How to get rid of tracking branch?

Call me clueless, but how the heck do I get rid of a tracking remote branch? I've cloned a repo locally, but in the clone I don't want to track all the topic branches of the origin. But git branch -d keeps saying it doesn't find the remote branch:

$ git version
git version 1.5.0
$ git clone mingw-git/ mingw-git2
[... all looks fine ...]
$ cd mingw-git2/
$ git branch -a
* devel
  origin/HEAD
  origin/devel
  origin/master
  origin/origin
  origin/repo-devel
$ git branch -d origin/repo-devel
error: branch 'origin/repo-devel' not found.
$ git branch -d remotes/origin/repo-devel
error: branch 'remotes/origin/repo-devel' not found.
$ git branch -d heads/remotes/origin/repo-devel
error: branch 'heads/remotes/origin/repo-devel' not found.
$ git branch -d refs/heads/remotes/origin/repo-devel
error: branch 'refs/heads/remotes/origin/repo-devel' not found.

How do I delete remote branches? Do I have to

 rm .git/refs/heads/remotes/origin/repo-devel

(I know I have to update the config, too, so that the next pull doesn't draw the branch in again, but I haven't done that at this point.)

-- Hannes