Introduction of Puccinia hemerocallidis into USA: Addition to the EPPO Alert List
In 2000, a new rust of daylily (Hemerocallis) was noticed in Florida, USA. After some taxonomic uncertainties, the pathogen was finally identified as Puccinia hemerocallidis (Basidiomycetes, Uredinales), a species which was previously only reported from Asia. Within a few months, daylily rust spread to many States. In addition, P. hemerocallidis was recently intercepted on imported Hemerocallis from USA by United Kingdom. Therefore, the EPPO Secretariat felt that it could usefully be added to the EPPO Alert List.
Puccinia hemerocallidis (Basidiomycetes, Uredinales – daylily (Hemerocallis) rust)
Why: Puccinia hemerocallidis came to our attention because of its recent introduction into USA and its very rapid spread there. In addition, it has been intercepted on Hemerocallis plants from USA by United Kingdom (see EPPO RS 2001/154), indicating that this fungus has a pathway to enter Europe.
Where: P. hemerocallidis originates from Asia.
Asia: China, Japan, Korea, Taiwan. There are records of P. hemerocallidis in Siberian collections of fungi, but no data could be found on its actual presence in Russia.
North America: USA. It was first found in Florida in 2000 and it has spread very rapidly to many US States (Alabama, Arkansas, California, Connecticut, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Mississippi, Missouri, Nebraska, New Jersey, North Carolina, Ohio, South Carolina, Tennessee, Texas, Wisconsin). There is suspicion that the fungus could also be present in Costa Rica, as symptomatic plants from this country have been intercepted by USA, but this has not been confirmed. The origin of the introduction into USA remains unknown, as Hemerocallis plants are mostly imported from South and Central America and not from Asia.
On which plants: P. hemerocallidis is a heteroecious rust. The aecial host is Patrinia spp. (Valerianaceae). The telial host is restricted to the genus Hemerocallis (Liliaceae), although there is a record of Hosta (Liliaceae) also being a host plant. However, preliminary inoculation studies done in USA failed to transmit the disease to Hosta. In USA, it is noted that so far, the disease has not been observed on Hosta, nor on Patrinia (which is apparently not a commonly grown ornamental). P. hemerocallidis can survive and multiply on Hemerocallis alone (asexual multiplication) in the absence of its aecial host.
Damage: First symptoms are bright yellow spots or streaks on the leaves followed by the appearance of yellow/orange pustules (containing orange spores). As the disease develops, leaves turn yellow and dry. Plants are not killed but are severely disfigured. In USA, a great variability in cultivar susceptibility has been observed. Although biological data is lacking, it has been observed that the disease has a short incubation period, symptoms appear 2-3 days after spore germination, and the production of new spores takes 7 to 14 days.
Transmission: Spores are disseminated by wind, plant handling (e.g. hands, shoes, clothes of workers…). Long distance spread can be ensured by exchanges of contaminated plants. It is not known whether crowns and roots of Hemerocallis can develop the disease (symptoms are only seen on leaves), but they can carry spores of the fungus on their surface.
Pathway: Plants for planting, crowns and roots of host plants from countries where P. hemerocallidis occurs.
Possible risks: Hemerocallis are common perennial garden plants in the EPPO region. Apparently, Patrinia are not common plants in Europe (Asian origin, used as ornamentals or medicinal plants), but the fungus can multiply and survive without its aecial host. Hemerocallis are usually considered easy to grow, and virtually free of pests and diseases. Chemical treatments are probably available (trials are conducted in USA), but further data is needed. The introduction of P. hemerocallidis would lead to the application of treatments on a crop which so far hardly needed them. It appears from the wide and rapid spread of P. hemerocallidis under various climatic conditions in USA, that it could survive in most parts of the EPPO region. The introduction of P. hemerocallidis could present a risk to nurseries growing Hemerocallis in the EPPO region, and would affect gardens and parks. It can be noted that the Australian Quarantine and Inspection Service is now taking phytosanitary measures (treatments of seeds and nursery stocks of Hemerocallis, Patrinia and Hosta) to prevent the entry of P. hemerocallidis.
EPPO RS 2001/153
Panel review date - Entry date 2001-08
Sources
AQIS Web site – Quarantine Alert. http://www.aqis.gov.au/icon/asp/ex_alertscontent.asp
Florida Department of Agriculture and Consumer Service – Pest Alert: Daylily Rust by T. Schubert & R. Leahy (showing pictures of the disease). http://doacs.state.fl.us/~pi/enpp/pathology/daylily-rust.html
NAPPO Pest Alert – Puccinia sp. http://www.pestalert.org
University of Georgia – Daylily Rust Alert. http://www.ces.uga.edu/Agriculture/plantpath/daylilyrust.html
USDA-APHIS - National Plant Board – Daylily Rust Pest Alert. http://www.aphis.usda.gov/npb/daylily.html
ARS-USDA Systematic Botany and Mycology Laboratory (SBML) - Systematic databases. http://www.indexfungorum.org/