Jochum Wiersma, University of Minnesota small grains specialist, Crookston, offers some the following advice on using glyphosate for pre-harvest weed control in small grains.
Don't spray wheat before the hard dough stage has been reached (30% grain moisture for wheat, 20% grain moisture for feed barley.)
Don't apply it to wheat or barley being grown for seed or on malting barley. It may reduce germination and/or vigor.
Do add an AMS for increased control of annual and perennial weeds, especially weeds stressed by dry weather.
Do not use AMS in place of NIS. Refer to labels for addition of other adjuvants.
Don't harvest within seven days of applications.