Diseases often set up forests for attack by insects. They also directly kill trees. The following diseases, parasites and declines are common to the Rocky Mountains.

Armillaria root rot (Armillaria mellea)

  • Affects all western conifers and some hardwoods.
  • Managing for multiple species, maintaining good tree vigor and minimizing wounding of trees can reduce losses to Armillaria.

Black Stain root disease (Leptographium wagneri)

  • Affects Piñon pine and Douglas fir.
  • Often found in association with piñon ips outbreaks.
  • Maintaining tree vigor helps in control.

Dwarf Mistletoes (Arceuthobium spp)

  • Multiple species infect virtually all western pines and Douglas fir.
  • Can predispose trees to attack by bark beetles.
  • Pruning/removal of infected trees can help control.
  • Evidence of smoke and heat from low-intensity fires killing mistletoes exists.

Fir decline

  • Appears to be a composite of root diseases (especially Armillaria), bark beetles, and tree competition.
  • Affects subalpine fir.
  • Maintaining good tree vigor though thinning may reduce tree loss.

Sudden Aspen Decline

  • Generally affects older trees and clones, but can impact younger clones under stress.
  • Most likely related to long-term drought and moisture stress.

Short Forestry can answer any questions or concerns you may have about tree diseases. Bruce Short has more than 35 years of experience in dealing with forest health.