134 ^IISC. PUBLICATION 273, U. S. DEPT. OF AGIUCULTURE 



Bakk-Beetle Control Projects 



The objective of bark-beetle control is to destroy such a high 

 percentage of the destructive beetles that the aggressive character 

 of an outbreak will be broken and the remaining infestation will be 

 held in check by natural control factors. This involves the treat- 

 ment of as nearly all of the infested trees within the natural bounda- 

 ries of an affected area as is feasible within physical limitations; 

 and if migrations threaten from neighboring areas these areas also 

 should be included in the control campaign. Beetle outbreaks, like 

 forest fires, if not promptly taken in hand, are soon apt to increase 

 beyond the practical limitations of artificial control measures. 



THE control unit - 



The size of the area that must be included in any control project 

 in order to obtain satisfactory results is an important point that 

 must be given consideration in making the control plans. The feasi- 

 bility of a project will frequently depend on the possibility of limit- 

 ing the control area to a unit that can be covered in a single season 

 with the available man power. 



First consideration mtist be given to the flight habits of the 

 beetles, and the control area should be made large enough to reduce 

 to a minimum the possibility of any large number of beetles flying 

 in from neighboring infested tracts. As far as possible, control 

 units shotild be bounded by natural barriers, stich as high ridges, 

 open valleys, or broad strips of timber of a different type. If these 

 are lacking, then the control area must include all infestation within 

 the flight range of the beetles. This range for practical purposes 

 depends on the intensity of the beetle population in any neighboring 

 area. For instance, in cases where a treated unit is surrounded by 

 scattered infestations of 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, heavy concentrated 

 infestations of the mountain pine beetle have in some cases appar- 

 ently 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. This is referred 

 to as ''spotting'" and is one of the most important phases of the 

 work, since the success of any control project depends primarily on 

 finding a high percentage of the infested trees. To accomplish this 

 the forest must be thoroughly and systematically searched by men 

 who know an infested tree when they see one. The work should 

 be begtin several days before the treating and should be planned so 

 as to keep it well ahead of the treating work (fig. 88). 



The strip method of spotting is the one best adapted to obtaining 

 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, locate the infested 

 trees, blaze them or mark them, and map their location so that they 

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



