186 MISC. PUBLICATION 278, U. S. DEPT. OF AGRICULTURE 
such timber. When large groups of infested trees are encountered, 
all spotters assist in marking all trees within the group, even though 
it extends over into the next strip. The spotter who has had the 
outside course should always be on the inside during the return 
trip, as he is familiar with the boundaries of his strip. 
The trees selected for treatment are marked in different ways, 
varying from a blaze to a cloth or card tag tacked upon the tree. 
When fags are used, it is a good plan to blaze and number the tree 
on the opposite side, as this permits the relocation of trees in case 
tags are destroyed. ‘The data placed upon tags will vary for each 
project, depending on what information is desired. Each tree should 
be numbered regardless of the type of mark used, so that a check 
can be maintained on the trees treated. After a tree has been 
treated the tag is removed, and ali tags are turned over to the project 
superintendent at the close of the day’s work and checked against 
the serial numbers of the trees marked within the area. 
BARK-BEETLE SUPPRESSION METHODS 
Methods of bark-beetle control must take into consideration the 
varying habits of the insect species, the trees affected, the locality, 
and the environmental conditions encountered. Methods effective 
in one area cannot be used in other areas even against the same in- 
sect because of differences in local conditions. Methods suitable for 
the control of an insect in a tree with thin bark cannot be used in 
cases where the same species is infesting a tree with thick bark. 
Differences in latitude and altitude have an important bearing on 
the success of the sun-curing method, and the differences of type and 
forest cover will often be a determining factor in the selection of 
a suitable control measure. It is often necessary to use two or 
more methods, even on a single project, because of differences in ex- 
posure or site conditions, the size of trees infested, or the height 
of the infestation in the trunk. 
Some of the methods that have been of greatest usefulness in the 
past are the following: 
(1) Burning methods; in which the trees are felled, partly peeled, and 
burned; felled and rolled into decks and burned; or burned standing. 
(2) Peeling methods; in which the bark is removed from the tree, and 
be Boa exposed to predators or left to die through exposure to the sun’s 
1eat. 
(3) Solar-heat method; in which the trees are felled and the insects killed 
by the sun’s heat without peeling the bark from the logs. 
(4) Submerging infested logs in water and drowning the insects. 
(5) Removing the infested trees from the woods through logging opera- 
tions before the insects have had time to emerge and escape. 
Since most of the destructive bark beetles confine their attacks 
to a few species of trees, control can be carried out by treating just 
the affected host trees. 
The fell-peel-burn method 
The fell-peel-burn method is one of the oldest for bark-beetle con- 
trol, yet one which is still used in the suppression of outbreaks of 
the western pine beetle and related species, the larvae of which 
burrow into the outer bark and are not exposed when the bark is 
peeled from the tree. 
