How do duplicate description tags affect in SEO

Hello,

I checked on my Google webmaster tool sitemap today and found some duplicate title tags. The reason is that I changed the seo friendly URLs a few months ago and now both new and old URLs are indexed, which show duplicate title tags and description tags.

For example:

/dating/united-states/ (old)

/online-dating/united-states/ (new)

They both have the same title and description tags.

Do you think the old urls (/dating/united-states/) will automatically deindex in the next few months?

If not,

Should I DISALLOW /dating/ from my robots.txt file to deindex it from Google?

Thanks very much!

Why not 301 the old url to the new??

If the old url is redirected to the new one then I wouldn't worry about it, it will fall out of the index within a few weeks.

I would wait to see if they fall off and if not do a 301 redirect.