Table 4 Mean % fruit damaged by apple maggot 

 fly. Means within a row followed by the same letter 

 are not significantly different at odds of 19:1. 



Date 



1 4 5 



Imidan Surround Untreated 



20 fruit sampled per replicate (total = 240 fruit 

 per treatment). 



50 fruit sampled per replicate (total = 600 fruit 

 per treatment). 



and hail damage that occurred in June. 



Mid- to late-season pests. After June 19, we revised 

 our sampling protocol to focus on one full-season experi- 

 mental treatment regimen (for Surround) in comparison with 

 both a standard interval-spray program (for Imidan) and a 

 control (untreated). From July 1 -August 15, we applied four 

 sprays (at 15-day intervals. Table lb) of either Imidan or 

 Surround, and compared levels of insect injury m each with 

 an untreated control. To monitor the buildup of all insect 

 pest injury, we sampled 20 fruit from the central tree of each 

 replicate (240 fruit per treatment) and recorded all insect 

 mjun,'. These samples were taken twice durmg the growing 



season, in mid-July and mid-August. As with early- 

 season pests, we increased samples at harvest to 50 fruit 

 per replicate (600 fruit per treatment). Although we 

 recorded damage from each pest individually, data here 

 are compiled into five groups: apple maggot, external 

 Lepidoptera (leafrollers and lesser appleworm), inter- 

 nal Lepidoptera (codling moth and oriental fruit moth), 

 San Jose scale, and mcidental pests (notably stink bug). 

 Despite a statewide apple maggot fly (AMF) popu- 

 lation that was extremely low, the test block in this study 

 endured substantial pressure from AMF in late August. 

 Even under relatively high pressure. Surround ( 1 .2% 

 AMF injury at harvest) actually outperformed Imidan 

 (8.3% AMF injury at harvest), and both treatments 

 yielded AMF injury levels significantly lower than the 

 untreated control (24.0% injury at harvest. Table 4). 

 These data strongly suggest that Surround holds prom- 

 ise for control of AMF equal to or better than calendar 

 sprays of Imidan, likely owing to the lengthy residual 

 effectiveness of Surround coverage in the absence of 

 substantial rainfall (as characterized the peak of AMF 

 pressure in late August, Figure 2). 



For external lepidopteran pests (combined leafroUer and 

 lesser appleworm), both Surround and Imidan yielded fruit 

 damage rates (16.7% and 20.5% damage at harvest, respec- 

 tively) far below damage inflicted in untreated controls 

 (40.5% damage at harvest, Table 5). Although no treatment 

 offered a level of control that is considered commercially 

 acceptable, this is likely again due to pest spill-over from 

 untreated trees (as seen with PC). As was the case with 

 control of apple maggot. Surround actually provided con- 

 trol of LR and LAW that was numerically superior to calen- 

 dar sprays of Imidan. 



're 

 01 



o 

 > 



E 

 o 



7 

 6 

 5 

 4 

 3 

 2 

 1 

 



6.52 



2;G8 — 2U24- 



■imr/ 



4.20 



^4^7- 



2.25 



iifc 



1,27 



-=■ 



0.83 



□ 



1A1 



D 



1.36 



5/1- 5/16- 6/1- 6/16- 7/1- 7/16- 8/1- 8/16- 9/1- 9/16- 

 5/15 6/1 6/15 6/30 7/15 7/31 8/15 8/31 9/15 9/30 



Dates (inclusive) 



Figure 2. Cumulative rainfall for each 15-day period from May 1 through September 30. Imidan and 

 Surround were applied on May 5, 15, 25, June 5, 15, July 1, 13, August 3, and 16. Actara was applied on 

 May 15, 25, and June 5. 



Fruit Notes, Volume 65, 2000 



25 



