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James A. Chatfield, Ohio State University Extension, Northeast District/Horticulture and Crop Science; Nancy A. Taylor, Erik A. Draper, Stephen Nameth, Joseph F. Boggs, |
All right, you caught us brambles are rarely, if ever, considered ornamental plants. Nevertheless, Buckeye Yard and Garden Liners Erik Draper and Dave Dyke are such fructophiles that they could not resist repeatedly reporting this dramatic disease in the BYGL this summer, so here is a short orange rust rap.
Orange rust (Gymnoconia peckiana) is the most important of several rust diseases that attack brambles. All varieties of black and purple raspberries and most varieties of erect and trailing blackberries are very susceptible. Orange rust does not infect red raspberries.
Infected plants can be easily identified shortly after new growth appears in the spring. Newly formed shoots are weak and spindly. The new leaves on such canes are stunted or misshapen and pale green to yellowish. This is important to remember when one considers control, because infected plants can be easily identified and removed at this time.
Within a few weeks, the lower surface of infected leaves are covered with blister-like pustules that are waxy at first but soon turn powdery and bright orange. This bright orange, rusty appearance is what gives the disease its name.
Rusted leaves wither and drop in late spring or early summer. Later in the season, the tips or infected young canes appear to have outgrown the fungus and may appear normal. At this point, infected plants are often difficult to identify.
In reality, the plants are systemically infected, and in the following years, infected canes will be bushy and spindly, and will bear little or no fruit.
For further information on this disease, including control measures, see OSU Extension Fact Sheet No. 3010-94, Orange Rust of Brambles; OSU Extension Bulletin 782-99, Brambles Production Management and Marketing; and OSU Extension Bulletin No. 506 B2, Ohio Commercial Small Fruit and Grape Spray Guide.