Mountain Pine Beetle

Region 2 Beetle Information

FAQ - Mountain Pine Beetle

2016 Forest Health Report

Beetle Biology

The mountain pine beetle (Dendroctonus ponderosae) is a native insect and is the most significant cause of mortality in ponderosa pine in the Black Hills. In the Black Hills, the mountain pine beetle has one generation per year and the adult flight period to new host trees typically occurs in July and August, peaking in early August. Larvae overwinter under the outer bark of host trees. Beetle maturation is completed the following spring. Timing of the life cycle guided treatments done under this strategy. The adult beetles host several blue staining fungi that they carry to their new host newly infested trees. The combined efforts of these two organisms, the beetle and the fungi, are why a tree dies within a year of the attack.

Epidemic History and Beetle Trends

Mountain pine beetle populations are generally at endemic levels, killing and reproducing in stressed or weakened trees, such as those struck by lightning or affected by root disease. For reasons not fully understood, beetle populations can increase dramatically to epidemic levels. Populations can be categorized as endemic, incipient or epidemic depending on the number of infested trees per acre (Schmid et al.  2007). As a native species, the mountain pine beetle has always been a part of the Black Hills forest ecosystem, with periodic epidemics. The first, and largest, record-ed epidemic in the Black Hills occurred from the late 1890’s through the early 1900’s and killed an estimated 90 percent of merchantable timber. Epidemics also occurred in the 1930’s, 1940’s, 1960’s and 1970’s, each lasting 8-20 years. The current epidemic began in 1996 and returned to endemic status in 2016. 



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