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 to 
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.t 
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 young 
growth in cut-over 
areas, a disease survey 
1S 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 
Fic. 11.—Fomes officinalis, chalk fungus, on western larch. 
1 Meinecke, E. P. Forest-tree diseases common in California and Nevada. U. S. For- 
est Service Manual, p. 62. Washington, D. C. 1914. 
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. P. Forest pathology in forest regulation. U. S. Dept. Agr. Bul. 275, 
62 p. 1916. 
Weir, J. R. Larch mistletoe: Some economic considerations of its injurious effects. 
U. S. Dept: Agr] Bull 317, ps 24. -91'6: k 
Weir, J. R. Mistletoe injury to conifers in the Northwest. U. S. Dept. Agr. Bul. 360, | 
p. 33-37. 1916. 
