Pruned 



trees. 



We selected a set of 10 mature Mcintosh/ 

 M.7 trees, spaced 20 by 30 feet, approximately 

 12 feet tall, with dense canopies. Trees were 

 divided into five pairs. One of each pair was 

 summer pruned on July 19 or 20,1994, while 

 the other was not pruned. A week later we hung 

 water-sensitive papers, or targets (1 in x 3 in), 

 on terminals in each tree. The papers turn fi^om 

 yellow to blue wherever water contacts the pa- 

 per, and therefore will show the pattern of spray 

 deposition where they are hung. The papers 

 were hung in a specific pattern in each tree, as 

 shown in Figure 1. The height locations were 

 designated "low", "mid", and "high", correspond- 

 ing to 5, 8, and 11 feet, respectively. Depth lo- 

 cations were designated "inner" and "outer", cor- 

 responding to less than two feet fi-om the trunk 

 and less than one foot from 

 the end of the outermost 

 branches, respectively. One 

 target was placed at each 

 location, both perpendicular 

 to the row and in line with 

 trunks in the row. Hence, 

 each tree had a total of 12 

 targets. 



After we hung the tar- 

 gets, an air blast sprayer de- 

 livering 140 gal/A and trav- 

 eling at 2.5 mph applied 

 water to the trees. Patterns 

 such as those shown in Fig- 

 ure 2 developed on the tar- 

 gets. In order to measure 

 accurately the amount of 

 spray deposition on the tar- 

 gets, we created computer 

 images of each target and 

 measured the percent of a 1 

 in X 1.5 in rectangle which 

 had been darkened. The 

 spray deposition patterns 

 were digitized using a 

 flatbed scanner Then, digi- 

 tized images were analyzed 

 using public domain image 

 analysis software (NIH Im- 

 age 1.55) on a personal com- 



puter. 



The only positioning factor which signifi- 

 cantly affected spray deposition was height (Fig- 

 ure 3). Percent coverage of targets at the five- 

 foot level averaged 77%, while coverage at eight 

 feet averaged 47%, and that at 11 feet aver- 

 aged 34%. The experiment also confirmed our 

 hypothesis that simimer pruning enhanced cov- 

 erage, i.e. 60% and 46% coverage for sunmier- 

 pruned and non-pruned trees, respectively. 

 While the interaction between height and prun- 

 ing was not significant, it was apparent that 

 the differences occiured primarily in the middle 

 and upper canopies. 



These findings have some practical impli- 

 cations. First, many problems with spray cov- 

 erage occur in the tops of relatively tall trees. 

 As the data show, deposition in the upper canopy 



Not Pruned 







11 ft 



•■• ri^- «•• 



■ % 





8 ft 



5ft 



Figure 2. Tjrpical spray patterns on water sensitive pa- 

 per placed in the outer canopies of pruned and non-pruned 

 apple trees. White areas on the left indicate areas cov- 

 ered by clothespin used to attach the papers to the termi- 

 nals. 



Fruit Notes, Summer, 1995 



