The cause of daylily rust is Puccinia hemerocallidis, a fungus native to Asia. The disease is identified by bright yellow- or orange-colored spots with raised pustules (bumps) on the foliage of affected plants, and by orange colored spores which emerge from the pustules. As symptoms progress, leaves turn yellow and dry up. Early rust infection may resemble a different, fairly common problem, daylily leaf streak, caused by the fungus Aureobasidium microstictum. The main difference between these two is that the rust fungus produces raised spots (pustules). Rust pustules will transfer orange powdery spores to a white tissue when it is rubbed over the infected leaves. This will not happen with any other daylily leaf disorder. By the time leaves turn yellow and dry up, diagnosis becomes very difficult without the aid of a laboratory analysis.
Control daylily rust by good sanitation in the garden. Remove and destroy all leaves in the fall so the fungus cannot overwinter. To prevent daylily rust, apply garden fungicides containing ingredients that control rust diseases prior to disease occurrence. Check the product label to see that it is cleared for use on daylily (or ornamentals) and for rust diseases. Contact your local Extension office for specific chemical recommendations.
