2 BULLETIN 799, U. S. DEPARTMENT OF AGRICULTURE. 
relation of various factors to the rots, and the means by which the 
loss may be reduced. This, in short, states the purpose of this 
bulletin. 
LOCAL PATHOLOGY OF WESTERN WHITE PINE. 
With the exception of the principal fungus (E chinodontvwrri tine- 
torium) attacking western hemlock and grand fir, all fungi occur- 
ring on other trees of the western white-pine type attack white pine 
to a greater or lesser degree. Until it is determined that the inter- 
relations of these fungi vary with different species of trees the con- 
ditions for fungous development may be considered very favorable. 
The western white-pine type of forest is described as having western 
white pine as the key tree and forming approximately 15 per cent 
or more of the stand. In some parts of its range (northern Idaho) in 
young stands western white pine forms as much as 50 per cent or 
more of the stand. The other species in the mixture are grand fir 
and western red cedar, the predominant trees of the type, and Doug- 
las fir, western larch, western yellow pine, and lodgepole pine. In 
many of the mixtures of the western white-pine type, the white pine, 
although intermediate as to tolerance, very rapidly gains on its asso- 
ciates and eventually overtops them or may even drive them from 
the stand. One of the results of this suppression of associate species 
is to promote the activities of fungi in the associate species, which 
in turn react on the white pine. Fully stocked or even pure stands 
of western white pine may be found extensively attacked. In the 
fully stocked stands the trees do not prune readily, causing the de- 
velopment of larger and older dead branches which are open to 
breakage and infection at an earlier age and also affecting the grade 
of lumber of the tree. In the pure stands, much suppression naturally 
results and fungous diseases are just as prevalent as in a mixed stand. 
Suppression in white pine is not always brought about by overcrowd- 
ing or by adverse conditions on sites having little protection. Xeeclle 
fungi may cause retardation by destroying the needles. Lophoder- 
mium pinastri, in its ascigerous stage and also in its pyenidial stage 
(Leptostr&ma) , is a very common needle fungus throughout the 
white-pine type and is a factor to be considered in suppression. 
Mistletoes rarely attack white pine within its merchantable range 
and may be overlooked as a cause of suppression. 
The three main wood-destroying fungi 1 for the areas studied are 
Trametes pini, Pohjporus schwein itzii, and Femes annoms. The first- 
named fungus, as the most important, is particularly active in west- 
ern white pine throughout its merchantable range. 
1 Weir, J. R., and Hubert, E. E. Forest disease surveys. U. S. Dept. Agr. Bui. 658, 
23 p., illus. 1918. 
