The easiest way to reduce comment spam is too turn off comment in Wordpress all together.  If you aren't promoting conversations and driving them then the chances are people won't be taking part that much and the benefits of comment content are being out weighed by your spam folders crushing size.

To Turn Of Wordpress Comments.

  1. Login to Wordpress
  2. Visit Settings / Discussion
  3. Untick the box "Allow people to post comments on new articles"

Turn Off Wordpress Comments