How to close access to a section on subdomains?

Question

Search Engine Optimization

There is an online store on opencrate with subdomains for different cities.
I deployed a blog in the site.ru/blog directory.
But the problem is that it is now available for each subdomain, creating unnecessary duplicates.
Is it possible to block access for subdomains to this directory?
I really don’t want to do a crutch through the closure from indexing in robots and set canonical as there are a lot of subdomains ..