196 MISC. PUBLICATION 2738, U. S. DEPT. OF AGRICULTURE 
ness of the terrain, the accessibility of the area, the current cost of 
labor, and so many other factors that it 1s impossible to give any 
specific costs which might apply to a given situation. Some idea 
of the approximate cost of the work, however, may be obtained from 
experience gained during the decade from 1921 to 1930. 
In the ponderosa pine region of California, Oregon, and Washing- 
ton the control of the western pine beetle cost on an average about $4 
per treated tree, with the cost In some cases dropping as low as $1.75 
per tree. In the control of the Black Hills beetle in ponderosa pine 
of the Rocky Mountain region the cost per tree averaged about $1.50 
with some costs as low as 75 cents per tree. 
The control of the mountain pine beetle in lodgepole pine forests, 
where either the solar-heat method or the fell-deck-burn method was 
used, cost on the average from 50 cents to $1 per treated tree, de- 
pending largely on the intensity of the infestation. Under similar 
conditions the solar-heat method is the cheaper of the two. 
The control of mountain pine beetle infestations in western white 
pine cost about $4.50 per tree, and in sugar pine, on account of its 
very large size, the costs sometimes amounted to as much as $16 per 
tree. 
For the treatment of a few scattered trees around summer homes 
or in inaccessible areas the costs will run higher than on large-scale 
projects. 
Bark-beetle control work has been in progress in western forests 
since 1911, and the results of this work have indicated rather 
definitely what can be expected in the control of some of the more 
important species (27). 
Wherever bark beetles have been primarily responsible for the 
death of trees, the application of control measures has resulted in 
reducing the infestation or in restoring the natural balance so as 
to bring the outbreak under control. With such aggressive tree- 
killing species as the mountain pine beetle and the Black Hills beetle, 
control work has been very effective in quickly suppressing outbreaks 
wherever a high percentage of the infested territory could be covered 
in a single season and the results were not nullified by migrations 
from distant areas. Western pine beetle epidemics have so fre- 
quently been partly dependent upon a weakened condition of the 
host tree that the results from control have not been so clear-cut. 
Infestations have been reduced, but unless the work is continued 
or conditions bring about improved tree resistance, the reductions 
brought about by control efforts are difficult to maintain, 
At best, remedial bark-beetle control is only a temporary expedient, 
or a method of suppressing outbreaks that have been brought about 
through some interruption, disturbance, or failure of the biological 
balance. The only permanent protection is through the management 
of forest properties so as to maintain the natural balance, or if this 
is broken by forces beyond man’s control, to be able to salvage the 
killed timber quickly enough to prevent excessive loss. 
