The roundheaded pine beetle is another native bark beetle to Colorado, closely related to mountain pine beetle, spruce beetle and Douglas-fir beetle. The range of this bark beetle extends north into southern Colorado from as far south as Guatemala; southern Colorado is the northernmost extent of its range.
Ponderosa pine is the only primary North American host tree species, though other pine species are attacked throughout Mexico and into Central America.
In Colorado, trees are attacked later in the year than with other Colorado bark beetles, from late August through November. With only one generation flying per year, these beetles attack a wide range of tree sizes and ages, typically after a prolonged drought period.
Outbreaks south of Colorado’s border are typically short in duration, though contiguous ponderosa pine forests in Dolores County have sustained increased mortality for the seventh consecutive year.
Roundheaded pine bark beetles are often associated with several other species of bark beetles, typically western pine beetle (D. brevicomis), pine engraver beetles (Ips spp.) and mountain pine beetle (D. ponderosae). These associated bark beetles, working in conjunction with one another, produce a “bark beetle complex” that results in tree injury and death.
Approximately 27,000 acres were affected in 2018 as the infestation intensifies in Dolores County. However, many of those acres were of low intensity, where the complex affected only small groups of trees. 27,000 acres of ponderosa pine were affected in 2018, compared to 11,000 acres in 2017.
- Although some acres are more intensely affected than others, approximately 52 percent of the ponderosa pine forest ecosystems in Dolores County have been affected since 2000.