First Report of Daylily Rust in the United States

In August 2000, rust symptoms were observed on the leaves of daylily plants (Hemerocallis sp. cv. Pardon Me) at a nursery in Dearing, GA. Based on urediniospore characters, the pathogen was tentatively identified as Puccinia hemerocallidis Thuem. Urediniospores were globose to ellipsoid and measured 19 to 30 × 17 to 22 μm (average size of 22 × 19 μm), corresponding to the previously reported description from Japan (1). Teliospores were absent from the sample but were found on daylily plants (cv. Star Struck) with symptoms similar to cv. Pardon Me from the same nursery in Dearing beginning in October 2000. However, the teliospores differed from those in the published description in that many one-celled teliospores (i.e., mesospores), measuring 32 to 43 × 14 to 19 μm (average size of 38 × 16 μm), were produced in addition to two-celled teliospores, which measured 41 to 53 × 16 to 21 μm (average size of 46 × 18 μm). Similar mesospores were present in a slide from an isotype specimen of P. hemerocallidis (US 72719) housed in the U.S. National Fungus Collection (Beltsville, MD). Daylily plants (cv. Pardon Me) were reinoculated with urediniospores by shaking infected plants over uninfected plants and exposing plants to 100% relative humidity for 24 h. Initial symptoms of small, discrete, yellow spots and streaks on the upper surfaces of leaves developed within 3 to 7 days, and uredia with urediniospores were evident at 7 to 14 days after inoculation. Daylily rust is native to Asia and may have been introduced into Georgia on plant materials sent from Central America. The original source of daylily rust is unclear because Central American producers also purchase and import plants from the United States for propagation and then sell divisions back to U.S. growers. Daylily rust is a disease of major concern for both daylily producers and gardeners. References: (1) N. Hiratsuka, et al. The Rust Flora of Japan. Tsukuba Shuppankai, Ibaraki, Japan, 1992.