Orange mites on my dog.

[Goslowlysideways]

Any idea how to treat them? Are they harvest mites?

Yes they could be harvest mites. Mine had them, spotted by groomer. Take dog to vet for a quick and cheap spray treatment.
Alternatively, leave it and dog will ingest them from licking, and be quite unwell, they can upset the dog’s stomach. I’m the end vets bill likely to be bigger! Good luck