Hail Damage to a Maturing Corn Crop

Hail damage occurred in a few Knox County fields after this past weekend’s (August 20 & 21) round of storms.  Some of you  have asked about the damage potential caused by these storms.

The following information can be found in Evaluating Hail Damage to Corn from the University of Nebraska.  https://extensionpublications.unl.edu/assets/pdf/ec126.pdf

Yield losses can occur from stand reduction, defoliation, and direct damage to the ear itself.  The fields I looked at were in the soft dough to “very” early dent stages.  Table III below shows the anticipated damage due to defoliation.

Table III. Estimated percent corn yield loss due to defoliation occurring at various stages of growth.”

Reprinted from the Com Loss Adjustment Standards Handbook FCIE-2508 (11-2009) 2010 and Succeeding Crop Years, National Crop Insurance Services. This system counts a leaf as fully developed when the leaf tip points to the ground (not fully developed collar).

To estimate total yield loss, consider the following example:

An early August hail storm strikes corn at the soft dough stage. There is defoliation and severe bruising of the ears. The defoliation is calculated at 90 percent.

  1. Ten ears are stripped of their husks and the row number and kernels/row are counted. There are approximately 300 kernels per ear, and on average 30 of these are bruised. This 10 percent direct damage is subtracted from 100 percent, as in the first example with stand reduction.
  2. Defoliation yield reduction ( Table III) for the remaining 90 percent at soft dough is 35 percent.
  3. To calculate yield loss at this point the 10 percent from direct damage is subtracted ( 100 – 10 = 90 percent). The remaining 90 percent is multiplied by 35 percent (90 x 0.35 percent loss). The result is 31.5 percent defoliation loss. The total loss would be from direct damage (10 percent) and defoliation loss (31.5 percent) for a total of 41.5 percent.

This is only an estimate of the percent yield loss. As with undamaged corn, extremely favorable weather during the rest of the growing season can cause actual yields to be higher than expected. Likewise, unfavorable weather can cause greater than anticipated reductions.

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