There are a few things you can try to stop your Yorkie from digging in the backyard:

1. Provide an alternative digging spot: Create a designated digging area in your yard where your dog can dig to their heart’s content. This could be a sandbox or a small patch of dirt.
2. Bury items of interest: Bury bones, toys, or other items your dog likes to dig for in the designated digging area. This will give your dog a specific spot to focus their digging efforts.
3. Exercise and mental stimulation: Make sure your dog gets enough exercise and mental stimulation. Dogs that are bored or have pent-up energy may turn to digging as a way to release it.
4. Train the “Leave it” command: Teaching your dog the “Leave it” command and consistently enforcing it will help your dog understand that digging in certain areas is not allowed.
5. Supervision: Keep an eye on your dog when they are outside and immediately redirect them when they start digging in the wrong area.
6. Deterrents: You can also try using deterrents such as spraying the area with bitter apple spray or placing chicken wire underground.

It’s important to remember that digging is a natural behavior for dogs and it can be difficult to completely eliminate it. By providing an appropriate outlet for the behavior and consistently reinforcing training, you can decrease the likelihood of your Yorkie digging in the backyard.