produce sugars through photosynthesis which are typically metabolized to generate energy for further plant growth.

Related:Why V5 corn stage is so important

“However, when cool temperatures slow plant growth or root development is restricted, sugars accumulate in the leaf and trigger anthocyanin pigment formation.”

Purple corn can also occur from a genetic response to bright, sunny days and cool nights, Quinn adds. Hybrid genetics play a role in whether a corn plant produces anthocyanin. Hence, there can be differences in hybrid response. The symptom often disappears with warmer temperatures. Yield losses should be negligible.

Phosphorus deficiency also produces purpling. It is possible that plants aren’t taking up enough phosphorus due to restricted roots, or soils could be truly low in phosphorus. But before you get the fertilizer spreader out, check soil test levels, Quinn advises. That’s especially true if purpling disappears as temperatures become warmer.

Across the rows:
Too much rain defines late spring

While planting is wrapping up, this spring will be remembered for challenges due to frequent, heavy rains. Here are reports from around the Midwest.

In Nebraska. “Wet, wet, wet! Even in eastern Nebraska where we had drought the past two years, the latest Drought Monitor shows marked improvement, thanks to several inches of rain — too much, really. There was quite a bit of washing, even on no-till fields that didn’t have cover crops.” — Curt Arens, editor of Nebraska Farmer

Editor’s note: The Crop Watch Newsletter from the University of Nebraska for May 24 led with “Corn and Soybean Survival in Saturated and Flooded Soils.”

In Illinois. “Our recent heavy rains occurred at the same time as 50% egg hatch for western corn rootworm in east-central Illinois. It will be interesting to see if that impacts rootworm population this year.” — Nick Seiter, Extension field entomologist, Champaign County, reported in The Bulletin, Illinois Crop Update, May 31 edition, compiled by Talon Becker

In Wisconsin. “The week ending June 2 was another wet week in Wisconsin. There were three days suitable for fieldwork due to persistent rains across the state, especially in the northern half. This rain is delaying alfalfa harvest and will likely affect quantity and quality this year.” — Fran O’Leary, editor of Wisconsin Agriculturalist

About the Author(s)

Tom J. Bechman

Midwest Crops Editor, Farm Progress

Tom J. Bechman became the Midwest Crops editor at Farm Progress in 2024 after serving as editor of Indiana Prairie Farmer for 23 years. 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.

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