Summer Pruning Increases 

 Coverage in Apple Canopies 



Daniel R. Cooley and Susan Lemer 



Department of Plant Pathology, University of Massachusetts 



In previous articles, we have described re 

 ductions in flyspeck as a result of summer prun 

 ing of dense apple canopies. The reductions de 

 pend to some extent on changes 

 in relative hirniidity, drying time, 

 amd perhaps temperature in the 

 apple canopy brought about by 

 summer pruning. We know this 

 because there is as much as 50% 

 less flyspeck in summer- 

 pruned canopies even when no 

 smnmer fungicides are applied. 



However, in spite of bringing 

 about significant reductions in 

 the amount of disease, summer 

 pruning alone does not control 

 flyspeck adequately. Summer 

 fungicide applications are neces- 

 sary to keep the disease at com- 

 mercially acceptable levels in 

 many orchards. We expect that 

 summer pruning may interact 

 with fungicides in terms of fly- 

 speck incidence, and that less 

 fungicide may need to be applied 

 in a summer-pruned orchard 

 compared with a non-pruned 

 one. We hypothesize that the 

 reduced disease pressure 

 brought about by the change in 

 canopy microclimate may re- 

 quire less fungicide to manage 

 the disease, either in terms of a 

 lower rate of fungicide per appli- 

 cation or less frequent applica- 

 tions. In addition, simimer prun- 

 ing probably improves penetra- 

 tion of fungicide into the canopy. 

 As a first step toward investigat- 

 ing the interaction of summer 



pruning with fungicide applications, we inves- 

 tigated the effect of sunmier pruning on spray 

 deposition in the canopies of semi-dwarf apple 



outer 



7 



11 ft 



low 



T 



8tt 



\ 



5ft 



i 



ij 



Figure 1. Placement of water-sensitive paper targets 

 in apple trees. 



Fruit Notes, Summer, 1995 



