Table 1 . --Comparison of estimates from bark- removal and radiographic sampling. 



Bark-removal Radiographic 



sampling sampling^ Significance 



-Average/ZO . 4 cm'' 



Brood number 



Observation 1 215.5 177.5 , P > 0.10 



Observation 2 83.2 78.3 P > 0.10 



Observation 3 48.2 40.6 P > 0.10 



Gallery cm 261.1 238.3 P > 0.10 



Gallery starts 10.0 8.9 P > 0.10 



^ Estimates made by two observers were averaged and the average was compared with the 

 estimates obtained by bark-removal sampling. 



Table 2 .--Comparison of observer estimates made independently 

 from the same sets of radiographs. 



Observer 1 Observer 2 Significance 



-Average/?>0 .4 cm"^- 



Brood Number 



Observation 1 171.5 183.5 P > 0.05 



Observation 2 . 82.9 73.6 P > 0.10 



Observation 3 45.2 36.0 P > 0.10 



Gallery cm 234.4 242.1 P > 0.10 



Gallery starts 6.3 11.5 P < 0.01 



Time . --An analysis of time required to accomplish sampling by the two methods 

 demonstrated that the bark-removal method is much faster than the radiographic method. 

 Time required for the first sample averaged 38.1 min per sample for the radiographic 

 method compared to only 16.3 min per sample for the bark-removal method (table 3). 

 Time required to accomplish the radiographic sample decreased during the second and 

 third samplings because no new slots had to be cut in the trees. In addition, fewer 

 insects in the last two samples speeded interpretation of radiographs. Also, a slight 

 saving occurred in exposure time, which changed from an average of 1.4 min per sample 

 for the first sample date to 0.78 min per sample for the last two sample dates because 

 of decreasing moisture in the wood and bark. Ratios of time (bark removal method: 

 radiographic method) ranged from 1:2.35 min per sample for the first sampling date to 

 1:1.66 min per sample for the third sampling date (table 3). 



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