Yes tea tree oil is a good natural remedy for killing mites on dogs.
I've had good luck using tea tree oil on my dogs mites and it killed the mites on the dog pretty quickly.
You can apply a few drops of tea tree oil to the dogs ears or wherever the dog has mites and within an hour or two the mites should be killed off.
You can also use apple cider vinegar to kill mites on your dog as well by applying some apple cider vinegar directly to the mites or even adding a cup or two of apple cider vinegar to a bath for the dog.
Then wash the dog in the apple cider vinegar bath to get rid of the mites on the dog.
You can also buy commercially available mite killer for your dog but the tea tree oil or apple cider vinegar also works great.