Some corn fields around the state have been showing symptoms of unusual twisted growth in recent weeks. The whorls of affected plants are tightly twisted, often bent over severely, and do not unfurl on a timely basis. One's natural instincts would blame the twisted growth on herbicide injury. But, in most cases, the cause is something entirely different.
The problem often occurs following a sudden return to optimum growing conditions preceded by a period of poor growing conditions. This year, much of Indiana's corn crop struggled through a cooler than normal and frequently cloudy May. Sunshine and warmer temperatures returned the first week of June and have pretty much continued since. Corn has responded by finally beginning to grow rapidly.
Certain hybrids react to such a change in growing conditions by basically going 'bonkers'. The upper whorls of the plants don't unfurl properly. Younger leaves deeper in the whorl continue to grow rapidly, but are unable to emerge from the unfurled upper leaves. The now tightly twisted whorl then bends and kinks from the pressure exerted from the younger leaves' continued growth.
At the peak of the problem, the appearance of these plants is indeed unsettling and one would think that the whorls would never unroll properly. Given another week, though, the majority of the affected plants do unroll and continue to grow normally. Yield effects from the period of twisted growth will be minimal, if any.
If you didn't notice the twisted growth to begin with, you may notice the appearance of 'yellow tops' across the field after the whorls unroll. The younger leaves that had been trapped inside the twisted upper leaves emerge fairly yellow due to the fact that they had been shaded for quite some time. Another day or two will green these up and the problem will no longer be visible.