Hemerocallis sp. (Daylily) Aureobasidium microstictum (leaf streak) causes reddish spots with yellowish margins that often result in brown streaks down the center of the
Don't confuse this disease with the relatively new (and much more important) disease called daylily rust, which is caused by Puccinia hemerocallidis.leaves. Usually this leaf disease does not cause the death of the plant.
Frost injury starts whitish but with time turns brown. The damaged tissue occurs on the tip of the leaves that were exposed at the time of the freezing weather.
The leaf streak fungus overwinters on dead plant material and when spores are released under the right weather conditions, the fungus can spread long distances.
Daylilies are very cold hardy. However when these plants are emerging from the soil and are growing vigorously - they are susceptible to frost injury. The frost injury often becomes infected with saprophitic fungi.
Fungicides and sanitation may be helpful.
Cover the daylilies carefully during freezing weather may help.