Originally published in Purdue Pest Management & Crop Production Newsletter (21 June 1996)

Rapid Growth Causes Twisted Whorls in Corn

R.L. (Bob) Nielsen , Agronomy Department , Purdue University, West Lafayette, IN 47907-1150
Internet address: rnielsen@purdue.edu

Some early-planted corn fields are showing symptoms of unusual twisted growth in recent days. 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. In fact, we saw identical symptoms in corn fields in 1995.

Twisted corn plantThe problem often occurs following a sudden return to optimum growing conditions preceded by a period of poor growing conditions. This year, what little corn that was planted in April and early May has struggled through a cooler than normal and frequently cloudy May and early June. Sunshine and warmer temperatures finally returned on about June 12. Early-planted 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. The growth stage where this phenomenon seems to occur is around five to six visible leaf collars (about knee-high).

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.

Yellow topIf 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.

Crinkly leaves In addition to being fairly yellow, the leaves will exhibit a crinkly surface caused by their restricted expansion inside the twisted whorl. Another day or two will green these up and the problem will no longer be visible.

Corn Growers Guidebook

For other information about corn, take a look at the Corn Growers Guidebook on the World Wide Web at http://www.agry.purdue.edu/ext/corn/

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