2013 ASHS Annual Conference

Mechanized sidewall shearing of the tree canopy of Tall Spindle apple orchards may offer the potential to reduce annual pruning costs of apple production. Although mechanical pruning was conducted in the 1960s and 70s, it was generally unsuccessful because it resulted in excessive regrowth and poor fruit quality due to vigorous rootstocks and the cutting of large limbs. However, current high-density Tall Spindle apple orchards are now more suitable to mechanized pruning due to the use of dwarfing rootstocks, a better managed and calm tree, and the presence of more small pendant fruiting branches (15–18 branches) when the tree is mature. We began 4 experiments in New York State in 2012 to evaluate the timing and severity of summer sidewall shearing on Tall Spindle and Super Spindle apple trees. Our main goal was to reduce pruning costs by 2/3 while maintaining a narrow fruiting wall with good light distribution but not create a vigor response in the tree. A second objective was to study the shoot response of several important apple cultivars in New York State to mechanized summer pruning timings and severities.  Our results show that summer sidewall shearing was fast and left the trees with a “manicured” look. The cost and time amounted to a fraction of the time (5%) to do manual summer pruning. At each of the summer timings the shearing process cut an average of only 28% if the growing points on the tree (range 22% to 38%). When the sidewall shearing was done at bloom there were some flowers cut off. However, when the sidewall shearing was done in June, July or August 4% to 6% of the fruits were cut off. The regrowth response of 4 cultivars on M.9 rootstocks was about 12–15 cm in shoot regrowth. Most of the short regrowth shoots terminated in a flower bud. There was a nonsignificant reduction in yield and crop value and a nonsignificant improvement in fruit color from summer shearing.