A landscape of dead pines

USGS scientist Jenny Briggs walks through a study site near Blue Feather Lakes in Colorado. The reddish-brown trees dotting the landscape have been killed by mountain pine beetles.

Mountain pine beetle outbreaks can result in the loss of millions of pine trees throughout western North America. The beetles lay eggs and develop in the bark of mountain trees, especially lodgepole, ponderosa, Scotch, and limber pines. The beetles carry bluestain fungus spores, which infect the trees and turn the sapwood a bluish color. Both the beetles and the fungi eventually kill their host trees.