A NATIONAL PLAN FOE AMERICAN FORESTRY 727 



spent each year for the protection of valuable timber stands. For 

 the past three years the Forest Service has spent from $100,000 to 

 nearly $200,000 annually, the Park Service from $40,000 to $50,000, 

 and the Bureau of Indian Affairs from $10,000 to $20,000. 



A candid appraisal of the results secured from the $1,000,000 spent 

 in the control of tree-killing bark beetles has been made by the Bureau 

 of Entomology. 2 In general it can be said that the value of timber 

 saved through this work has been a great deal more than the total 

 expenditures put into control. 



Control work has been directed against seven species of bark beetles. 

 Each of these beetles presents an entirely different problem in each 

 forest region and in each forest type. Consequently every project 

 must be considered separately, as attention must be given both to 

 the administrative and to the entomological features. Control 

 methods necessarily must be based upon information regarding the 

 seasonal history and habits of the insects, and also upon certain con- 

 ceptions and theories, the validity of which can be proven or dis- 

 proven only by trying out in practice. Early biological studies of 

 these tree-killing bark beetles resulted in the adoption of certain 

 control practices. These methods, although theoretically effective, 

 were admittedly too expensive to adopt under all circumstances and 

 it was recognized that much improvement was desirable. Even now 

 and for some time in the future this type of work will be largely 

 experimental in that uniformly good results cannot be guaranteed 

 until a background of experience is developed. The increasing 

 annual expenditures for control made it possible to experiment with 

 new technique with the result that the present average cost per tree 

 has been reduced by nearly half that of the average cost of a few 

 years earlier. 



The so-called ' 'sun-curing method" is used in the control of the 

 mountain-pine beetle in lodgepole pine in the vicinity of Crater Lake, 

 Oreg. This was first tested in 1925 and 1926 and has been applied 

 on an increasing scale up to the present time. It consists of simply 

 felling and limbing the tree, allowing it to lie exposed to the sun for 

 a few days and then turning the other side of the log to the sun's 

 exposure. The cost of treatment per tree in this park was reduced 

 from $1.75-$2 to 40-50 cents, depending on accessibility and seasonal 

 conditions. 



Again, with the same beetle in the enormous lodgepole pine infesta- 

 tions in Yellowstone National Park and the surrounding national 

 forests, a method was devised for burning the bark from the trees 

 while standing. This effectively killed the beetles and cost in the 

 neighborhood of 50 cents per tree when it was possible to get fuel 

 oil into the forest by road. The former type of control cost in the 

 same locality averaged $1.50-$2 per tree. 



The possibilities of tree medication for the control of bark beetles 

 have been experimentally tested for the past few years. This calls 

 for the injection of chemicals into the sap stream of the tree which 

 in turn will prevent the development of the bark beetle broods and 

 do away with the costly operations of felling and barking or burning 

 the tree. There appears to be much promise in this field but it is 

 yet too early to be confident of results. 



Journal of Forestry, vol. 29, no. 7, November 1931. 

 168342 33 vpl, X 47 



