I have a field of corn that was flood damaged and is now 2 to 5 feet tall and starting to tassel out. The flood got dirt in worl and resulted in leaves being cut off, so it doesn't shade the row very well.  Flood happen 4th of June and field has been very wet since. There is pigweed and johnson grass that is currently an inch tall. How far along would corn need to be for chemical to not hurt corn? 2-4D, Roundup for the grass, Dicamba, all of them together or something else. Still considering using paraquat and starting over.