Texas Cooperative Extension,
Texas A&M University, College Station, Texas

April 2004

USDA Daylily Rust Alert

from the USDA, APHIS

Daylily rust, by Dr. Larry Barnes, Texas A&M
Daylily rust, by Dr. Larry Barnes, Texas A&M

Material included in the USDA Daylily Rust Pest Alert at http://www.aphis.usda.gov/npb/daylily.html confirm that the daylily rust found on US plants in the summer of 2000 is Puccinia, and that to date infection has been limited to foliage.

The perennial Patrinia is an alternate host of Puccinia hemerocallidis, although infections have not been found on any of the six perennial Patrinia sold and grown in the US as ornamentals. Hostas are also suspected of being an alternative host. The USDA has labelled this rust as a serious pest because the incubation period is short and the spread rapid. Except for one bacteria, there are basically no diseases of daylilies in the US, and the plants are very common commercially. Daylily breeders typically send stock material to Costa Rica and other tropical areas for increase, and the first cases of rust appeared to be on plants returned to the United States from Costa Rica.

Aphid feeding damage on leaves can also be confused with early rust infection, as the symptoms are very similar. The leaf streak disease (Aureobasidium microstictum), is commo and widespread nationwide and symptoms can resemble daylily rust.

Positive identification is done by examination of the fungal fruiting bodies and by examining rust streaking on the plant. Dead foliage of affected plants is expected to be diagnosable, as the spores will remain associated with dried or dead material. At the present time, any and all suspect specimens should be sent to the Director, Agri-Systems, Texas Department of Agriculture, P. O. Box 12847, Capitol Station, Austin, Texas (512-463-1145) for rust screening. State labs will then forward rust specimens to the USDA APHIS Beltsville lab for confirmation.

It is suggested carefully removing and destroying infected foliage from plants on which rust is detected and on all the remaining plants in that bed. Fungicide treatments may be started on a 7-14 day schedule, depending on disease incidence and severity. Susceptible varieties may need to be eliminated for management to be successful.