MARKING RUIvES FOR IDAHO AND MONTANA 679 



yellow pine very rarely attacks lodgepole, and the species on Douglas 

 fir not at all. These two parasites should be considered wholly in re- 

 lation to their specific hosts when occurring in the lodgepole-pine type. 

 The rusts of lodgepole are also chiefly confined to the species and should 

 be considered chiefly from the standpoint of injury to reproduction. If 

 reproduction is infected, mature, full-sized trees will not result. The 

 infection of older growth may or may not interfere with the economy 

 of the situation. 



The Western Vcllozv-pine Type 



The western yellow-pine type usually occurs upon sites which are 

 drier and more open than the other types discussed, with the exception 

 of the lodgepole-pine type. Nevertheless, considerable heart rot is found 

 in the western yellow-pine type. This is true in the more moist or 

 higher stations of the type where it becomes associated with Douglas fir. 

 With the increasing density of the mixture, the yellow pine becomes 

 more defective, due in part to the introduction, into the formation, of 

 diseases usually associated with Douglas fir. Heavier marking should 

 be practiced under such conditions. Mistletoe (Razoitiiiofskya cam- 

 pylopoda) attacks the principal tree of the type and causes considerable 

 damage in certain localities, the young growth suffering the most dam- 

 age. The pine rusts (principally Cronartium pyri forme and C. Ulamen- 

 tosiim) are very common on yellow pine, causing damage and death to 

 the branches of mature trees and killing young growth by the formation 

 of large galls and cankers. 



Even before the cutting, the openness of the stand in this type, no 

 doubt, aids in the suppression of sporophore production. Yet this same 

 openness allows of a freer and wider distribution of the spores, once 

 they are formed, and, the stand being more or less pure, the spores will 

 fall on susceptible hosts. The stand left upon the area for a future cut 

 should be given every chance to develop a maximum of sound material, 

 and this can only be brought about by safeguarding the trees left upon 

 the area and preventing their infection. Diseased trees capable of pro- 

 ducing fruiting bodies of any of the various tree diseases (rots, rusts, 

 or mistletoes) should not be left as part of the stand reserved for a 

 future cut. These diseased trees, if left standing, will prove a means of 

 distributing the diseases, and the infection of sound young trees will 

 result. Since the majority of sales in the western yellow-pine type in 

 this region are managed under some form of selection cutting, recom- 

 mendations for pathological marking on such areas are identical with 



