Landscape - Septoria Leaf Spot of Rudbeckia

The following is information on Septoria leaf spot of Rudbeckia in the landscape.

Septoria leaf spot on brown-eyed Susan, Rudbeckia 'Goldstrum' can be found on some very small plants in the landscape. Infection this early could develop into some serious defoliation. To keep some leaves on heavily spotted plants (irregular brown spots on the leaves with small black fruiting bodies on the oldest spots), make a fungicide application with Daconil or other labeled fungicide.

Symptoms begin as small, dark brown lesions that enlarge from 1/8 to 1/4 inch in diameter. Although the lesions are usually rounded, there may be angles where leaf veins limit the spread of the fungus. Symptoms of this disease may be difficult to distinguish from those of angular leaf spot of Rudbeckia. Microscopic examination of the lesion will reveal black, flask-shaped structures called pycnidia that contain thousands of thread-like spores. 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.

To manage this disease, remove the infected leaves at the end of the growing season to reduce inoculum levels. Because leaf moisture is essential for infection to occur, increase air circulation around the foliage by properly spacing plants (and removing volunteer seedlings) to prevent over-crowding. As with other foliar disease problems, avoid overhead watering. Fungicides containing chlorothalonil or copper may protect new growth and reduce the spread of the disease. Preventative applications of fungicides should begin in late May to early June prior to the onset of symptoms.


Information from Bob Mulrooney, Extension Plant Pathologist, UD and "Diseases of Rudbeckia" by Janna Beckerman, Extension Plant Pathologist, University of Minnesota.

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.

Landscape - Spring Leaf Spots and Blotches

Fungal leaf spots and blotches can occur in susceptible landscape plants in the spring. The following is an article on the subject from the Rutgers Plant and Pest advisory.

What would springtime be without leaf spots? Leaf diseases are caused by a wide variety of fungal and (some) bacterial pathogens. Most ornamental plants are susceptible to one or more of these diseases. For example, one leaf spot that we commonly see in Delaware landscapes is Phyllosticta leaf spot of maple.

The fungi that cause leaf spots and blotch reproduce and spread by means of spores. These spores are produced in fruiting structures in leaf litter on the ground. Once splashed to developing tissue after budbreak, the spores germinate and penetrate the leaf surface. The fungus then grows throughout the leaf, killing the tissue as it goes and leaving spots or blotches that are often accompanied by a yellow halo. Look closely at the lower leaf surface of leaf lesions later in the summer, and you may see the small, dark fruiting structures that serve to produce inoculum the following spring.

Horsechestnut leaf blotch is truly spectacular when it develops following environmental conditions optimal for disease development. Lesions of this fungal disease, caused by Guignardia aesculi, first appear on horsechestnut and buckeye in the spring as watery blotches that turn brown within a few days and are bordered by a yellow band. The blotches coalesce, causing leaflets to distort and curl, and fall prematurely. The disease also affects petioles and fruit. From a distance, severely affected trees appear scorched, so get close and look at the leaves before making a diagnosis.

Since the development of leaf spots and blotch is favored by abundant moisture and cooler temperatures, management benefits from a few basic strategies: reduce leaf wetness and humidity in plantings (e.g., improve air-flow through proper spacing and weed management, irrigate during early morning hours, and avoid overhead watering); remove leaf litter to reduce fungal inoculum; and improve plant vigor to help reduce disease severity. Remember, however, that the environment drives theleaf-spotting process, so expect to see more following wet springs.

Fungicides are effective only if they are present on leaf surfaces at the time the fungi are producing spores. Fungicides applied after leaf lesions are visible are not effective. Most damage caused by the fungi that cause leaf spot and blotch is merely cosmetic, thus the use of fungicides for disease control in the landscape is not usually recommended unless plants are severely stressed. If desired, however, leaf spots may be prevented with foliar applications of azoxystrobin, Benefit, chlorothalonil, ConSyst, copper, iprodione, Junction, mancozeb, maneb, propiconazole, Spectro, Stature, thiophanate-methyl, or Zyban. In general, these preventive fungicides are applied at budbreak and the spray repeated twice at 7- to 14-day intervals. Fungicides labeled for horsechestnut leaf blotch include chlorothalonil, Junction, mancozeb, maneb, Manhandle, Spectro, Stature, or thiophanate-methyl, applied at budbreak and repeated every 7 to 21 days. As always, check individual labels for specific host and application rate recommendations.

Reprinted with minor changes from "Diseases of Landscape Ornamentals in the Springtime (Part I)" by Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University in the April 3, 2008 edition of the Plant and Pest Advisory; Landscape, Nursery, and Turf Edition.