This year, due to poor spraying conditions, wet planting conditions and increased resistance, there are a lot of fields with weed escapes. The fields look a lot like they did in the eighties and early nineties before Roundup Ready was part of our weed control. In those days, harvest aids were looked at to help with combining and reduce viable seed production.
At present, there are three chemicals labeled to use on soybeans as a harvest aid and three labeled on corn. In soybeans, Gramoxone is labeled for use when 65% of the seed pods have reached a mature brown color. The rate is 8-16 ounces and the high rate is needed for most weeds. Gramoxone needs to be applied 15 days before harvest and there is no haying or grazing the straw.
Aim also has limited activity on a small amount of weeds and a three day harvest interval. Check label for weeds controlled and other restrictions. Lastly, glyphosate does have a harvest aid label. It is seven days till harvest and 14 to 25 days for hay or graze restrictions depending upon rate used. Check the labels for more restrictions.
In corn, Gramoxone is also labeled at a rate of 1.2 to 2 pints. The high rate is recommended for most large weeds. It is to be applied after the corn is black layered. It is seven days before it can be harvested or grazed. 2,4-D is also labeled on corn as a harvest aid that you can spray after brown silk on some labels and after black layer on others, so check the labels.
It is seven days until it can be harvested or grazed. It will only kill broadleaf weeds but the Ester form is usually more effective. Glyphosate is also labeled on corn and has a seven day pre-harvest label and the same for grazing. If you think you have weeds resistant to glyphosate, it would not be a good choice as a harvest aid. Remember to read labels before all applications.