Pathogen: Collecephalus hemerocalli
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.
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.
Management: Cultivars vary in their susceptibility. Dead foliage from the preceding year should be removed. Poorly managed plants in overcrowded growing situations are more likely to become diseased. Disease is more severe early in the growing season, temperatures above 90F limits disease development.