] 94 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



was first advocated by Hopkins for the control of Dendroctonim 

 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 {o3a). 



This method serves the dual purpose of controlling the bark 

 beetles and salvaging timber that otherwise would be completely 

 worthless within a short time. '\"\niere 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 introdace 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 

 difBcult, so logging must be supplemented in many cases by the 

 ordinary control methods. 



MAINTENAJNTCE 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 migi^ations 

 occur, a T5-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 



