Puccinia hemerocallidis, Cause of Daylily Rust, a Newly Introduced Disease in the Americas

Daylilies (Hemerocallis spp., Liliaceae) are one of the most important cultivated perennial plants in the United States. Daylily rust, a serious disease caused by Puccinia hemerocallidis Thüm., was observed in Georgia in August 2000 (14) and was found in at least 20 other states and in Costa Rica in 2001. It was originally described from Russia, reported throughout the Japanese archipelago, and recorded from China (Manchuria), Korea, and Taiwan (4,5). Among the rust fungi, only P. hemerocallidis is known to infect Hemerocallis spp. This study was undertaken because initial observations of variation in urediniospore morphology and the presence of many nonseptate teliospores (mesospores) in the rust in the Americas suggested that it might be different from the Asian rust and that there might even be heterogeneity within the American rust. The type specimen of P. hemerocallidis from Siberia, Russia, was examined and compared with both recently and previously collected specimens from China, Costa Rica, Japan, Russia, Taiwan, and the United States. This report provides an expanded description with photomicrographs of the fungus causing daylily rust. Additionally, the internal transcribed spacer (ITS) region of the ribosomal DNA was sequenced for specimens from Costa Rica, Japan, Russia, and the United States to compare the rust fungus from the Americas with recently collected Asian specimens of P. hemerocallidis.