Survey of 575 Daylily Cultivars for Severity of Daylily Rust in a Southern Mississippi Landscape

Abstract

Daylily (Hemerocallis sp.) is a popular and widely planted herbaceous perennial in the landscape, with over 78,000 cultivars registered with the American Hemerocallis Society. Daylily performs well in full sun, heat, humidity, and periods of dry weather, and has generally been considered to be pest free. However, a rust disease (Puccinia hemerocallidis) was introduced in the United States on imported plants in 2000, quickly spreading to become a widespread problem on daylily in and beyond the southern United States. In Aug. 2013, 575 daylily cultivars (mostly newer hybrids) were surveyed for daylily rust in a large landscape planting that had not received any fungicide treatment during the 2013 growing season. Weather conditions during the growing season were favorable for daylily rust. Individual clumps were rated as 1 (no or little visual sign of infection), 2 (moderate infection), or 3 (severe infection). In this survey, 119 cultivars (21%) received a median rating of 1 or 1.5, 230 cultivars (40%) received a rating of 2, and 226 (39%) received a rating of 2.5 or 3. Most cultivars were represented by a single clump, and may thus be more susceptible to daylily rust than a single rating might indicate. Diploid cultivars were associated with lower daylily rust severity ratings than tetraploid cultivars.