Photo Gallery:
The images below come from a field planted in mid-April in westcentral Indiana. Emergence and initial appearance of the young plants were reported to be quite uniform.
By late May to early June, however, what had been uniform had turned ugly. Plant health ranged from good to death. Plant colors ranged from a nice green to pale yellow to necrotic. Plant size ranged from zero (dead) to six inches (stunted) to 18 inches (healthy) in height. Leaf stage ranged from zero (dead) to V2 (stunted) to V4 (healthy).
Inspection of stunted or dead plants revealed a number of contributing stress factors. The most common factors appeared to be the destruction of the seed by seed rots or a seedling blight affecting the mesocotyls. The randomness of the affected areas attests to the randomness of the occurrence of disease organisms throughout the soil.
What is important to recognize is that the damage to the seed and/or mesocotyls occurred while the seedling was still strongly dependent on the seed for nourishment, sometime before about leaf stage V2. Loss of the seed and/or the mesocotyl, the 'pipeline' from the seed to the above-ground photosynthetic 'factory', at such an early developmental stage resulted in the severe stunting and/or death of the seedlings. The risk of such damage to corn is greater whenever the corn is developing at a very slow pace such as was experienced throughout Indiana in late April and early May of 2000.
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Image 1 Emerged uniformly, looked good for a few weeks, turned ugly in late May. |
Image 2 Healthy 'normal' plant at leaf stage V4 (four visible leaf collars). |
Image 3 Whole plant view of healthy 'normal' plant at leaf stage V4. |
Image 4 Root system of healthy V4 plant, depicting healthy mesocotyl. |
Image 5 Seminal root system of healthy V4 plant. |
Image 6 Stunted plant at leaf stage V2. |
Image 7 Whole plant view of stunted V2 plant. |
Image 8 Cause of stunting: Damage to kernel, likely by wireworm or seedcorn maggot. |
Image 9 Closeup view of insect-damaged kernel. |
Image 10 Another stunted plant at leaf stage V2. |
Image 11 Whole plant view of stunted V2 plant. |
Image 12 Cause of stunting: Seed rot and diseased mesocotyl. |
Image 13 Stunted plant that is dead, but doesn't know it. |
Image 14 Whole plant view of stunted (dead) plant depicting diseased mesocotyl and absence of kernel. |
Image 15 Closeup view of diseased mesocotyl and absence of kernel. |
Image 16 View of another nearby field with similar stand problems, but where damage occurred mostly in lower, wetter areas of the field. |
Image 17 Another stunted V2 plant that is dead, but doesn't know it. |
Image 18 View of diseased mesocotyl of stunted (dead) plant. |
Image 19 Stunted V3 plant with diseased mesocotyl. |
Image 20 Closeup view of diseased mesocotyl. |
For more information about seedling diseases of corn, browse through these recent newsletter articles from around the Midwest.