Increasing and epidemic populations of the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae) were detected and evaluated in the southcentral Black Hills. Mortality of ponderosa pine, Pinus ponderosa Dougl. ex Laws., in the area increased each year since 1988 and was six times greater in 1991 than in 1989. Survey results indicate an average of 29 trees killed per acre by this bark beetle from 1989 through 1991 in the Bearhouse project area. Infestation is especially concentrated in the Bear Mountain Basin area, where between 27 and 103 trees per acre have been killed, and a large beetle population is expected to emerge in August 1992. Bark samples of overwintering larvae collected from 54 trees at 11 sample sites averaged 23% live brood; heavy winter kill of larvae was apparent. Live brood averaged 7.6 per 0.25 sq. ft. overall, but ranged from 1.5 to 18.8 per 0.25 sq. ft. for different plots. In August 1992, populations of MPB are expected to remain stable or decline slightly at most sites, while at least a couple sites are expected to increase potentially as much as 2-fold. Stands throughout the evaluated area have a moderate to high risk of attack by mountain pine beetle and are near or within areas currently under moderate to severe beetle pressure. Strategies to mitigate the impact of this epidemic are proposed.
- mountain pine beetle,
- ponderosa pine,
- Black Hills
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