I once tried a hot water dip for daylilies to try and kill bulb mites. The plants survived but unfortunately I don't remember the temperature I used. I might have a note somewhere - a friend tried the same thing at a slightly higher temperature than I did but her daylilies died fom the hot water treatment. Whether it was hotter than the chysanthemum rust treatment I don't know. With daylily anatomy I'm thinking it may not get hot enough between the leaves (which I imagine you'd mostly cut off). I'd test it to see if the plant would survive that temp but my daylilies are all buried under snow. (Just curious, why "small crowns"?).
Refrigeration isn't likely to kill daylily rust, and freezing may well need to kill the foliage in order to kill the rust inside, in which case there's the risk of killing the whole plant. Also cold per se doesn't kill daylily rust spores. Daylily rust does persist in areas of the USA that freeze periodically in winter. If the leaves can survive the freezing there's a chance the rust fungus body (mycelium) can survive inside them. I've had daylily leaves survive -8C (17.6F) here and still be capable of being infected with daylily rust when I tested them indoors.
Some people use the following method to reduce (not guaranteed to eliminate) the risk of transferring rust to another garden:
http://web.ncf.ca/ah748/newpla...
