Recovery and Assessment of Hail Damaged Corn

  • Hail damage to corn can occur as reduced leaf area, bruising, or plant death.
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  • Proper assessment of corn damage is critical to help determine yield potential after a hail event.
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  • Hail-damaged corn should be scouted and monitored for stalk rots and lodging as the season progresses so that fields can be targeted for an early harvest if necessary.
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Assessment

 
13;10;Potential yield loss in corn due to hail damage can result from hail-damaged leaves, plant bruising, or stand loss caused by plant death.

Understanding the severity of each of these factors is important to accurately assess the extent of hail damage and how yield potential will likely be affected.  Evaluating the health of the growing point can be done soon after the storm, but making a decision regarding the yield potential of the field is premature because the plants have not been given enough time to recover.  To accurately assess potential yield loss from hail, corn plants should be evaluated 7 to 10 days after the storm.  At that time, it should be possible to more accurately distinguish between living plants and plants unable to withstand the hail damage or subsequent disease infection.

Leaf Defoliation and Bruising

If hail damage occurs when corn is in the V2 to V6 growth stage, potential yield loss is greatly influenced by whether or not the growing point was above ground.  The growing point is near the soil surface at the V6 stage, making the seedlings more susceptible to hail damage.  When the growing point is below the soil surface or in the leaf whorl, plant damage due to hail rarely results in significant loss of stand or yield potential.  Keep in mind that leaf damage usually looks worse than it really is, especially in the first few days after a storm (Table 1).  Shredded leaves that remain green and attached to the plant will often continue to produce photosynthates for the plant.

Assessing the extent of stem and whorl bruising and how it affects the health and productivity of the plant is difficult.  Bruising may allow an avenue for infection, which can increase the risk for stalk lodging later in the season.  Fields that contain severely bruised plants may need to be evaluated at the end of the season.

Stand Losses

After V10, potential yield loss and stand reductions are at nearly a 1 to 1 ratio (for example: 80% stand = 80% yield potential).  Yield losses due to stand reductions are additive to yield losses due to defoliation.  Stand loss at this stage will likely result in considerably greater loss of yield potential compared to leaf defoliation.

Estimating Potential Yield Loss

Defoliation, stand loss, plant bruising, possible disease infection of damaged plants, lodging later in the season, and environmental conditions during the remainder of the growing season are factors involved in estimating potential yield loss.  Growers should scout for and monitor stalk rot and lodging, increased nitrate levels in fields intended for animal feed, and late-season weed flushes due to increased light penetration in defoliated areas.  Potential yield loss figures due to damaged or missing plants are only estimates.  True yield loss from a hail storm cannot be fully determined until harvest.

Sources: Lauer, J. 1994. Assessing hail damage in corn. University of Wisconsin Cooperative Extension. Online: http://corn.agronomy.wisc.edu (verified 6/16/13); Nielsen, R. 2001. Hail damage in corn: moving beyond grief to damage assessment. Purdue University Cooperative Extension. Online: www.agry.purdue.edu (verified 6/18/13).
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