This is certainly the time of year we can expect hail storms to occur throughout Georgia. Fortunately, it doesn’t occur in a wide spread pattern but where it does, it can do plenty of damage as most of us have experienced. In the context of this blog, the question is how much damage is enough to cause yield loss in corn or other crops. Fortunately, in corn, there is a very good publication which has become the national standard of hail damage assessment and has been published in the National Corn Handbook. The following is a url of “Assessing Hail Damage in Corn” in the National Corn handbook: http://corn.agronomy.wisc.edu/Management/pdfs/NCH01.pdf .
Corn can be quite resilient if the damage occurs at specific growth stages. The key is to properly assess the damage to both leaves and stalks. The pdf provides tables and narratives on how to read the tables to determine damage. Make sure to look at the figures to better understand the information to correlate the damage and potential yield loss.
You can figure loss by plant loss or tissue damage. For example: to roughly assess the impact of the damage, first determine the amount of defoliation that occurred. The tables list growth by the whole leaf method (total leaves exposed) rather than a V-# stage (upper most mature). Carefully determine the growth stage. Let’s say you know by the V stage method that you are a V7, it is likely that you will see 10 or 11 leaves exposed. If 40% of the top most leaf is exposed count it. So, let’s say you have corn at the 11th leaf stage then. Look at table 3, go to 11 leaf gs in the left-hand column, look across the topline, per cent leaf area destroyed. If 80% of the leaf area is gone, look down under 80% to the row at 11th leaf and you will see expected yield lose to be ~14%. My greatest concern is the amount of leaf tissue damaged in the stalk. Some damage penetrated deeper than the upper exposed leaves which can increase the loss due greater photosynthetic area production loss. Hopefully we will not see damage later in the season, as the amount of yield loss increases with age. If you corn crop only had 7 leaves exposed and less than 75% was loss, then the yield loss potential is expected to be minimal (5%).
AS I said, corn is fairly resilient. Corn at the V3-4 stage generally suffers little yield loss but if the storm is severe, and the plant loss is great, then some considerations should be given to a 2nd replant. Because, you may have a lot of fertilizer applied and herbicides that would damage cotton, soybeans or peanuts, the management inputs of a corn crop may preclude one of the obvious choices. Because, we are still in April, the potential economic gain may be to kill the remaining plants and plant a corn crop. Yield potential is still fairly good for corn planted this time of the year. However, we must still manage the crop if the damage is not severe and the crop potential still warrants it. It is important to continue to irrigate and protect the crop from diseases by spraying a fungicides and insecticides as needed. Corn can be quite ugly under light to moderate damage and the damage LOOK severe, but in my experience, it is a “food making machine” and still produce a very profitable yield. If you need help assessing the damage, give your county extension agent or consultant a call to walk through it with you. It can be stressful, yes but over the years I have found the information in the table to be good.