Corn Hail Damage and other Storm Issues

Corn fields in several areas of the state unfortunately took a beating from hail and wind associated with storms May 20-22.  Several different types of damage may have occurred depending upon the type of storm, including hail damage, lodging and green snap.

This verification field had about 50% defoliation at silking and still made 150 bu/a, despite also running out of irrigation water three weeks before maturity last year.

Damage and yield loss associated with hail is primarily related to the loss of leaf area.  However, only leaf area completely removed from the plant or dead is considered defoliated for yield loss assessment purposes.  Considerably more leaf area may be stripped or otherwise mutilated, but if this leaf tissue remains alive and green, it is not considered to be defoliated or destroyed.

Severe hail damage during vegetative stages may not reduce yield as much as perceived, because undamaged leaves within the stem later emerge.

The degree of corn yield reduction resulting from hail damage also depends greatly on crop growth stage.  For plants in the vegetative growth stages, leaves not yet emerged and the critical growing point, should largely be protected and later emerge to resume normal physiological processes, including light interception and photosynthesis.  Corn at or near tassel is most vulnerable to defoliation resulting from hail because all leaves are emerged and corn is most sensitive to reduced photosynthesis or current energy production during the early reproductive stages.  Thus, corn is generally most sensitive to damage resulting from hail at or near tassel stage.  As kernels develop and progress towards maturity, corn plants will more readily allocate stored energy to kernels, making yield reduction resulting from defoliation less substantial, compared to the early reproductive stages.

High winds during rapid vegetative growth may completely “greensnap” stalks, rendering those plants a total loss.

Greensnap is a term describing corn stalks completely broken off by high winds. This phenomenon normally occurs during rapid vegetative growth stages when corn is around three feet tall until nearly tassel.  Greensnap is much more common in the windy plains states, but Mississippi corn has suffered several instances during the last few years. During mid to late vegetative stages the stalk is rapidly developing and may be somewhat brittle, particularly when sunny, favorable weather promotes rapid growth, preceding a windstorm. Stalk breakage normally occurs well below where the ear normally develops.  Therefore, yield reduction is closely correlated with the percentage of snapped stalks. Several factors, including corn hybrid, high nutrient levels, in‐season nitrogen application, row orientation perpendicular to the wind direction, high plant population, and plentiful soil‐water availability and timing are known to influence greensnap.

High winds may also cause stalks to blow down during the season.  This is a variation of what we typically refer to as “root lodging,” which normally occurs near when physiological maturity occurs.  However, if this occurs during the season, plants will attempt to right themselves.  Their ability to stand back up is generally much better the younger plants are, as smaller, lighter stalks are easier to re-orient.  Plants normally compensate as much as they can within a week or so following a wind-storm.  The lower stalk often goose-necks or bends, if the stalk is too heavy to completely right itself.