border habitat. Percent fruit injured on interior trees 

 of baited-sphere plots was not correlated with values 

 prescribed for tree size or quality of pruning. 



Conclusions 



Our findings for 2003 indicate that assigning 

 distances between odor-baited spheres (on perimeter 

 trees of plots in commercial apple orchards) according 

 to an index incorporating characteristics of four 

 environmental variables (tree size, quality of pruning, 

 cultivar susceptibility, and border habitat) resulted in a 

 level of AMF control no different from that achieved 

 by sprays of insecticide in 2003 and no different from 

 that of arbitrary assignment of distances between odor- 

 baited perimeter spheres in the same plots in 2001 and 

 2002. Only 61-67% as many spheres were used under 

 our new index system for determining distances 

 between spheres in 2003 as under the arbitrary system 

 used in 2001 and 2002. 



Correlation analyses suggested that the index used 

 here for assigning distances between odor-baited 

 spheres on perimeter trees was reliable with respect to 

 values prescribed for cultivar susceptibility and border 

 habitat, but for future use it may require adjustment 

 with respect to tree size and quality of pruning. Some 

 of the analyses showed a significant negative 

 correlation between tree size or quality of pruning and 

 fruit injury by AMF or captures of AMF by interior 

 monitoring traps, suggesting that distances between 

 spheres prescribed by the index used here may have 

 been too great to ensure high performance in plots of 

 large and/or poorly pruned trees. One potential solution 

 to this possible shortcoming would be to prescribe a 

 value of less than 1 (rather than the value of 1 used 

 here) for perimeter trees of large size and poor pruning. 

 Doing so could, in some cases, require that spheres be 

 placed closer than 6 yards apart. Conversely, for small- 

 size perimeter trees that are pruned well, it may prove 

 possible to assign a value 4 or more (rather than the 

 value of 3 used here) and achieve acceptable control 

 of AMF using odor-baited spheres positioned greater 

 than 18 yards apart (the maximum distance apart 

 allowed here). 



On average, each of the 12 plots in this study 

 received 24 odor-baited sticky spheres 1 2 yards apart 

 on perimeter trees that encompassed about 1 acre of 

 orchard. We estimate that it cost about $10 per sticky 



sphere for all materials and labor ($1.50 tor sphere, 

 Tangletrap, and odor plus $8.50 for labor to apply sticky, 

 deploy spheres, periodically clean spheres of insects 

 and debris, and replenish sticky). The estimated cost 

 per plot of controlling AMF using odor-baited sticky 

 spheres was therefore $240, compared with an 

 estimated cost of about $45 per plot for control using 

 insecticide (materials, spray equipment, and labor). If 

 odor-baited sticky spheres were used to encompass a 

 block of 10 acres rather than a 1 acre plot of apple 

 trees, then 72 spheres (at 12 yards apart) would have 

 been needed, costing a total of $720, or $72 per acre. 

 This still IS substantially greater than the cost of applying 

 insecticide to control AMF ($45 per acre) and calls 

 into question the economic wisdom of using sticky 

 spheres for this purpose. 



Ultimately, a replacement for sticky spheres is 

 needed that is both less expensive and less messy to 

 deploy and maintain. Such a replacement is on the 

 horizon in the form of a red sphere topped by a disc 

 comprised of spinosad (as insecticide), sugar (as 

 feeding stimulant) and paraffin wax (as binder) (see a 

 following article in this issue). Under high humidity, 

 morning dew, or rainfall, spinosad and sugar seep from 

 the disc onto the sphere surface, where they are ingested 

 by alighting AMF, which then die. The total annual cost 

 per odor-baited sphere of this type, amortized over a 

 10-year period, is estimated by its manufacturer (Pest 

 Management Innovations, Harpers Ferry, West Virginia) 

 to be about $3. Following initial deployment, such disc- 

 capped spheres would require no further attention 

 through harvest. Deploying odor-baited, disc-capped 

 spheres on penmeter apple trees at distances prescribed 

 by an index such as that put forward here could render 

 behavioral control of AMF as effective and affordable 

 as insecticide sprays, especially for large blocks of apple 

 trees that are on dwarfing rootstock and well pruned. 



Acknowledgements 



We thank Eliza Gray, Guadalupe Trujillo and 

 Mareanna Ricci for technical assistance and Jaime 

 Pifiero for statistical analyses. This study was 

 supported by a USDA Northeast region SARE grant, 

 a USDA Northeast Region IPM grant, a USDA Crops 

 at Risk grant, and the Massachusetts Society for 

 Promoting Agriculture. 



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14 



Fruit Notes, Volume 69, Spring, 2004 



