cal trend toward successively greater PC damage on exte- 

 rior compared with interior zones as the season progressed 

 (Figure 5). 



Conclusions 



Results suggest that PC infestation patterns vary accord- 

 ing to tree size and sampling date, which is directly related 

 to phenological stage of fruit development. With respect to 

 the vertical plane of tree branches, results for large trees 

 suggest greater damage (expressed as numbers of scars and 

 percentages of mjured fruit) at the tree top on all sampling 

 dates, coinciding with previous reports of other researchers 

 who found that PC scars in scout (Granny Smith) apples 

 were detected only in the upper halves of large (Mcintosh 

 and Cortland) trees. For medium trees, the latter was true 

 during the first sampling date, although differences were not 

 significant. Our findings of a rather uniform infestation pat- 

 tern among sectors of small trees does not concord with a 

 report by Choumard and collaborators (1994), who showed 

 that in Quebec, PC oviposition scars were most abundant at 

 the middle-level of small apple trees. 



With respect to orientation of branches of small and 

 large trees, our findings are in agreement with those of Le 

 Blanc and collaborators (1984), who found no differences 

 in oviposition scar frequencies according to the four cardi- 

 nal points of the compass. For branches of medium trees 

 during samplings 4 and 5, oviposition scars were most abun- 

 dant on the West side of tree crowns. This location corre- 

 sponds to the area where substantially more PC adults were 

 found present at sunset (time of day when most oviposition 

 activities occur), as confirmed by branch tapping performed 

 on medium-sized trees on different days. 



Determination of PC infestation patterns on exterior vs. 

 interior zones of tree branches is an aspect that has not been 

 evaluated heretofore. In general, no significant differences 

 m PC damage were found for external vs. internal zones of 

 branches of medium or large trees. However, as the season 



progressed, external zones of branches located at tops of 

 both medium and large trees seemed to be the most prone to 

 PC injury. 



We used two indicators of PC injury because total num- 

 bers of PC scars may not correlate directly with numbers of 

 fruit injured given that multiple wounds on a single fruit 

 may be inflicted by either a single PC or multiple PCs. For 

 the most part, these indicators were consistent with each other 

 in our study. Our next step will be to determine if there is a 

 correlation between fruit damage and numbers of PC adults 

 captured by branch-mimicking black cylinder traps placed 

 in different tree sectors. This will allow us to determine the 

 best trap position within host tree canopies for the capture 

 of PCs. 



We conclude that damage to fruit by PCs is more likely 

 to occur at the tops of large (and possibly medium) trees, 

 particularly early in the season, with no influence of brancii 

 orientation. As the season progresses, external zones of 

 branches located at tree tops become more prone to attack 

 by PC than do internal zones of branches. 



Ackno H'ledgm ents. 



This study was supported with funds provided by a 

 USDA Northeast Regional IPM grant, a Hatch grant, and 

 the New England Tree Fruit Research Committee. 



References Cited 



Chouinard, G, Hill, S.B., and Vincent, Ch. 1994. Spatial 

 distribution and movements of plum curculio adults within 

 caged apple trees. Entomologia Experimentalis et Applicata 

 70: 129-142. 



Le Blanc, J.-RR., S.B. Hill, and R.O. Paradis. 1984. Ovipo- 

 sition in scout-apples by plum curculio, Conotrachelus 

 nenuphar (Herbst) (Coleoptera: Curculionidae), and its re- 

 lationship to subsequent damage. Environmental Entomol- 

 ogy 13: 286-291. 



it it *k it it 



Fruit Notes, Volume 65, 2000 



41 



