Susceptibility of foxtail pine and western white pine to limber pine dwarf mistletoe in northern California

This study confirms that foxtail pine (Pinus balfouriana) should be classified as an occasional host and western white pine (P. monticola) as a secondary host of limber pine dwarf mistletoe (Arceuthobium cyanocarpum) in northern California. Thirty temporary circular plots (6 m radius) were established around dominant, severely infected western white pines near Mount Eddy, Trinity County, CA. Within these plots, species, diameter at 1.3 m above the ground, and dwarf mistletoe rating (6 class system) were determined for each live tree over 1.37 m in height. Thirty-five and 75% of the foxtail pines and western white pines, respectively, sampled near large, severely infected western white pines were infected. None of the Low's fir (Abies lowiana) or Jeffrey pine (P. jeffreyi) observed in the plots were infected, and these species are classified as immune to limber pine dwarf mistletoe.