Common Forest Insects & Diseases
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.
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. If you are uncertain about the type of insect or disease, or do not know how to treat them, contact your local CSFS forester to conduct a homesite assessment of the trees on your property.
2012 Forest Health Aerial Survey Results
On Feb. 6, 2013, the U.S. Forest Service and Colorado State Forest Service released the results of the annual aerial insect and disease survey in Colorado.
The survey indicates that the spread of the mountain pine beetle epidemic has slowed dramatically, while the spruce beetle outbreak is expanding.
Mountain Pine Beetle
- The mountain pine beetle epidemic expanded by 31,000 acres, down from last year's reported increase of 140,000 acres.
- This brings the total infestation to nearly 3.4 million acres in Colorado since the first signs of the outbreak in 1996.
- Most mature lodgepole pine trees have now been depleted within the initial mountain pine beetle epidemic area.
- However, the infestation remains active from Estes Park to Leadville.
- In contrast, the spruce beetle outbreak is expanding, with 183,000 new acres detected in 2012.
- This brings the total acreage affected since 1996 to nearly 1 million acres (924,000).
- Areas experiencing the most significant activity are on the San Juan and Rio Grande National Forests in southern Colorado.
- Spruce beetles typically attack spruce trees downed by high winds. Once the populations of spruce beetles build up in the fallen trees, the stressed trees surrounding them offer little resistance to attack.
- Similar to mountain pine beetle, the increase in spruce beetle activity is due to factors that increase tree stress, including densely stocked stands, ongoing drought conditions and warmer winters.
Aerial survey maps and related materials are available on the USFS Region 2 website.
Learn More About Common Forest Insects and Diseases
- Mountain Pine Beetle
- Ips Beetle
- Dwarf Mistletoe
- Common Insects & Diseases of Aspen
- Spruce Bark Beetle
- Western Spruce Budworm
- Insect & Disease Publications
2012 Forest Health Report
- 2012 Report on the Health of Colorado's Forests (3.9 MB PDF)
Aerial Survey Maps from the 2012 Report
- 2012 Insect & Disease Activity in Colorado Forests (164 KB PDF)
- 1996-2012 Progression of Forest Insect & Disease in Colorado (205 KB PDF)
CSFS Insect & Disease Quarterly Reports
- November 2011 (369 KB PDF)
- May 2011 (2.7 MB PDF)
- February 2011 (2.3 MB PDF)
- November 2010 (291 KB PDF)
- August 2010 (373 KB PDF)
- May 2010 (690 KB PDF)
- February 2010 (396 KB PDF)
- November 2009 (2.3 MB PDF)