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Effect of Cherry Leaf Spot on Nursery Black Cherry Seedlings and Potential Benefits from Control. Glen R. Stanosz, Forest Pathologist, Pennsylvania Department of Environmental Resources, Bureau of Forestry, Division of Forest Pest Management, Middletown 17057-5021. . Plant Dis. 76:602-604. Accepted for publication 16 January 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0602.

A study was conducted to quantify the effect of leaf spot caused by Blumeriella jaapii on black cherry seedlings in a nursery. The severity of leaf spot, which had developed from naturally occurring inoculum, was visually estimated on leaves collected from untreated and benomyl-treated subplots in August 1990. Leaves were counted and seedling height, caliper, and area of collected leaves were measured. The number of seedlings with diameters ?0.40 cm (5/32 in.), the minimum acceptable, was determined before seedlings were lifted in spring 1991. Lower leaves and leaves from untreated subplots were more frequently placed into greater leaf spot severity categories than higher leaves or leaves from treated subplots. Mean leaves per seedling, height, and caliper values were less for untreated seedlings than for treated seedlings, and untreated subplots yielded approximately half as many seedlings of minimum-acceptable diameter as treated subplots. Leaf spot severity was positively correlated with seedling density in untreated subplots. Leaf area tended to be smaller in more dense subplots, and the number of seedlings of minimum-acceptable diameter was negatively correlated with seedling density in both untreated and treated subplots. The control of leaf spot and the regulation of seedling density can increase the efficiency of black cherry seedling production in nurseries.

Keyword(s): Coccomyces, Prunus serotina.