METHODS OF CONTROL AND PREVENTION 267 



Up to the present time such measures have not been under- 

 taken on an adequate scale and insect epidemics have be- 

 come more frequent. Where the epidemics occur in mature 

 timber the loss at the present day should be far less than in 

 the past, because logging operations can be directed so as to 

 utilize the insect injured timber. Extensive attacks upon 

 reproduction and middle aged timber or to inaccessible bodies 

 of mature timber afford the greatest hazard because such 

 losses cannot be salvaged. 



Methods of Control and Prevention. — Eventually the ne- 

 cessity of developing a systematic plan for the control and 

 prevention of injury by insects will be accepted as just as 

 fundamental as is similar action to secure fire protection. 



The intensive methods of prevention and control possible 

 in the protection of shade and orchard trees cannot be applied 

 to forest crops, because of their high cost in relation to the 

 value of the resource threatened. Dr. Hopkins^ estimates 

 that at least 30 per cent of the estimated loss due to insects 

 can be controlled or prevented by proper forest management 

 without appreciable extra cost. 



The complete extermination of an injurious insect is prac- 

 tically impossible. As Hopkins ^ explains this is unneces- 

 sary. "Experience has demonstrated that it is only neces- 

 sary to reduce and weaken its forces 75 per cent or more. It 

 cannot 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 becoming destructive." 



Methods of prevention and control may be summarized 

 under the following headings: 



(a) Protection and increase of the natural enemies of the 

 injurious insects. 



