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Valley’s pinon forests in jeopardy

The Roaring Fork Valley is ripe for an infestation of a beetle that will wipe out pinon trees covering thousands of acres, according to a top forestry expert on the West Slope.

John Denison, the district forester for the Colorado State Forest Service, said the conditions in the valley make the pinon susceptible to a specific pest known as the Ips beetle.

“There are too many trees competing for too little water,” said Denison recently after touring the site of a potential forest-thinning project on the slopes above Basalt.



He said the Ips beetle favors pinon, which is the predominant tree covering the valley walls from Glenwood Springs to Woody Creek. Pinon can also be found on the south-facing slopes of the upper valley, like in the Hunter Creek Valley, according to Pitkin County wildlife biologist Jonathan Lowsky.

Pinon trees are particularly thick in the middle and lower valley, like on the lower slopes of Basalt Mountain between Basalt and El Jebel, and throughout Missouri Heights.




Denison said there are spots in the Roaring Fork Valley where the beetle has already attacked. Drought has stressed the trees, making them susceptible. The valley’s pinon and juniper forests also tend to be older, and they haven’t been cleared or burned for decades, he noted.

Similar pinon forests in the Cortez and Durango areas have been wiped out in recent years.

“As far as you can see, it’s just brown trees,” Denison said. “The whole Roaring Fork Valley will be surprised how quickly it can affect it.”

He estimated that 80 percent of the trees could die. The needles of dead trees change from green to yellow to reddish brown.

The beetle will fly up to two miles to reach host trees, according to the Colorado State University Cooperative Extension Web site. Stressed trees give off a chemical signal that is picked up by the male Ips beetles. The females follow.

“Once the beetles have invaded an area, emerging beetles are likely to attack neighboring pinon even if the trees are relatively healthy (nonstressed),” the CSU Web site said.

Healthy trees can fend off the beetles by releasing pitch, which drowns the pests or forces them out.

A different but related type of beetle is attacking pine trees on higher ground. The latest White River National Forest Plan designated the Fryingpan River drainage as susceptible to an outbreak of mountain pine beetle.

A study “revealed that 46 percent of the 10,501 acres of lodgepole pine” for which data had been collected were at moderate to high risk and 3 percent was at high risk, according to the Forest Plan.

The Healthy Forest Restoration Act passed by U.S. Congress this year could result in the Forest Service approving special projects aimed at reducing the risk of beetle infestations.

Denison said thinning of pinon forests could also reduce competition and stress among trees and make them less susceptible to Ips beetles. However, he suspects the spread of the beetle will be quicker than the thinning of the thousands of acres of pinon forests.

Therefore, Denison said, it’s just a question of “when” an Ips infestation strikes the Roaring Fork Valley, not “if” it strikes.

“Yeah, I’m convinced it is,” he said.

[Scott Condon’s e-mail address is scondon@aspentimes.com]


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