Deisel is a big digger too and we haven't been able to stop him. I have tried everything that has been suggested to me...

putting pepper in the hole....he just eats it

putting hot sauce in the hole....well he likes that too

(sounds grose) but putting his poop in the hole....he just digs it out with the rest of the dirt

So I even got them a sandbox.....well he does dig in there but he still does everywhere else too!!! Don't know some of these things may work for you...