Thinning the Pinon-Juniper Forest to Improve Pest Resistance

Source: Peter Barth, Assistant District Forester, Colorado State Forest Service, Montrose, Colorado

Note: There is not extensive history nor documented research in dealing with the cultural treatment of the pinon-juniper forest to improve pest resistance. These are only my observations based on my experience in dealing with forest dynamics and bark beetles in Colorado. Recommendations will be updated as more supporting information becomes available.

Pest Management Considerations
  • Ips engraver bark beetle (and associated Ceratocystis blue stain fungus)
  • Black stain root disease
  • Twig beetles
Recommended Treatments
  • 1) Thin trees properly to increase the available light, water, and nutrients for remaining trees (note: trees infested with bark beetles or infected with black stain root disease require special actions)
    Spacing Guidelines
    Diameter at base Desired trees/acre Spacing between trees (in feet)
    4 inches 458 - 687 8 - 10
    6 inches 204 - 306 12 - 15
    8 inches 115 - 172 16 - 19
    10 inches 73 - 110 20 - 24
    12 inches 51 - 76 24 - 29
    14 inches 37 - 56 28 - 34
    16 inches 29 - 43 32 - 39
    18 inches 23 - 34 36 - 44
    20 inches 18 - 27 40 - 49
    22 inches 15 - 23 44 - 54
    24 inches 13 - 19 48 - 58

    • Limit tree cutting to winter months (November 1 through March 15)
    • Avoid damage to residual trees during tree cutting operations
    • Cut stumps low to ground (6 inches or less)
    • Remove forest products off-site or in the case of firewood stockpiles...
      block wood, stack away from trees, and cover with clear plastic for greenhouse effect
    • Avoid use of heavy equipment and minimize vehicle traffic in tree areas
    • Promptly dispose of slash (tops and branch) prior to March 15:
      Options for Disposal
      Chip
      Remove Bark
      Bury
      Haul to approved site away from forest trees
      Cover with plastic
      Pile away from trees (in a safe, clear area) and burn during winter snow cover *

      * Check with your local fire department or fire chief regarding burn requirements

  • 2) Maintain adequate moisture to plants by providing additional/supplemental water during drought periods; Don't over-water trees, especially pinon and juniper

    Minimize turfgrass in tree areas as the moisture requirements of most sod-forming grasses are much higher than trees native to Log Hill Mesa.

  • 3) Avoid damaging trees caused by bark scraping, root injury, or soil disturbance. This includes damage resulting from:
    • road and trail construction
    • soil excavating
    • foundations and pavement in forested areas
    • trees used for fence or sign posts, phone lines, hammock or tent supports, etc.
    • firewood stacks and brush piled near standing trees
  • 4) Replace over-mature forest gradually with young, fast-growing seedlings
  • 5) Diversify forest with plantings of ponderosa pine and Rocky Mountain juniper at higher elevations, or where supplemental irrigation is available
  • 6) Prune lower branches of pinon and ponderosa pine (no more than 1/3 of green crown)
  • 7) Prune out dead and dwarf mistletoe-infected branches
  • 8) Promptly cut and treat trees infested by bark beetles (special handling required)
  • 9) Remove groups of trees associated with black stain root disease (special handling required)

    Note: This information was summarized for residents of Log Hill Mesa, Ouray County, Colorado Forest Pest Workshops, February 22, 1997.


This page was updated on April 26, 2014