CORN Newsletter: 2009-32, September 21, 2009

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C.O.R.N Newsletter 2009-32
September 21, 2009 - September 28, 2009

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"Blunt Ear" Syndrome Appearing in Ohio Corn Fields
by Peter Thomison


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I have received several reports in recent weeks of “beer can” ears, an abnormal condition in which corn ear length is markedly shortened. This ear abnormality has also been referred to as ear stunting or “blunt ear” syndrome. This year the anomaly has also been reported in Indiana (http://www.kingcorn.org/news/timeless/BluntEars.html) and Pennsylvania (http://fcn.agronomy.psu.edu/2009/fcn0925.cfm#c).

Two key visual symptoms associated with ear stunting are ears that are much shorter than normal and a considerable section of the ear tip that has not produced kernels. This latter symptom appears to be related to poor pollination, perhaps the result of tight husks preventing and/or delaying normal silk emergence. These husks tightly cover stunted ears and may not provide adequate space for silks to emerge normally. Beer can problems may be often associated with multiple ear shoots per node. Several nodes of the affected plant may exhibit stunted ears and multiple ears per node. To compare beer can ear symptoms with other ear development problems check our abnormal ears web page [online]http://agcrops.osu.edu/corn/documents/AbnormalCornEarsPoster_000.pdf
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Corn plants with stunted ears generally appear healthy with normal husk formation and growth. However, husks may appear somewhat pointed, probably because husks were more tightly wrapped around the much smaller ear enclosed. At harvest, plants with stunted ears often turn purple due to an accumulation of sugars in the leaf and stalk tissue. Ear stunting is often localized within fields (e.g. head rows and border rows or patches within fields) with only a small percentage of plants (<1-5%) affected.

Little is known concerning possible causes of this abnormal ear development. The problem may be related to a low temperature stress or shock during ear development between the 5-leaf collar stage and 12-leaf collar stage. In 1992, a year during which corn ear stunting was widely observed across the Corn Belt, the only common factor shared by fields exhibiting ear stunting problems seemed to be low temperature (down to near freezing) in late June during ear size determination. The localized occurrence of beer can ears within a field supports speculation that some stress may be impacting ear development of a limited number of plants, which are at a highly sensitive growth stage.
No consistent relationships between soil fertility levels, herbicide programs or corn diseases are evident. Hybrids also appear to differ in susceptibility to the problem.

In 2007, and to a lesser extent 2006, there were reports of “arrested ear” development in several Corn Belt states. Arrested ears were characterized by a range of symptoms, and in some cases seemed to resemble beer can ears. However, there were some important distinctions. Some ears exhibited varying degrees of stunting with limited kernel formation. Some ear shoots carried either no ear or only the short remnant of an ear. Often silks were absent or limited. Some of the most pronounced arrested ear damage was associated with foliar fungicide applications made with ground equipment during the two week period prior to tasseling. In various postmortem assessments, it was noted that arrested ear injury frequently occurred in fields where the foliar treatments included non-ionic surfactants. Now, there is preliminary evidence from Purdue University and University of Illinois evaluations conducted in 2008 that suggests that the cause of some of these arrested ear problems may actually be due more to surfactants than fungicides.

For more information about these ear development anomalies, check the following online articles:

Nafziger, E. 2008. More ear oddities, and a possible cause. The Bulletin, Univ. of Illinois. [on-line]. Available at http://www.ipm.uiuc.edu/bulletin/article.php?id=1033
(URL accessed 9/21/09).

Nielsen, R.L., W. Wise, C. Gerber. 2008. Arrested ears resulting from pre-tassel applications of pesticide & spray additive combinations. Corny News Network, Purdue Univ. [on-line]. Available at http://www.kingcorn.org/news/articles.08/ArrestedEars-1209.html (URL accessed 9/21/09).

Nielsen, R.L. (Bob). 2009. Blunt Ear Syndrome....Again. Corny News Network, Purdue Univ. [online] http://www.kingcorn.org/news/timeless/BluntEars.html. (URL accessed 9/21/09).

Roth, G. 2009. Arrested Ear Development. A Nagging Problem That Won’t Go Away. Penn State Field Crop News [online] http://fcn.agronomy.psu.edu/2009/fcn0925.cfm#c (URL accessed 9/21/09).

Thomison, P. and A. Geyer. 2007. Abnormal corn ears. Ohio State University Extension. ACE-1. [online] http://agcrops.osu.edu/corn/documents/AbnormalCornEarsPoster_000.pdf
(URL accessed 9/21/09).

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

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