Daylily Rust
Puccinia hemerocallidis
Not much is known about the biology of Puccinia hemerocallidis.  Different varieties of daylily have different susceptibilities to the rust.  The spores can be spread by wind or by human movement of plants.  This rust requires two distinct host plants for the completion of the full life cycle.  Another reported host common in the landscape industry includes Hosta.  The status of Hosta as a host is not yet considered conclusive.  All daylilies are native to Asia, and until the summer of 2000 daylily rust had only been reported in Asia. Its distribution includes tropical to temperate climates.  Therefore, it could conceivably survive in a wide range of climates in the U.S.  Fungicidal treatment is considered a viable option for control.  Most broad-spectrum contact and systemic fungicides are expected to be effective against this rust disease.  This plant is widely used in commercial and domestic landscaping.  The large number of daylilies in the U.S. coupled with its short life cycle could result in a fast spread of the rust.

 
click for enlarged view: