Recognizing rapid growth syndrome in corn

The last three weeks of May were quite challenging for most Illinois growers. The month started out with several days of cool, cloudy weather, providing minimal heat units and leading to slow and inconsistent corn growth.

Ironically, by the third week of May, a rapid increase in temperature and sunlight occurred for several days, increasing the heat units needed for plant growth.

History and experience show that when corn plants are exposed to prolonged cool-weather stress followed by a rapid, consistent warm-up, corn growth and development can increase almost exponentially.

In other words, the corn plant actually may be growing too fast. In fact, several locations throughout Central and Southern Illinois were reporting new corn leaf stages occurring about every two days by the third week of May.

When corn plants undergo such a rapid change in growing conditions, they tend to want to grow too fast.

Oftentimes, this can lead to new leaves wrapping or twisting inside the whorls, not emerging as they should. This phenomenon often is referred to as rapid growth syndrome.

The key identifying feature of rapid growth syndrome is the wrapping and twisting of the whorl leaves. In many cases the whorls of corn plants between the V5 and V7 stage emerge tightly wrapped and almost appear as a long rattail.

Oftentimes, the wrapped whorl will bend over and almost touch the ground.

While the exact culprit for this phenomenon is not completely understood, it is believed by most universities that during the rapid growth phase, the newer, smaller, leaves developing in the whorl are rushing to reach sunlight.

However, since the older leaves are still transitioning into rapid growth, these newer leaves are forced to wait for emergence. As these newer leaves continue to try to push their way through the whorl, they become almost entangled.

This can be seen if you slowly unfurl the whorl. There will be multiple leaves wrapped together.

It is important to recognize that despite the appearance of affected plants, complete recovery usually occurs quickly with little to no effect on yield.

Generally, the only remaining sign may be the occurrence of a few bright “yellow tops” that stand out in your field when you are driving down the road.
These yellow tops are simply the leaves that were tied up in the whorl -- void of sunlight. A few days of sunshine and these will disappear almost overnight.