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ARS Home » Southeast Area » Poplarville, Mississippi » Southern Horticultural Research Unit » Research » Publications at this Location » Publication #316290
Title: Survey of 575 Daylily Cultivars for Severity of Daylily Rust in a South Mississippi Landscape

Author
item BLYTHE, EUGENE - Mississippi State University
item Pounders Jr, Cecil
item ANDERSON, MICHAEL - Mississippi State University
item WATTS, EARL - Southern Daylilies
item WATTS, BARBARA - Southern Daylilies

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2015
Publication Date: 8/25/2015
Citation: Blythe, E.K., Pounders Jr, C.T., Anderson, M., Watts, E., Watts, B. 2015. Survey of 575 Daylily Cultivars for Severity of Daylily Rust in a South Mississippi Landscape. HortTechnology. 25(4)pgs. 551-564.

Interpretive Summary: Daylilies (Hemerocallis species) are popular and widely planted herbaceous perennials in the landscape, with over 78,000 cultivars registered with the American Hemerocallis Society. Daylilies perform well in full sun, heat, humidity, and periods of dry weather, and have generally been considered to be pest-free. However, a disease called daylily rust was introduced into the U.S. on imported plants in 2000, quickly spreading to become a widespread problem on daylilies in and beyond the Southern U.S. Identification of rust-resistant and rust-susceptible daylily cultivars is of benefit to breeders, commercial growers, and home gardeners, particularly in helping to reduce the time and expense involved in repeated fungicide applications in nurseries and landscapes. In August, 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 infections), 2 (moderate infection), or 3 (severe infection). In this survey, 21% of the surveyed cultivars received a median rating of 1 or 1.5, 40% received a rating of 2, and 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.

Technical Abstract: Daylilies (Hemerocallis spp.) are popular and widely planted herbaceous perennials in the landscape, with over 78,000 cultivars registered with the American Hemerocallis Society. Daylilies perform well in full sun, heat, humidity, and periods of dry weather, and have generally been considered to be pest-free. However, a rust disease (Puccinia hemerocallidis), was introduced in the U.S. on imported plants in 2000, quickly spreading to become a widespread problem on daylilies in and beyond the Southern U.S. In August 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 infections), 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.