SALT LAKE CITY (AP) -- Spruce trees are dying in Utah's forests, the victims of an infestation that is natural but from which some forests may not recover from for hundreds of years.
In the Manti-LaSal National Forest alone, an estimated 75,000 acres of spruce trees are dead or dying.
The forest will come back but not for at least 300 years.
The die-off is "pretty extreme," said Diane Cote, Manti-LaSal's forest silviculturist. "This and what has happened in Alaska are some of the worst we've ever documented."
A spruce beetle infestation has spread like wildfire through drought-weakened and aged trees.
Fishlake National Forest may be next, and Dixie National Forest also seems in danger. A spruce beetle kill has been sighted in the Uinta Mountains, and in the Upper Provo River watershed, beetles are killing spruce, fir and pine."
Cote said spruce beetles are a naturally occurring pest that take old and weakened trees, but when many trees are old, crowded together and stressed at the same time, a triggering event can have widespread results.
The last time a big die-off happened may have been about 300 or 400 years ago. Now, this generation of trees is vulnerable.
Spraying to protect trees against beetles is difficult because the infestation is so dense.
"There's so many bugs hitting these trees that they can't win," Cote said. Agency workers can't move fast enough to get ahead of them.
Forest workers spray protective chemicals on trees in some campgrounds, trying to save "high-value" trees where the public visits. But if a tree is tall, they can't spray all the way to its top, and the bugs still get to it.
Logging to get rid of nearby infested trees can save some stands. But that can't stop the spread of the spruce mortality.
"We're losing almost everything over 16 inches" in diameter, Cote said. About 90 percent of trees more than 10 inches in diameter are going, also.
But small trees, young ones that grew after recent lightning strikes opened a place, have a better chance.
"While it is a catastrophic effect on spruce ... this is normal, and the spruce will recover in time."
For a century or so, "we'll probably go through a cycle" in which subalpine firs grow, die, catch fire because of all the dead spruce, and grow again.
Gradually, firs will grow that seeds from the scarce remaining spruces and will take hold.
"Over time, probably 300, 400 years," Cote said, "we'll have a forest like we have now."
(Copyright 2004 by The Associated Press. All Rights Reserved.)