ABSTRACT
Collections of Heterobasidion spp. from Nebraska, Colorado, Arizona, and New Mexico were identified based on the sequence of the internal transcribed spacer region of the ribosomal DNA. The North American variant of Heterobasidion annosum sensu stricto was found on Pinus ponderosa and Juniperus virginiana in central Nebraska, southern Colorado, central Arizona, and southern New Mexico. The North American variant of H. parviporum was found on Abies concolor and Picea engelmannii in southern Colorado and central New Mexico. The pathogens were not found in a survey of conifer forests in Wyoming and the Black Hills of South Dakota. Historical records of annosus root disease are reviewed by host group to gain more insight into the potential distributions of the respective pathogens. An apparent lack of overlap in host range suggests that substitution of tree species may be a useful management approach in some cases.
