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



Bud and twig moths, tip weevils, and twig beetles not only damage 

 and deform the terminal shoots but at times become so numerous as 

 to 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 operations 

 have been swept by aggressive infestations of engraver beetles. 



The destruction of trees especially valuable from a recreational or 

 aesthetic standpoint has recently come into prominence because of 

 rapid progress in the development of forest recreation. The impor- 

 tance of forest cover on national parks, game preserves, and other 

 recreational areas cannot 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 suppression than might be reasonable on a strictly 

 commercial stand. 



Injuries to the wood of living trees are manifested in lumber as 

 defects greatly reducing its value. 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. Green 

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

 lumber, rustic construction, poles, posts, cross ties, and all manner 

 of finished products, from flooring to furniture, are attacked. Losses 

 in finished products are particularly heavy, since they include cost 

 of manufacture or replacement, or both. Losses of this class, it is 

 esthnated, amount to from 0.5 to 5 percent of the total value of vari- 

 ous classes of finished products. 



INDIRECT LOSSES 



Besides direct damage through destruction of trees and forest 

 products, forest-tree insects cause important indirect losses in the 

 way of reduction in forest growth and alteration of the stand from 

 valuable to inferior species. 



In some forest t3'pes insects often are one of the chief limiting 

 factors in successful management. They frequently upset well-or- 

 ganized plans aimed at the continuous production of forest crops. 

 In the western white pine and lodgepole pine forests of the northern 

 Bocky Mountain region bark beetles so affect the proportion of 

 species as to convert many stands to entirely different composition. 

 In Modoc County, Calif., a bark-beetle epidemic in a mixed second- 

 growth stand of ponderosa pine and white fir killed out all the pine 

 and converted the stand into pure fir. , 



Much less frequentl}^ the effect of insect activity on stand compo- 

 sition is beneficial. In the Yosemite and Crater Lake National Parks^ 

 for instance, lodgepole pine stands completely destroyed by bark 

 beetles have been succeeded by stands of the hemlock-fir type, which, 

 for park purposes at least, is far superior to the lodgepole pine type. 



Certain defoliators, even though they do not kill the timber, may 

 cause a cessation or reduction of growth which may increase the ro- 

 tation period of the stand by from 5 to 10 or more years, or they 

 may so weaken the trees as to make them easy prey for tree-killing 

 bark beetles. Such defoliation may be local and confined to a single 

 tree species, or may spread over an enormous area and involve sev- 



