Management of rust on day lilies
In 2000, daylily rust was first detected in the Southeast and quickly spread throughout much of the country due to widespread movement of the pathogen on infected stock and subsequent establishment in the landscape. Daylily rust can negatively affect the production, distribution, sales and cultivation of daylilies because infected plants often are not marketable. Differences between isolates of Puccinia hemerocallidis in the ability to cause lesions on some cultivars of daylily suggest that genetic subdivisions termed “races” of P. hemerocallidis are present in the U.S. A race of the fungus carrying a non-virulent (or avirulent) gene would not be able to infect a daylily host with a corresponding gene for resistance but would cause disease on a daylily cultivar lacking this gene. UGA plant pathologists collected 16 isolates of Puccinia hemerocallidis over a four-year period to test for their infection type on 21 daylily cultivars. Differences in disease responses between isolates confirmed the presence of different pathotypes of the fungus. Soil drenches and foliar sprays were evaluated in field experiments in Griffin in 2010 and 2011. The presence of races of the daylily rust fungus suggests that cultivars of daylily previously thought to be immune to the pathogen could be at risk of infection. The use of single drench applications of fungicide for season-long disease control would reduce the labor costs associated with multiple foliar applications of fungicide.