2014 Highlights from the Black Hills Aerial Photography Interpretation Project

Newly released analysis of high resolution aerial photography of the Black Hills of South Dakota and northeastern Wyoming reveals that the mountain pine beetle epidemic is continuing. However, there are signs that the epidemic is slowing.  Approximately 16,500 acres were identified with new trees fading from mountain pine beetles’ prior year attacks, compared to 34,000 acres in 2013.  About 15,600 of the affected 2014 acres occurred in South Dakota in Custer, Lawrence, Meade and Pennington counties and approximately 900 acres of new tree mortality were identified in the western Black Hills in Crook and Weston counties in Wyoming.

Analyses of high resolution aerial photography taken since 2010, indicates over 111,000 acres have been affected by the mountain pine beetle epidemic.  When combined with less precise maps sketched by human observers in aircraft from 1996 – 2009, it is estimated that over the last 18 years, 438,000 acres have been affected to varying degrees by mountain pine beetle on the Black Hills National Forest and adjacent lands (Figure 1).

Mountain pine beetle brood surveys were conducted at 15 locations by US Forest Service entomologists in July, 2014.  Results showed mostly static to decreasing populations.  Numbers of larvae in sampled trees have dropped significantly from when the epidemic was rapidly expanding through the early 2000’s.

US Forest Service entomologists also conducted extensive ground surveys of new and prior year infested trees after the 2014 beetle flight period.  Results indicate that overall beetle populations are declining, but there are still several areas of significant beetle activity.  Beetle activity was classified for each survey line as low, moderate or high, with low being less than 3 trees per acre, moderate as 3-9 trees per acre and high being 10 or more trees per acre (Figure 2).  Based on these categories, 60% of areas are low, 23% moderate and 17% high.  Notable areas of high activity were found west of Lead in the north and west of Hill City in the south.  Many forested areas that survived within the area burned in 2000 by the Jasper Fire are now being attacked by mountain pine beetles.

Although both aerial photo analysis and ground surveys show overall mountain pine beetle populations slowly declining from prior years, there are areas in the Black Hills that continue to be at high risk for mountain pine beetle expansion, especially in the west central part of the Hills near the South Dakota/Wyoming state line, the northwest corner of the Hills and southeast of Custer. 

Active forest management and removal of infested trees are helping to reduce populations in some areas and thinning forests supports resistance to beetle attack.  Forest managers report that non-commercial treatment of infested trees, timber harvest and commercial thinning are making a difference (Figures 3 and 4).

red dots on mapFigure 1. Mountain pine beetle activity on the Black Hills National Forest 1996-2014

red blue yellow dots on map of Black Hills National ForestFigure 2. 2014 mountain pine beetle sample points and associated beetle infestation level (low, medium and high) in the Black Hills National Forest.(USFS Forest Health Protection, Rapid City Service Center).

mountains with pine beetle killed trees with no needles mixed in with green forestFigure 3. Mountain pine beetle caused tree mortality surrounding thinning treatments on Flag Mountain in the Black Hills. (Photo: Blaine Cook)

aerial view of beetle killed trees removed leaving only sparse green forestFigure 4. Thinned forest area in mountain pine beetle affected forests near Custer Peak in the Black Hills.  (Photo:  Ken Marchand)