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



Douglas-fir tussock moth, the spruce budworm, and the hemlock 

 looper. In 1893-95 the pine butterfly practically wiped out the 

 mature ponderosa pine stand on 140,000 acres of the Yakima 

 Indian Reservation in Washington. Since then less severe out- 

 breaks of this insect have occurred from time to time. In 1931-32 

 the Douglas-fir tussock moth destroyed a high percentage of the 

 Douglas-fir stands on 300,000 acres of the Colville National Forest 

 in northeastern Washington. Again in 1945 a serious outbreak 

 developed on 410,000 acres of fir forests in Idaho and eastern 

 Oregon and Washington. Along the coast of Oregon and north 

 to Alaska the hemlock looper appears about every 10 years and 

 completely destroys the western hemlock and associated trees 

 over large areas. A disastrous outbreak took place in western 

 Oregon and Washington in the years 1889 to 1891, followed by 

 major outbreaks in 1919-21, 1929-32, and 1943-45. However, 

 defoliators in general cause little widespread destruction. 



Forest plantations are particularly subject to destructive in- 

 sects, chiefly because a plantation is usually made up of a large 

 planting of one kind of tree. Many plantations are established on 

 soils not especially suitable for the tree species used, and the poor 

 condition of the planting invites insect damage. Young trees and 

 second-growth stands are often seriously damaged by insects that 

 feed on the terminals. Bud and twig moths, tip weevils, and twig 

 beetles not only damage and deform the terminal shoots but at 

 times kill out seedlings, saplings, and poles over large areas. Pine 

 plantations in the Nebraska sand hills have been badly set back by 

 tip moths. Many areas of second-growth pine near logging opera- 

 tions have been swept by aggressive infestations of engraver 

 beetles. 



Rapid progress in the development of forest recreation has 

 called attention to the destruction of trees especially valuable for 

 recreational or aesthetic use. The importance of forest cover on 

 national parks, game preserves, and other recreational areas can- 

 not be estimated in board-feet values. Insect depredations which 

 mar the beauty or destroy the protective value of the forest cover 

 on park and other recreational areas justify higher expenditures 

 for control work than might be considered reasonable on a com- 

 mercial stand. 



Injuries to the wood of living trees greatly reduce the value of 

 lumber. Furthermore, all kinds of forest products, from the time 

 the tree is felled and for many years after the wood is put into 

 use, are subject to destruction by insects. Losses in green sawlogs 

 and storm-felled timber, green-sawed and seasoned lumber, rustic 

 construction, poles, posts, cross ties, and all manner of finished 

 products are particularly heavy, since they include cost of manu- 

 facture or replacement, or both. Losses of this class are estimated 

 at 0.5 to 5 percent of the total value of various classes of finished 

 products. 



INDIRECT LOSSES 



Besides direct damage through destruction of trees and forest 

 products, forest insects cause important indirect losses in reducing 



