Aerial Detection Survey: Highlights for 2012

Aerial Survey Results Documents

Mountain Pine Beetle

  • Mountain pine beetle has affected 3.4 million acres in Colorado since 1996.
  • The epidemic has slowed down in many areas of Colorado and Wyoming (Figure 1) as large pine trees have been depleted in the core outbreak areas.
  • Forested areas affected by mountain pine beetle expanded by 31,000 acres in Colorado, 53,000 acres in Wyoming and 11,000 acres in South Dakota.
  • In Colorado, mountain pine beetle was active on 264,000 acres in 2012 and 170,000 of that was in ponderosa pine.  This activity in ponderosa pine occurred primarily in the northern Front Range counties of Larimer with 164,000 acres and Boulder with 5,100 acres.  These numbers may have been higher but the High Park fire burned over 80,000 acres in Larimer County prior to our flights. Mountain pine beetle activity has slowed down along the southern and western fronts despite availability of susceptible host trees.
  • In Wyoming, mountain pine beetle was active on 129,000 acres statewide.  Pine forests on the Bighorn National Forest showed the lowest levels of mountain pine beetle activity in Wyoming’s National Forests.   MPB activity decreased on the Medicine Bow National Forest from 313,000 acres in 2011 to 13,000 acres in 2012.  Mountain pine beetle activity also decreased on the Shoshone National Forest from 139,000 acres in 2011 to 50,000 acres in 2012 and decreased on the Bridger-Teton National Forest from 86,000 acres to 15,000 acres.  It is primarily active in high elevation lodgepole and whitebark pine stands in the northwest part of the state.
  • Mountain pine beetle activity in the Black Hills of South Dakota and northeastern Wyoming was active on 31,000 acres in 2012 and has affected a total of 416,000 acres since 1996.
  • In Nebraska, mountain pine beetle activity documented in ponderosa pine on the Wildcat Hills in 2011 was not observed by the 2012 flights.  In 2012, nine acres of mountain pine beetle activity were observed.
graph showing pine beetle acres in colorado

Figure 1. Annual acres affected by mountain pine beetle in Region 2.


Spruce Beetle

  • Spruce beetle activity was detected on 311,000 acres in Colorado in 2012. Of these 183,000 acres are in areas not previously mapped as having spruce beetle activity (new acres). This increase of activity is indicative of a rapidly expanding outbreak (see Figure 2). In some areas, the outbreak has moved through entire drainages in the course of one year.  In the most heavily impacted drainages, nearly every mature spruce has been killed from the creek bottoms all the way up to the high elevation krummholz.
  • Since 1996, spruce beetle has affected 924,000 acres in Colorado.
  • In south central Colorado, spruce beetle epidemics expanded on the San Juan (19,000 new acres out of 39,000 active acres), Rio Grande (102,000 new out of 165,000 active acres), Grand Mesa (8000 new acres out of 24,000 active acres), Gunnison (34,000 new acres out of 44,000 active acres), and San Isabel (1,200 new acres out of 1,700 active acres) National Forests. Activity continues on the White River (3,000 active acres).
  • In northern Colorado spruce beetle caused new tree mortality along the Medicine Bow and Rabbit Ears Mountains and is active on 32,000 acres in Grand, Jackson, and Larimer Counties. Much of this activity is found from Cameron pass to Willow Creek pass and west along the Rabbit Ears Range.  Scattered pockets of spruce mortality continue to be observed on 1,200 acres in Routt County.  Relatively low levels of mortality continues to be observed 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 on the Medicine Bow National Forests and adjacent lands, spruce beetle activity is declining with a reduction in activity from 41,000 active acres in 2011 to 9,000 active acres in 2012 leaving behind areas of dead spruce on 117,000 acres where the outbreak has been active since 1996.
  • In northwestern Wyoming in the Shoshone and Bridger-Teton National Forests, spruce beetle killed spruce on 16,000 acres.  Spruce beetle has been active here for years 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 is confined in smaller localized areas in the northern Big Horn Mountains in Big Horn, Sheridan and Johnson Counties.
  • A substantial amount of windthrow occurred in the fall and winter of 2011 and 2012 in central Colorado in spruce and mixed conifer stands in areas where spruce beetle has not been observed in recent years. The 2012 ADS flights documented 117 blowdown polygons on a total of 4,100 acres in Colorado.  This is cause for concern as windthrown spruce provides prime breeding habitat for spruce beetles that can move into adjacent standing trees.
graph illustrating acres killed by spruce beetle in 2012 in colorado

Figure 2. Annual acres affected by spruce beetle in Region 2.


Douglas-fir beetle

  • Douglas-fir beetle activity was detected on 27,000 acres in Colorado.  Windthrown Douglas-fir in Colorado may provide breeding habitat for Douglas-fir beetle. 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.
  • Douglas-fir beetle activity affected only 1,100 acres in Wyoming.  Many areas have been previously affected by Douglas-fir beetle have many dead standing trees. 

Western balsam bark beetle

Western balsam bark beetle activity was detected on 221,000 acres in subalpine firs across Colorado and on 14,000 acres in the USFS R2 portion of Wyoming.  These infestations were generally widespread but kill fewer trees per acre than other bark beetles currently active in the state.  This tree mortality is often associated with root disease in these high elevation forests.

Western spruce budworm

  • Western spruce budworm activity increased in Colorado in 2012.  Aerial surveys detected 217,000 acres affected in the state in 2012. This insect is a defoliator that feeds on the new needles of white fir, Douglas-fir and less notably on spruce and subalpine fir.  Activity was found mainly on the San Isabel, San Juan, and Rio Grande National Forests.
  • In the USFS R2 portion of Wyoming, 16,000 acres of western spruce budworm damage was detected with activity concentrated in the NW corner of the state.   

Rusty Tussock Moth

In 2011, 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 had not previously been observed causing damage in the Rocky Mountain Region.  It usually occurs much further north and does not typically feed on pines.  Ground observations indicate that the population is still active but it was not visible from the air in 2012.

Aspen Conditions

The Region’s aspen forests continue to recover from dieback and tree mortality that peaked in 2008 following years of drought.