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Four Easy Steps to Assess Corn Hail Damage

July 5, 2018

Early summer thunderstorms not only bring heavy rain, but can often bring hail as well. In corn, hail can lead to yield loss from stand reduction caused by plant death and leaf-area reduction caused by damage to the leaves.

If your corn fields are hit hard by hail, follow these 4 steps to assess and make management decisions to maintain your yield potential:

1.) Allow the crop to recover after a hail storm

In order to allow enough time for the corn plant to show regrowth, wait 5 to 7 days after the storm to evaluate. Regrowth is important in determining what viable plants you will have per acre.

2.) Determine the growth stage of the plant

Damage will increase as growth stage of the corn increases. The growing point is protected under the soil until V5 (5 visible collars). There is more potential for stand loss after V5 as the growing point emerges above the soil

3.) Assess viable plants per acre

To examine the health of the growing point during seedling stages, split the plant lengthwise.

  • A whitish-yellow color indicates good health
  • A discolored and soft growing point indicates plant dying

Stand losses from hail damage will usually be minimal in corn smaller than the V6 growth stage. Estimate the number of plants with a bruised growing point that will form a secondary infection. Bruised plants that are infected will be easily visible within 5-7 days after a hail storm.

Use this chart to determine the number of viable plants per acre:

This chart shows the determined number of viable plants per acre

4.) Compare yield potential of reduced stand vs. yield potential of replanting

Use this table from the Iowa State University Extension to decide whether to take action:

This chart shows relative yield potential of corn by planting date and population.


Though hail damage isn’t ideal for hybrid health, properly assessing damage and making appropriate management decisions will help your fields in the long run. Speak with your local NK® retailer to determine a best course of action for your acres.

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