We put down wire when a new dig begins for current pup.
Previously resorted to sprinkling cayenne (BIG bottles @ Sams) in the areas prone to digs.
Per
Dogdchatforum.com:
Reasons why dogs dig
Digging is instinctive behavior for a dog. Dogs may dig for any of the following reasons
* They are bored
* It's fun
* They are hot
* They are trying to escape
* They are lonely
* They have excess energy
* You have put nice smelling (to a dog) fertilizers in the garden
If you can find out the reason for your dog's digging then you can usually find a solution.
To stop the digging try to alleviate the boredom.
If you leave your dog alone in the yard for long periods of time provide him with something to do. Leave him with bones to chew or toys to play with. Food dispensing toys are available or you can use hollow bones which you can fill with a tasty treat. Kong toys, hollow bones and such can be stuffed with a bit of spread cheese, spread meats, cheese cubes, hot dog chunks, semi-soft dog treats, canned dog food, kibble etc. Buster Cubes and similar toys have various compartments inside that hold kibble. Your dog has to roll them around or manipulate them to free the kibble. The dog has to work and chew to get the treat out. If you hide these toys, the dog also gets to enjoy the hunt and seek for a reward. Sturdy chew toys such as hard-pressed rawhide are also popular.