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Symptoms, Association, and Pathogenicity of Discula campestris, a Cause of Sugar Maple Seedling Anthracnose. Glen R. Stanosz, Assistant Professor, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706. . Plant Dis. 77:1022-1026. Accepted for publication 21 June 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-1022.

Mortality of sugar maple (Acer saccharum) seedlings during their first season of growth occurred in 1989 and 1990 in northern Pennsylvania stands infested with pear thrips (Taeniothrips inconsequens). Leaves became spotted and water-soaked, then collapsed or dropped, and upper portions of stems became necrotic. Ten samples, each consisting of five symptomatic seedlings, were collected in June from each of five stands (one in 1989, four in 1990) and incubated 24 days in moist chambers. Acervular conidiomata and conidia of a fungus identified as Discula campestris were observed on leaves of 247 of 250 seedlings. The fungus was isolated from one seedling of each sample (50 of 50 attempts). Wounding of leaves followed by inoculation with a sprayed conidial suspension resulted in collapse of leaves and mortality of laboratory-grown seedlings. Unwounded inoculated seedlings did not die, and leaf symptoms were less frequent and less severe. D. campestris should be considered among the causes of foliar symptoms and mortality of sugar maple seedlings, especially those injured by pear thrips.