10 



BULLETIN 658, U. S. DEPARTMENT OF AGRICULTURE 



ciple, and whenever forestation of an area either by natural or arti- 

 ficial reproduction is contemplated it would be extremely unwise t<> 



overlook the risks to the young growth incurred by possible disease. 

 A pathological map would serve to give the previous location of dis- 

 eased trees, as well as the location of diseased uncut areas surround- 

 ing the sale area and the localities and sites where diseases seem most 

 prevalent, and would also serve to indicate whether the seed trees 

 left, if any. were of a group which was heavily diseased or not. Dis- 

 eased trees of any kind left as seed trees or otherwise on or surround- 

 ing a cut-over area always act as distributing points of disease to the 



young growth occupy- 

 ing the near-by areas. 

 For this reason atten- 

 tion has recently been 

 centered upon the in- 

 troduction and strict 

 enforcement of sanita- 

 tion clauses in all tim- 

 ber - sale operations. 1 

 These clauses include 

 the removal by burn- 

 ing of all heavily in- 

 fected standing trees 

 and all cull material 

 left on the area and 

 strongly advise the use 

 of healthy trees as seed 

 trees instead of dis- 

 eased ones. 



For the same reason 

 as given above for the 

 protection of you n g 

 growth in cut-over 

 areas, a disease survey 

 is even more necessary 

 upon proposed nursery sites, present nursery sites, and all plantation 

 sites. Wherever young trees are grown in close proximity to heavily 

 diseased native trees or alternate hosts of forest-tree rusts there 



1 Meinecke, E. I*. Forest-tree diseases common in California and Nevada. U. S. For- 

 est Service Manual, p. 02. Washington, D. C. 1014. 



Weir, J. R. Some factors governing the trend and practice of forest sanitation, in 

 Forestry Quart., v. 13, no. 4, p. 489. 1915. 



Meinecke, E. 1'. Forest pathology in foresl regulation. U. S. Dept. Agr. Bui. 275, 

 <;- p. ion;. 



Weir, .1. R. Larch mistletoe: Sonic economic considerations of its injurious effects, 

 r. S. Dept. Agr. Bui. ::iT, p. ^4. 1916. 



Weir, .1. K. Mistletoe injury to conifers i;i (lie Northwest. 1". S. Dipt. Agr. Bui. 360, 

 p. ::::-::T. 1916. 



Fig. 11. — Fomcs officinalis, chalk fungus, on western larch. 



