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Twisted Whorls in Corn (06/22/17)

About this time last year, I wrote about twisted whorls in corn.

Twisted Whorls in Corn

About this time last year, I wrote about twisted whorls in corn. This year the problem appears to be more widespread, and in some fields, the proportion of the plants affected is higher than previously observed (Figure 1).

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This phenomenon is called the twisted whorl syndrome or buggy whipped corn. As leaves unfurl from these twisted whorls, they are yellow in color until a few days after they are fully exposed to sunlight. If it is not already the case, we should see bright yellow leaves appearing in affected fields in the next few days.

The cause of the twisted whorl syndrome is a physiological response induced by significant changes in temperature during certain vegetative growth stages. It is not caused by a growth regulator-type herbicide (at least in the cases I have reviewed), which may cause similar symptoms when misapplied. A warm period followed by a cool period (length not defined) or a cool period followed by a warm period (a rapid growth spurt followed by slow development) seem to disrupt the way that leaves develop, causing leaf deformations that eventually result in twisted whorls. It is most commonly observed at the V5 to V7 growth stages. Younger leaves as they appear are crinkled, which may partially explain why they have difficulty emerging from the whorl normally (Figure 2). Why some plants are impacted and others nearby are not is a bit of a mystery. There are differences in the response of hybrids, which may explain why two adjacent fields planted at about the same time have different levels of symptoms (Figure 3). I walked through one of our hybrid trials at Prosper and in the 86 plots evaluated found 12 hybrids highly susceptible (nearly all plant showing symptoms), 28 moderately susceptible, and 48 showing little or no twisting.

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Past observations suggest that most of the tightly twisted leaves will unfurl and the plants will resume normal development. Others writing about this syndrome indicate that it does not cause a yield loss. The severity of the symptoms this year make me believe that yield loss is possible. Certainly, plants whose leaves never unfurl will not develop a productive cob. I plan to observe some of the most severely affected plants through their development this season in order to get a better handle on the potential impacts of this problem on yield.

 

Joel Ransom

Extension Agronomist for Cereal Crops

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