Moldy ear and kernel sprouting problems have been reported in parts of Ohio especially west central and NW Ohio. The title photo by Sam Custer, Extension Educator in Darke County and the photo below by Dr. Pierce Paul is a good illustration of what is being found in some fields:
The moldy ears have been attributed primarily to Diplodia ear rot (see article in this issue of the C.O.R.N. newsletter by Dr. Pierce Paul). As has been the case in past years, the moldy ears and kernel sprouting are often associated with upright ears. Ears that remain erect after physiological maturity (black layer development) are more likely to promote molds and kernel sprouting because they trap water (especially at the base of the ear and slow kernel drying. These ears may also be affected by opportunistic organisms taking advantage of the moist, nutritious environment at the base of the ear.
There are several factors that determine whether a corn ear remains erect or “droops” (points downward) following physiological maturity. Ears of corn normally remain erect until sometime after physiological maturity has occurred (black layer development), after which the ear shanks eventually collapse and the ears droop (Nielsen, 2011). However, ears may droop in drought-stressed fields that have not yet reached physiological maturity. A loss of turgidity in the ear shank due to water stress, possibly combined with some cannibalization of carbohydrates in the ear shank may eventually cause the ear shank to collapse, resulting in ear drooping. In certain hybrids, ears remain upright following physiological maturity (or remain erect for a longer duration) which can be related to a shorter ear shank. According to some seed company agronomists, prior to the development of Bt hybrids, corn breeders tried to reduce ear drop due to European corn borer damage by shortening ear shanks. Some of that germplasm has continued to be used in more recent hybrids. These agronomists acknowledge the concerns that upright ears are slower to dry or more prone to ear molds and indicate that companies are looking for more droopy shanks to help protect ears from water damage. However, they contend that there are other genetic components to these traits and that the effects of upright ears on fungal infections may not be as pronounced as is widely thought.
In addition to genetic differences among hybrids, environmental conditions and cultural practices may affect ear orientation during the drydown period prior to harvest. In ongoing OSU field research that compares multiple hybrids varying in maturity at two SC and NW Ohio locations, differential responses to plant population for % ear erectness (at maturity) were observed. At these test sites, % erect ears usually decreases significantly as plant population increases. These results suggest that factors other than hybrid genetics can determine if an ear is in an erect or droopy position at harvest. For more on ear rots and kernel sprouting, check out the following - “Troubleshooting Abnormal Corn Ears” online at http://u.osu.edu/mastercorn/
Nielsen, R.L. 2011. Are Your Ears (of corn) Sagging? Corny News Network, Purdue Univ. [On-Line]. Available at http://www.kingcorn.org/news/timeless/Droopy.html (verified 9-19-16)