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Insects and diseases pose two of the most serious threats to a tree’s health.

As soon as you notice any abnormality in your tree’s appearance, you must begin a careful analysis to gain an understanding of the problem.

By examining the specific symptoms of damage and understanding their causes, you can make a reasonable diagnosis of the problem and select the proper treatment.

Learn More About Common Forest Insects & Diseases in the Golden Area


Douglas-fir Tussock Moth

  • A moth with larva which attack and defoliate Douglas-fir as well as spruce and true fir species
  • Defoliates starting from the top of the tree and working downward
  • Control: Biological or chemical products are effective in springtime while new growth is appearing
Tussock Moth Larva

Emerald Ash Borer

  • A beetle which attacks  and kills all true native North American ash trees, including green, white, black and blue ash, and their cultivars
  • Lays eggs on the bark of an ash tree which subsequently hatch and burrow into the wood eventually girdling and killing the tree
Emerald ash borer. Photo: Dan West

Ips Beetle

  • A bark beetle that attacks pine and spruce. In Colorado piñon ips commonly attack piñon pines.
  • There are 11 species of ips found in Colorado.
  • Control: Maintain vigorous tree health, insecticides can be used.
Adult Ips Beetles in a piñon pine

Mountain Pine Beetle

  • Bark beetle that attacks pines including: lodgepole, ponderosa and bristlecone.
  • Attracted to stressed trees and prefer large old trees
  • Control: Maintain healthy stands or use Verbonone, an anti-aggregation pheromone that “repels” the beetles, chemical treatment
Mountain Pine Beetle


Dwarf Mistletoe

  • Affects all ages & sizes of ponderosa and lodgepole pines, as well as Douglas fir and piñon pine to a lesser degree.
  • Parasitic plant that robs tree of nutrients & water, which causes growth reduction, poor tree form, loss of wood quality and subsequently premature death
  • Control: Prune mistletoe infected branches and/or remove infected trees
Dwarf Mistletoe

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