;[gQ MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



damage or the course the epidemic may take if no control is under- 

 taken, and conckisions as to the success of a bark-beetle project 

 can only be deduced on the basis of an estimate of what would 

 have happened if no control work had been undertaken. Control 

 measures applied during the decline of an outbreak often tend to 

 place an inflated value upon the results obtained. On the other 

 hand, control undertaken during the time an outbreak is building 

 to an epidemic may show little reduction in damage and give the 

 appearance of failure. The best that can be done is to compare the 

 trend of the epidemic on the treated area subsequent to control with 

 that on a similar neighboring area where no work w^as done. 



To protect valuable forest areas from bark-beetle outbreaks cer- 

 tain steps should be taken. These may be summarized as follows : 



(1) A general reconnaissance or detection survey of valuable 

 forest types subject to bark beetle epidemics should be made each 

 year to detect the beginning of any outbreak. If an outbreak is 

 indicated, a decision should be reached by the ow^ners or those respon- 

 sible for forest protection as to whether timber values in or adja- 

 cent to the site of a detected outbreak warrant the probable expense 

 of a control operation. If so — 



(2) An extensive bark-beetle survey should be undertaken, usually 

 under the supervision of a competent forest entomologist, to deter- 

 mine {a) the trend of the outbreak and the possibilities of natural 

 control; (b) The area involved in the infestation and threatened 

 by it; (c) wdiat areas must be included in the control program; (d) 

 the number of trees that will require treatment, and the area that 

 must be covered in the first season; and {e) the probable cost and 

 results to be expected. In the light of the complete information 

 furnished by the extensive survey, a decision can be reached as to 

 the need and justification for applying artificial control measures, 

 and whether or not the necessary cooperation of all affected owners 

 can be obtained and the work adequately financed. If control work 

 is decided upon, then — 



(3) A control campaign should be outlined and prompt and thor- 

 ough control measures should be applied to all units showing epi- 

 demic trend within the project area. This should be followed by 

 treatment of such outlying areas as may jeopardize results in the 

 cleaned units. 



(4) A maintenance control program should be continued until a 

 natural balance has been restored. 



Detection of Bark-Beetle Outbreaks 



If forests are to be protected from serious damage or destruction 

 by bark beetles, incipient outbreaks must be promptly discovered and 

 reported. If such a system is consistently carried out, it will greatly 

 reduce the ultimate cost of protection and prevent the building up 

 of disastrous and uncontrollable infestations. 



The first reporting of outbreaks devolves upon the timber owners, 

 the State or Federal forest rangers, or others who are primarily 

 responsible for the protection of forests. Such work is analogous 

 to that of the forest-fire detection system. 



This detection work should be so planned that all valuable forest 

 types subject to bark-beetle outbreaks are given some measure of 



