Avoid over-head irrigation. In the fall, remove dead foliage from around the base of the plants and dispose of the clippings, as the fungus will over-winter on senesced foliage, and spores will be produced the next spring to infect new leaves. Examples of resistant daylily cultivars include: Betty Bennet, Edna Spalding, Ella Pettigrew, Globe Trotter, Nancy Hicks, Pink Superior, Ron Rousseau, Sudie, Tropical Tones, Upper Room, and Winsome Lady.
To control leaf streak the fungicide thiophanate-methyl or myclobutanil may be applied to slow disease development and to protect susceptible new growth from infection. Begin sprays as new growth appears. Make 3 or 4 applications at 2-week intervals. If you use fungicides of course.
