Hemerocallis (Daylily) Disease Guide: Leaf Spots, Rust, and Crown Rot

Managing Diseases in Daylily Production

Daylilies (Hemerocallis) face several fungal leaf diseases, crown rot, and physiological disorders. Cultivar susceptibility varies significantly, making cultivar selection an important disease management tool.

Colletotrichum Leaf Spot (Leaf Scorch)

Colletotrichum dematium causes leaf tissue death in streaks along mid-vein.

Management: Remove infected leaves. Destroy leaf debris season-end. Avoid overhead irrigation.

Leaf Streak (Red Leaf Streak)

Aureobasidium microstictum causes reddish flecks with mid-vein yellowing, oval dead spots, premature leaf death; wet shiny white spore masses on brown leaves in wet conditions. Cultivars vary greatly in susceptibility.

Management: Remove infected leaves. Destroy debris season-end. Avoid overhead irrigation. Apply fungicides.

Rhizoctonia Crown Rot

Rhizoctonia spp. (usually following freeze injury) cause slender grassy foliage, few flower stalks, crown rot/death.

Management: Protect crowns from freezing.

Russet Spot

Reddish leaf spots. Cause unknown.

Rust

Puccinia hemerocallidis causes bright yellow upper leaf spots/streaks with yellow-orange spores underneath. Also occurs on Patrinia spp. (possibly Hosta but not observed in US). Most cultivars susceptible.

Management: Remove infected leaves, immediately bag for disposal (keep bag closed). Apply fungicides.

Integrated Daylily Health Practices

Key strategies: cultivar selection for disease resistance (especially leaf streak); sanitation (remove infected leaves, destroy season-end debris); overhead irrigation avoidance; freeze protection for crowns; immediate bagging/disposal of rust-infected leaves (prevents spore spread); and fungicide applications for susceptible cultivars. The wide variation in cultivar susceptibility makes resistant variety selection the most sustainable long-term management strategy.