Effectiveness of Peripheral-row vs. 

 All-row Sprays against Plum Curculio 



Ronald Prokopy 



Department of Entomology, University of Massachusetts 



Studies by Chouinard et al. (1992) and Vincent et 

 al. (1997) suggest that spraying only peripheral rows 

 of trees as opposed to all rows of trees can be an 

 effective approach to plum curculio (PC) control in many 

 Quebec apple orchards. This approach is rooted m the 

 presumption that most PCs overwinter in woods or 

 hedgerows outside of orchards and when entering 

 orchards in spring do not move beyond peripheral rows 

 of apple trees before settling down to feed and lay eggs. 

 The proportion of overwintering PCs that satisfies this 

 presumption under New England conditions is uncertain. 

 Such uncertainty invites evaluation of peripheral-row 

 vs. all-row sprays against PC in New England orchards. 



Here, in 2003 in one orchard in Vermont and two 

 orchards in New Hampshire, we compared three 

 different approaches to spraying PC that differed m 

 location of trees (peripheral vs. interior rows) 

 designated to receive sprays. 



Materials & Methods 



There were three experimental plots in each 

 orchard. Each plot contained seven rows of apple 

 trees. The perimeter row of each plot bordered 

 woods. All rows within a plot were of the same 

 length (80- 1 20 yards). All plots in the same orchard 

 received the same insecticide at each spray event 

 against PC: Avaunt in orchard X and Guthion in 

 orchards Y and Z (each at label-recommended 

 rate). 



Treatment protocols in each orchard were as 

 follows: 



Plot Petal fall spray P' & 2"'' cover spray 



A 

 B 

 C 



All rows 

 All rows 

 Rows 1 and 2 



All rows 

 Rows 1 and 2 

 Rows 1 and 2 



The petal fall spray was applied within 5 days after 

 90% petal fall (June 1, June 4, and June 8, 



respectively, for orchards X, Y, and Z). The first cover 

 spray was applied when fruit on odor-baited trap trees 

 reached a pre-determined threshold of two fresh 

 egglaying scars out of 100 fruit sampled beginning 7 

 days after the last insecticide spray. A trap tree baited 

 with one dispenser of attractive pheromone (grandisoic 

 acid) plus four dispensers of attractive fruit odor 

 (benzaldehyde) was located at the center of the 

 perimeter row of each plot. In all, 33 or 34 fruit were 

 sampled twice per week on each trap tree, giving a 

 total of 100 fruit per sampling date across all three trap 

 trees in an orchard. In response to sampling information, 

 the first cover spray was applied on June 1 5 in each 

 orchard. Sampling fruit on trap trees indicated no need 

 to apply a second cover spray in orchards X and Y, 

 whereas orchard Z received a second cover spray on 



Table 1. Effectiveness of different spray treatment 

 protocols for controlling plum curculio (PC) in three 

 commercial apple orchards. 



Fruit with PC injury (%) 



Orchard 



Plot A** 



PlotB** PlotC** 



X 

 Y 

 Z 



Average 



1.7 

 0.9 

 0.3 



1.0a 



1.9 

 0.3 

 1.0 



1.1a 



2.0 

 1.1 

 6.5 



3.2a 



* Average values followed by the same letter are not 

 significantly different at odds of 19: 1 . 

 ** Plot A: all rows sprayed at petal fall and first and 

 second cover. Plot B: all rows sprayed at petal fall; 

 only rows 1 and 2 sprayed at first/second cover. Plot 

 C: only rows 1 and 2 sprayed at petal fall and first 

 and second cover. 



Fruit Notes, Volume 69, Winter, 2004 



