Mountain Pine Beetle

Understanding MPB

Mountain pine beetle (MPB) Dendroctonus ponderosae is a native and naturally occurring insect that attacks our ponderosa and lodgepole pine forests.

The beetle carries the bluestain fungus, a disease that clogs the tree’s vascular system, causing it to die. A tree that has the fungus may not show the effects for many months.


Mountain Pine Beetle Populations

Under normal conditions, MPB populations remain small and isolated and only individual trees are affected; however, every 10 to 20 years, MPB populations increase to epidemic levels and entire tree stands can be killed. Recent surveys have shown an increase in MPB populations along the northern Front Range. 

Jefferson County experienced a similar epidemic in the mid-1970s through the early 1980s and again in the late 1990's. Hundreds of thousands of ponderosa pine trees were killed and millions of dollars were spent on control measures. When MPB populations increase, measures should be taken to prevent widespread damage.


Why Does This Happen?

Most ponderosa pine trees currently infested with MPB are stressed because their stands have not been properly managed. The best way to protect your trees from MPB is to thin them correctly. Closely spaced trees must compete for water, sunlight and nutrients, making them weak an unable to resist insect attack. A healthy tree is able to produce enough sap to drown the invading pine beetle, "pitching it out."