zabalex - 7:02 pm on Oct 31, 2011 (gmt 0)
Apart from doing a request in google webmaster for domain change, you should disallow bots to crawl blog directory. Specify the below line in robots.txt file and upload it in the root directory.
Now you can do a URL removal request in google webmaster tools to remove the entire directory from the search result. Make sure to do a 301 redirect of blog subdomain main domain.