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Etiology

Cryptosphaeria Canker and Libertella Decay of Aspen. Thomas E. Hinds, Research plant pathologist, USDA, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO 80526; Phytopathology 71:1137-1145. Accepted for publication 26 January 1981. 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, 1981. DOI: 10.1094/Phyto-71-1137.

A recently discovered, widely distributed canker disease of aspen and other poplars throughout the Rocky Mountain region is described. Inoculations with ascospore and conidial isolates of Cryptosphaeria populina show the fungus is capable of causing branch, sprout, and sapling mortality, trunk cankers, and the discoloration and decay of aspen stems previously associated with its imperfect stage, Libertella sp. The greatest average canker elongation 50 mo after September inoculations was 33.5 cm with sapwood decay and discoloration extending to 401 cm. The fungus caused an average weight loss of 13.5% in bark, 27.0% in sapwood, and 19.1% in heartwood blocks. Incidence of decay in living trees in Colorado was 7.8%, increasing from the poorer sites to the better sites, and increasing with diameter class. Sapwood discoloration around and beyond the infection perimeter exhibits a yellowish fluorescence under ultraviolet light as does a water filtrate of the fungus grown in culture. Other aspen canker and decay fungi and their cultural filtrates exhibit similar fluorescence, which suggests that sapwood discoloration may be the result of materials produced by fungal pathogens rather than by the host response.