Latin name: Septoria rudbeckiae, Septoria leaf spot

Plant family affected: Rudbekia – Black-eyed Susan

Date/Location of specimen:
1 June 2009 on my black-eyed Susans in Akron
2 http://www.extension.umn.edu/garden/yard-garden/flowers/diseases-of-rudbeckia/img/fig1.jpg

Description: The fungus Septoria rudbeckiae is one of the most common foliar pathogens of Rudbeckia. Symptoms begin as small, dark brown lesions that enlarge from 1/8 to 1/4 inch in diameter. Spores are produced in late spring and early summer, causing leaf spots on the lower leaves. The spores of the fungus are dispersed by splashing water, with lesions first appearing on lower leaves and later developing on upper leaves as the season progresses.

This fungus pretty much wiped out several mass plantings on Rudbeckia in my Akron landscape, in spite of application of fungicide. I just couldn’t spray enough times.

Control: “For maximum control, application of a protectant fungicide should be made periodically throughout the growing season (check label for instructions on spray interval and rate). This is impractical for most gardeners, however. I try to plant something in front of them to hide the unsightly leaves, instead.” – Beverly Shaw, Advanced Master Gardener, Purdue University. 2

References:
1 http://www.extension.umn.edu/garden/yard-garden/flowers/diseases-of-rudbeckia/
2 https://www.ppdl.purdue.edu/PPDL/expert/Rudbeckia_leaf_spot.html
Collection Sample # 1 of 5 DISEASES

Master Gardener Class Horticulture Portfolio