INSECTS INJURIOUS TO FOREST TREES 



^^^HE true relation of forest insects to forest conservation has not generally 

 l^J been fully recognized, yet the annual loss of standing timber that is 

 ^*"^ killed or reduced in value by injurious insects is estimated by the Bureau 

 of Entomology of the United States Department of Agriculture, through its 

 expert in charge of forest insect investigations. Dr. A. D. Hopkins, at 

 $62,500,000. If this estimate is approximately correct it will at once be seen 

 that insect control assumes an importance beside fire control in any scheme of 

 forest conservation. 



Fortunately, while this danger to our forest trees has been given so little 

 popular attention, no subject relating to our forests has received more thorough 

 and exact scientific investigation. The Bureau of Entomology, starting ten 

 years ago with very little knowledge of the conditions, has accumulated in that 

 period a notably full and exact knowledge of the life-history and habits of the 

 principal species of insects that are destructive to our forest trees, and not 

 only that but also, based upon it, a clear conception of means and methods of 

 control, so that Dr. Hopkins does not hesitate to say with absolute certainty 

 that these species can be controlled so as to be comparatively harmless. This 

 conclusion is based not upon laboratory work and theory, but upon results 

 actually accomplished on so large a scale as to afford positive proof of the fact. 

 The results of the Bureau's work in this field have been made accessible in a 

 series of circulars of the Bureau of Entomology, prepared by Dr. Hopkins,* 

 and in the bulletins from which they are derived. 



In this connection it is worth while to note that an important work is now 

 being done in the Northwest through cooperation of the United States Forest 

 Service, the states, and private owners, under the direction of United States 

 Bureau of Entomology experts. This is on the largest scale yet undertaken. 

 It is the beginning of a system of field stations to be established by the Bureau 

 of Entomology in every forest district. By means of these stations the expert 

 knowledge of the bureau can be made available and forest rangers, state forest 

 officers, and the foresters and cruisers of private owners can be trained to put 

 into practice the principles of scientific insect control. For it must always 

 be remembered that successful control must be based upon complete knowledge 

 of the insects and must be rightly dii'ected. It would not be wise for laymen 

 to undertake this work even after a study of the publications summarized in 

 this article, without expert direction. And here is where the value of the 

 Bureau of Entomology comes in, for it places at the command of land owners, 

 at insignificant cost, expert scientific knowledge of the highest type. 



INSECTS WHICH KILL FOREST TREES 



Of all classes of insects which attack our forest trees and their products, 

 the bark beetles of the species Dendrocfonus are the most serious menace to 

 our forests, and fortunately are among the best known and understood. It is 



♦Circular No. 125. Insects Which Kill Forest Trees. 

 Circular No. 126. Insects Injurious to the Wood of Living Trees. 

 Circular No. 127. Insect Injuries to the Wood of Dying and Dead Trees. 

 Circular No. 128. Insect Injuries to Forest Products. 

 Circular No. 129. Insects in their Relation to the Reduction of Future Supplies 



of Timber, and General Principles of Control. 

 These circulars are all revised extracts from Bulletin No. 58, Part V., Bureau of 

 Entomology, United States Department of Agriculture. 



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