Douglas-fir dwarf mistletoe
Last updated on January 30, 2025Arceuthobium douglasii
Douglas-fir dwarf mistletoe is the only mistletoe that frequently attacks Douglas-fir.
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Description
Douglas-fir dwarf mistletoe infection causes reduced vigour, height, and radial growth. Infection also lowers wood quality due to stem infection, and increases the probability of infection by secondary fungal pathogens. A primary characteristic of this mistletoe are the large witches' brooms that can reach up to 5 to 10 metres in height. Infection to nearby trees may be the result of forcibly ejected seeds that can travel up to 15 metres.
Douglas-fir mistletoe is found in the southern interior ranges of the host tree.
Host tree species
Primarily Douglas-fir although grand fir and interior spruce are occasionally attacked. Trees of all sizes and ages are attacked.
Damage symptoms
Spiketops and mortality are common. Stem infections are characterized by large, elongated, and flattened cankers, or by spindle-shaped swellings of the stem. The stem may also have small individual burls as a result of numerous infection sites.
Infected trees growing in open stands are more severely damaged and, as infected branches frequently break, infected trees present a hazard at recreational sites.
Identification images
Further reading
Read more about Douglas-fir dwarf mistletoe in the Field Guide to Forest Damage in B.C. (PDF, 6.5MB)