Evaluate hail damage in corn

By Jeff Coulter, Seth Naeve and David Nicolai, University of Minnesota Extension

ST. PAUL, Minn. (6/10/2008) — A band of hail passed through east central Minnesota last week, damaging corn fields in Sibley and Nicollet counties. Area corn plants lost 50 to 100 percent of their leaf area due to the storms.

We spoke with growers in this area and visited damaged fields on June 9.

Answers to many of the producers’ questions about corn yield loss and the need for replanting can be found in a University of Minnesota Extension online guide for evaluating corn damage and making replant decisions, available at: www.extension.umn.edu/distribution/cropsystems/DC5700.html.

Here are a few key points from that publication, “Corn Growth and Development and Management Information for Replant Decisions.”

• Corn that has been 100 percent defoliated at the 7-droopy or 5-collared leaf stage will only lose about 9 percent of it’s grain yield if the growing point is not damaged. Leaf loss occurring earlier will have a smaller effect on yield.

• Since the growing point of corn is located below the soil until the plant has about 6 collared leaves, corn can be cut off at the soil surface prior to this stage and still survive. Corn plants generally produce 18 to 20 leaves, and corn cut when it has 6 droopy or 4 collared leaves still has about 12 to 14 leaves left to emerge.

• Growing points located below the surface can be damaged by large hail stones landing on soft soil. It is important to check the growing points of damaged plants by digging them up and splitting their stalks down the middle. Healthy growing points will be firm and white to yellow in color. If damaged, the growing point will be watery and orange to brown in color.

• Plants with damaged growing points should be considered dead. When determining your remaining yield potential, first obtain a guide for evaluating crop damage. Then, identify the growth stage when the plants were damaged, make numerous stand counts to determine the number of live plants remaining, and estimate the percent of leaf area lost.

• It is important to remember that a poor stand of corn that was planted on time will out-yield a perfect stand that was planted late. For example, 100 percent defoliation of a cornfield at the 7-droopy or 5-collared leaf stage with 16,000 live plants per acre remaining has only lost about 35 percent of its original yield.

• A similar field reduced to 14,000 plants per acre would have about 42 percent yield loss. In comparison, a perfect stand of corn planted on June 14 has already lost 35 percent of its yield potential due to late planting.

Any use of this article must include the byline or following credit line:
Jeff Coulter is a corn specialist with University of Minnesota Extension, Seth Naeve is a soybean specialist with University of Minnesota Extension, and David Nicolai is an Extension educator in crops management.

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URL: http:// www3.extension.umn.edu/extensionnews/2008/haildamageincorn.html  This page was updated June 11, 2008 .
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