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Environment / Sustainability

Pine beetles only one threat according to 2009 Report on Health of Colorado's Forests

March 3, 2010

Mountain pine beetles have received widespread attention lately, but urban trees and nearly half a million acres of spruce and fir in Colorado also face significant insect and disease threats.

Comprehensive overview of insect and disease problems

The 2009 Report on the Health of Colorado’s Forests highlighted these and other concerns in a comprehensive overview of insect and disease problems currently jeopardizing the state’s forests.

The Colorado State Forest Service released the report March 3 at the annual Joint Ag and Natural Resources Committee Hearing in Denver.

“Spruce beetles have killed nearly all of the large, mature spruce trees in the San Juan Mountains near the headwaters of the Rio Grande River,” said Jeff Jahnke, state forester and director of the Colorado State Forest Service.

Spruce beetle infestation

Jahnke said the state’s spruce beetle infestation nearly doubled in size last year; the beetles were active on approximately 114,000 acres of high-elevation Engelmann spruce in 2009, mostly in southern Colorado.

Western spruce budworm—a defoliating insect pest that has increased its footprint in Colorado—also is affecting Engelmann spruce, as well as Douglas-fir and white fir. The budworm affected 382,000 acres last year, or more than twice the area impacted in 2008.

Urban pests of concern

The CSFS report also listed several urban pests of significant concern:

  • Thousand cankers disease of black walnut trees already has killed many trees in Boulder and Colorado Springs. The disease continued to spread in urban areas last year, including Denver and its suburbs.
  • Gypsy moths again have been detected in the state; the CSFS trapped three individual moths along the Front Range in 2009. If the moth established itself here, many species of broadleaf and conifer trees would be threatened.
  • Emerald ash borer remains a potential threat, but to date has not been detected in the state. This non-native insect, which has killed millions of ash trees in the Midwest, could infest several ash species popular as shade and ornamental trees in Colorado’s urban forests.
  • Mountain pine beetles have been detected in more municipal areas.

1 million acres of logepole pine infected

"Mountain pine beetle continued to attack pines in urban areas along the Front Range,” said Bill Ciesla, aerial survey coordinator for the CSFS and lead author of the 2009 report. “In 2009, a few attacks were even seen as far east as Sterling."

The report indicated that the mountain pine beetle remains the dominant forest pest in the state, with active infestations on 1 million acres of lodgepole pine. Jahnke said the CSFS is increasing its monitoring and management activities on state and private lands to address forest health concerns.

For more information about the forest health report or tips on how to identify and manage tree pests, visit the Colorado State Forest Service website.

Contact: Kimberly Sorensen
Phone: (970) 491-0757