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

A rust of daylilies was introduced recently into North and Central America. In order to confirm the identity of this rust as Puccinia hemerocallidis, numerous specimens from Costa Rica and the United States were examined morphologically and compared with specimens from China, Japan, Russia, and Taiwan. In addition, the internal transcribed spacer (ITS) region of the ribosomal DNA was sequenced from six representative fresh specimens from the Americas and Asia. We conclude that the rust introduced into the Americas is P. hemerocallidis, for which a modern description is provided with illustrations of the uredinial and telial stages.