Scouting for diseases: Daylily leaf streak
Pathogen: Collecephalus hemerocalli. (view images)
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. 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.
Information is from the new field guide A Pocket Guide for IPM Scouting in Herbaceous Perennials. Ordering information, call 517-353-6740 or visit: http://www.ipm.msu.edu/pdf/pocketGuidesLandsc07.pdf