Pests and potential problems
Dwarf mistletoe is a common pest of white fir. The parasitic plants germinate on white fir branches and force their roots into the phloem of the host branch. Dwarf mistletoe weakens the tree and leaves it susceptible to fungal infections and insect attacks. It also creates stem cankers that leave the wood weak and unsuitable for use as lumber.
Wounding, as a result of mechanical injuries, fire, insects, or frost cracks, promotes or provides entrance for fungi into white fir trees. Annosus, Armillaria, laminated root diseases, yellow cap fungus, Indian paint fungus, and white pocket rot reduce plant productivity and cause wood decay and mortality. Fungal infections also promote susceptibility to insect infestations.
The fir engraver beetle (Scolytus ventralis), a member of the bark beetle family, causes high mortality in white fir stands. The beetle bores holes into the main stem, often in bark crevices at the branch and trunk junctions. Once under the bark, adults engrave egg galleries into the sapwood, disrupting the flow of water and nutrients to that portion of the plant. The appearance of yellowed or reddened branches on an otherwise green tree is early evidence of fir engraver infestation. Fir engravers can kill the plant. The only known preventative is proper maintenance of white fir trees.
White fir in shallow soils can be damaged by strong winds. The chances of windthrow are increased when neighboring trees are removed.
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