SARATOGA (AP) - Infestations by three species of beetles have begun taking a toll on trees in Medicine Bow National Forest.

Mountain pine beetles have killed large numbers of lodgepole pine in the Bear Mountain area outside Encampment. Spruce bark beetles have killed spruce around the Snowy Range, and fir engraver beetles have been killing fir trees in the same areas.

"It's unusual to have all three epidemics going on at once," forester Terry DeLay said.

The Routt Divide Blowdown - strong winds that blew down thousands of trees in 1997 - started the spruce bark beetle epidemic across the Colorado line in Routt National Forest.

Drought and warm winters have likely caused the epidemics to spread, said Routt National Forest forester Andy Cadenhead.

In parts of the Mount Zirkel Wilderness in Routt National Forest, beetles have killed all trees smaller than 7 inches in diameter.

In the Snowy Range, beetles have prompted forest officials to close Silver Lake Campground so they can try to bring the infestation under control. That part of the forest has large stands of tall, old spruce trees that are susceptible to attack because of their age, DeLay said.

Little can be done about the Bear Mountain epidemic, however, because it is in a roadless area. "Like our wilderness areas, we let nature take its course there, and it's taking its course," DeLay said.

He said the epidemics will likely continue until an especially cold winter kills the beetles.