If a spam detection plugin (Akismet or TypePad AntiSpam) thinks that their comment is spam, Then the conditional CAPTCHA asks commenters to complete a simple CAPTCHA task. If commenter pass,it will be allowed into the spam queue otherwise the comment will be automatically discarded or trashed. This is a simple text based CAPTCHA and also allow you to use reCAPTCHA.
1. Download Conditional CAPTCHA WordPress plugin. Download link.
2. Unzip and upload it to your WordPress wp-content/plugins directory.
3. Login to wp-admin. In your admin dashboard click plugins and activate the Conditional CAPTCHA WordPress plugin.
4. Then go to Plugins menu and select Conditional CAPTCHA.
5. Select your options and click Update settings.