Mountain Pine Beetle
The Mountain pine beetle is one of several native bark beetle species found in Wyoming, but it is the most widely recognized due to its significant impacts on pine forests across the region. This small insect attacks a variety of pine species, including lodgepole, ponderosa, limber, and whitebark pine.​
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Mountain pine beetles kill trees by boring through the bark and laying eggs in the inner bark layers. As the larvae hatch and feed beneath the bark, they disrupt the tree’s ability to transport water and nutrients. In addition, the beetles introduce a fungus known as Blue-stain fungus into the sapwood. This fungus further blocks the tree’s vascular system and interferes with water movement, accelerating tree mortality. The combined effects of larval feeding and fungal infection typically result in the death of the host tree within a year.
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Large-scale outbreaks can occur when environmental conditions favor beetle survival, such as extended periods of drought or large stands of mature pine trees. During severe infestations, entire forested landscapes may be affected. In 2011, aerial surveys estimated that more than 3.3 million acres of federally managed forest in Wyoming had been impacted by mountain pine beetle activity, highlighting the widespread ecological and economic effects of the pest.
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In recognition of the threat posed by this insect, the 1973 Wyoming Legislature designated the mountain pine beetle as a state pest under the state weed and pest law. This designation enables county Weed and Pest Control Districts, coordinated through the Wyoming Weed and Pest Council, to assist landowners with management efforts.
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Weed and Pest Control Districts work closely with the Wyoming State Forestry Division and the timber industry to support programs that help reduce beetle impacts. These programs may include public education, monitoring and early detection, chemical treatment cost-share programs for high-value trees, sanitation cutting, and the hiring of professional sawyer crews to remove and properly dispose of infested trees. Such collaborative efforts help protect forests, reduce wildfire risk associated with dead timber, and support the long-term health of Wyoming’s forest ecosystems.
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