Home-Page Contact Form Spam

Dear Developers,

we use your theme for a website. Everything works just fine, but there is a spam issue with the contact form on home page, that is integrated in theme. Since i launched the site, the amount of spam mails is huge. Is there a way to put a recaptcha or something in this contactform? I already tried the plugin recaptcha by ash matadeen, but no success with the contact form.

Thank you for your help.