Many corn fields took a beating from hail associated with the storm on April 26-27. Fortunately, the critical growing point of young corn plants should be underground until plants reach the V6 growth stage or are more than 12” tall. Thus, corn younger than V6 has the physiological capability to completely recover from heavy defoliation. However, recovery is highly dependent upon favorable weather conditions to promote vigorous growth.
Also, hail damage is somewhat unique from other types of physical injury, such as frost, liquid nitrogen fertilizer burn, and sand-blasting, because stems may also sustain physical injury. Severe stem bruising or damage can impede development of the growing point and emergence of subsequent leaves attempting to emerge. Therefore, this can contribute to stand loss. In my experience, plants around the V5-V6 growth stage may be more vulnerable than younger plants because their stalk size is fragile enough to sustain injury from large hailstones, but is also sizeable enough to obstruct development of vegetation.
Also, the larger the amount of damaged stem, the more difficult recovery may be, compared to a stem which is cleanly cut (above the growing point). If the growing point is not injured, corn at the V7 growth stage (20-30” height) can sustain extensive defoliation with very little yield loss.
In order to fully assess potential damage, you must give the plants some time. You should see some vegetative growth begin to emerge from the damaged “whorl” in 4-5 days, given favorable growing conditions. Ponded water, soil saturation or cool, cloudy conditions will hamper or slow recovery and potentially increase stand loss.
Erick Larson, Extension Grain Specialist