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.
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
Mountain Pine Beetle
Spruce Beetle
Douglas-fir Beetle
Western Balsam Bark Beetle
Western Spruce Budworm
Mountain Pine Beetle
| 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected | |
| Colorado | 2,400 | 3,100 | 3,383,000 | 3,385,000 |
| Wyoming | 70 | 550 | 2,040,000 | 2,040,000 |
| South Dakota | 40 | 330 | 430,000 | 433,000 |
| Nebraska | 0 | 0 | 470 | 470 |
| Colorado County | 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected |
| Adams | 0 | 0 | 1 | 1 |
| Alamosa | 0 | 2 | 420 | 420 |
| Archuleta | 0 | 0 | 16,000 | 16,000 |
| Boulder | 9 | 20 | 140,000 | 140,000 |
| Chaffee | 490 | 130 | 84,000 | 84,000 |
| Clear Creek | 40 | 240 | 82,000 | 82,000 |
| Conejos | 1 | 0 | 4,800 | 4,800 |
| Costilla | 0 | 0 | 4,600 | 4,600 |
| Custer | 0 | 10 | 37,000 | 37,000 |
| Delta | 0 | 2 | 8 | 9 |
| Dolores | 0 | 5 | 1,200 | 1,200 |
| Douglas | 5 | 8 | 34,000 | 34,000 |
| Eagle | 0 | 0 | 194,000 | 194,000 |
| El Paso | 80 | 100 | 13,000 | 14,000 |
| Elbert | 1 | 30 | 540 | 570 |
| Fremont | 20 | 90 | 35,000 | 35,000 |
| Garfield | 8 | 0 | 11,000 | 11,000 |
| Gilpin | 80 | 170 | 57,000 | 57,000 |
| Grand | 0 | 4 | 581,000 | 581,000 |
| Gunnison | 1,300 | 1,100 | 6,600 | 7,400 |
| Hinsdale | 0 | 0 | 3,200 | 3,200 |
| Huerfano | 0 | 60 | 26,000 | 26,000 |
| Jackson | 30 | 0 | 366,000 | 366,000 |
| Jefferson | 70 | 410 | 36,000 | 36,000 |
| La Plata | 0 | 0 | 12,000 | 12,000 |
| Lake | 0 | 0 | 11,000 | 11,000 |
| Larimer | 0 | 1 | 809,000 | 809,000 |
| Las Animas | 0 | 70 | 13,000 | 13,000 |
| Mesa | 0 | 140 | 6,000 | 6,100 |
| Mineral | 0 | 0 | 790 | 790 |
| Moffat | 0 | 0 | 16,000 | 16,000 |
| Montezuma | 0 | 0 | 690 | 690 |
| Montrose | 0 | 250 | 3,600 | 3,800 |
| Ouray | 0 | 6 | 2,000 | 2,000 |
| Park | 260 | 180 | 138,000 | 138,000 |
| Pitkin | 10 | 3 | 22,000 | 22,000 |
| Pueblo | 0 | 0 | 21,000 | 21,000 |
| Rio Blanco | 0 | 0 | 44,000 | 44,000 |
| Rio Grande | 0 | 0 | 3,400 | 3,400 |
| Routt | 0 | 0 | 346,000 | 346,000 |
| Saguache | 40 | 50 | 43,000 | 43,000 |
| San Miguel | 0 | 0 | 4,100 | 4,100 |
| Summit | 0 | 0 | 143,000 | 143,000 |
| Teller | 0 | 50 | 9,900 | 9,900 |
| National Forest | 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected |
| Arapaho-Roosevelt | 5 | 90 | 1,167,000 | 1,167,000 |
| Bighorn | 50 | 100 | 27,000 | 27,000 |
| Black Hills | 60 | 650 | 452,000 | 452,000 |
| Grand Mesa-Uncompahgre-Gunnison | 1,000 | 1,400 | 19,000 | 20,000 |
| Medicine Bow-Routt | 30 | 6 | 1,401,000 | 1,401,000 |
| Pike-San Isabel | 800 | 430 | 304,000 | 304,000 |
| Rio Grande | 40 | 40 | 38,000 | 38,000 |
| San Juan | 1 | 5 | 28,000 | 28,000 |
| Shoshone | 5 | 10 | 697,000 | 697,000 |
| White River | 20 | 4 | 386,000 | 386,000 |
Spruce Beetle
| 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected | |
| Colorado | 29,000 | 19,000 | 1,907,000 | 1,912,000 |
| South Dakota | 0 | 0 | 130 | 130 |
| Wyoming | 5,000 | 2,800 | 577,000 | 578,000 |
| Colorado County | 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected |
| Alamosa | 340 | 0 | 3,500 | 3,500 |
| Archuleta | 0 | 370 | 58,000 | 58,000 |
| Boulder | 70 | 70 | 6,700 | 6,700 |
| Chaffee | 6,200 | 4,400 | 46,000 | 47,000 |
| Clear Creek | 8 | 30 | 2,000 | 2,000 |
| Conejos | 20 | 50 | 105,000 | 105,000 |
| Costilla | 690 | 890 | 19,000 | 19,000 |
| Custer | 830 | 230 | 39,000 | 39,000 |
| Delta | 20 | 70 | 35,000 | 35,000 |
| Dolores | 370 | 270 | 29,000 | 29,000 |
| Douglas | 0 | 0 | 360 | 360 |
| Eagle | 40 | 9 | 6,400 | 6,500 |
| El Paso | 40 | 20 | 530 | 540 |
| Fremont | 0 | 0 | 23,000 | 23,000 |
| Garfield | 1 | 40 | 4,500 | 4,500 |
| Gilpin | 0 | 0 | 100 | 100 |
| Grand | 3,000 | 1,600 | 75,000 | 76,000 |
| Gunnison | 5,200 | 1,400 | 146,000 | 146,000 |
| Hinsdale | 2,800 | 1,400 | 277,000 | 277,000 |
| Huerfano | 720 | 250 | 16,000 | 16,000 |
| Jackson | 240 | 80 | 94,000 | 94,000 |
| Jefferson | 0 | 0 | 120 | 120 |
| La Plata | 2,300 | 2,600 | 46,000 | 47,000 |
| Lake | 40 | 10 | 830 | 840 |
| Larimer | 100 | 20 | 95,000 | 95,000 |
| Las Animas | 20 | 20 | 1,100 | 1,100 |
| Mesa | 30 | 520 | 51,000 | 51,000 |
| Mineral | 60 | 30 | 236,000 | 236,000 |
| Moffat | 0 | 0 | 730 | 730 |
| Montezuma | 40 | 110 | 6,800 | 6,900 |
| Montrose | 0 | 1 | 710 | 710 |
| Ouray | 20 | 40 | 4,200 | 4,200 |
| Park | 1,600 | 1,100 | 21,000 | 22,000 |
| Pitkin | 160 | 8 | 13,000 | 13,000 |
| Pueblo | 250 | 70 | 4,500 | 4,500 |
| Rio Blanco | 0 | 0 | 3,700 | 3,700 |
| Rio Grande | 0 | 10 | 94,000 | 94,000 |
| Routt | 2 | 0 | 86,000 | 86,000 |
| Saguache | 80 | 0 | 218,000 | 218,000 |
| San Juan | 2,700 | 2,900 | 30,000 | 30,000 |
| San Miguel | 270 | 610 | 5,500 | 6,000 |
| Summit | 3 | 0 | 1,700 | 1,700 |
| Teller | 290 | 90 | 3,300 | 3,400 |
| National Forest | 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected |
| Arapaho-Roosevelt | 350 | 270 | 91,000 | 91,000 |
| Bighorn | 190 | 170 | 24,000 | 24,000 |
| Black Hills | 0 | 0 | 130 | 130 |
| Grand Mesa-Uncompahgre-Gunnison | 7,400 | 3,600 | 357,000 | 358,000 |
| Medicine Bow-Routt | 300 | 680 | 314,000 | 315,000 |
| Pike-San Isabel | 9,900 | 6,200 | 147,000 | 148,000 |
| Rio Grande | 400 | 60 | 624,000 | 624,000 |
| San Juan | 3,600 | 5,700 | 267,000 | 269,000 |
| Shoshone | 4,700 | 2,600 | 381,000 | 382,000 |
| White River | 210 | 100 | 32,000 | 32,000 |
Douglas-fir Beetle
| 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected | |
| Colorado | 9,700 | 17,000 | 466,000 | 480,000 |
| Wyoming – R2 | 330 | 350 | 331,000 | 331,000 |
| Colorado County | 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected |
| Alamosa | 70 | 30 | 250 | 280 |
| Archuleta | 280 | 410 | 40,000 | 40,000 |
| Boulder | 0 | 0 | 290 | 290 |
| Chaffee | 320 | 920 | 3,600 | 4,500 |
| Clear Creek | 2 | 2 | 1,100 | 1,100 |
| Conejos | 5 | 90 | 6,100 | 6,200 |
| Costilla | 50 | 310 | 3,200 | 3,500 |
| Custer | 890 | 620 | 8,300 | 8,700 |
| Delta | 8 | 40 | 4,200 | 4,200 |
| Dolores | 210 | 480 | 5,900 | 6,300 |
| Douglas | 90 | 1 | 46,000 | 46,000 |
| Eagle | 780 | 400 | 14,000 | 14,000 |
| El Paso | 50 | 20 | 5,900 | 5,900 |
| Elbert | 0 | 0 | 1 | 1 |
| Fremont | 640 | 1,100 | 17,000 | 18,000 |
| Garfield | 440 | 290 | 37,000 | 37,000 |
| Gilpin | 0 | 0 | 70 | 70 |
| Grand | 20 | 6 | 1,400 | 1,400 |
| Gunnison | 460 | 3,000 | 38,000 | 41,000 |
| Hinsdale | 520 | 170 | 17,000 | 17,000 |
| Huerfano | 370 | 410 | 3,600 | 4,000 |
| Jackson | 0 | 0 | 590 | 590 |
| Jefferson | 160 | 9 | 12,000 | 12,000 |
| La Plata | 680 | 1,200 | 18,000 | 19,000 |
| Lake | 1 | 6 | 120 | 120 |
| Larimer | 3 | 300 | 2,500 | 2,800 |
| Las Animas | 30 | 90 | 6,300 | 6,400 |
| Mesa | 440 | 490 | 10,000 | 10,000 |
| Mineral | 230 | 930 | 13,000 | 14,000 |
| Moffat | 40 | 20 | 1,100 | 1,100 |
| Montezuma | 70 | 230 | 8,300 | 8,400 |
| Montrose | 70 | 490 | 11,000 | 11,000 |
| Ouray | 60 | 60 | 19,000 | 19,000 |
| Park | 20 | 50 | 1,800 | 1,900 |
| Pitkin | 670 | 550 | 15,000 | 15,000 |
| Pueblo | 120 | 20 | 4,900 | 4,900 |
| Rio Blanco | 230 | 170 | 9,900 | 10,000 |
| Rio Grande | 180 | 930 | 10,000 | 11,000 |
| Routt | 110 | 60 | 5,100 | 5,100 |
| Saguache | 1,100 | 2,900 | 43,000 | 46,000 |
| San Juan | 10 | 50 | 2,000 | 2,100 |
| San Miguel | 310 | 370 | 17,000 | 18,000 |
| Summit | 20 | 20 | 530 | 550 |
| Teller | 1 | 4 | 1,800 | 1,800 |
| National Forest | 2022 Acres Affected | 2023 Acres Affected | 1996-2022 Cumulative Acres Affected | 1996-2023 Cumulative Acres Affected |
| Arapaho-Roosevelt | 10 | 310 | 2,400 | 2,700 |
| Bighorn | 0 | 20 | 27,000 | 27,000 |
| Grand Mesa-Uncompahgre-Gunnison | 1,100 | 2,800 | 70,000 | 72,000 |
| Medicine Bow-Routt | 20 | 50 | 14,000 | 15,000 |
| Pike-San Isabel | 1,800 | 2,900 | 74,000 | 77,000 |
| Rio Grande | 1,300 | 4,700 | 49,000 | 52,000 |
| San Juan | 1,200 | 2,200 | 86,000 | 88,000 |
| Shoshone | 260 | 300 | 204,000 | 204,000 |
| White River | 1,600 | 1,200 | 37,000 | 38,000 |
Western Balsam Bark Beetle
| 2022 Acres Affected | 2023 Acres Affected | |
| Colorado | 35,000 | 27,000 |
| Wyoming – R2 | 5,900 | 4,100 |
| Colorado County | 2022 Acres Affected | 2023 Acres Affected |
| Archuleta | 20 | 1 |
| Boulder | 570 | 290 |
| Chaffee | 100 | 40 |
| Clear Creek | 580 | 680 |
| Conejos | 6 | 0 |
| Custer | 0 | 2 |
| Delta | 110 | 470 |
| Dolores | 230 | 780 |
| Eagle | 3,700 | 2,400 |
| Garfield | 1,500 | 1,600 |
| Gilpin | 210 | 50 |
| Grand | 2,500 | 1,500 |
| Gunnison | 1,200 | 1,700 |
| Hinsdale | 4 | 8 |
| Huerfano | 0 | 3 |
| Jackson | 2,300 | 1,300 |
| La Plata | 1 | 30 |
| Lake | 790 | 610 |
| Larimer | 780 | 530 |
| Las Animas | 0 | 10 |
| Mesa | 2,400 | 3,800 |
| Mineral | 40 | 40 |
| Moffat | 1,500 | 750 |
| Montezuma | 90 | 220 |
| Montrose | 300 | 120 |
| Ouray | 150 | 290 |
| Park | 140 | 70 |
| Pitkin | 830 | 850 |
| Rio Blanco | 5,100 | 3,400 |
| Rio Grande | 7 | 1 |
| Routt | 5,100 | 3,400 |
| San Juan | 20 | 60 |
| San Miguel | 50 | 420 |
| Summit | 1,400 | 960 |
| National Forest | 2022 Acres Affected | 2023 Acres Affected |
| Arapaho-Roosevelt National Forests | 3,200 | 2,100 |
| Bighorn National Forest | 180 | 150 |
| Grand Mesa, Uncompahgre, Gunnison National Forests | 3,600 | 5,600 |
| Medicine Bow-Routt National Forests | 9,800 | 5,200 |
| Pike-San Isabel National Forests | 980 | 730 |
| Rio Grande National Forest | 50 | 50 |
| San Juan National Forest | 230 | 990 |
| Shoshone National Forest | 510 | 410 |
| White River National Forest | 9,600 | 6,800 |
Western Spruce Budworm
| 2022 Acres Affected | 2023 Acres Affected | |
| Colorado | 112,000 | 202,000 |
| Wyoming- R2 | 33,000 | 18,000 |
| Colorado County | 2022 Acres Affected | 2023 Acres Affected |
| Archuleta | 180 | 8,800 |
| Chaffee | 8,300 | 8,200 |
| Conejos | 1,000 | 950 |
| Costilla | 570 | 1,700 |
| Custer | 180 | 370 |
| Delta | 1,400 | 18,000 |
| Dolores | 1,800 | 860 |
| Douglas | 10 | 0 |
| Eagle | 0 | 980 |
| El Paso | 200 | 390 |
| Fremont | 9,300 | 3,300 |
| Garfield | 430 | 7,100 |
| Gilpin | 0 | 60 |
| Grand | 650 | 630 |
| Gunnison | 31,000 | 45,000 |
| Hinsdale | 1,700 | 2,900 |
| Huerfano | 130 | 1,100 |
| Jackson | 0 | 460 |
| Jefferson | 480 | 650 |
| La Plata | 420 | 4,600 |
| Lake | 590 | 930 |
| Larimer | 260 | 120 |
| Las Animas | 80 | 3,900 |
| Mesa | 2,300 | 18,000 |
| Mineral | 1,700 | 1,000 |
| Moffat | 180 | 1,200 |
| Montezuma | 470 | 1,100 |
| Montrose | 150 | 5,100 |
| Ouray | 1,700 | 1,800 |
| Park | 27,000 | 27,000 |
| Pitkin | 2,800 | 15,000 |
| Pueblo | 0 | 20 |
| Rio Blanco | 0 | 3,600 |
| Rio Grande | 80 | 290 |
| Routt | 510 | 4,700 |
| Saguache | 9,600 | 9,400 |
| San Juan | 60 | 140 |
| San Miguel | 650 | 560 |
| Summit | 350 | 350 |
| Teller | 6,300 | 1,200 |
| National Forest | 2022 Acres Affected | 2023 Acres Affected |
| Arapaho-Roosevelt National Forests | 310 | 190 |
| Bighorn National Forest | 1,300 | 760 |
| Grand Mesa, Uncompahgre, and Gunnison National Forests | 27,000 | 74,000 |
| Medicine Bow-Routt National Forest | 2,900 | 8,300 |
| Pike-San Isabel National Forests | 30,000 | 31,000 |
| Rio Grande National Forest | 3,000 | 4,100 |
| San Juan National Forest | 3,000 | 16,000 |
| Shoshone National Forest | 16,000 | 13,000 |
| White River National Forest | 4,500 | 29,000 |