Daylily rust is a fungus whose spores can travel for many miles on the wind and carry the infection from one end of a continent to the other. Although it is not a new disease, it is relatively new to North America, first identified in the year 2000 in the southeastern United States. Many gardeners unknowingly purchase infected daylily bulbs and innocently introduce rust into their garden, neighborhood and town. Daylily rust will not likely kill its host, but it does kill the foliage and prevent the daylily from blooming.
Verify that your daylilies have rust. Leaf streak, spring sickness and other non-rust diseases look similar to daylily rust. Consult an expert at your local nursery, cooperative extension service or use the photos at the American Hemerocallis Society website to confirm a rust infection.
Remove the foliage from your daylily at the first sign of rust infection. Use your garden shears to cut the plant back so it is no more than one inch above the level of the soil. Also cut any healthy lilies within the vicinity of the rust infection. Burn or bury the leaves. Do not dispose of them in your green waste or compost bin.
Treat your daylilies with a contact fungicide and a systemic fungicide, alternating them. Follow the manufacturer's instructions for use. Alternating fungicides reduces the risk of your daylilies developing fungicide resistance. Fungicide treatment may need to be repeated as often as every 7 to 14 days. Continue fungicide use until all traces of rust are gone.