30 BULLETIN 14 9 9, U. S. DEPARTMENT OF AGRICULTURE 
On the limited areas where cutting all mature and defective trees 
leaves a stand consisting only of seedlings or saplings, special provi- 
sion must be made for seed trees. These are needed to provide for 
complete stocking and to insure against total loss of productivity 
through fire. An average of at least two, and preferably four to 
six well-spaced trees, of seed-bearing size, to the acre should be left. 
Trees with spike tops or other defects may serve if absolutely neces- 
sary, but usually sound trees will be available. Particular attention 
should be given to leaving seed trees along the edges of openings and 
on ridges. 
iMIXOK MEASUKES 
Sanitation and insect control. — Mistletoe is a parasitic plant which 
draws its sustenance from the soft inner bark of several species of 
trees and results in abnormal form, slackened growth, and gradual 
death of the tree. In this region damage from this source is gen- 
erally most severe to lodgepole pine and western yellow pine, al- 
though Douglas fir is the hardest hit of any species in the western 
portion. Heaiuly infected trees are characterized by a general ap- 
pearance of unthriitiness; poor, thin crowns; sickly, pale-colored, 
and often short needles; distorted branches, many dead or dying; 
and the presence of " witches' brooms.*' Infected trees, as far as 
practicable, should be cut; but where soil conditions are poor it may 
never be possible to eradicate this parasite entirely. 
Lodgepole pine is subject to canker infections which cause rot and 
often result in breakage at the point of infection. Trees with large 
cankers and trees rendered unmerchantable on account of rot should 
be cut to j^revent the spread of the disease to other green trees. Those 
with smaller infections in a dormant condition and not seriously 
weakening the tree should be cut only when this can be done with 
benefit to surrounding trees. 
The number of trees cut for sanitation does not exceed an average 
of 2 or 3 per acre, save in some overmature stands in the lodgepole 
pine type, where as many as 15 unmerchantable diseased trees may 
be found on an acre. The expense of cutting such trees of saw-log 
size usually averages about 25 cents each. Charged against the 
merchantable cut, this usually does not exceed 10 cents a thousand 
board feet, or in extremely overmature stands 35 to -10 cents a thou- 
sand. This does not take into consideration the stumpage value of 
the sound portions of the trees, and which may equal or even exceed 
the actual cost of cutting. 
Invariably some damage occurs throughout the forest as a result 
of insect infestations of a normal character. It would be difficult if 
not entirely impractical to attempt to eliminate all losses from this 
source, but such infestations should be observed and control measures 
undertaken at the proper time so as to avoid the development of 
serious epidemics. Even though enormous damage results at the 
time, such infestations eventually come to an end through the work 
of natural parasites. Reproduction will come in again, but the an- 
nual yield will be seriously reduced for many years. 
The most serious epidemic thus far is the bark-beetle attack which 
is now in progress in the lodgepole pine type in Montana. An 
epidemic of spruce budworm in progress for several years in the 
Douglas fir type in the Shoshone National Forest in northwestern 
