Wet conditions during the grain filling period in corn can sometimes result in sprouted kernels in the ear. It is uncertain now how much sprouting has occurred due to the widespread rain during the past few days, but it would be good to do some assessment prior to harvest for this issue.
I have noticed some sprouting this week in Centre County and noticed some last month as well, but it is too early to tell if it will be a widespread issue. Sprouted kernels can occur on the butt ends of corn ears, especially in hybrids that have the ears remaining upright during drydown.
Water accumulates at the bottom of the husk and favors sprouting in that part of the ear. Sprouting can also occur on tip kernels where the end of the ear has been exposed due to good late season growth.
Sprouting is caused by excessive exposure to moisture during grain fill, which leaches out some of the abscisic acid from the kernels. Abscisic acid is a plant hormone that acts as a germination inhibitor in developing grain and keeps it from germinating prematurely. The grain loses its dormancy and is susceptible to germination.
Insect injury can also impact hormone levels in immature kernels and lead to sprouting. Normally, abscisic acid declines as the grain matures, which permits germination of mature kernels. Mature kernels then can be at risk of germination as well if they encounter excessive moisture and temperatures above 50°F.
If you see lots of sprouting, take steps during combining, drying, and storing to remove as many as you can to maintain good grain quality. For a good review of sprouting and its management, review the factsheets from Purdue, Premature Corn Kernel Sprouting, and the University of Wisconsin, Wet Fall Weather, Flooding, Kernel Sprouting and Molds.