Douglas Fir Bark BeetleThe Douglas fir bark beetle enters the bark where it introduces a fungi and creates galleries in the phloem - the layer under the bark that transports nutrients from the leaves throughout the tree. The galleries serve as habitat for the beetle larvae which feeds on the phloem. When mature the beetles exit the trees to find a new "host" tree.When a region is not in a drought a healthy tree can "pitch-out" an attacking bark beetle with sap. The beetles can be successful when a tree is stressed by drought, disease, or old age, or when the beetle population overwhelms a tree. In many cases, the fungi introduced by the beetle clogs the phloem and kills the tree.The Forest Service ResponseThis hillside of dead trees was considered to be a wildfire hazard. Public campgrounds, private cabins, and the watershed were at risk. To reduce the wildfire risk, the Forest Service cuts a "fuel break" beginning where the trees regenerated after the 1959 tornado. Commercial trees were harvested and smaller trees and underbrush were removed by small prescribed fires.To protect the Shell Falls Visitor Center the Forest Service used "anti-aggregative" pheromones to deter bark beetles. Beetles normally use pheromones to attract mates or send messages. The man-made pheromones reduce beetle attacks by sending the message, "this tree is full - go someplace else," thereby protecting the trees near the visitor center.Many of the majestic Douglas fir trees in Shell Canyon were killed between 2002 and 2006 from the Douglas fir bark beetle.After years of drought many of the 150-200 year old Douglas fir trees became less resistant to the relentless attack from the bark beetles.
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