Yes, I have tried sprinkling cinnamon directly on the rhizomes,
but I have no real opinion if it is effective or not, as I only done it a few times and it was not very serious, as I still relied on bleach to sanitize the rhizomes. Based on what I read about rot preventing in potatoes I'm thinking one would probably need to apply cinnamon before rot becomes an issue, as a preventive measure. I don't believe it is a cure. Without intentionally attempting to infect rhizomes, and having a control group, it would also be very difficult to properly measure effectiveness, but infecting rhizomes on purpose is not for me!