Effects of Dormant Pruning, Summer Pruning, Scoring, and Growth Regulators on Growth, Yield, and Fruit Quality of ‘Delicious’ and ‘Cortland’ Apple Trees

Abstract

Summer pruning 6-year-old trees of ‘Cortland’ apple ( Malus domestica Borkh.) for 3 consecutive years in either early July or early August reduced trunk circumference increase the year of pruning and increased terminal growth the following year. Terminal growth on 8-year-old ‘Red Prince Delicious’ trees summer-pruned in August for 3 consecutive years was similar to dormant-pruned trees, and trunk circumference increase was reduced the last 2 years. Fruit size and soluble solids were reduced the last 2 years. Fruit size and soluble solids were reduced by summer pruning ‘Cortland’ but not ‘Red Prince’. Flowering, fruit set, yield, flesh firmness, flesh calcium, and storage disorders were not affected by summer pruning of either cultivar. Terminal growth of ‘Cortland’ trees was reduced the year of scoring and the following year. Bloom was increased the year following scoring. Scoring ‘Red Prince’ for 3 consecutive years consistently reduced terminal growth and increased yield the second and third years. Corrective dormant pruning (CDP) on ‘Red Prince’ reduced bloom but not yield the first year. In the 2 subsequent years, bloom, fruit set, and yield were not affected by CDP and the practice alleviated the problem of tree crowding. Summer pruning on ‘Cortland’ trees followed by a postbloom spray of butanedioic acid mono(2,2-dimethyl hydrazide) (daminozide) of 1500 ppm showed promise as a way to control tree growth, increase flower bud formation, and fruit set.