by Dan Quinn

Pollination is one of the most critical periods for yield determination in corn. Good pollination is largely determined by successful synchronization between silk elongation, tassel emergence and pollen shed. In certain conditions, poor pollination and kernel development can result in significant reductions in kernel numbers and yield.

Typically, one of the most common causes of poor pollination is delayed silk emergence, often due to drought conditions. This can result in missing kernels at tips of ears. However, in certain instances, the opposite can happen. When silks emerge too early, missing kernels are observed at the base, or butt, of the ear.

Silk elongation in corn typically begins near the base of the ear and is initiated during the V12 to V14 vegetative growth stages. The first silks to emerge from the husk are from the lower portion of the ear. Silks will continue to emerge for about one week. Once silks have emerged from the husk, they will start to elongate at a rate of 1 to 2 inches per day, slowing over time.

In addition, silks will cease growth once they come in contact with pollen grains. Therefore, if pollen is not available, silks will continue to elongate for about nine days following emergence, which can result in excessively long growth.

In certain cases, silks can emerge from the husk multiple days prior to pollen shed. This response is counterintuitive to what many have been taught. Conventional wisdom is that the tassel always emerges before silks.

Enter modern hybrids

However, many modern hybrids have improved genetics, which include improved drought tolerance. One way these genetic improvements combat drought stress is through quicker and more vigorous silk emergence. That helps reduce the risk of delayed silk emergence caused by drought.

Therefore, when growing conditions are more favorable, silk emergence can occur too quickly, which results in the earliest-emerging silks losing viability before pollen is shed. These silks are connected to kernels at the butt of the ear. The result is poor pollination and missing kernels at the butt.

POLLINATION WOES: Poor pollination and missing kernels at the butt of this ear were caused by silks emerging too early prior to tassel presence and pollen shed. (Photo by Brian Early, Pioneer field agronomist)

The bottom line is that favorable growing conditions combined with cooler weather, sufficient soil moisture and cloudy conditions can sustain silk growth and elongation, causing silks to emerge too soon. They become excessively long, which can also cause pollination issues due to silks overlapping or shading other silks.

Monitor pollination success

Overall, it is important to check pollination success and kernel development during the growing season. In addition, pay attention to silk development, elongation and where on the ear kernels are missing. This will help you understand where issues with pollination may have occurred.

For more information, check out an article Bob Nielsen, a Purdue Extension corn specialist who is now retired, published in 2018. See Unusually Long Silks in Corn at the Corny News Network, sponsored by Purdue Extension.

Quinn is a Purdue Extension corn specialist. Contact him at [email protected].