Tabic 1 Relationship between numbers of plum curculio adults captured by unbaited pyramid and twig-mimic 

 traps and percent fruit showing injury by plum curculio across all 16 replicates of each tree size treatment m 

 commercial orchards in 1998. 



Number of adults captured 

 per sampling period 



Tree size 



Sampling period 



Pyramid 



Twig mimic 



Cumulative fruit 

 injury (%) 



positions in 48 blocks of trees in commercial orchards. 

 In each block, one trap was placed immediately adja- 

 cent to the tiTjnk of a perimeter tree, one trap was 

 placed at the midway point between the perimeter tree 

 and the first interior tree, and one trap was placed at 

 the margin of the nearest woods. Data from this study 

 extended our 1996 findings. Irrespective of trap posi- 

 tion, captures of PC in unbaited pyramid traps did not 

 reflect accurately the need for or proper timing of in- 

 secticide spray. A second (preliminary) study was 

 conducted m 1 997 intended to develop a trap to moni- 

 tor PC abundance and activity within tree canopies. 

 From this work, we developed a twig-mnnicking black 

 cylinder trap as an alternative to trunk-mimicking black 

 pyramid traps. 



In 1998, we repeated and expanded our trial of 

 trap types in the same 48 commercial orchard blocks 

 used in 1997. We compared the performance of black 

 pyramid trunk traps with black cylinder canopy traps 

 as indicators of the potential for PC injury. 



Materials & Methods 



As in 1997, traps were placed in six blocks of trees 

 in each of eight commercial orchards. All blocks con- 

 tained 49 trees (seven rows of seven trees each) of 

 mixed cultivars. Of the six blocks in each orchard, two 

 were considered high tree density (M.9 rootstock), two 

 medium tree density (M.26 rootstock), and two low 

 tree density (M.7 rootstock). 



Prior to bloom, we placed two unbaited black pyra- 

 mid traps in each of the 48 blocks, each trap adjacent 

 to the trunk of a perimeter tree (the most effective 

 postion for traps of this type). We also placed two 

 unbaited black hollow cylindrical (3 inches diameter x 

 12 inches height) twig-mimic traps in perimeter trees 

 of each block, kept in a vertical position within the 

 canopy by a clipped twig (Figure I ). In early May 

 1998, when all traps were placed, we knew of no at- 

 tractive odor which could be used in conjunction with 

 these traps (sec study of odors attractive to PC, this 



10 



Fruit Notes, Volume 63 (Number 3), Summer, 1998 



