A mountain pine beetle brood does not cluster around parent adults

Photo Credit

USDA photo by Jose Negron

Mountain pine beetle-caused tree mortality in a lodgepole pine stand in Snowy Range, Wyoming. Note trees showing different stages of attacks. Understanding these small-scale spatial patterns needs clarification.

Developing tools for managing bark beetles is of relevance to public and private land managers, but tools and decisions need to be based on the thorough understanding of biological processes of the insect and how these processes may be affected by climate change. Understanding spatial clustering of mountain pine beetle attacks at various scales needs clarification as managers work to keep forests healthy.

Mountain pine beetles generally have a one-year life cycle, where larvae develop during the winter and emerge as in the spring to attack trees. However, some adult mountain pine beetles survive over winter and re-emerge early in their second spring to attack trees before the new generation of beetles emerges. Previously, it wasunknown whether these adults aided the new generation in finding host trees to attack.

In a new study, scientists followed early-emerging adult beetles and late-emerging brood beetles to examine the locations and clustering of the trees each group attacked. They found evidence of clustering of attacked trees within each generation, but no evidence of clustering of trees that were attacked by both groups.

This is the first quantitative small-scale analysis of spatial patterning of trees attacked by mountain pine beetle early-emerging parent adults and later-emerging brood adults.