INSECT ENEMIES OF WESTERN FORESTS 181 



inspection for insects each year. This work does not need to be 

 intensive, but at least it should disclose whether trees are dying 

 through any forests tract, and, if so, the probable cause of death, 

 and the extent of the trouble. 



If trees are observed to be dying either singly or in groups, they 

 should be examined and the cause of the trouble determined. If 

 there is no evidence of recent forest fires, insects may be suspected 

 as the responsible agents. If so, a closer examination of foliage, 

 twigs, or bark should show what primary insect is involved. The 

 keys and accompanying discussions in the early part of this manual 

 (pp. 28, 58, 60, 95) should be helpful in making this diagnosis. If 

 the cause of death cannot be satisfactorily determined, an expert 

 should be called in or samples of the work and the insects present 

 sent to an entomologist for his study. Samples taken from the mid- 

 dle height of the stem are more apt to include the primary destruc- 

 tive bark beetles than if taken near the ground or in the tops where 

 secondary insects are often most abundant. 



Information as to the extent of the damage can be determined by a 

 red-top survey or by strip counts made along roads or trails. The 

 methods to be discussed under "Extensive bark-beetle surveys'*^ are 

 applicable to this preliminary work, but the field work need be only 

 in sufficient detail to give a rough approximation of the location, 

 extent, and intensity of the infestation. 



The prompt reporting of the first signs of a bark-beetle outbreak 

 will greatly reduce the ultimate cost of suppression. On most 

 national forests the rangers are required to make at least one annual 

 reconnaissance of their districts and report the conditions as to insect 

 infestations. In this way bark-beetle outbreaks are promptly 

 brought to the attention of the forest officers and a decision can be 

 made as to whether a more extensive survey or immediate control 

 operations are required. 



Extensive Bakk-Beetle Surveys 



After an infestation has been reported by the men on the ground, 

 and before control operations are started, there is usually need 

 for a more complete field examination or extensive survey to deter- 

 mine the intensity, size, and character of the infestation, whether or 

 not control operations are justified, and how large an area must be 

 included to make such work effective. 



The importance of obtaining all possible information as to the 

 extent and severity of a bark-beetle outbreak before control 

 measures are started can hardly be overemphasized. Without this 

 information the need and feasibility of control and the magnitude 

 and probable cost of the proposed operation cannot be determined. 

 No project should be undertaken without fairly accurate knowledge 

 of conditions in all surrounding watersheds. Furthermore, the 

 actual operation of control projects cannot be efficiently planned 

 unless such data are available. 



One of the first things to be done is to determine the trend of the 

 infestation — whether normal, increasing, or decreasing — and the 

 possibility that natural-control factors will soon become operative. 

 This is done by a thorough study of brood conditions and a compari- 

 son of past with current losses. Control measures need not be 



