232 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



the western pine beetle, reinfestation in the first year following 

 treatment has been limited to a zone within a mile of the 

 boundaries. On the other hand, some heavily concentrated in- 

 festations of the mountain pine beetle have apparently migrated 

 across 30 miles of open country to reinfest control units. 



Spotting 



The first step in connection with any control project is to locate 

 and mark all infested trees requiring treatment. The success of 

 any control project depends primarily on finding a high percentage 

 of the infested trees. To accomplish this the forest must be thor- 

 oughly and systematically searched by men who know an infested 

 tree when they see one. The spotting should be begun several days 

 before the treating and should be kept well ahead of it (fig. 106). 



Figure 106. 



-Ponderosa pines spotted for treatment in Black Hills beetle 

 control, Kaibab National Forest, Ariz. 



The strip method of spotting is the one best adapted to obtain- 

 ing a systematic 100-percent coverage of the area and is the one 

 now used on nearly all western bark-beetle projects. According 

 to this method, a compass man and from two to four spotters 

 run strips of uniform width back and forth across the area, 

 mark the infested trees and map their location so that they can 

 be found by the treating crews. With a three-man crew the com- 

 pass man, who is usually the chief of the party, runs an accurate 

 compass line, paces the distances traveled, records data relative 

 to trees marked for treatment, constructs a map showing their 



