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Disease Note.

First Report of Stem Cankers Caused by Cytospora Specie on Alnus incana in Oregon. G. M. Filip, Department of Forest Science, Oregon State University, Corvallis 97331. C. A. Parks, Pacific Northwest Research Station, USDA Forest Service, 1401 Gekeler Lane, La Grande, OR 97850. Plant Dis. 75:1286. Accepted for publication 11 July 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-1286B.

Cankers on stems of dead and dying mountain alder (Alnus incana (L.) Moench) were observed in the Grande Ronde River drainage near La Grande, Oregon, in 1985. Cytospora sp. (L. J. Spielman, personal communication) was isolated from necrotic tissue at canker margins. Koch's postulates were conducted by isolating the fungus from cankers on affected alder, inoculating healthy stems in the field, and reisolating the fungus from newly developed cankers. This is the first report of Cytospora sp. causing stem cankers on Alnus spp. in Oregon (2). From empirical and experimental data, stem wounds appear to be required for infection and disease development. Stem wounds in Oregon can be caused by several factors, including large mammals, but mass movement of river ice also periodically wounds and kills trees and shrubs in riparian zones (1). The disease does not appear to affect associated shrub species Crataegus douglasii Lindl. and Cornus stolonifera Michaux.

References: (1) G. M. Filip et al. Northwest Sci. 63:211, 1989. (2) L. J. Spielman. Can. J. Bot. 63:1355, 1985.