If you pick corn too early, your corn will be more susceptible to disease. That's because the corn is not pollinated yet and the pollinating insects have not come out yet. Once the insect sets come out, they will start to pollinate your corn and that will help it grow better.
If you wait too long, though, the insects may move on to other areas of the farm and won't return until next year. If they don't make another stop before they leave, then your crop won't grow as well as it would have without them stopping by.
If you pick corn too early, it may not grow as large and produce fewer tasseles- which is the top of the stalk that holds the flowers that produce corn kernels. It also has a weaker stalk, meaning there are fewer leaves and less food for pollinators like birds and bees.
Picking corn too early can have a negative impact on yield, crop quality, plant vigor (the strength of the plant), and pollination.