Daylily leaf streak starts as long yellow streaks that turn a reddish brown. Heavily infected leaves scorch back and die early.
The disease is favored by moderate temperatures and wet conditions. Daylily streak can spread by splashing water droplets. Although you can’t manage the rain, you can time irrigation so that your plants are watered in the morning. This allows leaves to dry out quickly and reduce conditions that favor disease development. A mature daylily planting can be crowded leading to poor air circulation and prolonged periods of leaf wetness. Good plant spacing will improve air flow and help to dry out plants quickly. The disease can also be moved on tools, so avoid working around wet plants
Inspect plants when purchasing them and always start with healthy, disease-free plants (ie no spots on the leaves). If just one plant in the landscape is showing symptoms, you might be able to stay ahead of the disease by picking off and dispose infected leaves. Daylily leaf streak will overwinter in the leaf litter, so cleaning up the flower bed will help to reduce the amount of disease that is carried over to the next growing season. If daylily leaf streak shows up annually, it might be worth isolating the problem daylily from the rest of the planting.
The best strategy for managing day lily leaf streak…is through the use of resistant cultivars. Disease susceptibility varies and lists of resistant varieties are not easily available. A few varieties reported by Clemson University are: Betty Bennet, Edna Spalding, Ella Pettigrew, Globe Trotter, Nancy Hicks, Pink Superior, Ron Rousseau, Sudie, Tropical Tones, Upper Room, and Winsome Lady. (https://hgic.clemson.edu/factsheet/daylily-diseases-insect-pests/) (Judy O’Mara)