Hypoxylon Canker Incidence and Mortality in Naturally Occurring Aspen Clones. S. P. Falk, Former Graduate Research Assistant, Faculty of Environmental and Forest Biology, State University of New York, College of Environmental Science and Forestry, Syracuse 13210. D. H. Griffin and P. D. Manion. Professors, Faculty of Environmental and Forest Biology, State University of New York, College of Environmental Science and Forestry, Syracuse 13210. Plant Dis. 73:394-397. Accepted for publication 22 November 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0394.

A survey of stem canker caused by Hypoxylon mammatum in 29 clones of Populus tremuloides in central New York showed that incidence increased with tree size, but mortality was highest in small trees. Cankers low on the bole were associated with mortality. Small stems had more cankers below the lowest living branch. The frequency of cankers above the lowest living branch increased with tree size, suggesting that the infection court occurs on branches. With increasing tree size, cankers on branches originate farther away from the bole and fewer cankers cause mortality. Considerable variation existed in disease incidence and mortality among the clones and four sample locations.

Keyword(s): canker location, population variation.