Ear Tip-Back in Corn

Tip-back ears can be found virtually every year when scouting corn fields prior to harvest. Causes are several and can mainly be a result of stress occurring during or after pollination. Understanding the potential cause of ear tip-back this year could help manage or reduce the potential in future crops.

When you pull back the husks and evaluate your corn crop, you may observe there are poorly developed or no kernels near the ear tip (Figure 1). Tip-back is the term that describes kernels missing or undeveloped on the tip end of the corn ear. This can be a common occurrence even under good irrigated growing conditions. Kernels at the ear tip often abort because the plant can’t support them. Tip-back may have no effect on corn yield as long as the kernel numbers are high.

Any kind of stress to the plant resulting in low sugar levels (energy) before, during, and after pollination can result in a loss of kernels on the ear. However, causes of ear tip-back generally occur at or after pollination. Tip-back can occur from the failure of ovules near the ear tip to be fertilized. A silk is attached to each ovule to receive pollen for fertilization and development of a kernel. Silks emerge last from ovules near the ear tip, and these ovules can run the greatest risk of not being fertilized when stress occurs that delays silking or interferes with the synchrony of the pollination process. Kernel development is dependent on available energy produced by photosynthesis during the first few weeks after pollination. Kernels towards the base of the ear are the first to receive available energy. Any shortage of energy during this time will likely cause kernel abortion near the ear tip.

 

Figure 1. Ear with a form of tip-back.

Many conditions can cause tip-back or kernel set to be less than desirable:

Heat Stress - If the plant is under severe heat stress, pollen can dry out and become non-viable. Even after successful fertilization, heat stress occurring in the weeks following pollination can cause fertilized ovules to abort. This normally occurs in the youngest kernels located at the tip of the ear. High night temperatures can increase plant respiration and expend energy that otherwise could be used for kernel development.

Drought Stress - This can result in delayed silking and the ovules near the tip of the ear not to be fertilized. Drought conditions also reduce transpiration and photosynthesis which can cause kernels at the tip end to abort. Irrigation during the critical time of pollination and kernel development helps to reduce the effects of drought and silk retardation.

Excessive Irrigation or Wet Conditions - Saturated soils can damage root systems, stunt or halt physiological processes in the plant, and promote nutrient loss. These conditions can also help to escalate heat stress effects.

Cloudy Conditions - Extended periods of cloud cover or particulate matter from dust and forest fires can further exacerbate the effects of heat stress by reducing solar radiation and the rate of photosynthesis. Should this occur during pollination, pollen may not be released when the silks are receptive. This could be evident at different areas of the ear, depending on when the stress occurred and which silks were available. Kernel development can be limited by long periods of smoky conditions caused by wildfires during the reproductive growth of corn.

Nutrient Deficiencies - Nitrogen or Potassium deficiency can result in poorly filled ear tips.

Corn products can show different amounts of tip-back, which can be taken as an indication of their tolerance to stress. Individual corn products may characteristically have unfilled ears and yet have high yield potential.

Although unfilled tips can be alarming, favorable growing conditions following the kernel loss event, can allow the plant to produce deeper, wider, and heavier test weight grain. This can help offset the kernel loss and help preserve a potential yield goal.

When tip-back or reduced kernel set is found, regardless of the reason, there is nothing that can be done to change the situation for the current crop. Weather and some of these stress conditions cannot be controlled. However, other factors such as tillage, fertility, population management, irrigation, seed product selection, and insect and weed control are manageable and may help reduce potential ear tip-back. Knowing the potential cause for tip-back this year could help manage or reduce the potential in future crops.