Photo Gallery:
These images illustrate poor kernel set symptoms in corn and were taken on the 17th and 20th of August in a number of corn fields in westcentral Indiana and represent a number of different hybrids from several seed companies. Planting dates were similar among the fields (late April).
The primary cause of the poor and/or scattered kernel set appear to have been extensive silk clipping by either corn rootworm or Japanese beetles during pollination. The varying degrees of damage are likely related to the timing of the silk clipping relative to the timing of pollen capture among plants. For example, silk clipping on an ear where pollen capture by the silks and ovary fertilization was nearly complete resulted in less barrenness than where silk clipping occurred before significant pollen capture had occurred. One underlying reason for such variability among plants would be uneven development of the plants themselves. Plants that had emerged later or were otherwise retarded in their development due to plant stresses would have silked a bit later and been more attractive to silk clipping insects.
The secondary cause of poor kernel set in the tips of the ears where no silk clipping had occurred was likely due to excessively warm nights during silking and/or lack of pollen when the tip silks emerged.
| Example #1 of plant to plant variability for poor kernel set. | ||
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1: Two adjacent plants, the ear of one with undamaged silks, the other with silks completely removed by insect feeding. |
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2: Closer view of ear with silks still attached. |
Image 3:
 Closer view of ear with severe silk clipping extending into the husk leaf tissue. Note the damaged silk ends that would have been non-receptive to pollen germination. |
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Image 4:
 Both ears exhibit barrenness. The barren tip of the one on the left was caused by excessively warm nights and/or lack of pollen. The scattered kernel set of the one on the right was caused by excessive silk clipping by corn rootworm or Japanese beetles. |
Image 5:
 The likely insect culprit was corn rootworm. The circumstantial evidence in the field was the presence of severely 'goose-necked' stalks resulting from root lodging caused by extensive rootworm larvae feeding. |
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| Example #2 of plant to plant variability for poor kernel set. | ||
Image 1:
 These ears were from a different field and different hybrid; but illustrate the same extreme variability for kernel set observed in other fields. As with the other fields, severe silk clipping was associated with severe barrenness. |
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| Example #3 of plant to plant variability for poor kernel set. | ||
Image 1:
 Another example of variability between adjacent plants for kernel set success. |
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Image 2:
 The less severe barrenness was the result of pollination failure, likely due to lack of pollen at the time the tip silks emerged. |
Image 3:
 The more severe barrenness was the result of pollination failure plus kernel abortion. |
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| Example #4 of plant to plant variability for poor kernel set. | ||
Image 1:
 Variability among three adjacent plants for severity of silk clipping. |
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Image 2:
 Closer look at variability among three adjacent plants for severity of silk clipping. |
Image 3:
 Variability among three adjacent plants for severity of barrenness due to silk clipping. |
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| Example #5 of plant to plant variability for poor kernel set. | ||
Image 1:
 Variability for maturity of ear, i.e., uneven plant development within the field. |
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Image 2:
 Variability for silk clipping and barrenness related to maturity of ear, i.e., uneven plant development within the field. |
| Example #1 of severe barrenness associated with severe silk clipping. | ||
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1: Severe silk clipping of ear that looks otherwise normal in size. |
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2: Closer view of ear with severe silk clipping extending into the husk leaf tissue. Note the damaged silk ends that would have been non-receptive to pollen germination. |
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3: Nearly complete barrenness resulting from severe silk clipping during pollination. |
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| Example #2 of severe barrenness associated with severe silk clipping. | ||
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1: Severe silk clipping of ear that looks otherwise normal in size. |
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2: Closer view of ear with severe silk clipping extending into the husk leaf tissue. Note the damaged silk ends that would have been non-receptive to pollen germination. |
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3: Barren tip and some scattered kernel set resulting from silk clipping. |
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| Example #3 of severe barrenness associated with severe silk clipping. | ||
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1: Severe silk clipping of ear that looks otherwise normal in size. |
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2: Closer view of ear with severe silk clipping extending into the husk leaf tissue. |
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3: Note the damaged silk ends that would have been non-receptive to pollen germination. |
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4: Nearly complete barrenness resulting from severe silk clipping during pollination. |
| Example #4 of severe barrenness associated with severe silk clipping. | ||
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1: Severe silk clipping of ear that looks otherwise normal in size. |
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2: Closer view of ear with severe silk clipping extending into the husk leaf tissue. Note the damaged silk ends that would have been non-receptive to pollen germination. |
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3: Scattered kernel set resulting from severe silk clipping during pollination. |
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| Example silk clipping severity with later plantings of corn. | ||
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1: Ears from four planting dates, ranging from 27 April to 11 June. |
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2: Ears from four planting dates, with husks removed. Note the dramatic silk clipping in the ears from the later two plantings. |
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3: Ears from four planting dates, with husks and silks removed. Note the severe barrenness in the later two plantings caused by the extensive silk clipping. |
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4: 17 August: Corn rootworm beetles still feasting in silks of a later planting of corn. |
For other
information about corn, take a look at the Corn Growers Guidebook on the World
Wide Web at http://www.kingcorn.org