The phenology and impact of Caliciopsis arceuthobii on lodgepole pine dwarf mistletoe, Arceuthobium americanumThis article is one of a collection of papers based on a presentation from the Stem and Shoot Fungal Pathogens and Parasitic Plants: the Values of Biological Diversity session of the XXII International Union of Forestry Research Organization World Congress meeting held in Brisbane, Queensland, Australia, in 2005.

Arceuthobium americanum Nuttal ex Engelmann in Gray (lodgepole pine dwarf mistletoe) causes significant losses to the timber industry. The fungus Caliciopsis arceuthobii (Peck) Barr shows high specificity to Arceuthobium spp., and therefore infection of A. americanum was monitored for 4 years to determine the effect of this fungus on fruit production. The contribution of stand-level and locally produced inoculum in the infection process was also studied to better understand the epidemiology of the pathogen. Over the period of the study, C. arceuthobii caused an average annual fruit reduction of 58%. When the contribution of local and stand-level inoculum was modelled, the results suggested that on A. americanum infections with ≥ 4 ascospore-producing immature fruit, more than half of the new C. arceuthobii infections on the same plant are derived from locally produced ascospores. The effect of the fungus on the host suggests that it has potential as a biological control agent for A. americanum, and furthe...