Insects and diseases pose two of the most serious threats to a tree’s health. As soon as any abnormality is discovered in a tree’s appearance, measures should be taken to diagnose the problem.

2020 Insect & Disease Activity in Colorado Forests

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2020 Individual Insect Activity & Information

Roundheaded Pine Beetle

Roundheaded pine beetle activity has affected approximately 52 percent of the ponderosa pine forest ecosystems in Dolores County since 2000.


Spruce Bark Beetle

Severe outbreaks continued in portions of the San Juan Mountains, West Elk Mountains and Sawatch Range; the southern reaches of the Sangre de Cristo Mountains; and portions of north-central Colorado.


Douglas-fir Beetle

Widespread groupings of tree mortality occurred in portions of the northern Sawatch Range; northern areas of the La Garita Mountains, south of Gunnison; the Needle Mountains near Lake City; and the San Miguel River drainage.


2020 Report on the Health of Colorado’s Forests

2020 Report on the Health of Colorado's ForestsThe 2020 Report on the Health of Colorado’s Forests (7 MB PDF) contains a comprehensive statewide insect and disease update, covering indigenous and exotic pests in Colorado’s conifer and deciduous forests.

Up-to-date photos, maps and charts in the report tell the complex story of how insects and diseases are affecting Colorado’s forests.

By examining specific symptoms of insect or disease damage, you can make a reasonable diagnosis of the problem and select the proper treatment.

If you are uncertain about the type of insect or disease or do not know how to treat them, contact your local CSFS Field Office to conduct a home-site assessment of the trees on your property.

Learn More About Insects & Diseases in Colorado


More insect and disease publications

2019 Forest Health Report Story Map

CSFS Forest Entomologist Dr. Dan West has produced an Esri Story Map for the 2019 Forest Health Report, which tells the story of how data was collected to compile the report, and offers users an interactive way to find out about forest conditions in their area.