Cultural Practices for Prevention and Mitigation of Mountain Pine Beetle Infestations

In recent years, the mountain pine beetle, Dendroctonus ponderosae Hopkins, has impacted 8.9 million hectares of forests in the western United States. During endemic populations, trees weakened by other agents are often colonized by D. ponderosae but may be difficult to detect due to their scarcity. Once populations reach incipient levels, tree defenses are often insufficient in deterring mass attacks, and populations rapidly increase causing substantial levels of tree mortality under certain circumstances. There are two general approaches for reducing the negative impacts of D. ponderosae on forests. Direct control involves short-term tactics designed to address current infestations by manipulating beetle populations and includes the use of fire, insecticides, semiochemicals, sanitation harvests, or combinations of these treatments. Indirect control is preventive and designed to reduce the probability and severity of future infestations by manipulating stand, forest and/or landscape conditions by reducing the number of susceptible host trees through thinning, prescribed burning, and/or alterations of age classes and species composition. We review tree, stand, and landscape factors associated with D. ponderosae infestations and analyze the effectiveness of treatments for preventing and mitigating undesirable levels of tree mortality. We describe the current state of our knowledge and identify gaps for making informed management decisions.