Cloudy Weather and Kernel Abortion Affect Indiana Corn Crop

As corn harvest season kicks off, farmers in Indiana are noticing a common issue: incomplete kernel set, or "tip back," where the ears of corn do not fill completely to the tip. This problem can arise from two main causes: poor pollination or kernel abortion after successful fertilization. Distinguishing between these is crucial because they occur at different times and are influenced by different environmental stressors.

Poor pollination happens when ovules are not fertilized due to factors like drought, excessive heat, or prolonged wet weather during pollen shed. On the other hand, kernel abortion occurs when fertilization is successful but the kernel stops developing due to stress. Cloudy weather, which reduces photosynthesis, is a significant but often overlooked stressor during early grain fill. Research shows that a 50% reduction in light during this period can lead to a 16% reduction in kernel number per row, with tip kernels being the most susceptible.

The 2026 growing season in Indiana saw excessive rainfall and cloudy conditions, which may have contributed to kernel abortion. Solar radiation data from West Lafayette indicated that average and cumulative solar radiation were below previous years' averages, with several days experiencing significant reductions. For fields that pollinated in mid-to-late July, these low-radiation periods coincided with the critical early kernel development stage, potentially exacerbating the issue.

When scouting ears at harvest, farmers should determine whether missing kernels resulted from failed pollination or abortion. Blank cob tissue suggests pollination issues, while small, shriveled kernels indicate abortion. Fields pollinating in mid-to-late July should be compared with the timing of cloudy conditions and other stresses. While some tip back is natural, widespread abortion may indicate a combination of stresses, including reduced solar radiation.