CONCLUSIONS 



The results of the season's work lead to the following conclusions. In 

 the areas sampled, root diseases are common in mature western white pine, the 

 most common being shoestring root rot caused by Armillaria mellea , a fungus 

 which is apparently a widespread saprophyte in the soils of the western white 

 pine type. Since evidence of root infection by this fungus can be found in 

 apparently healthy trees as well as in obviously unhealthy and dying trees, 

 and since increment reductions attributable to infection have occurred for 

 many years, it must be concluded that infection is of long standing in certain 

 trees . 



The precise role of root diseases, especially shoestring root rot, in 

 the decadence of mature pine stands, is as yet uncertain. Whatever their role 

 may be, and whatever the role of endemic infestation of the mountain pine 

 beetle may be, it appears unlikely (but not impossible) from the meager data 

 at hand that root diseases increase the probability of attack and death by 

 the mountain pine beetle. 



Specific information is still lacking on (1) the prevalence of root 

 diseases in mature western white pine on different sites; (2) the relation 

 of tree age and method of stand establishment to susceptibility; (3) the 

 relative aggressiveness and virulence of existent strains of Armillaria mellea 

 and other root pathogens; (4) the effects of individual site factors on re- 

 sistance of the tree and aggressiveness of the fungi; (5) the influence of 

 root infection on beetle attack; and (6) the relative susceptibility of the 

 different tree species which composes the western white pine type. Informa- 

 tion on these questions would assist in the intelligent formulation of 

 practioal recommendations for the reduction of losses in the remaining virgin 

 stands as well as in the managed stands of the immediate future. 



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