Aerial Detection Survey: 2011 Results
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Mountain Pine Beetle
• For all pine species (lodgepole pine, ponderosa pine, limber pine, whitebark, and bristlecone), mountain pine beetle has affected 3.3 million acres in Colorado, 3.3 million acres in Wyoming and 389,000 acres in South Dakota.
• The epidemic has slowed down in many areas of Colorado and Wyoming as the availability of large pine trees to attack has been depleted.
• The mountain pine beetle affected area in northern Colorado and southern Wyoming expanded by 140,000 acres in Colorado and 68,000 acres in southern Wyoming and has affected 4.2 million acres since 1996.
• In Colorado, mountain pine beetle was active on 752,000 acres in 2011 and 275,000 of that was in ponderosa pine. This activity in ponderosa pine occurred primarily in the northern Front Range Counties of Larimer with 254,000 acres and Boulder with 18,000 acres.
• In Wyoming, mountain pine beetle was active on 719,000 acres and epidemics expanded onto 167,000 previously uninfested acres statewide. Pine forests on the Bighorn National Forest showed the lowest levels of mountain pine beetle activity in Wyoming’s National Forests.
• Mountain pine beetle activity in the Black Hills of South Dakota and Wyoming increased from 22,000 acres to 44,000 acres to 67,000 over the last three years.
• Spruce beetle activity in Engelmann spruce was detected on 262,000 acres in Colorado and 76,000 acres in Wyoming in 2011. Since 1996, spruce beetle has affected 1.2 million acres in Colorado and Wyoming.
• In south central Colorado, spruce beetle epidemics expanded on the San Juan, Rio Grande and Grand Mesa National Forests, and are now being detected on the southern portions of the Gunnison National Forest and on the Wet Mountains in the San Isabel National Forest. Spruce beetle populations are rapidly expanding in some areas causing entire drainages to be infested in the course of one year. In some cases nearly every mature spruce has been killed in multiple drainages, from the creek bottoms all the way up to the high elevation krummholz.
• In northern Colorado spruce beetle caused new tree mortality along the Medicine Bow and Rabbit Ears Mountains in Grand, Jackson, and Larimer Counties, with scattered pockets of spruce mortality along various mountain ranges in Routt and Summit Counties of Colorado. Scattered mortality continues to occur in and adjacent to the Mt. Zirkel Wilderness in Routt County which lost much of the mature spruce to spruce beetles in the early 2000’s following a large windthrow event in 1997.
• In south central Wyoming, the spruce beetle continued at epidemic levels on the Sierra Madre, Snowy Range, and Medicine Bow Mountains in Albany and Carbon Counties.
• In northwestern Wyoming’s Absaroka Mountains in and adjacent to the Shoshone National Forest, spruce beetle continues to kill spruce and many areas have few surviving mature spruce remaining. Spruce beetle activity is more localized and slightly increasing in portions of the Wind River Range. In north central Wyoming spruce beetle caused tree mortality continues to be confined in localized areas in the northern Big Horn Mountains in Big Horn, Sheridan and Johnson Counties.
• Douglas-fir beetle impacted 25,000 acres in Colorado and 1,500 acres in Wyoming.
• Levels of Douglas-fir tree mortality vary widely from scattered mortality in some stands to almost the total loss of mature Douglas-fir in others.
Western Balsam Bark Beetle
• Western balsam bark beetle activity was detected on 180,000 acres in subalpine firs across Colorado and 35,000 acres of the Region2 portion of Wyoming. These infestations were generally widespread but kill fewer trees per acre than other bark beetles currently active in the Rocky Mountain Region. This tree mortality can also be associated with root disease in these high elevation forests.
Western Spruce Budworm
• Western Spruce Budworm activity continues to decline for a second year in southern Colorado. Aerial surveys detected only 90,000 acres affected in the state this year compared to 213,000 in 2010 and 382,000 acres in 2009. This insect is a defoliator that feeds on the new needles of white fir, Douglas-fir and less notably on spruce and subalpine fir.
Rusty Tussock Moth
• Aerial surveys detected over 2,000 acres of defoliation of lodgepole pine in Wyoming’s Big Horn Mountains caused by the Rusty Tussock Moth. This insect has not previously been observed causing damage in the Rocky Mountain Region. It usually occurs much further north and does not typically feed on pines.
• The Region’s aspen forests continue to recover from dieback and tree mortality that peaked in 2008 following years of drought.
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