EFFECTS OF SUMMER PRUNING ON GROWTH AND YIELD OF APPLE 

 TREES AND ON FRUIT QUALITY 



William J. Lord and Duane W. Greene 

 Department of Plant and Soil Sciences 



Recent results from England, South Africa, Europe, and the 

 United States indicated that late summer pruning can restrict 

 growth, increase red color on fruit, increase leaf Ca, reduce 

 the incidence of bitter pit, increase fruit flesh Ca, and reduce 

 internal breakdown in storage. In England Preston pruned by the 

 established spur method. Tliis involved the removal of strong 

 laterals not needed for new branches and shortening of weak ones 

 to 3 inches to induce spur formation. Laterals of medium vigor, 

 mainly on the tree periphery, were not pruned. Subsequently, 

 these were shortened to a spur, or removed when crowding occurred 

 or they became too large. Laterals from spur systems or induced 

 spurs were shortened to 1 inch. In the United States, the trees 

 were summer pruned by removing all current season's shoots. 

 Terblanche et al. in South Africa removed all current season's 

 growth of the bearing units as well as excessive shoot growth. 

 Only sufficient shoots were left to serve as future bearing units. 

 Utermark in West Germany drastically reduced leaf area by remov- 

 ing growth beyond the outermost fruiting spur on each branch. 



The summer pruning techniques that enhanced fruit quality 

 seem severe and time consuming, and contradictory findings have 

 been reported. Thus, this experiment was designed to compare 

 effects of summer pruning with winter pruning and to evaluate 

 methods that fruit growers might adapt. 



Studies With Red Prince Delicious 



These trees planted at 14 foot x 21 foot spacing, were badly 

 crowded by the end of their 8th growing season in 1977. Stubbing 

 cuts (cuts made in 2 or 3 year-old-wood to reduce the length of 

 limb) were necessary for passage of equipment prior to harvest in 

 1977. Pruning treatments were initiated in 1978 and consisted of 

 1) light dormant pruning (to simulate current pruning practices of 

 growers), 2) corrective dormant pruning, and 3) corrective dormant 

 pruning-plus- summer pruning in early- August . 



Corrective dormant pruning was initiated in March, 1978 and 

 consisted of removal of 1-2 large limbs per tree that caused crowd- 

 ing and/or competed with the leader. Removal of very few large 

 limbs was necessary during the 1978-79 dormant pruning season and 

 none were removed in 1979-80 season. Tree height was lowered by 

 about 2 feet and a limb renewal program was initiated in the top 

 third of the tree. The limb renewal program consisted of rem.oving 

 some of the stronger branches or their length was shortened by 

 cutting to a weak lateral branch. All water sprouts were removed 



