Common Forest Insects & Diseases
Insects and diseases pose two of the most serious threats to a tree’s health. 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.
Common Insects & Diseases in Colorado
Current Insect & Disease Activity in Colorado
Explore where insects and diseases are currently affecting forests in Colorado. This map shows data from an aerial survey conducted by the Colorado State Forest Service and U.S. Forest Service.
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Forest Health Story Map
CSFS Forest Entomologist Dr. Dan West produces an Esri Story Map for the annual Forest Health Report. Explore the story map to learn how insect and disease data are collected during an annual aerial survey and find out more about forest conditions in your area.
Current Insect and Disease Activity by County and National Forest
Mt. Pine Beetle
Spruce Beetle
Douglas-fir Beetle
W. Balsam Bark Beetle
W. Spruce Budworm
Round-headed Pine Beetle
Mt. Pine Beetle
| 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected | |
|---|---|---|---|
| Colorado | 1,500 | 3,376,000 | 3,381,000 |
| Wyoming R2 | 140 | 2,039,000 | 2,039,000 |
| CO plus S.WY | 1,500 | 4,285,000 | 4,287,000 |
| South Dakota | 0 | 433,000 | 433,000 |
| Nebraska | 0 | 470 | 470 |
| Colorado County | 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected |
| Adams | 0 | 1 | 1 |
| Alamosa | 0 | 420 | 420 |
| Archuleta | 0 | 16,000 | 16,000 |
| Boulder | 5 | 140,000 | 140,000 |
| Chaffee | 290 | 83,000 | 84,000 |
| Clear Creek | 20 | 82,000 | 82,000 |
| Conejos | 1 | 4,800 | 4,800 |
| Costilla | 10 | 4,600 | 4,600 |
| Custer | 4 | 36,000 | 37,000 |
| Delta | 0 | 8 | 8 |
| Dolores | 0 | 1,200 | 1,200 |
| Douglas | 0 | 34,000 | 34,000 |
| Eagle | 9 | 194,000 | 194,000 |
| El Paso | 5 | 13,000 | 13,000 |
| Elbert | 0 | 540 | 540 |
| Fremont | 0 | 35,000 | 35,000 |
| Garfield | 1 | 11,000 | 11,000 |
| Gilpin | 70 | 56,000 | 57,000 |
| Grand | 0 | 581,000 | 581,000 |
| Gunnison | 760 | 4,900 | 5,600 |
| Hinsdale | 0 | 3,200 | 3,200 |
| Huerfano | 10 | 26,000 | 26,000 |
| Jackson | 50 | 364,000 | 366,000 |
| Jefferson | 40 | 36,000 | 36,000 |
| La Plata | 0 | 12,000 | 12,000 |
| Lake | 0 | 11,000 | 11,000 |
| Larimer | 0 | 809,000 | 809,000 |
| Las Animas | 0 | 13,000 | 13,000 |
| Mesa | 0 | 6,000 | 6,000 |
| Mineral | 0 | 790 | 790 |
| Moffat | 0 | 16,000 | 16,000 |
| Montezuma | 0 | 690 | 690 |
| Montrose | 70 | 3,500 | 3,600 |
| Ouray | 0 | 2,000 | 2,000 |
| Park | 90 | 138,000 | 138,000 |
| Pitkin | 0 | 22,000 | 22,000 |
| Pueblo | 0 | 21,000 | 21,000 |
| Rio Blanco | 0 | 44,000 | 44,000 |
| Rio Grande | 0 | 3,400 | 3,400 |
| Routt | 0 | 345,000 | 346,000 |
| Saguache | 60 | 43,000 | 43,000 |
| San Miguel | 0 | 4,000 | 4,100 |
| Summit | 0 | 143,000 | 143,000 |
| Teller | 6 | 9,900 | 9,900 |
| National Forest | 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected |
| Arapaho and Roosevelt National Forest | 30 | 1,167,000 | 1,167,000 |
| Bighorn National Forest | 40 | 27,000 | 27,000 |
| Black Hills National Forest | 0 | 452,000 | 452,000 |
| Grand Mesa, Uncompahgre, and Gunnison National Forest | 760 | 17,000 | 18,000 |
| Medicine Bow and Routt National Forest | 50 | 1,401,000 | 1,401,000 |
| Nebraska National Forest | 0 | 30 | 30 |
| Pike and San Isabel National Forest | 410 | 302,000 | 303,000 |
| Rio Grande National Forest | 60 | 37,000 | 38,000 |
| San Juan National Forest | 0 | 28,000 | 28,000 |
| Shoshone National Forest | 40 | 697,000 | 697,000 |
| White River National Forest | 10 | 386,000 | 386,000 |
Spruce Beetle
| 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected | |
|---|---|---|---|
| Colorado | 53,000 | 1,866,000 | 1,899,000 |
| Wyoming R2 | 15,000 | 571,000 | 576,000 |
| CO plus S.WY | 54,000 | 1,987,000 | 2,020,000 |
| South Dakota | 0 | 130 | 130 |
| Colorado County | 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected |
| Alamosa | 40 | 3,400 | 3,400 |
| Archuleta | 20 | 57,000 | 58,000 |
| Boulder | 500 | 6,300 | 6,700 |
| Chaffee | 12,000 | 38,000 | 44,000 |
| Clear Creek | 250 | 1,400 | 2,000 |
| Conejos | 300 | 105,000 | 105,000 |
| Costilla | 3,300 | 16,000 | 19,000 |
| Custer | 800 | 36,000 | 39,000 |
| Delta | 5 | 34,000 | 35,000 |
| Dolores | 2,200 | 27,000 | 29,000 |
| Douglas | 0 | 370 | 360 |
| Eagle | 30 | 6,300 | 6,400 |
| El Paso | 30 | 470 | 500 |
| Fremont | 0 | 23,000 | 23,000 |
| Garfield | 30 | 4,500 | 4,500 |
| Gilpin | 0 | 100 | 100 |
| Grand | 4,800 | 72,000 | 75,000 |
| Gunnison | 9,900 | 141,000 | 144,000 |
| Hinsdale | 4,600 | 276,000 | 277,000 |
| Huerfano | 2,300 | 13,000 | 16,000 |
| Jackson | 300 | 94,000 | 94,000 |
| Jefferson | 0 | 120 | 120 |
| La Plata | 1,700 | 43,000 | 45,000 |
| Lake | 90 | 690 | 790 |
| Larimer | 2,000 | 94,000 | 95,000 |
| Las Animas | 160 | 800 | 1,100 |
| Mesa | 3 | 51,000 | 51,000 |
| Mineral | 50 | 236,000 | 236,000 |
| Moffat | 0 | 730 | 730 |
| Montezuma | 6 | 6,700 | 6,800 |
| Montrose | 50 | 650 | 710 |
| Ouray | 460 | 3,600 | 4,200 |
| Park | 3,700 | 18,000 | 21,000 |
| Pitkin | 20 | 12,000 | 12,000 |
| Pueblo | 120 | 3,300 | 4,500 |
| Rio Blanco | 0 | 3,700 | 3,700 |
| Rio Grande | 5 | 94,000 | 94,000 |
| Routt | 5 | 85,000 | 86,000 |
| Saguache | 210 | 218,000 | 218,000 |
| San Juan | 2,800 | 28,000 | 29,000 |
| San Miguel | 240 | 5,200 | 5,300 |
| Summit | 20 | 1,600 | 1,700 |
| Teller | 80 | 2,800 | 3,100 |
| National Forest | 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected |
| Arapaho-Roosevelt National Forests | 970 | 90,000 | 91,000 |
| Bighorn National Forest | 440 | 23,000 | 23,000 |
| Black Hills National Forest | 0 | 130 | 130 |
| Grand Mesa, Uncompahgre, Gunnison National Forests | 14,000 | 349,000 | 355,000 |
| Medicine Bow-Routt National Forests | 560 | 297,000 | 314,000 |
| Pike-San Isabel National Forests | 19,000 | 118,000 | 145,000 |
| Rio Grande National Forest | 490 | 622,000 | 623,000 |
| San Juan National Forest | 4,800 | 262,000 | 265,000 |
| Shoshone National Forest | 14,000 | 376,000 | 380,000 |
| White River National Forest | 110 | 32,000 | 32,000 |
Douglas-fir Beetle
| State | 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected |
|---|---|---|---|
| Colorado | 8,000 | 450,000 | 458,000 |
| Wyoming R2 | 710 | 330,000 | 331,000 |
| CO plus S. WY | 8,600 | 465,000 | 474,000 |
| Colorado County | 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected |
| Alamosa | 10 | 180 | 190 |
| Archuleta | 100 | 39,000 | 40,000 |
| Boulder | 10 | 280 | 290 |
| Chaffee | 50 | 3,300 | 3,300 |
| Clear Creek | 5 | 1,100 | 1,100 |
| Conejos | 9 | 6,100 | 6,100 |
| Costilla | 50 | 3,100 | 3,200 |
| Custer | 460 | 6,900 | 7,500 |
| Delta | 20 | 4,200 | 4,200 |
| Dolores | 180 | 5,500 | 5,700 |
| Douglas | 90 | 45,000 | 46,000 |
| Eagle | 740 | 12,000 | 13,000 |
| El Paso | 130 | 5,700 | 5,900 |
| Elbert | 0 | 1 | 1 |
| Fremont | 180 | 16,000 | 16,000 |
| Garfield | 640 | 36,000 | 36,000 |
| Gilpin | 9 | 60 | 70 |
| Grand | 40 | 1,300 | 1,300 |
| Gunnison | 800 | 37,000 | 38,000 |
| Hinsdale | 220 | 16,000 | 16,000 |
| Huerfano | 150 | 3,100 | 3,300 |
| Jackson | 0 | 570 | 590 |
| Jefferson | 240 | 11,000 | 12,000 |
| La Plata | 110 | 18,000 | 18,000 |
| Lake | 0 | 120 | 120 |
| Larimer | 6 | 2,500 | 2,500 |
| Las Animas | 100 | 6,200 | 6,300 |
| Mesa | 700 | 9,100 | 9,600 |
| Mineral | 200 | 13,000 | 13,000 |
| Moffat | 30 | 1,000 | 1,100 |
| Montezuma | 80 | 8,100 | 8,200 |
| Montrose | 520 | 10,000 | 11,000 |
| Ouray | 360 | 19,000 | 19,000 |
| Park | 30 | 1,800 | 1,800 |
| Pitkin | 610 | 13,000 | 14,000 |
| Pueblo | 20 | 4,700 | 4,800 |
| Rio Blanco | 160 | 9,800 | 9,800 |
| Rio Grande | 90 | 9,900 | 9,900 |
| Routt | 90 | 5,000 | 5,000 |
| Saguache | 430 | 42,000 | 42,000 |
| San Juan | 10 | 2,000 | 2,000 |
| San Miguel | 330 | 17,000 | 17,000 |
| Summit | 10 | 510 | 520 |
| Teller | 6 | 1,800 | 1,800 |
| National Forest | 2021 Acres Affected | 1996-2019 Cumulative Acres Affected | 1996-2021 Cumulative Acres Affected |
| Arapaho-Roosevelt National Forests | 30 | 2,300 | 2,400 |
| Bighorn National Forest | 1 | 27,000 | 27,000 |
| Grand Mesa, Uncompahgre, and Gunnison National Forests | 1,900 | 67,000 | 69,000 |
| Medicine Bow-Routt National Forests | 470 | 14,000 | 14,000 |
| Pike-San Isabel National Forests | 980 | 72,000 | 73,000 |
| Rio Grande National Forest | 690 | 47,000 | 48,000 |
| San Juan National Forest | 460 | 85,000 | 85,000 |
| Shoshone National Forest | 130 | 204,000 | 204,000 |
| White River National Forest | 1,600 | 34,000 | 36,000 |
W. Balsam Bark Beetle
| State | 2021 Acres Affected |
|---|---|
| Colorado | 16,000 |
| Wyoming R2 | 11,000 |
| CO plus S.WY | 32,000 |
| Colorado County | 2021 Acres Affected |
| Archuleta | 5 |
| Boulder | 690 |
| Chaffee | 160 |
| Clear Creek | 1,100 |
| Conejos | 10 |
| Custer | 6 |
| Delta | 240 |
| Dolores | 150 |
| Eagle | 2,400 |
| Fremont | 20 |
| Garfield | 1,100 |
| Gilpin | 550 |
| Grand | 1,900 |
| Gunnison | 1,800 |
| Hinsdale | 10 |
| Jackson | 1,800 |
| Lake | 420 |
| Larimer | 1,100 |
| Mesa | 2,500 |
| Mineral | 80 |
| Moffat | 770 |
| Montezuma | 10 |
| Montrose | 350 |
| Ouray | 330 |
| Park | 370 |
| Pitkin | 680 |
| Rio Blanco | 3,400 |
| Rio Grande | 0 |
| Routt | 5,200 |
| Saguache | 0 |
| San Juan | 5 |
| San Miguel | 30 |
| Summit | 1,200 |
| National Forest | 2021 Acres Affected |
| Arapaho-Roosevelt National Forests | 4,400 |
| Bighorn National Forest | 20 |
| Grand Mesa, Uncompahgre, Gunnison National Forests | 4,300 |
| Medicine Bow-Routt National Forests | 6,400 |
| Pike-San Isabel National Forests | 980 |
| Rio Grande National Forest | 80 |
| San Juan National Forest | 100 |
| Shoshone National Forest | 180 |
| White River National Forest | 6,800 |
W. Spruce Budworm
| State | 2021 Acres Affected |
|---|---|
| Colorado | 92,000 |
| Wyoming- R2 | 39,000 |
| CO plus S.WY | 92,000 |
| Colorado County | 2021 Acres Affected |
| Alamosa | 50 |
| Archuleta | 0 |
| Chaffee | 8,300 |
| Conejos | 620 |
| Costilla | 990 |
| Custer | 500 |
| Delta | 0 |
| Dolores | 1,700 |
| Eagle | 0 |
| El Paso | 1,100 |
| Fremont | 10,000 |
| Garfield | 0 |
| Grand | 1,500 |
| Gunnison | 15,000 |
| Hinsdale | 1,600 |
| Huerfano | 500 |
| Jefferson | 130 |
| La Plata | 640 |
| Lake | 310 |
| Las Animas | 50 |
| Mesa | 0 |
| Mineral | 2,000 |
| Moffat | 60 |
| Montezuma | 1,900 |
| Montrose | 1,200 |
| Ouray | 540 |
| Park | 25,000 |
| Routt | 710 |
| Saguache | 12,000 |
| San Juan | 160 |
| San Miguel | 1,500 |
| Summit | 50 |
| Teller | 3,700 |
| National Forest | 2021 Acres Affected |
| Arapaho-Roosevelt National Forests | 10 |
| Bighorn National Forest | 2,000 |
| Grand Mesa, Uncompahgre, and Gunnison National Forests | 12,000 |
| Medicine Bow-Routt National Forest | 830 |
| Pike-San Isabel National Forests | 26,000 |
| Rio Grande National Forest | 4,800 |
| San Juan National Forest | 4,400 |
| Shoshone National Forest | 22,000 |
| White River National Forest | 30 |
Round-headed Pine Beetle
| Colorado County | 2021 Acres Affected |
|---|---|
| Dolores | 4,300 |
| La Plata | 120 |
| Montezuma | 230 |
| Montrose | 310 |
| San Miguel | 550 |
| National Forest | 2021 Acres Affected |
| San Juan National Forest | 4,500 |
| Grand Mesa, Uncompahgre and Gunnison National Forests | 1,900 |