22 BULLETIN 799, U. S. DEPARTMEITT OF AGRICULTUEE. 



number of dead branches on trees of the bottom sites. Site is ap- 

 parently responsible for a greater percentage of sporophores de- 

 veloping on the trees of the bottom sites. An average for the bot- 

 tom sites gives a distribution of 11 sporophores to every 10 trees, 

 while the slope sites have 8 sporophores to every 10 trees. The pro- 

 portion of live and dead sporophores to the total sporophores is 

 about equal on each type of site, 93 per cent alive and 7 per cent 

 dead. The proportion of live and dead sporophores to the total, in 

 the case of the largest sporophores, shows a percentage approaching 

 that already given, also showing very little variation in respect to 

 site. A greater number of sporophore-bearing trees are found upon 

 the bottom sites. 



METHODS OF CONTROL. 



From the study of the data presented, it appears that the control 

 of diseases in western white pine under the present stage of forestry 

 in the Northwestern States will be a difficult matter and subject to_ 

 extensive rather than intensive methods. The high economic value 

 of the tree and the large amount of loss due to' rot are two important 

 factors which make it imperative that steps be taken at least to 

 check the diseases and that attempts be made to reduce the annual 

 loss of sound material brought about by the spread of the casual 

 organisms. 



There are two methods of control which present themselves as 

 practicable under the present methods of forest management. These 

 two methods work hand in hand. The first method is primarily 

 based upon the rotation of the stand or the felling age. It is evident 

 from a study of the data presented that if the stand is cut before any 

 sporophores are produced, or before they are produced in any great 

 numbers, the spread of the diseases will be effectively checked. The 

 data show that a certain age class represents the period in the stand 

 which develops a maximum of sporophores. This period in western 

 white pine is represented hj the 121 to 160 age class. This age 

 class has 43 per cent of the total trees bearing sporophores for the 

 bottom sites and 45 per cent for the slope sites. Both the next lower 

 and the next higher age classes have smaller percentages for the two 

 types of site than the 121 to 160 age class. If the felling age of west- 

 ern white pine is kept within the 101 to 120 age class there is every 

 reason to believe that the infected trees will be cut down before they 

 reach the age of maximum sporophore production. Most of them 

 will no doubt be cut down before any fruiting bodies whatever 

 appear. This is the most desirable result and is particularly true 

 for the slope sites. 



The second method is fundamentally concerned in the strict appli- 

 cation of proper pathological marking rules and the consequent re- 



