378 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1941 



the spruce. The eastern spruce beetle was also a factor in killing 

 overmature spruce. Insects were thus important in the production 

 of the extensive stands of white pine of early logging days — giant 

 trees 300 or more years of age overtopping a spruce-fir-hardwood 

 understory. 



The application of entomological knowledge to forest management 

 must go hand in hand with practical developments in forest utiliza- 

 tion. Many schemes have been suggested for handling timber stands, 

 particularly second growth, to avoid some specific insect damage. 

 Many of these may eventually be applied but most of them are still 

 impractical because of economic considerations. 



FROM DIRECT BARK BEETLE CONTROL TO SELECTIVE LOGGING OF 



SUSCEPTIBLE TREES 



Probably the most persistent effort in the application of entomo- 

 logical knowledge to the management of timber stands has been 

 expended for the prevention of bark beetle losses in the ponderosa 

 pine type of California and Oregon. 



During the period of increasing control work, while we were utiliz- 

 ing our overmature reserves of timber, many of the disadvantages 

 of direct control became apparent, particularly the costliness and 

 the variability of the results and the fact that much of the timber 

 treated could seldom be utilized but had to be left in the woods to 

 decay. 



That the western pine beetle (pi. 1) should have been one of the 

 first insects for which definite suggestions were made for substituting 

 management for direct control is easily understood. Extensive stands 

 of increasingly valuable timber were at stake, losses in the best-quality 

 timber were increasing, biological studies and control efforts were 

 pushed more energetically than for any other beetle, and, most impor- 

 tant, it was realized early in the study of this species that it showed a 

 decided preference for trees with certain recognizable characteristics 

 and that advantage might be taken of this preference in marking 

 timber sales. 



Hopkins (1909b) notes the preference of this beetle for "larger, best 

 matured trees." 



Pearce (1920) pointed out that "beetle activities in our pine forests 

 not only represent a serious economic loss but must be taken into con- 

 sideration in planning for sustained yield." 



Craighead (1925a) expressed this idea as follows: 



Generally speaking, the western pine beetle appears to prefer overmature, slow- 

 growing, decadent trees, particularly those on poorer sites * * ♦ There is no 

 doubt, however, that successful management of the western yellow pine is Just 

 as intimately tied up with this beetle problem as it is with fire or with the 

 silvical characteristics of the tree and that the beetles' ability to increase ia 



