24 BULLETIN 799, TJ. S. DEPARTMENT OF AGRICULTURE. 
It is found that an average rot percentage of 7 represents the 
proportion of sound wood rotted by these agencies in the stands of 
timber classified under the western white-pine type. This represents 
a loss of $7,201,250, or 1,658 million feet B. M., in the forests of f 
British Columbia, Oregon, Washington, Idaho, and Montana. 
The data indicate that the factor of age is prominent in deter- 
mining the amount and stage of decay in a stand. The age of 
earliest infection was found to be approximately 50 years for the 
trees in general for the Cceur d'Alene region of Idaho. 
Site is found to have a bearing upon the rot in the stand. The 
bottom site, in general, is found to be more favorable to the devel- 
opment of fungous diseases. Site, apparently, has no great effect 
upon the percentage of trees infected, both sites showing approxi- 
mately the same percentage. A larger percentage of the slope trees 
were in the heavier infected age classes. This was not the case for 
the bottom sites, and therefore a direct comparison of the total 
percentage of trees infected gives figures which are higher for the 
slope sites than would otherwise be true. In general, a greater rot 
percentage, a greater percentage of infected trees, a greater amount 
of butt-rot, a greater degree of injury, and a larger average num- 
ber of sporophores per tree are recorded for the bottom sites than 
for the slopes. This indicates that the bottom sites are more favor- 
able to the development of fungous diseases. 
With increased age up to a certain point comes an increase in the 
number of sporophore-bearing trees and an increase in the degree 
of injury. 
The maximum production of sporophores is found to occur in the 
121 to 160 age class. The 101 to 120 age class presents, in so far as 
the rot data show, favorable figures upon which to determine a 
pathological felling age. 
The high economic value of the tree coupled with the large amount 
of loss annually sustained through heart-rotting fungi makes it 
highly necessary to attempt control methods. 
The loss due to rots may be reduced by the application of control 
methods aiming to prevent the spread of the organisms causing 
decay. 
Proper pathological marking rules and practical methods for the 
disposal of infected slash on sale areas are recommended as methods 
of control. 
ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
5 CENTS PER COPY 
