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Etiology

Insect Wounds as Infection Sites for Hypoxylon mammatum on Trembling Aspen. Neil A. Anderson, Professor, Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108; Michael E. Ostry(2), and Gerald W. Anderson(3). (2)(3)Formerly forestry technician, now associate plant pathologist, and principal plant pathologist, respectively, North Central Forest Experiment Station, St. Paul, MN 55108; (3)Present address: Forestry Sciences Lab., USDA Forest Service, Concord-Mast Road, Box 640, Durham, NH 03824. Phytopathology 69:476-479. Accepted for publication 5 November 1978. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-476.

Two plantations of aspen (Populus tremuloides) from controlled crosses were established to study the process of infection by Hypoxylon mammatum and host resistance to this canker-causing fungus. The Rosemount, MN, plantation was in an agricultural area, the Langlade, WI, plantation in an aspen forest. Of the 169 cankers on trees at the Rosemount plantation, 95% originated in galls induced by Saperda inornata (Coleoptera: Cerambycidae). Less than 1% of the total galls were infected. At the Langlade plantation, seven hypoxylon cankers originated in oviposition wounds formed by Cicada sp., and four cankers in S. inornata galls. Infection of aspen by H. mammatum through S. inornata galls has been observed in wild aspen.