Aspen working to stop beetle spread
ASPEN ” Since finding trees infested with the very same mountain pine beetle that is devastating forests all across Colorado, city of Aspen officials are taking steps to prevent further spread.
“This would be without a doubt the largest number of pine beetle strikes we’ve seen,” said Stephen Ellsperman, the city’s parks and open space director.
The beetles, though native to the area, are for unknown reasons traveling in swarms and boring into lodgepole and Scotch pine all across the state, Ellsperman said. The beetles lay eggs, cutting off the flow of water and nutrients and eventually killing the tree before finding a new host.
Chris Forman, Aspen’s city forester who manages some 8,500 trees in the city limits, is plotting the infested trees on a GIS map in the hope of preventing the beetles from spreading in 2008.
Out of the 5,168 “street trees” on the city of Aspen’s right of ways, Forman said 164 trees are either lodgepole or Scotch pine and susceptible to the beetle. And of the 2,463 trees in city parks, 79 pines are vulnerable, Forman said.
The survey does not account for trees in homeowners’ backyards, Forman said.
“It’s not going to sweep through and completely wipe us out in town,” Forman said. “But I’m not going to kid myself and say we aren’t going to lose any trees. We will.”
Aspen’s more diverse forest population of Douglas fir, aspen, cottonwood and pinyon pines protect the area from the kind of wholesale forest loss that is happening near Vail and in Grand County, Forman said.
Spraying the trees can be effective, but there is no treatment once the beetle takes hold of a host tree, Forman said.
Ed Berkheimer, owner of Earthwise Horticultural, said his crews regularly spray trees with the chemical Onyx to prevent beetle infestation, but Berkheimer said it might be too late to prevent beetles from spreading in 2007.
“We usually try to have our sprays done by late June or early July,” Berkheimer said, before the beetles fly to new host trees in July and early August.
“My hunch is that the majority have already flown. We’re definitely at the tail end,” Berkheimer said.
But spraying could be an prevent beetles from spreading further in June and July of 2008, Berkheimer said.
Business in mountain beetle prevention in Aspen has increased “a little bit each year,” Berkheimer said, but mostly because residents see the effect beetles have on forests in other parts of the state.
But while other trees have just a few beetle hits ” evidenced by cones of pine pitch oozing out of holes in trees ” Berkheimer said the beetle carries a kind of fungus that can kill a tree even before a full beetle infestation.
“These insects go for trees that are under stress,” Ellsperman said. And keeping trees healthy in the early stages can prevent a massive attack.
When beetles bore below the bark, trees emit sap in an effort to eject the parasite. The more sap, the healthier the tree and chances for survival, according to Forman.
From his informal survey of local lodgepole and Scotch pine in city of Aspen parks and right of ways, Forman said many trees look strong.
“There’s a good chance (the tree) is throwing those beetles out,” Forman said.