Similar problem here during the wet season. We've managed to shut off access in most places, but we've a couple of spots they always seem to find a way in. Mothballs have some effect, we tried traps but handling and disposing is an issue, best we found, but brutal, was to drop the trap into a large bucket of water and leave for 20 minutes. Glue traps laced with food and poison pellets is the preferred method, also brutal but more hands off. It's a problem that always seems to return, regardless what you do.