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.
Gunnison Field Office – Insects & Diseases
2020 Insect & Disease Activity in Colorado Forests
2020 Individual Insect Activity & Information
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.
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
The 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.
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
- Aspen Common Insects & Diseases
- Douglas-fir Beetle
- Douglas-fir Tussock Moth
- Dwarf Mistletoe
- Emerald Ash Borer
- Fir Engraver Beetle
- Ips Beetle
- Mountain Pine Beetle
- Spruce Beetle
- Western Spruce Budworm
- Aspen and Poplar Leaf Spots (203 KB PDF)
- Bark Beetles: Are Your Trees At Risk? (2.4 MB PDF)
- Diagnosing Tree Disorders (77 KB PDF)
- Douglas-fir Beetle – 2016 Quick Guide (561 KB PDF)
- Dwarf Mistletoe Management (127 KB PDF)
- Emerald Ash Borer – Quick Guide (6 MB PDF)
- Fir Engraver Beetle – Quick Guide (6.8 MB PDF)
- Landowner Guide to Living with Bark Beetles (2.7 MB PDF)
- Spraying Trees to Protect Against Mountain Pine Beetle (43 KB PDF)
- Spruce Beetle – 2014 Quick Guide (493 KB PDF)
- Western Spruce Budworm (5.5 MB PDF)