Yes you need to work on the “leave it” command. In the meantime, he can’t be unsupervised in the backyard.

I have sprayed this on plants my puppy used to eat, and even on her legs when she started licking her legs so bad they bled. It worked.

https://www.amazon.com/gp/product/B084SMR5Y3/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

Agree about the 'high value' treat alternative. Our instructors had us play a game called 'drop it'. You do it regularly and reward with HVT. So they become accustomed to eating something else when you say the phrase. If it's an urgent situation you don't have to have the treat, but they build the habit.

How about a muzzle? Our Lab started chewing on our wooden fence so whenever she goes out in the backyard now, she wears a muzzle.

I'd put him on a retractable leash in the backyard and practice the "leave it" command. Like with eating things inside, I just wouldn't give him that opportunity and all the freedom until he can behave.

Try luring him with a delicious treat instead. When he starts chowing down on dirt, call him with the most delicious treat.

Our 8-month old large breed puppy has recently begun eating clumps of dirt and sometimes mulch. He's done this before, but never to this extent. I know it isn't all that uncommon, but he will actually eat a lot! Like several large mouthfuls of dirt clumps and mulch. When we try to stop him he runs across the yard to another section of the buffet... and so the frustation goes. He seems to be ok, but does get the runs about 1 day out of every 3. He's on Purina Pro Plan Large Breed Puppy kibble, and a healthly weight.

We've used the bitter apple spray inside the house for a prior dog with some success - but that stuff doesn't come in large quantity bottles or concentrate (as far as I can see). So I'm trying to figure out what I could possibly spray or put down in the areas of our backyard where he regularly likes to dig up clumps of dirt or mulch and eat it - in an attempt to deter this behavior? Also looking for something that won't kill the grass or plants and (obviously) is safe for him to ingest.

I've considered sprinkling cayenne pepper, but wasn't sure if that's safe, I clearly would not want him getting it in his eyes. Any suggestions? Whatever it is, I need enough to cover several spots in the yard.