orchard borders. The best flyspeck prediction model 

 included inoculum index, number of borders, and slope. 

 We applied the model parameters derived here to 

 flyspeck incidence at 1 3 orchards in 2000 and compared 

 the resulting predicted values with observed flyspeck 

 incidence. The best-fit regression for the data 

 (R^=0.27) is presented in Figure 1. Given the high 

 "background noise" of variability in this kind of 

 investigation (different years, orchards, blocks, sizes 

 of trees, cultivars, prunmg regimens, types of borders, 

 etc.), we were gratified to see almost 30% of the 

 variability in flyspeck incidence explained by these 

 three site factors. 



We applied the same model in 2001 to predict 

 flyspeck in 1 1 of the same orchard blocks used in 2000. 

 The relationship between model-predicted flyspeck and 

 actual flyspeck in the apples was not close (only 2% 

 of the variability was explained). However, 2001 was 

 very dry during most of the growing season, and 2000 

 was a very wet year. Weather factors as well as 

 differences in blocks at the different sites may have 

 made a bigger difference in a drier year. We plan to 

 develop a more comprehensive flyspeck model that 

 combines static orchard factors with dynamic weather 

 factors such as leaf wetness and rainfall. It would be 

 useful to adjust for accumulations in moisture during 

 a growing season. We may find that we need different 

 models for wet years as opposed to dry years. The 

 starting point, however, and key factor in rating a block 



for flyspeck risk will probably always be a measure of 

 how much inoculum is in the orchard border areas at 

 the beginning of the growing season. 



This study identifies several factors which can 

 combine to produce an environment which supports 

 flyspeck: density of flyspeck on alternate host plants 

 in borders, number of borders, distance from apples 

 to border, and slope of the block. Modification of 

 this environment in a number of ways, such as summer 

 pruning, clearing-back borders or removing host plants 

 or inoculum, or using high-density dwarf plantings 

 could reduce flyspeck pressure considerably. The most 

 stable management plans will involve several 

 strategies, such as border management, orchard design, 

 aggressive pruning, monitoring weather components, 

 and careful fungicide selection and timing. 



A cknowledgem en ts 



We are grateful to the growers who participated in 

 the three phases of this study: Keith Arsenault, Gerry 

 Bieme, Bill Broderick, Dave Chandler, Dave Cheney, 

 Aaron and Dana Clark, Tom Clark, Don & Chris 

 Greene, Tony Lincoln, Wayne Rice, Dave Shearer, Joe 

 Sincuk, Tim Smith, Mo Tougas, Bob Tuttle, and Steve 

 Ware & the folks at Davis Farms. This work was also 

 supported by State/Federal IPM Funds, SAKE Grant 

 #97 LNE 97-90 (USDA 96-COOP-1-2700), and a 

 Northeast Regional IPM Competitive grant. 



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Fruit Notes, Volume 67, Winter, 2002 



