Sitewide adsense - Any way to turn off ads on individual posts?

Hey guys, We have adsense built into the theme for different page sections at grandmashomeremedies dot com. I would like to disable adsense for some individual posts, but the php isn't working. Any ideas?

I've tried this with no luck.
<?php if( !is_single('URL-SLUG') ) : ?>
~ adsense code ~
<?php endif; ?>

Thank you for your time!