Cob tissue has no kernels on the last one or more inches of the ear tip. Ovules at ear tip are not fertilized.
Poor fertilization of ear tip ovules at silking; poor pollination of ear due to asynchronous pollen shed and silking (poor “nick”) due to severe drought and high temperatures; inadequate pollen supply due to uneven crop development, herbicides, insect feeding and silk clipping. Phosphorus shortages also interfere with pollination. The presence of barren tips should not always be cause for concern? Favorable growing conditions may result in a larger number of potential kernels per row than normal. So even if corn ear tips are not filled completely, due to poor pollination or kernel abortion, yield potential may not be affected significantly, if at all, because the numbers of kernels per row may still be above normal. The presence of ears consistently filled to the tip may actually indicate that a higher plant population is needed to optimize yields.
Follow recommended guidelines for minimizing crop stress, including maintaining appropriate soil fertility, adjusting planting depth with varying soil conditions, and selecting adapted hybrids and seeding rates consistent for soil yield potential and date of planting. Avoid planting too early in wet soils. Minimize weed competition with effective herbicide application and/or timely cultivation.
Abendroth, L. 2005. Examine corn ears now for clues to earlier stresses. Univ. of Nebraska Extension Crop Watch (September 16, 2005). Available at: http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1301&context=cropwatch [URL verified 1/16/2019].