Aerial Detection Survey: 2016 Wyoming

Aerial Detection Survey: 2016 Wyoming Highlights Mountain Pine Beetle Mountain pine beetle activity has returned to low levels across Wyoming after large epidemics affected approximately 3.5 million acres beginning in the late 1990’s. Aerially detected outbreaks statewide declined to 6,300 acres in 2016. Mountain pine beetle activity was noted on about 3,000 acres of high elevation limber and whitebark pines, primarily in western Wyoming, where it had not previously been observed during the recent epidemic (Figures 1 and 2). Ground surveys of mountain pine beetle activity in the ponderosa pines in northeastern Wyoming’s Black Hills indicate significant improvement, although scattered tree mortality from engraver beetles is visible (Figure 3). This area has been monitored by detailed aerial photo interpretation in cooperation with Wyoming State Forestry Division and neighboring forestry agencies and industries in South Dakota. South central Wyoming including Medicine Bow National Forest and adjacent lands in Carbon, Albany, Converse, Natrona, Laramie and Platte counties - Mountain pine beetle activity in this area remains low with about 600 acres of limber pine affected in 2016. Dead standing trees are common, but no new activity was observed in lodgepole or ponderosa pines. Western Wyoming including Shoshone, Wasatch-Cache and Bridger-Teton National Forests and adjacent lands in Lincoln, Sublette, Uinta, Fremont, Park and Teton counties- Mountain pine beetle activity declined from 30,000 acres in 2015 to 4,100 acres in 2016. North central Wyoming including Bighorn National Forest and adjacent lands in Bighorn, Johnson, Sheridan and Washakie counties- Large areas of forest remain unaffected, yet susceptible, to mountain pine beetle. In 2016, mountain pine beetle was detected on about 700 acres. North east Wyoming including Black Hills National Forest and adjacent lands in Crook and Weston counties – Aerial photo interpretation has shown lower levels of mountain pine beetle- killed trees in recent years. 2016 photo analysis of affected acres is not yet available, but ground surveys indicate mountain pine beetle has returned to low levels. Ground and aerial observations do indicate elevated tree mortality from engraver beetles in some areas, such as Inyan Kara Mountain (Figure 3). Engraver beetles are often associated with drought conditions. Figure 1. Annual acres of observed mountain pine beetle activity in Wyoming. Not all areas are surveyed every year. Update Figure 2. Mountain pine beetle activity in Wyoming 2000 – 2016. Figure 3. Trees killed by engraver beetles on Inyan Kara Mountain in northeastern Wyoming. Photo: Ryan DeSantis Spruce Beetle Spruce beetle activity declined from 68,000 acres in 2015 to 34,000 acres in 2016 and occurred primarily in western Wyoming (Figure 4). New spruce mortality expanded onto 20,000 previously uninfested acres. Since 1996, 702,000 acres have been affected by spruce beetle statewide, leaving many areas of large dead standing spruce in higher elevations (Figure 5). South central Wyoming including Medicine Bow National Forest and adjacent lands in Carbon and Albany counties- Spruce beetle-killed trees were observed on about 240 acres in 2016. This occurred in areas where spruce beetle activity has been previously detected and large areas of dead standing spruce are common. A total of 120,000 acres in this area have been affected by spruce beetle since 1996. Western Wyoming including the Absaroka Mountains in and adjacent to the Shoshone and Bridger-Teton National Forests in Lincoln, Sublette, Uinta, Fremont, Hot Springs, Park and Teton counties - Spruce beetles continued to kill spruce on approximately 34,000 acres and many areas have few surviving mature spruce. Current activity is greatest in Teton, Sublette and Fremont counties. North central Wyoming including the Big Horn Mountains in Big Horn and Sheridan Counties- Approximately 160 acres of spruce beetle-caused tree mortality was observed. Figure 4. Annual acres of observed spruce beetle activity in Wyoming. Not all areas are surveyed every year. Figure 5. Spruce Beetle activity in Wyoming 2000 - 2016. Douglas-fir Beetle Past tree mortality from Douglas-fir beetle has been detected on over 430,000 acres, primarily during the early and mid-2000’s (Figure 6). But, it has remained at low levels for several years with only 100 acres affected in 2016. Figure 6. Douglas-fir mortality on the Bighorn National Forest’s Shell Canyon. Subalpine Fir Decline - Subalpine fir is widespread across Wyoming’s high elevation forest but intensity of tree mortality is often less (figure 7) than seen in associated spruce. Over successive years, accumulated mortality can become more noticeable (Figure 8). In 2016, 25,000 acres had varying levels of subalpine fir killed by western balsam bark beetle and associated fungi. Figure 7. Subalpine fir mortality is often detected at low levels across large acres. Figure Photo: Kendra Schotzko. Figure 8. Over time, low levels of subalpine fir mortality can accumulate into more significant levels of overstory mortality. Western spruce budworm Defoliation of Douglas-fir and some spruce by western spruce budworm was detected on over 211,000 acres, most notably in western Wyoming. Western spruce budworm larvae feed on the needles of Douglas-fir, subalpine fir and Engelmann spruce in the spring. Larval feeding can cause growth loss, top killing and tree mortality, if heavy defoliation (Figure 9) occurs for multiple years. Defoliation of large areas imparts a brownish cast to the forest (Figure 10). Figure 9. Shoshone (Clarks Fork) budworm, 2016. Photo: Kendra Schotzko. Figure 10. Budworm damage in the Powder River Basin, Wyoming, 2016. Photo: Al Dymerski .

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