Spam spam spam

Hi,

I know it’s been discussed before in many posts but I can’t find a working solution yet to my spam problem.

I allow guests on my directory to add a listing so they don’t have to be registered to add listing.

I’m getting tons of spam listings every day. Is there a simple way to add a Captcha to the form?? I’ve installed a few captcha plugins already but they only work for registering, leaving comments, login…

I also tried Spam Protection plugin but no joy.

Ideas pleases?

Thanks