How much is he eating? A lot?
I may not be in the majority but my dogs will sometimes eat small pieces of sticks, leaves, etc. They also regularly graze on grass and weeds/bushes. As long as they aren't doing it excessively, I pretty much leave them alone.
However if your dog is eating a lot/getting sick, you'd need to work on cleaning up the yard and removing as much of the items he is eating. Keep him on leash and work on a leave it command with him - but just removing this kind of debris as much as you can will be the easiest fix.