A rust fungus newly found on nursery daylilies in the U.S.
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Name: Puccinia hemerocallidis
Fungi: Basidiomycota: Urediniomycetes: Uredinales: Pucciniaceae
Common Names: daylily rust
Daylily species are undemanding perennials, long cultivated and naturalized in many areas. They are very popular in North America where thousands of new cultivars have been introduced since 1950. Daylily rust appears to be very aggressive, especially on the daylily variety "Pardon Me". Following inoculation of the leaves, infection occurs two to three days later, eventually killing the foliage. Spread to other daylilies in a nursery is also rapid.
Daylily producers often develop varieties in the U. S. and send those to Costa Rica and other tropical areas for propagation. The daylilies are then shipped back to U. S. nurseries in the spring and early summer. The infected plants found in GA came from Costa Rica, but it is possible that the rust could have been introduced into the U. S. first, and then sent to Costa Rica. Most of the foliage is removed from the daylily tubers before shipment, making it difficult to detect the fungus at ports-of-entry. The tubers could be carrying rust spores, which are impossible to detect visually.
Hosts: Numerous daylily species (Hemerocallis spp.), Patrinia species (Patrinia spp.), and Hosta species (Hosta spp.).
Vector(s)/Dispersal: Dispersal of the rust fungus could occur by movement of the host plant as an ornamental, medicinal plant, or vegetable. Plant propagation by division may also aid in dispersal.
Australia (Queensland); China; Japan; Korea; Russia; U. S. (confirmed in nurseries or plant dealerships in 24 states). Its distribution includes tropical to temperate climates.
Quarantines: Daylily rust was mentioned by Stevenson in Foreign Plant Diseases in 1926, and therefore would probably be considered a pest of quarantine significance.
Puccinia sp. can be identified on daylily leaves by typical rust streaking, and raised yellow-orange to rust-brown pustules on the underside of the leaf. Fungal spores can also be found on dried or dead leaf material and tubers. Positive identification is done by examination of these spores (e.g. urediniospores, teliospores, etc.).
This rust is heteroecious, that is, it requires two different hosts to complete its life cycle. Early stages infect Patrinia sp., and cultural control practices show that severity of infection may be reduced by growing daylilies without Patrinia species nearby.
FL Dept. of Agriculture, Division of Plant Industry
National Plant Board
Warning: The information in this archived item was not confirmed with the appropriate National Plant Protection Organization and is provided solely for informational purposes. Please use this information with caution.