40 



BULLETIN 1490. U. S. DEPARTMENT OF AGRICULTURE 



In oak the black checks are larger, often 6 inches long over an 

 area of several square inches. In quarter-sawn boards they appear 

 as dark distorted or curly wood and run through many layers of 

 wood, while in bastard-sawn boards they form black scars several 

 inches long by 1 or 2 wide. In the Ozark Mountains of Arkansas 

 this is a very common defect. 



Timber from softwoods or hardwoods is not seriously reduced in 

 strength by such defects, but the wood is lowered in grade and 

 rendered useless for finishing, turning, staves, and woodenware. It 

 can, however, be used for structural material or for purposes for 

 which the marred appearance will not be detrimental. Since black 



check is always the 

 result of injury to 

 the living tree, it is 

 not preventable, from 

 the lumberman's 

 standpoint. 



DEFECTS CLASSED AS 

 BLUING OR STAINING 



Bluish -black 

 streaks or stains in 

 the sap wood of pine, 

 especially in southern 

 yellow, western yel- 

 low, and sugar pines, 

 as well as in certain 

 hardwoods, such as 

 red gum or sap gum, 

 are classed as bluing. 

 This defect occurs 

 either in the standing 

 tree or in recently 

 cut green logs or 

 green lumber and is 

 caused by fungi de- 

 veloping from spores 

 which are no doubt 

 carried by insects. 

 In pines the bluing 

 directly follows in- 

 festation by tree-killing bark beetles 41 in the standing trees (fig. 

 44) {29). This defect can be prevented only by the control of 

 tree-killing bark beetles. Similar staining defects are caused by many 

 ambrosia beetles 42 in both the living trees and green saw logs and 

 green, freshly sawn lumber. (Figs. 4, 9, and 13.) This staining can 

 be prevented in green saw logs by prompt utilization of the green 

 logs; by placing them in the mill pond soon after cutting; or by 

 sun-curing. When the lumber is sawn it should be either kiln-dried 

 or air-seasoned rapidly. Bluing is not always dependent on bark 

 beetles (1$). 



Fig. 43. — Black check in oak, caused 

 borer (Goes sp.) in the living tree, 

 healed over 



>y round-headed 

 The wound has 



Dendroetonus spp. 



a Gnathotrichus, Xyleborus, Platypus, etc. 



I 



