The Effect of Hail Damage in Corn

Hail can be one of the most unpredictable and destructible natural events to impact a growing corn crop. In a matter of minutes, healthy corn can be reduced to a twisted mess of plant material. However, corn is an amazing plant that can recover quickly depending on the growth stage at the time of the hail event. The resiliency of corn helps maintain as much yield potential as possible.

Evaluating Corn Crop Damage
One-third of hailstorms occur from June to September during prime corn growing time. As a result, this 3-month period is when the greatest corn loss from hail occurs, according to the University of Nebraska–Lincoln. Check your corn crop after a hailstorm as the leaf loss area can have several side effects.

The greatest losses from hail damaged corn are defoliation, especially during the pollination stage. Hail also impacts yield potential from direct plant damage (wounds) and reduced plant stands, depending on the crop stage when the event occurred. When corn reaches the V6 growth stage, the growing point emerges from the soil surface. A hail event can significantly impact the growing point of the plant, resulting in reduced plant stand and yield potential.

Assessing a field’s plant stand and plant health following a hail event is important for replant decisions. A healthy growing point will have a light-colored appearance with a firm texture. New leaves emerging every 3-5 days indicate normal growth. A corn plant with a hail damaged growing point will have a distinct yellow to brown, water-soaked appearance with a mushy texture.

Evaluating Stands: Plant Population and Distribution 

It is important to determine the plant population and distribution (uniformity) of the existing stands. Count the number of viable plants in 1/1,000th of an acre and multiply by 1,000 to obtain plant population per acre. Take enough counts in the field to represent the existing stand. Plants that are weak or questionable in growth should occasionally be omitted.

After plant population and health have been evaluated, yield potential of the current stand versus replanting can be determined. Table 1 can be used to estimate stand potential. The yield values (expressed as a percent of maximum) are based on uniform distribution of plants within the row(s), which is not usually the case after a hail event.

Simulated Hail Agronomy in Action Trial 

To help visualize the effect of hail on a growing corn crop, a trial at York, NE, was used. Damage treatments were applied to cause a similar loss in leaf area of varying degrees of severity. A string trimmer was used to cause the simulated damage at approximately the V7-V8 growth stage. Four individual rows were damaged to various levels ranging from 10% to 100% loss of leaf area (Figure 1). No stand loss resulted in this simulated event. Regrowth was monitored weekly up to flowering (Figures 2 and 3).

Recovering Leaf Area Loss
The plants with simulated hail damage defoliation were quickly able to recover, with new leaves emerging from the whorl within 3 days of the original loss. Within 20 days of the simulated event, well over 50% of the defoliated plants were able to recover even in the most severe treatment. This study saw no “buggy whipping” or twisting of the plant leaf whorl that is sometimes associated with hail events.

Impact of Hail Damage in Corn on Yield Potential 
Hail can reduce corn yield potential in 2 direct ways: by the reduction of crop stand and through the loss of leaf area. Final yield is dependent on the severity of damage and the crop growth stage when the hail event occurred. Previous researchers have reported minimal reduction in yield with early-season defoliation. For example, at V13, a 60% loss in leaf area only resulted in a 13% loss in yield (Table 2).

Small reductions in final stands prior to V8 typically also result in minimal yield penalty due to the ability of a corn plant to compensate for the stand loss early. However, later season stand loss usually results in a one-for-one ratio in yield loss. For example, a 10% reduction in stand will result in a 10% reduction in yield potential.

Demo Harvest Results
Corn ears were hand harvested at 15% moisture from each treatment row in the demo (Table 3). The row with 100% loss of leaf area resulted in an 18% reduction in yield compared to the other rows with less severe loss of leaf area. Current USDA percent leaf area loss charts based off more extensive trialing suggests 100% leaf loss at V7-V10 would only result in a 9%-16% yield loss (Table 2). The other damaged rows saw no significant variation of yield due to leaf loss.

Reactive and Proactive Management Strategies
Reactive and proactive management approaches alike can lessen the impact of hail damage to your corn crop. Reactively, determine the growth stage of your corn when it hailed. The amount of leaf and plant damage that occurred can help you estimate yield loss. If your crop experiences hail stress, fungicides can aid in water and nutrient uptake, stalk quality and disease protection.
Although reactive practices can help minimize hail injury, it’s always better to be proactive. Choosing corn hybrids that mature faster enables the crop to advance growth stages more quickly, and, therefore, have a better chance of withstanding hail. But when hail hits during reproductive corn stages, it’s critical to scout for damaged ears. By checking corn for crushed kernels, you can calculate yield loss for all acreage hurt by hail. If you live in an area that regularly receives hail, be proactive and use the Golden Harvest online product finder to select hybrids with earlier relative maturities.

Summary
While hail may be one of the most destructive events to a corn crop, corn plants can recover quickly under good growing conditions, depending on the timing of the event and growth of the corn. Hail can be devastating to any crop. Allowing the crop to recover by assessing the field 5-7 days after a hail event will help you make the most informed replant and management decisions.

For more information on managing hail damage in corn, contact your local Golden Harvest Seed Advisor.

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