My dog eats small twigs and leaves. He'll be sniffing around the ground, and boom he's eaten some little thing. How can I get him to stop doing this? I could teach him "leave it", but he eats the stuff so quickly I'm not sure that will help.
I feel your pain. My pup is 11 months old. She too loves eating every treasure she finds in the grass. And like yours she too is so fast that most times she has almost finished chomping it down before I even notice.
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.
Our dog does the same, she'll eat anything she can find. We live in a townhouse neighborhood and there's no way to control what ends up on the ground when we take her for walks.
Twice in the last three weeks she's thrown up A LOT in the house. She gagged and hacked for a few hours and tried to lick everything on the floor in the house. Dust, her own hair sheddings, anything...
Despite numerous efforts to stop him our dog used to eat sticks, branches, etc. then he got a splinter in his mouth that got infected and needed antibiotics. I am still training leave but it depends on the object, so most of the time I watch the ground to spot the sticks before he does, but if there's a big risk I use a basket muzzle because I don't want to risk infection again.