Estimates of the incidence of mistletoes in pinyon-juniper woodlands of the Coconino National Forest Arizona

The relative incidence of mistletoes found in pinyon-juniper woodlands is estimated for the Coconino National Forest, Arizona, using a roadside survey. Approximately 50% of the pinyon-juniper woodlands surveyed were infested with juniper mistletoes (Phoradendron juniperinum or P. capitellatum). In contrast, only about 12% of the areas surveyed were infested with pinyon dwarf mistletoe (Arceuthobium divaricatum). In these infested woodlands, 70% with juniper mistletoes and 44% with pinyon dwarf mistletoe were lightly infested. Most areas where pinyon dwarf mistletoe populations were observed (90%) also had juniper mistletoe (P. juniperinum) present, but many juniper mistletoe populations observed had no pinyon dwarf mistletoe (50%), although pinyon pine was common at those locations. Therefore, pinyon dwarf mistletoe is frequently co-distributed with juniper mistletoe as has been suggested by other investigators, but juniper mistletoe frequently occurs where there is no pinyon dwarf mistletoe present.