Table 5. --Time analysis of radiographic and bark-removal methods 

 to sample mountain pine beetle populations. 



Observation 



1 2 3_ 



- - - Man-minutes - - - 



RADIOGRAPHIC METHOD 



Cutting slots in trees 



60 







Setting up and taking down equipment 



60 



60 



60 



Determining moisture content of trees 



60 



60 



60 



Kauiograpu in g aiici iiiuviug cmjipiiicuL ±iuiii 









tree to tree 



300 



285 



285 



Sealing saw slots in trees 



60 



60 



60 



Developing and fixing film 



60 



60 



60 



Interpreting radiographs 



257 



127 



80 



Summarizing counts from overlays 



60 



48 



44 



Totals 



917 



700 



649 



Ave rage /sample 



38.2 



29.2 



27. 



BARK -REMOVAL METHOD 









Removing bark and counting insects 



360 







Coating exposed wood with wax 



30 







Total 



390 







Average/sample 



16.3 







Ratios (bark-removal : radiographic) 1:2.35 1:1.79 1:1.66 



One might expect the saving of time experienced with radiographic sampling when 

 insect numbers were fewer to carry over to bark-removal sampling as well. However, 

 this saving did not occur because more time was required to remove the drier and 

 tighter bark in the latter samples. 



Cost. --The initial cost of equipment needed to sample populations by the two 

 methods was not considered; only the cost of expendable items used during the sampl- 

 ing process and sampling time were evaluated. The radiographic method cost a total of 

 about $46, or 64 cents per sample, more for materials than the bark-removal method. 

 Costs were film $32, developer $7, and fixer $7. 



Total costs for time (based on GS-5 level) and materials follow: bark-removal 

 method, $1.01 per sample; radiographic method, first date, $3 per sample, second date, 

 $2.44 per sample, and third date, $2.31 per sample. 



Assessment of mortality factors .--k major disadvantage of the radiographic method 

 was the inability of the observers to assess mortality from the radiographs. Some 

 predators could be seen and counted on the radiographs. The only one of consequence 

 was Medetera aldrichii IVheeler (Diptera: Dolichopodidae) . Dead beetles that had dried 

 completely were not often detected ; those that were, usually could not be assigned to 

 specific mortality causes. In addition, larvae that had recently died, but still con- 

 tained much moisture, could not be distinguished from living larvae. The bark-removal 



7 



