4 INSECT DAMAGE TO MINE PEOPS, 



barked props, especially props cut from insect-killed, fire-killed, or 

 other dead standing timber, should be thoroughly inspected before 

 thej'^ are placed in the mine and all props showing serious damage by 

 insects discarded. The presence of wood-boring insects can be de- 

 tected by sawdust-like boring du-t that is expelled from their bur- 

 rows and lodges in crevices in the bark. 



PREVENTION OF INJURY TO TIMBERS BY TERMITES AFTER PLACEMENT. 



As previously stated, the seasoning that prevents injuiy before 

 placement will delay and under some conditions even prevent injury 

 to mine timbers by termites after placement, since moisture or incip- 

 ient decaj' is necessary for destructive work. In consequence, sea- 

 soning is recommended where it is impracticable to treat timbers 

 with chemical preservatives. 



Methods of superficially treating props by brushing the exterior 

 Avith various chemical preservatives Avill be teniiDorarily effective in 

 keeping out termites, if the work is thoroughly done and both ends 

 are also treated. Where the basal area is left untreated, termites 

 will enter the prop through the untreated portion. It will readily 

 be seen that neither brushing nor spra^'ing the exterior of the prop 

 after placement in the mine, as is sometimes practiced, is effective 

 in keeping out termites, since the end that sets in the ground could 

 not be treated, and it is usually here that termites attack the props. 



Before treating timber with chemical preservatives, especially where 

 the brush method is used, it is essential that the timber be thoroughly 

 seasoned, otherwise penetration will be retarded. 



Impregnating props intended for permanent service with creosote 

 by some standard process (either by the " open-tank " or by the 

 ejdinder-pressure processes) will keep out termites and other wood- 

 boring insects and preserve the props for a much longer period than 

 they would last untreated. 



Publications of the Forest Service should be consulted for infor- 

 mation on general methods of treating timbers with preservatives 

 and the relative efficiency of various methods and chemicals.^ 



Approved : SMn-HSONiAN institution libraries 



James Wilson, 



Secretary of Agriculture. 

 Washington, D. C, April 10, 1912. 3 9088 01272 8259 



1 See especially Bulletin 107 of the Forest Service, U. S. Department of Agriculture, 

 " The Preservation of Mine Timbers." 

 [Cir. 156] 



additional copies of this publication 

 ■t\- may be procured from the SuTERrNTEND- 

 ENT OF Documents, Government Printing 

 Office, Washington, D. C, at 5 cents per copy. 



