Montrose Field Office – Insects & Diseases
Insects and diseases can pose serious threats to a forest’s health. Our foresters monitor insect and disease activity and trends, and respond to emerging threats to our communities’ forests.
Common Insect & Disease Concerns
By properly identifying the tree’s species and examining the specific symptoms of damage, you can make a reasonable diagnosis of the problem and select the proper treatment using this guide to Diagnosing Tree Disorders.
If your questions cannot be resolved with the information provided, please email the Montrose Field Office or call us at (970) 249-9051. Our foresters are available for consultation regarding insect and disease concerns.
Forest Insect & Disease Aerial Survey
The annual survey is led, coordinated and funded by the U.S. Forest Service. A small fixed-wing aircraft is flown between 1,000 to 1,500 feet above the treetops while surveyors mark on a map the location, number and identity of trees affected by insects or diseases. The CSFS has assisted in the aerial survey since the 1970s and began playing a larger role in 1997.
For more information, visit our Common Forest Insects & Diseases page.
Statewide Publications
Local Insects & Diseases by Tree Species

Ponderosa Pine
- Dwarf Mistletoe Management (127 KB PDF)
- Mountain Pine Beetle (362 KB PDF)
- Ips Bark Beetles (298 KB PDF)
- Ponderosa Pine Needle Miners (623 KB PDF)
- Twig Beetle (109 KB PDF)
- Ponderosa Pine Budworm (624 KB PDF)
- Product Use to Prevent Mountain Pine Beetle (2.3 MB PDF)
Piñon Pine
- Piñon Pine Diseases and Insects (297 KB PDF)
- Ips Beetle Update (24 KB PDF)
- Ips Bark Beetles (298 KB PDF)
- Tiger Moth Caterpillar – U.S. Forest Service
Aspen

- Aspen and Popular Leaf Spots (203 KB PDF)
- Sudden Aspen Decline in Colorado (2.3 MB PDF)
- What’s Happening in Colorado’s Aspen Forests? (1 MB PDF)
- Cankers on Western Quaking Aspen – U.S. Forest Service
- Cytospora Canker (87 KB PDF)
- Poplar Borer (115 KB PDF)
- Tent-Making Caterpillars (88 KB PDF)
- Poplar Twig Gall (144 KB PDF)
Douglas-fir
- Douglas-fir Beetle – 2016 Quick Guide (561 KB PDF)
- Douglas-fir Tussock Moth – 2015 Quick Guide (5.4 MB PDF)
- Dwarf Mistletoe Management ( 127 KB PDF)
- Using MCH to Protect Trees and Stands from Douglas-fir Beetle Infestation – U.S. Forest Service
- Western Spruce Budworm (5.5 MB PDF)
White Fir

- Fir Engraver – U.S. Forest Service Management Guide
- Fir Engraver – U.S. Forest Service Leaflet
- Western Spruce Budworm (5.5 MB PDF)
Spruce
- Spruce Beetle Quick Guide (493 KB PDF)
- Cooley Spruce Gall Aphid – U.S. Forest Service
Subalpine Fir
- Western Balsam Bark Beetle – U.S. Forest Service
- Armillaria Root Disease – U.S. Forest Service
- Western Spruce Budworm (5.5 MB PDF)
Ornamental Tree Insects, Diseases and Disorders
- Emerald Ash Borer Quick Guide (6 MB PDF)
- Gypsy Moth (409 KB PDF)
- Thousand Cankers Disease of Black Walnut (335 KB PDF)
- Aphids on Shade Trees and Ornamentals (43 KB PDF)
- Honeylocust Diseases (100 KB PDF)
- Leafmining Insects (128 KB PDF)
Other
- Magnesium Chloride Toxicity in Trees (1 MB PDF)
- Bacterial Wetwood (176 KB PDF)
- Bark Beetles: Are Your Trees at Risk? (2.4 MB PDF)