194 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
was first advocated by Hopkins for the control of Dendroctonus 
beetles. He proposed that the infested logs be removed from 20 to 
50 miles from the forest so that the beetles emerging from them 
would find no trees to attack. Often this method has been followed 
unwittingly by logging operators who have cut infested trees and 
sent them to distant mills or burned the slabs; and this, together 
with the removal of beetles in recently felled green logs, explains the 
absence of insect-killed trees around many going logging operations. 
Of late years this method has come more and more into favor with 
the opening up of forest tracts and the development of truck log- 
ging, which has made possible the removal of scattered infested 
trees at comparatively low costs (53a). 
This method serves the dual purpose of controlling the bark 
beetles and salvaging timber that otherwise would be completely 
worthless within a short time. Where the method can be used it 
is economical and sometimes can be carried out with a small imme- 
diate profit from the operation in addition to suppressing the beetle 
outbreak. Even if the logging operation is carried out at a loss of 
from $1 to $2 per thousand board feet of timber, it is better than 
spending $3 or $4 a thousand feet to fell the trees and burn them or 
leave them in the woods, as is the case with the usual control opera- 
tions. The reduction of infestation by either method will be the 
same, 
In inaccessible areas the method cannot be applied except at a cost 
in excess of that of the ordinary control methods, and of course 
cannot be used in the control of bark beetles attacking unmerchant- 
able species of trees whose chief value lies in the protection of water- 
sheds or as a forest cover in parks and recreational areas. Moreover, 
bark beetles introduce blue stains which discolor the sapwood before 
there is any possibility of salvage, and thus reduce the value of the 
material. In ponderosa pine areas it rarely pays to salvage tops or 
trees less than 22 inches in diameter, and such unmerchantable mate- 
rial must be burned to complete the control operation. Because of 
immediate blue staining the value of the logs taken out of the woods 
is reduced approximately 50 percent below that of green logs, so 
returns from the operation must be computed on that basis. If the 
method is to be effective, the beetles on an entire unit must be de- 
stroyed in a single season, which means that the logging operation 
must frequently be extended over a very large area. This is often 
difficult, so logging must be supplemented in many cases by the 
ordinary control methods. 
MAINTENANCE CONTROL 
One season’s treatment of an area will rarely be sufficient to bring 
an outbreak under control. Even with the most careful spotting and 
treatment some infestation will be missed that will give rise to new 
infestation the following year. A follow-up program, or mainte- 
nance control, is therefore necessary ‘until the normal balance is 
restored and the bark beetles reduced to an endemic status. 
With infestations of the mountain pine beetle, unless migrations 
occur, a 75-percent reduction is usually obtained following the first 
season’s work, and one or two seasons of maintenance work will 
usually bring the epidemic under complete control. In western pine 
