Cinnamon doesn't kill them, but it messes up their scent-tracking, so they can't follow the scent trail they've laid down to the food source anymore.

It should be fairly fresh cinnamon. Cinnamon oil makes much less of a mess, but it's harder to find.

You'll see them running around wildly and frantically trying to clean the scent off their antennae when they get close to it. It used to make me feel mean when I was younger, but I've become hard-hearted in my old age.