MSU Extension Integrated Pest Management

Fungal leaf spots

Pathogen

Collecephalus hemerocalli.

Hosts

Hemerocallis.

The disease was named for these streak symptoms along the leaf’s midrib.

Symptoms

Elongated brown lesions, which are lengthwise on the foliage, surrounded by a chlorotic halo. Lesions that affect the midrib of a leaf cause the leaf to senesce from the lesion to the leaf tip. Tissue in the center of the leaf becomes necrotic, creating a dead streak down the middle of the infected leaf. Flower production may be decreased.

Initial symptoms are tan leaf spots surrounded by chlorotic halos.

Spread

Diseased plant material can introduce the pathogen into a production area. C. hemerocalli produces wind-borne spores on infected leaves. Sclerotia, an overwintering structure, are produced on dead or dying foliage.

Severely infected leaf.

Management

Cultivars vary in their susceptibility. Remove dead foliage from the preceding year. Poorly managed plants in overcrowded growing situations are more likely to become diseased. The disease is more severe early in the growing season. Temperatures above 90°F limit disease development.

Leaf streak symptoms are readily visible in a planting bed.

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