Fun Facts

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In Colorado pine beetles (primarily Mountain Pine Beetle) and fir beetles (Douglas-fir beetle/Western Balsam Bark Beetle) are native pests that kill trees by cutting off nutrient flow, often driven by drought and warmer temperatures. Pine beetles attack ponderosa and lodgepole, while fir beetles target Douglas-fir and subalpine fir, with distinct species-specific tree preferences and management strategies. 

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Mountain Pine Beetle (MPB) in Colorado 

• Target Trees: Primarily lodgepole, ponderosa, and limber pine.

• Signs: Small, rice-sized insects, they cause blue-gray staining in wood and create "pitch tubes" (reddish sap blobs) on the bark. Needles turn yellow or red-brown about 9 months after attack.

• Activity: Active in the Front Range and southwest Colorado.

• Distinction: They are brown to black, about 1/8 to 1/3 inch long, and their rear end (wing cover) is smoothly curved. 

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Fir Beetle (Douglas-fir and Western Balsam) in Colorado 

• Target Trees: Douglas-fir beetle attacks mature Douglas-fir; Western Balsam bark beetle attacks subalpine fir.

• Signs: Similar to pine beetles, Douglas-fir beetles cause foliage to turn from green to red-brown.

• Activity: Douglas-fir beetle is widespread, especially in central and southern Colorado, often attacking trees already stressed by fire or disease.

• Distinction: These beetles generally attack larger-diameter trees (over 14 inches). 

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Key Differences

• Tree Host: Pine beetles = Pine trees. Fir beetles = Fir trees (Douglas-fir/Subalpine).

• Size: Pine beetles are generally slightly smaller than Douglas-fir beetles.

• Damage Profile: In 2024, Western balsam bark beetle was noted as the deadliest in some areas, while Douglas-fir beetle impact increased. 

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Management

• Prevention: The best approach is keeping trees healthy through proper watering and avoiding overcrowding, as both beetles favor drought-stressed, crowded forests.

• Control: Once a tree is infested and the needles turn red, the beetles have likely left, and the tree cannot be saved; removing infested trees before beetles emerge can help. 

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