24 BULLETIN 199, U. S. DEPAKTMENT 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 $7,201,260, or 1,658 million feet B. M., in the forests of 

 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 Coeur 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. 



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