Daylily Rust

Daylily rust is caused by the fungus Puccinia hemerocallidis and was introduced into the southeast United States in 2000. While the host range of this disease is limited to Hemerocallis spp. and Patrinia spp., it is especially serious because of the popularity and wide use of daylilies in ornamental plantings.

The disease causes numerous small orange to yellow raised spots, called pustules, to appear on the underside of daylily leaves. The pustules produce dusty, orange spores. These spores spread disease among daylilies in mild summer weather. Leaves may also have yellow to brown streaks similar to those of daylily leaf streak, another fungal disease, but daylily leaf streak does not produce orange pustules.

Infection with daylily rust causes a reduction in bloom and weakens the plant. In some cases a rapid decline in plant health is observed.

Daylily leaf showing symptoms of daylily rust

This disease spreads quickly over long distances through wind dispersal and the movement of infected plant material by people. Daylilies are often moved with no leaves and a few spores clinging to the crown of the plant are nearly impossible to detect. In addition symptoms may not be noticeable or present during the early stages of development.

The best way to manage daylily rust is to prevent the disease from ever becoming established. This can be done by planting disease free material and by using resistant varieties. Isolate any new plants from existing plants to observe them for symptoms. New plants can also be treated before planting with an appropriate fungicide, but this is no guarantee that disease will be prevented and may harm plants that are in poor condition.

If despite your best efforts disease becomes established a combination of sanitation and fungicide sprays is an effective way of controlling the disease. In the fall clean up all plant residue and remove any highly susceptible variety. Destroy plant material by burning or burying. When disease symptoms are observed remove all affected foliage and cut all daylilies in the vicinity to the ground. New foliage can be protected with a fungicide as it emerges. It is very important to continually remove and destroy infected foliage as this will reduce the inoculums in the area and make the fungicide sprays more effective.

Daylily infected with daylily rust

If you suspect you have daylily rust or would like more information on control please contact Ann Gibbs at 287-3891 or ann.gibbs@maine.gov

Websites with more information:

Cornell University Daylily Rust Fact Sheet List of susceptible varieties, treatment options, disease biology

Florida Department of Agriculture Pest Alert Pictures of symptoms, treatment options

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Daylily Rust