I was told years ago that those stupid little plastic windmills can help with that. The wind will spin it and the vibration will carry down the metal rod into the ground. Moles/voles are supposed to hate it. I'm not sure if it's true but anytime I start noticing mole/vole activity near any of my gardens I stick on in the ground and I've never lost any plants *knock on wood*.

I have had some feeding on cannas but not much. To be honest I can't even remember the incident specifically but noted it in a thread I started on the Carolina forum about plants that they like to eat. I have added Canna glauca 'Panache'(my favorite) and a couple of others since then with no incident.