Peridermium bethelii: A Rust Associated with Lodgepole Pine Dwarf Mistletoe. Frank G. Hawksworth, Research Plant Pathologist, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO 80526. Christine S. Dixon, Former Graduate Student, Department of Botany and Plant Pathology, Colorado State University, Fort Collins 80523; and Richard G. Krebill, Assistant Director, Intermountain Forest and Range Experiment Station, Missoula, MT 59806. Plant Dis. 67:729-733. Accepted for publication 3 December 1982. 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, 1983. DOI: 10.1094/PD-67-729.

The rust fungus Peridermium bethelii, which is associated with dwarf mistletoe (Arceuthobium americanum) in lodgepole pine (Pinus contorta), has generally been considered synonymous with Cronartium comandrae. P. bethelii, however, differs in its smaller, less-pyriform aeciospores, apparent lack of spermagonia, later aecial sporulation period, and constant association with dwarf mistletoe. Attempts to infect mistletoe-infected pines were either unsuccessful or inconclusive and potential alternate hosts have not been found. Field evidence suggests the rust may be autoecious.