Introduced Pests Outreach Project

Daylily rust

(Click on an image below to see the captioned full-size version)
Figure 1
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Figure 6

Scientific Name (of causal agent): Puccinia hemerocallidis
Common Name (of disease): Daylily rust

Known Hosts:
Daylily rust has been reported on numerous daylily varieties (Hemerocallis spp.).
Highly susceptible varieties include Pardon Me, Lemon Yellow, Pandora’s Box, Karie Ann, Colonel Scarborough, Quannah, Ming Toy, Double Buttercup, Russian Rhapsody, Irish Ice, and Imperial Guard.

Patrinia, an ornamental plant, is the alternate host for this pathogen. To date no rust infections have been reported on Patrinia sp. in the United States.

Symptoms on daylilies:
Initial symptoms of small, yellow spots and streaks on upper leaf surfaces.
Rust first appears as small, watered-soaked spots on leaves which expand and a pustule forms at the center (Figure 1).
The raised yellow-orange to rust-brown pustules on the underside of leaves can easily be seen with a small magnifying glass (Figure 2).
The “tissue test” is useful in determining if the symptoms you see can be attributed to daylily rust. When a white tissue is run over the surface of pustules, one can see a stain left behind by the orange-yellow spores (Figure 3).
Infections have been found on the leaves and scapes but not the tubers of the plant (Figure 4).

Similar disease symptoms or insect damage:
Leaf streak disease (Aureobasidium microstictum) is a common and widespread disease of daylily in the U.S. (Figure 5).
If you run a tissue along the leaf of a plant with leaf streak, no orange stain will result.
-- Daylily leaf streak fact sheet from the Florida Department of Agriculture and Consumer Services
-- Daylily Rust and Daylily Streak Comparison - UMass Extension Greenhouse Crops and Floriculture Program

Daylily Spring sickness. For more information visit (Figure 6)
Aphid feeding damage may also be confused with the symptoms of daylily rust.
Other substances on the leaf surface such as other plants seeds or pollen could be mistaken for daylily rust pustules.

Fact sheets and references:
Daylily rust information page
Excellent images of daylily rust and a lot of information on daylily rust

University of Massachusetts Fact Sheet: Daylily Rust
Information on symptoms, biology, life cycle, susceptible varieties, diagnosis, and treatment

Daylily rust fact sheet from Ontario Ministry of Agriculture and Food

Cornell University Daylily Rust Fact Sheet

last reviewed February 2022

Massachusetts Department of Agricultural Resources
Massachusetts Introduced Pests Outreach Project is a collaboration between the Massachusetts Dept. of Agricultural Resources and the UMass Extension Agriculture and Landscape Program. This website was made possible, in part, by a Cooperative Agreement from the United States Department of Agriculture's Animal and Plant Health Inspection Service (APHIS). It may not necessarily express APHIS' views.