72 SOME INSECTS INJXJEIOUS .TO FOEESTS. 



serious damage prevented, with little or no ultimate cost over that 

 involved in forest management and business methods. (Hopkins, 

 19046, 1906a, 1908a, 1909&.) 



There are, of course, certain insects and certain injuries which, 

 under present conditions and available information, can not be con- 

 trolled or prevented, but it is very evident that if the information 

 now available through the publications of the Department of Agri- 

 culture and through direct correspondence with its experts is properly 

 utilized in the future it would result in the prevention of at least 30 

 per cent of the estimated annual waste of forest resources that has 

 been caused by insects within recent years, and thus contribute greatly 

 to the conservation of forest resources. 



GENERAL PRINCIPLES OF CONTROL. 



The ordinary spraying and similar methods employed in dealing 

 with fruit and shade tree insects are, of course, not available for 

 practical appli(ption in the case of forest trees. But there are other 

 and less expensive methods of accomplishing the desired results. 



In all efforts to control an outbreak or prevent excessive loss from 

 forest insects it should be remembered that as a rule it is useless to 

 attempt the complete extermination of a given insect enemy of a 

 forest tree or forest product. Experience has demonstrated that it 

 is only necessary to reduce and weaken its forces 75 per cent or more. 

 It can not then continue an aggressive attack, but must occupy a 

 defensive position against its own enemies until conditions resulting 

 from avoidable negligence and mismanagement by the owners of the 

 forests and manufacturers of forest products favor its again becom- 

 ing destructive. Forest insects can thus be easily kept under control 

 by good management. 



The desired control or prevention of loss can often be brought about 

 by the adoption or adjustment of those requisite details in forest 

 management and in lumbering and manufacturing operations, stor- 

 ing, transportation, and utilization of the products which at the 

 least expenditure will cause the necessary reduction of the injurious 

 insects and establish unfavorable conditions for their future multipli- 

 cation or continuance of destructive Avork. 



It is, however, of the utmost importance that any adjustment or 

 modification in management or business methods should be based on 

 expert technical knowledge or advice relating to the species, habits, 

 life history, and natural enemies of the insects involved and the es- 

 sential features of the methods for their control. This should be 

 supplemented by expert knowledge or advice on the principles of 

 technical and applied forestry in the proper management, care, and 

 utilization of the forest and its resources, and still further supple- 

 mented by practical knowledge and experience relating to local con- 



