MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



Figure 2. 



-Bark beetles, not fire, destroyed this si 

 Yosemite National Park. 



md of lodgepole pine in 



estimated that during the 10-year period ending in 1932 these 

 losses amounted to 7,250 million board feet, more than 36 million 

 trees having been killed in one national forest alone. Many mature 

 lodgepole pine forests throughout the West have been virtually 

 destroyed by this bark beetle since 1910, or are in the process of 

 destruction. During the 10-year period 1923-32 the mountain pine 

 beetle is also estimated to have destroyed 110 million board feet 

 of valuable western white pine stands in northern Idaho and 1,280 

 million board feet of sugar pine in California. 



An outbreak of the Engelmann spruce beetle between 1940 and 

 1950 is estimated to have killed 4,100 million board feet of Engel- 

 mann spruce in Colorado, representing about 20 percent of the 

 total spruce in the State. On the White River Plateau in Colorado 

 95 percent of the merchantable spruce trees were killed. 



It must be clearly understood that these loss estimates cover 

 the normal, as well as the unusual drain on the forest. In the pon- 

 derosa pine type bark beetles kill a few trees every year. Normal 

 losses on good sites of 20 to 40 board feet and on poor sites of 



