As a gardener in PA, where we've been known to have very very cold winters (well below zero F), I can state positively that the cold winter weather DOES NOT KILL daylily rust, even though the plants disappear completely. The only control (not cure) that I have found is to cut the plants right to the ground at the end of their flowering season and remove every bit of the foliage (don't compost it...bag it for the trash). The new growth that comes up will be clean but there's no guarantee it wont come back becuase I believe the spores will persist in both the soil and any dead/cut foliage that was not removed.
