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Yearbook of Agriculture 1949 



ing pulp mills. The practicability of a 

 pulp mill in Colorado using dead and 

 green wood is being explored. 



SEVERAL LESSONS have been well 

 learned. Underlying the rapid develop- 

 ment of this outbreak was the great 

 windfall of 1939. This sort of disaster 

 is something that can neither be fore- 

 seen nor prevented, and it may happen 

 again. The aftermath of heavy bark 

 beetle losses can be prevented, how- 

 ever, if measures can be taken in time 

 to prevent the build-up of populations. 

 Where it is feasible, the salvage of all 

 windthrown timber within 2 years after 

 it is blown down will deprive the beetles 

 of their favorite breeding material. 



Direct-control measures applied be- 

 fore an infestation becomes general 

 over a large area should prove effec- 

 tive. We know that the insect can be 

 destroyed by peeling and burning the 

 infested bark, by burning the infested 

 logs, or by the application of toxic 

 penetrating sprays. For example, a 

 mixture of oil and orthodichloroben- 

 zene has proved to be effective when 

 applied to the bark of infested trees or 

 logs. Further research may develop 

 new methods and insecticides which 

 can be applied from the air so as to 

 reduce costs and permit their use over 

 difficult terrain. 



Basic to any use of direct-control 

 methods is a well-organized system of 

 surveys that will detect the local cen- 

 ters of infestation and present a com- 

 prehensive picture of the infestation 

 before heavy increases occur. 



Research may also point the way to 

 forest-management practices based on 

 an adequate knowledge of the ecology 

 of Engelmann spruce stands and the 

 role of the beetle in their natural ro- 

 tation. There is a good possibility that 

 the Engelmann spruce beetle can be 

 held in check by indirect methods. In- 

 dications are that in healthy growing 

 forests severe epidemics are less apt to 

 occur. More access roads will permit 

 cutting to take place in the most over- 

 mature and decadent timber. Sanita- 

 tion cuts apparently must first be made 



without too much consideration of a 

 sustained-yield policy for management 

 of the species. 



Until we know more about the 

 forces that bring these sudden uprisings 

 of bark beetle populations and can 

 devise either direct or indirect methods 

 of dealing with them, Engelmann 

 spruce stands will continue to be sub- 

 ject to the hazards of devastating 

 beetle-caused losses. In this most re- 

 cent outbreak in Colorado, the best we 

 can do now is to accept what the 

 beetles have left us in the forest and 

 strive for better ways of controlling the 

 beetles next time. 



N. D. WYGANT is an entomologist in 

 charge of the Forest Insect Laboratory 

 in Fort Collins, Colo., in the Division 

 of Forest Insect Investigations, Bureau 

 of Entomology and Plant Quarantine. 

 A graduate of Purdue University and 

 New York State College of Forestry, 

 Dr. Wygant joined the Department in 

 1935. He has worked on insect prob- 

 lems affecting shelterbelts in the Great 

 Plains and the bark beetle and other 

 forest-insect problems in California 

 and the central and southern Rocky 

 Mountain region. 



ARTHUR L. NELSON is assistant 

 regional forester in charge of the Divi- 

 sion of Timber Management, State 

 and Private Forestry, Forest Service, 

 Denver. After graduation from the 

 University of Minnesota, he entered 

 the Forest Service in 1923 and was 

 assigned to timber-survey work on the 

 Bighorn National Forest in Wyoming. 

 He worked on the Black Hills, Routt, 

 and Roosevelt National Forests; sub- 

 sequently he was supervisor of the old 

 Leadville Forest and the Nebraska, Rio 

 Grande, and Ouachita National For- 

 ests. From 1941 to 1944 he was assist- 

 ant chief of the Division of Timber 

 Management in Washington, D. C. 



For further information about re- 

 search, the reader is referred to other 

 articles in this chapter, Insects, Dis- 

 eases, Parasites, and to the chapters on 

 Company Forests and The National 

 Forests. 



