Poor development of kernels on corn ear tips is common not only in gardens, but also in large commercial plantings. Several explanations have been suggested as the cause, including nutrient deficiency, loss of foliage because of disease with correspondingly lower food manufacturing capacity, cool temperatures during ear maturity, and low moisture. Corn is cross-pollinated by wind-blown pollen from the male flowers, or tassels, at the top of the plant to the female flowers, or silks, about midway up the stalks. Each kernel develops from an individually pollinated silk. Kernels develop near the middle and base of the ear first with those at the tip developing last. When unfavorable conditions occur, such as those previously mentioned, kernels pollinated first will take precedence over those pollinated last. This often results in failure of the kernels near the tip to develop properly.
For more information on this and other topics related to corn production, contact your state extension corn specialist or your local extension educator/agent.
Here is the link to the corn extension specialists: state extension corn specialists.