Forest Health Resources

A list of diseases, pests and other ailments that may affect your trees. Click on the bolded titles to view a PDF with more information.

  • Annosus Root Disease — Infected trees suffer root and butt decay, and root mortality, resulting in reduced vigor, windthrow, and predisposition to bark beetles and mortality.
  • Armillaria Root Disease — Caused by parasitic fungi, every state has reported cases, resulting in mortality, root decay, and growth reduction.
  • Black Pine Leaf Scale — A type of armored  insects that, concealed under their shells, attach to host trees and suck out sap and sometimes injecting toxic enzymes into the tree.
  • Douglas Fir Beetle — Harsh conditions, such as post fire, snow and ice storms, and downed trees are susceptible to Douglas Fir Beetle outbreaks, causing environmental disturbances.
  • Douglas Fir Tussock Moth — Outbreaks of these moths cause immense defoliation and mortality of trees, and can last several years due to prolific reproduction.
  • Magnesium Chloride Chemical Injury — Trees are harmed by chemicals that seep into them from runoff, insecticides, and other chemical applicants, resulting in root uptake, de-foliage, browning, and other injury.
  • Mountain Pine Beetle — These beetles live beneath the bark of most pine trees and fester dense forests, creating mass mortality in forests within a few years.
  • Pine Engraver Beetle — Mainly attracted to Ponderosa Pines, these beetles cause damage to vulnerable trees and slash piles, particularly damaging to unthinned young tree stands.
  • Sequoia Pitch Moth — Larvae grows under the bark and upper layers of trees, causing pitch masses that create fire hazards, and cause severe damage to the base of trees.
  • Spruce Bud Worm — Infestations of this worm result in defoliation, top-killing, severe economic loss in tree growth, and tree mortality.
  • Western Gall Rust — The rust mainly grows on Lodgepoles and Ponderosa Pine, causing swellings that affect the form, lumber content, and growth rate.
  • Western Pine Beetle — Aggressively attack and kill tree stands, particularly Ponderosa Pines, attacking both healthy and vulnerable dense forests.