Saturday, August 9, 2008

Landscape and Nursery - Leafspot on Rudbeckia

Leafspot is becoming a problem on some Rudbeckias, especially "Goldsturm". The following is an article on the subject from the University of Maryland.

Leafspot Problems on Rudbeckias

Steve Clancy, Town Creek Landscaping, and Steve Sullivan, The Brickman Group, have noticed an unusually large amount of leaf spotting on foliage of Rudbeckia this season. Steve Sullivan sent a picture of a bed of Rudbeckia fulgida var. sullivantii 'Goldsturm' with severe damage on the foliage from leaf spot which is turning the foliage almost black while a planting on another species or cultivar looks just fine. I spoke with Leanne Pundt of Connecticut Extension and she passed along that may growers were seeing leafspot on Rudbeckia fulgida var. sullivantii 'Goldsturm' but saw very little leafspot on Rudbeckia fulgida. She said many of their growers were just growing the straight species to avoid the leafspot problems. I spoke with a local wholesale producer of perennials in Central Maryland to see if he observed similar occurrence of leafspot on 'Goldsturm' compared to straight species R. fuligida. He confirmed he was seeing a similar situation where 'Goldtrum' was heavily infected with leafspot while R. fulgida straight species were in good shape. He also mentioned that other perennial growers were observing the same thing. The puzzling thing is why a cultivar of the same species would be so easily susceptible to leafspot disease. The black-eyed susan, Rudbeckia hirta, which is an annual that usually reseeds itself, does have some problems with leafspot, but it apparently does not have the high incidence that R. fulgida 'Goldsturm' is having. We would be interested to find out if our landscape managers or growers are observing more incidence of leafspot on one species over another.

Reprinted from the August 1, 2008 edition of the TPM/IPM Weekly Report for Arborists,
Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

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