When a rust like residue is seen on your daylily foliage is not from nearby rusty nails. This rusty yellow orange substance is actually a fungus that appears mostly on the under side of the leaves and looks like many small dots or pustules. If you are not sure what you are seeing just wipe the leaf with a clean white tissue and if you get streaks of yellow orange you have rust. Technically it is a fungus called Puccinia hemerocallidis. This Daylily rust is not likely to kill your Daylilies but it can make them look really bad. We have not noticed any bud or bloom damage from this Rust Fungus. There are some fungicides available to treat your plants. If you chose not to use fungicides you should remove the affected foliage and the brown dead leaves but keep them far away as even the dead leaves can spread the rust from the blowing wind. For Daylilies grown in the warm southern climate this rust problem can be severe. In the northern climate the prolonged cold will either kill the rust fungus or cause it to go dormant. For more detailed information see https://www.daylilies.org/ahs_dictionary/daylily_rust.html
Daylilies Delight 