34 BULLETIN 722, U. S. DEPARTMENT OF AGRICULTURE. 
in a solution of such forest-regulation problems as are appreciably 
influenced by the presence of decay in the stand. When once the 
forester reaches the point in his calculations upon a proposed sale 
where he can determine a certain rot percentage as the maximum to be 
considered in a stand in order to secure the required amount of sound 
material at a minimum cost, with this rot percentage as a basis it 
will be comparatively easy to compute the cutting age of that stand. 
METHODS OF CONTROL. 
The methods of control applicable to such types as are here under 
discussion can be little other than extensive. The foregoing data, 
owing to the small number of trees included in some of the age classes 
and to apparently unavoidable errors, are not to be one as exact 
in determining the cutting age but are given merely as an aid to this 
determination. Thieme control methods can not be applied to 
logging operations where extensive logging methods are practiced. 
“Methods such as can be readily incorporated into the usual routine of 
logging operations and conforming to the practice of the Forest 
Service are the only ones which can hope to fill the need for forest 
sanitation among the all-practical lumbermen and foresters. Inten- 
sive control can be practiced to a limited extent only upon such sales 
areas as warrant the additional cost. 
The control of wood-destroying fungi is not a matter comparable to 
the curative treatment of human disease, but is solely dependent for 
its success upon prevention. With few exceptions there is no help for 
a stand after it is once attacked by the fungus; hence, if preventive 
measures are to be effective they must precede the infection, or at 
least precede the period when the production of spores endangers the 
remaining healthy trees. There are several methods applicable to the 
hemlock type, and these can be grouped under two heads, sanitation 
clauses in timber sales‘ and pathological rotations. Under the 
first come such suggestions as girdling, killing by burning of infectious 
cull material and piled brush, thinning, and the direct cutting and 
burning of infected material. Under the second appear such methods 
based upon a study of the area in question as would lead to a cutting 
cycle aiming to secure the maximum amount of sound material with 
a minimum risk of future infection and at a minimum of cost. Each 
particular sale area has its individual variations affecting the patho- 
logical condition of the stand. The species in the mixture and the 
relative percentage of each, the slope and exposure, the moisture 
conditions, the cost of logging, the value of the species in the stand 
(in fact, all the environmental and economic factors) have to be 
taken into consideration before an ee can be made to determine 
a method of uo 
1 Meinecke, HE. P. Op. cit., p.62. 1914. 
