1§5 MISC. PUBLICATION 273, 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 tags 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 all 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 

 the insects exposed to predators or left to die through exposure to the sun's 

 heat. 



(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-f eel-hum 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. 



