228 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



discussions in this manual should be helpful in making this diag- 

 nosis. If the cause of death cannot be determined, an expert should 

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

 be sent to an entomologist for study. Samples taken from the 

 middle height of the stem are more likely to include the primary 

 destructive bark beetles than those taken near the ground or in 

 the tops, where secondary insects are often most abundant. 



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 in the next section 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 out- 

 break 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 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 con- 

 trol operations are required. 



EXTENSIVE BARK-BEETLE SURVEYS 



After an infestation has been reported by the men on the 

 ground, there is usually need for a more complete survey to 

 determine 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. This ex- 

 tensive survey is usually made by experts in forest-insect control 

 who have had experience in estimating bark-beetle losses and 

 planning control campaigns (18). 



The importance of obtaining all possible information before 

 control measures are started can hardly be overemphasized. With- 

 out 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. 



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 comparison of past with current losses. Control measures 

 need not be applied to normal or rapidly declining infestations. 



The next step is to determine what areas must be included in 

 the control program, the number of trees that will require treat- 

 ment, and the probable cost of the work. 



The methods to be used in such work will depend on the 

 character of the country, the size of the area involved, the degree 

 of accuracy desired in the results, and the time and money 

 available. The simplest and least expensive type of survey is made 

 by viewing the country from lookout points and making counts 



