THE GENUS DENDROCTONUS. 



65 



EFFECTS ON COMMERCIAL VALUE OF THE WOOD. 



The commercial value of the wood of trees killed by this beetle is 

 reduced by the bluing of the sapwood (fig. 29), often before the leaves 

 begin to turn yellow, though the heartwood, especially of the larger 

 spruce and yellow pine, usually remains sound for many years after 

 the trees die; both the sap and heartwood of the smaller trees, and 

 even of the large pitch, loblolly, and Table Mountain pine, deteriorate 

 rapidly (figs. 2-6, 27), and 

 therefore must be utilized 

 immediately after the 

 trees begin to die, in order 

 to save anything of com- 

 mercial value. 



Serious losses of a sec- 

 ondary nature, both of 

 dead and adjoining living 

 timber, may result from 

 fires started in the dead 

 timber. Therefore the 

 prompt utilization of the 

 beetle-infested trees and 

 the prevention of forest 

 fires are important to ob- 

 viate total destruction of 

 the timber. 



FAVORABLE AND UNFAVOR- 

 ABLE CONDITIONS FOR THE 

 BEETLE. 



Favorable conditions 

 for the multiplication and 

 spread of the beetle are 

 found in areas of large, 

 matured timber and 

 where the trees are fre- 

 quently struck by light- 

 ning, felled, or injured by 

 storms, etc., during the 

 summer months. 



Fig. 27.— A forest of Table Mountain pine, Mineral County, 

 W. Va., seven years after it was killed by the southern 

 pine beetle. (Original, from photograph.) 



The odor from the exposed wood, and perhaps from the wilting 

 foliage of a few trees cut in the midst of a healthy growth of pine dur- 

 ing the summer, serves to attract this species, apparently from a long 

 distance, and to induce attack on the surrounding healthy trees. 

 Therefore, any irregular or sporadic local cutting of timber for fuel 

 or any limited purpose during the summer months furnishes most 

 89535— Bull. 83, pt. 1—09 6 



