When my dear dog was a puppy - it grossed my husband out! My dog thought he was at a buffet at the steakhouse!!! No kidding...
I heard everything from dog trainers and the vet - he wasn't getting what he needed in his diet, he saw his mommy doing it and he's mimmicking her, etc. I tried EVERYTHING!!!! Then a dog trainer mentioned tabisco sauce...I thought, way too hot it would make him sick....plus you have to be very fast after they go to put something on it! I tried and he didn't like that at all - didn't "eat it" though. BUT, I just couldn't stand the thought of him ingesting tabasco sauce (imagine that LOL)
So I decided to keep him on a leash while he went. After he did his duty, I'd give a firm "Leave It" and I made him move away and sit (or just kept him away) and picked it up. I had to be VERY persistent though and Surprisingly enough, he just learned to walk away! I NEVER thought he'd do that!!!
It's frustrating to see them do that, good luck - I hope something works for ya!