Frequency and Severity of Ponderosa Pine Dwarf Mistletoe in Relation to Habitat Type and Topography in Colorado. Laura M. Merrill, Research Pathologists, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins 80526. Frank G. Hawksworth, and William R. Jacobi. Research Pathologists, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins 80526, and Associate Professor, Department of Plant Pathology and Weed Science, Colorado State University, Fort Collins 80523. Plant Dis. 71:342-344. Accepted for publication 19 August 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, 1987. DOI: 10.1094/PD-71-0342.

Relationships between forest habitat types, topographical and stand factors (slope, aspect, elevation, topography, configuration, site index, and basal area), and the frequency and severity of ponderosa pine dwarf mistletoe (Arceuthobium vaginatum subsp. cryptopodum) were assessed in Colorado. A total of 547 plots (171 infested with dwarf mistletoe) were established in eight habitat types. A. vaginatum occurred most frequently and was most severe on the driest ponderosa pine (Pinus ponderosa) sites, which are typically the P. ponderosa / Muhlenbergia montana habitat type. Severity of dwarf mistletoe was least in the wetter P. ponderosa / Quercus gambelii habitat types common in southwestern Colorado.