By Greg Luce

Pioneer Hi-Bred agronomist

The relationship between temperature and moisture in the bin determines the length of time corn can be successfully stored. The chart below, from the USDA, was developed for corn with normal harvest damage. Low-quality grain may store only half as long. It will be especially important this year to monitor the condition of stored grain because of the extreme moisture variances that may occur within a given field. Notice how quickly relatively small changes in grain moisture and temperature can bring corn out of condition in a very short time.

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Death of top leaves in corn. Bob Nielsen from Purdue University had a recent article on what seemed to be an unusual pattern of leaf senescence (death) in corn this year. Typically, we think of plants dying from the bottom up, however, this year several fields died not only from the bottom up but the top down. Below are some explanations for this phenomenon:

--Research from the late 70s and as recent as 2004 suggest that simultaneous upper and lower leaf senescence may not be that unusual from a physiological standpoint. Several hybrids in these studies exhibited this type of death.

--Death of top leaves can be a direct result of drought stress. Prior to death these fields will exhibit a gray-green color. This usually affects the entire field.

--Anthracnose stalk and root rot can kill plants in this fashion. This type of death will be found randomly from plant to plant across a field rather than affecting the entire field.

--European corn borer (ECB) tunneling damage can cause upper parts of the plant to die prematurely. Many times the upper part of the plant will turn a red color prior to death. This is a result of sugar accumulation in the upper part of the plant. Sugars are being produced, but because of ECB tunneling they cannot translocate to the ear. Again, this will occur randomly from plant to plant across the field.

Uneven plant and ear height is evident in some cornfields across the area. This is usually due to an early season stress that caused some plants to lag behind unaffected plants. This stress can include many factors: uneven planting depth, dry or cloddy conditions at planting, Pythium seedling disease, insect damage, etc. However, the most common factor causing uneven plant height this year is the frost damage we experienced early in the season. Even though many of the frosted plants survived, the randomness of the severity was quite dramatic. One plant might be completely "burnt" to the ground while the one next to it was unaffected. This is hard to explain, but each corn plant lives within its own unique "micro-environment." Corn plants may be only 7 inches apart but the most subtle differences in their immediate environment, such as residue cover or topography, can have dramatic effects. Micro-environment differences also are quite evident when noticing the randomness of stalk rots within a row of corn.

Editor's note: Crop Talk is brought to you by agronomists serving your community to keep you informed about current growing conditions and important management issues. Greg Luce, Mexico, Mo., is an agronomist with Pioneer Hi-Bred International, Inc.

Date: 9/22/05

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