Corn Fields Having Sustained Hail Injury May not Benefit from a Foliar Fungicide

Tom Allen, Extension Plant Pathologist
By Tom Allen, Extension Plant Pathologist June 6, 2012 21:31

Corn Fields Having Sustained Hail Injury May not Benefit from a Foliar Fungicide

Hail injury can manifest itself into a situation where the symptom appears similar to purple leaf sheath or a disease situation.

Over the past several weeks we’ve encountered tremendous hail damage in corn fields.  Leaf shredding is one of the more common symptoms associated with hail injury and the greatest source of yield loss as a result of hail injury (see: http://www.mississippi-crops.com/2012/05/27/corn-hail-damage-and-other-storm-issues/).  However, in addition to leaf shredding, bruising or direct penetration of the stalk may occur that will produce a symptom similar to purple leaf sheath (see: http://www.mississippi-crops.com/2012/06/04/dont-sweat-the-small-stuff-disregard-those-purple-to-black-spots-against-the-corn-stalk-at-the-base-of-the-leaf-collar/) especially following the response of nutrients being released from the plant and facultative saprophytes feeding on the nutrients. But, upon more careful inspection some of the “bruises” will be on the stalk itself rather than the portion of the stalk that is surrounded by the leaf.  In some rare situations, and more than likely in field settings where continuous corn has been grown, pathogenic organisms could infect the plant more easily since an injured plant is stressed.  However, over the past several years researchers have applied fungicides in response to hail injury and simulated hail injury and been unsuccessful in observing a dramatic yield and/or economic benefit.  For a brief description of a simulated hail injury study:

See: http://cropwatch.unl.edu/web/cropwatch/archive?articleID=4184924

For the full length research article refer to:

http://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-94-1-0083

As I briefly mentioned last year, little if any data is available to support the statement that a fungicide will benefit a field that has sustained hail injury.  Moreover, in most cases, saprophytic organisms will be the main group of organisms to compromise an injured plant.  Bacteria, fungi, and yeasts can all infect/infest a hail injured plant.  However, if bacteria and yeasts cause a stain that appears symptomatic of a “disease”, applying a fungicide will likely not alleviate the issue, especially since most of the organisms will be secondary to the injury (e.g. saprophytic).  Presently, I am aware of only two trials that were conducted to determine how a fungicide might benefit hail injured corn.  One of those is linked above, the other one is not published and not available on the internet and was conducted in a hail-injured soybean field in Missouri.  In short, fungicide treated plots were not economically, mathematically, or statistically different than the untreated plots.  Remember, the loss of leaf surface area and the resulting reduction in photosynthetic leaf area will result in the greatest potential yield loss. Fungicides don’t mend shredded leaves, they prevent yield loss as the result of a disease causing fungus.

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Tom Allen, Extension Plant Pathologist
By Tom Allen, Extension Plant Pathologist June 6, 2012 21:31
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