Bark Beetle

Pine trees often use extruding sap as a defense mechanism for remove pine beetle larva from under their bark.

NPS/ Kenneth Ingham

Though beetle outbreaks can kill entire forests, the beetles themselves are not an invasive species. Bark beetles occur naturally in pine forests and different beetle species have evolved in tandem with different tree species. At Parashant National Monument, the ponderosa pine hosts the mountain pine beetle (Dendroctonus ponderosae), and the pinyon pine hosts the pinyon ips (Ips confuses).

Under natural conditions, the bark beetles act like fire in a forest, removing a portion of trees from the population. In a healthy forest, this beetle activity functions as a natural check and balance in the ecosystem. Trees killed by the beetle return nutrients to the soil, and the forest is opened up so that the remaining trees complete less for resources.

Today’s forests suffer from factors that make them more susceptible to high levels of bark beetle mortality. Climate-related issues, including prolonged drought, have deprived tree of the water it takes to produce sap for driving out the beetles. Fire suppression and urbanization have created prime forest real estate where the bark beetle can reproduce.

To combat pandemic infestation, good forestry practices are critical. Managing forest density with prescribed and natural fire, thinning, and careful timber harvest can return forests to healthy conditions. With abundant resources, individual trees are more likely to fight off the beetles.