Gramoxone, also known generically as Paraquat, has never been labeled for that use.  In 2001, about a million bushels of the Kansas wheat harvest was embargoed by Kansas Department of Health and Environment after several farmer/applicators sprayed their weedy wheat fields with the herbicide, and the grain made it's way to the local elevators.  I don't recall the final destination of that contaminated wheat but I'm thinking it got sold as animal feed. In an age when herbicide residues can be detected in the parts per trillion range, off label use of herbicides can prove to be a costly adventure.