. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. THE GENUS DENDROCTONUS. Ill EFFECTS ON COMMERCIAL VALUE OF THE WOOD. The commercial value of the Douglas fir trees killed by the beetle is not seriously impaired for several years after they die, except that the sap wood discolors and otherwise deteriorates, but the heart wood of large trees may remain sound for twenty years or more. On the other hand, if they are seriously attacked by wood-boring insects the wood may deteriorate rapidly. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions f
. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. THE GENUS DENDROCTONUS. Ill EFFECTS ON COMMERCIAL VALUE OF THE WOOD. The commercial value of the Douglas fir trees killed by the beetle is not seriously impaired for several years after they die, except that the sap wood discolors and otherwise deteriorates, but the heart wood of large trees may remain sound for twenty years or more. On the other hand, if they are seriously attacked by wood-boring insects the wood may deteriorate rapidly. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication and de- structive work of this bark- beetle are found in the drier regions, where the growth of the trees is slow and where the older trees are frequently injured by fire, storms,.land- slides, etc., as also in the more isolated sections of the forests in such a region where no continued timber-cutting operations are carried on. Unfavorable conditions for attack on living timber are found in moist regions, where the growth of the trees is vig- orous, as in the coast, Cas- cade, and Sierra sections of Washington, Oregon, and California, and especially in those sections in which con- tinued timber-cutting opera- tions are carried on under a system of lumbering or forest management which requires that the matured or older timber, as well as that which is dying and "beetle infested/' be taken out, and where the younger, vigorous timber is protected from injury by fire and other causes. METHODS OF CONTROL. Whenever in a given locality it is positively determined that this species is attacking and killing the Douglas fir, bigcone spruce, or western larch, and that the bark of living and dying trees contains. Fig. 68.—The Douglas fir beetle: Section of log with bark removed, showing brood galleries marked and grooved on surface of wood. (Author's illustration.). Please note that these images are extracted from scanned page images that may have been digital
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