Dwarf mistletoe (Arceuthobium spp.) is a common forest pest in the Western United States.
The variety that had caused the “witches broom” [top two pictures] in this Douglas-fir (Pseudotsuga menziesii) and others that affect the Pine family can be a major problem in the forestry industry.
However, this parasitic plant is less of a problem in landscapes and urban trees due to plant spacing and diversity. The sticky seeds that are hydrostatically launched are unable to find an appropriate host. Also, if it is caught early it can be easily pruned out.
The actual dwarf mistletoe plant can be seen growing out of a Douglas-fir stem and cambium [second and third from top] as well as what the plant itself looks like next to the needles of the tree [bottom].
