Great Basin Naturalist


Douglas-fir dwarf mistletoe (Arceuthobium douglasii) was found parasitizing Pacific silver fir (Abies amabilis) in northern Siskiyou County, California. This is the first report of Douglas-fir dwarf mistletoe on this host. Approximately 40% of the Pacific silver firs near heavily infected Douglas-firs were infected. The low level of infection on Pacific silver fir, unusually large swellings at the points of infection, and poor shoot production on infected branches indicate some degree of host-parasite incompatibility.