Initial Landscape Evaluation of Daylily Cultivars for Rust Resistance

Daylilies (Hemerocallis sp.) are popular perennials in the Southern U.S. because they thrive in full sun, heat, humidity, and periods of dry weather. Daylilies are generally considered to be pest-free. However, a rust disease (Puccinia hemerocallidis), which was introduced into the U.S. on imported plants in 2000, has become a prevalent problem on daylilies in the lower South. Through the cooperation of a daylily grower in south Mississippi, we evaluated a large landscape collection of 575 newer cultivars which had not been sprayed with fungicides to prevent infection by daylily rust during the summer of 2013. The warm, damp summer of 2013 was ideal for spread of daylily rust. Plants were rated at the end of the summer on a 1 to 3 scale with 1 showing very little or no disease, 2 showing moderate infection (approximately 33% infected leaves), and 3 showing severe infection. A total of 119 clones received a median rating of 1 or 1.5 and are thus worthy of further evaluation for resistance to daylily rust. Some of these clones may be more susceptible to the disease than a single rating might reveal. Planting rust-resistant daylily clones would eliminate the time and expense of spraying plants to prevent daylily rust.