Table 1 . For apple orchard plots that received insecticide application on rows 1 and 2 

 whenever a pre-set threshold of 1, ,2 or 4 freshly injured fruit out of 50 fruit sampled 

 on a trap tree was reached 7 days or more after the preceding application, mean number 

 of insecticide applications and mean percent fruit injured by plum curculio in samples 

 of 100 fruit per row taken during the first week of July. 



*Means in each column followed by the same letter are not significantly different at 

 odds of 19:1. 



rows 1 and 2 combined increased successively (though 

 not significantly) from 1.61 to 2.33 and 2.39% as the 

 pre-assigned threshold calling for spray application 

 increased successively from 1 to 2 and 4 freshly-injured 

 fruit out of 50 fruit sampled on trap trees (Table 1 ). 

 The same was true for fruit sampled from rows 3-7 

 combined (Table 1), where injury increased 

 successively from 0.43 to 0.71 and 0.82% with 

 increasing pre-assigned threshold. Combined injury fi"om 

 all rows in a plot shows that whole-plot injury averaged 

 0.77, 1.17, and 1.27%, respectively, for plots having 

 pre-assigned thresholds of 1 , 2, or 4 injured fruit out of 

 50 fruit sampled on a trap tree. 



Conclusions 



Findings from the first article in this issue indicate 

 that a whole-block spray against PC is needed at petal 

 fall to control PCs that many have overwintered within 

 or immigrated into interior rows. Findings from that 

 article also suggest that effective control of PC after a 

 whole-block petal fall spray can be attained by applying 

 insecticide only to perimeter rows 1 and 2. 

 There appears to be no need to continue spray all rows 

 m a block against PC after an all-row spray shortly 



after petal fall. 



To know 

 where and when 

 to apply post- 

 petal-fall spray to 

 control PC, 



findings here 

 suggest that a 

 threshold of 1 

 freshly injured 

 fruit per 50 fruit 

 sampled on an 

 odor-baited 

 perimeter-row trap 

 tree may be used 

 provisionally as an 

 indicator of the 

 need to apply an 

 insecticide spray 

 to all trees on 

 rows 1 and 2 to 

 prevent block- 

 wide damage from 

 exceeding an injury level of 1%. Further, our data 

 suggest that a spray-driven threshold of 2 or more 

 freshly injured fruit per 50 fruit sampled on a trap tree 

 may be too great to prevent block-wide damage from 

 exceeding \%. 



Further studies are needed to confirm the provisional 

 threshold suggested fi"om results here. Special attention 

 should be paid to assessing effects of orchard 

 architecture (size of blocks, spacing of trees, 

 arrangement of cultivars, size, and pruning of trees, etc.) 

 on candidate thresholds. 



A ckn o H'ledgm ents 



We are sincerely grateful to the growers who 

 allowed use of orchards blocks for this experiment and 

 who responded rapidly when sampling indicated the need 

 for insecticide treatment: Keith Arsenault, Gerry Beime, 

 Bill Broderick, Dave Chandler, Bob Davis, Don and 

 Chris Green, Tony Lincoln, Mo Tougas, Bob Tuttle, and 

 Steve Ware. This work was supported by funds from a 

 USDA Northeast Regional IPM grant, a USDA 

 Northeast Regional SARE grant, and Massachusetts 

 Society for Promoting Agriculture. 



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Fruit Notes, Volume 69, Winter, 2004 



15 



