Resistance of daylily cultivars to the daylily rust pathogen, Puccinia hemerocallidis

Daylilies (Hemerocallis sp.) have traditionally been considered to be pest-free. However, a rust disease caused by Puccinia hemerocallidis Thum. has become an increasing problem in the United States since 2000. The objective of this study was to evaluate daylily cultivars for resistance to daylily rust. From a greenhouse evaluation of 84 inoculated cultivars, 14 (17%) were classified as resistant; 13 (15%) were classified as moderately resistant; 22 (26%) were classified as moderately susceptible; and 35 (42%) were classified as fully susceptible. Several cultivars displayed very high levels of resistance and may be utilized by breeders to develop cultivars with improved resistance to daylily rust. Information about the resistance and susceptibility of cultivars also will help commercial growers and gardeners select cultivars that have the potential to dramatically reduce damaging outbreaks of rust.