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Chondrostereum purpureum Associated with Decline of Betula papyrifera in Thunder Bay, Ontario. J. A. McLaughlin, School of Forestry, Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1. E. C. Setliff, School of Forestry, Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1. Plant Dis. 74:331. Accepted for publication 26 February 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0331E.

Dieback and decline of white birch (Betula papyrifera Marsh.) of all age classes are evident throughout Thunder Bay. In September 1986, the wound pathogen Chondroslereum purpureum (Pers.:Fr.) Pouz. was observed fruiting on a declining young white birch. [n late summer of 1988, two more trees were observed with C. purpureum basidiocarps. Subsequently, a survey for this fungus was conducted in the city to assess its association with trees showing symptoms of decline. Discolored wood was extracted from areas near branch or trunk wounds on 26 of 39 symptomatic trees. Fifteen of these trees yielded cultures of C. purpureum. Also, basidiocarps of C. purpureum were found on B. pendula Roth. Acer sacchorinum L., and a Malus sp. with decline symptoms. The pattern of disease incidence on birch was reminiscent of silver leaf disease reported in an orchard in Wisconsin (1). C. purpureum has been previously noted as the most common fungus found in brown-stained white birch wood and one of the most common fungi found in association with trunk defects and decay. These results raise the question of what role this fungus plays in the complex and economically important phenomenon known as birch decline.

Reference: (1) E. C. Selliff and E. K. Wade. Plant Dis. Rep. 57 :473. 1973.