Subdomain with Dupe Content Accidentally Indexed - Traffic Tanked

Okay well I released a new version of my site, and the new version has a side bar with some affiliate links. They are not straight affiliate links they actually link to some new pages on my site that 301 redirect.

By accident I left the links as being http://stage.mydomain.com instead of http://www.mydomain.com. Now the stage subdomain is indexed in Google which is a complete duplication of my whole site.

Obviously this wasn't ever supposed to be indexed by Google. I noticed since the date I updated my site (and this stage subdomain was indexed) my traffic really tanked.

What is the best course of action here? Take down the stage subdomain so it 404's or 301 redirect back to www? Right now I have a 301 redirect in place.

Everything is pretty jacked up now, for example, if I search in Google with a page title (in quotes) like "Page Title | MyDomain" I don't even see my page at all.

The pages are indexed though if I use the "site:" operator.

Thanks in Advance

you don't need the 301 redirect as the subdomain has no backlink power.
just add a nofollow no index tag and make sure you don't have any more links or sitemap links to that subdomain.

alternately you can use robots.txt to block the sub domain.there are some features in Web Master tools too.

Just copy your site and paste it on the subdomain bro

Block your subdomain from being indexed. Google will give priority back to your main site.