I have had no good answers for the calls on how to control ryegrass that escaped the glyphosate burndown in emerged corn. 

Herbicides like Accent or Steadfast will not control ryegrass. Liberty tankmixed with atrazine on LL corn would burn the ryegrass back some and is the only even fair option that is available.

In cotton or soybean the best option is a clethodim based system. In the Mississippi Delta where the ryegrass is 100 percent resistant to glyphosate, they are utilizing 16 ozs of Select Max as their best treatment and still not getting complete control. 

In Tennessee, where the ryegrass population ranges in glyphosate tolerance from moderate to, in some locations, highly resistant, a tankmix of clethodim (Select Max 10 ozs) plus glyphosate (Roundup PowerMax 32 ozs) has proven to be effective. Both cotton and soybeans can be planted back immediately after a clethodim application.

Flooded corn

There have been reports of some corn fields due to flooding have an insufficient stand to keep.  There are several options to control a thin corn stand and replant back to corn.  Some of these options, like Select Max, need a waiting period before it can be planted back to corn. 

Others, like tankmixes of paraquat plus atrazine, corn may be replanted right away.  Please find the results of a study Angela McClure and I conducted several years ago on destroying freeze damaged corn and replanting back to corn. We repeated the study the next year on a good stand of corn and got the same results. In this publication you will find a number of different herbicide options  that did a good job controlling an unwanted stand of corn.