May. These early storms are responsible for only minor corn yield losses, however, because the corn either has not yet been planted or is too small to be damaged significantly. Even when fields are severely damaged early in the growing season, they can often be replanted. On the other hand, about a third of all hailstorms occur between June and September. Hail affects yields primarily by reducing stands and defoliating the plant.
Defoliation causes most of the losses.
Thus, knowing how to recognize hail damage and assess probable loss is a very valuable decision-making aid. For instance, proper assessment of yield loss after an early-season storm can help you determine whether or not to replant or understand how an insurance adjuster determines yield loss. An accurate estimate of loss from a late storm is important for making correct harvesting and marketing decisions. In this publication, we will examine how hail damages the corn plant, how the degree of damage can be determined and how the extent of yield loss is estimated. Prior to, and for some time after emergence, the corn plant is affected very little by hail damage.