Daylily Rust?
These daylilies are the most suseptible: PARDON ME, STELLA D'ORO, GERTRUDE CONDON, CRYSTAL TIDE, COLONEL SCARBOROUGH, STARSTRUCK, JOAN SENIOR IMPERIAL GUARD, and DOUBLE BUTTERCUP.
What can you do? Fungicides known to be effective against rusts AND labeled for use on daylilies include propiconazole (Banner Max), oxycarboxin (Plantvax, check for availability), flutalonil (Contrast), azoxystrobin (Heritage), myclobutanil (Systhane), daconil, and mancozeb. You must remove infected foliage and burn. They also say you can bury it, but I wouldn't. It seems to me that the rust could still survive. Do not compost.
There is more instructions on Dr. Tim Schubert's site. There are some picture of the infected plant and the pathogen. Another helpful site is the Upstate Daylily Society one.
My thoughts on this subject are that we growers of daylilies need to be vigilant about cultural practices and inspecting our plants for the first signs of infection. Perhaps, we need to destroy plants that are very suseptible. Almost all the hybridizers will not use unhealthy plants to create new ones and we know they usually practice good cultural habits. It pays to know the genetics behind the plants that you buy.