184 MISC. PUBLICATION 278, U. S. DEPT. OF AGRICULTURE 
BARK-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 
torest 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 must 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 should be bounded by natural barriers, such 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 begun 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 ali 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 
