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Etiology

A Snowmold Disease of Mountain Big Sagebrush. D. L. Nelson, Research plant pathologist, USDA Forest Service, Intermountain Research Station, Shrub Sciences Laboratory, Provo, UT 84601; D. L. Sturges, research forester, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Forestry Sciences Laboratory, Laramie, WY 82070. Phytopathology 76:946-951. Accepted for publication 20 March 1986. 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, 1986. DOI: 10.1094/Phyto-76-946.

A sagebrush snowmold disease, induced by an unidentified fungus, results in extensive death of mountain big sagebrush in areas of heavy snow deposition in Wyoming, Utah, and Colorado. A fungus with septate, hyaline hyphae with unique knobby wall projections has been isolated that reproduces field symptoms of snowmold in coldroom inoculation tests. It has not been induced to sporulate in culture. In temperature growth studies the isolate grew from -4 to 24 C, with an optimum near 8-12 C. In southern Wyoming, snowpack temperatures in the sagebrush crown zone ranged from -4 to -16 C in early winter; in late winter the snowpack warms and becomes isothermal at 0 C.