The mountain pine beetle tunnels into the trunk and lateral branches 6″ or more in diameter, feeding on the inner bark, disrupting the flow of water and nutrients in the tree. The beetles also spread blue stain fungus which also disrupts the flow of water and nutrients. The combination of beetle and fungus often kills the tree within a few weeks, but it may take almost a year for the needles to turn red./span>
Mountain pine beetles are the most impactful insect pest the pine forests of the Rocky Mountain states. They can kill millions of trees during an epidemic, which occur about every 10 to 30 years. The mountain pine beetle attacks mostly stressed, mature (over 8″ in diameter) ponderosa pine and lodge pole pines. During an epidemic they may attack almost all the large trees in the area.
Beetles feeding and breeding under the bark. Many times there will be sap filled holes showing on the exterior of the tree.