The use of highly feathered trees can make high-density apple plantings more profitable through enhanced precocity and increased early yield. Currently, nurseries are asked to provide highly feathered trees with wide branch crotch angles. The use of plant growth regulators (PGRs) can play a key role when it comes to branch induction; however, dose and timing both need to be tested to enhance branching without compromising other tree quality attributes. Over the last 4 years, we have conducted studies of the use of MaxCel® (6-benzyladenine) and Promalin® (a mixture of 1.8% 6-benzyladenine and 1.8% GA4+7) in comparison with Tiberon™ SC (cyclanilide) at several nurseries in NY, WA, DE, Ontario (Canada), and Chile. The best results were obtained with four applications of MaxCel® or Promalin® (400 mg·L−1) beginning when leader growth reached 70 cm above the soil line and reapplied at 10–14 days intervals. Promalin® was a slightly less effective branching agent than MaxCel®. On the other hand, Promalin® stimulated leader growth resulting in improved final tree height, whereas MaxCel® induced the widest branch angles. Overall, we observed good response and quality ratings with ‘Cameo’, ‘Cripps Pink’, ‘Enterprise’, ‘Fuji’, ‘Ambrosia’, ‘Crimson Crisp’, ‘Gingergold’, and ‘Granny Smith’, whereas less quality ratings were observed on ‘Ambrosia’, ‘Cortland’, ‘Goldrush’, ‘Honeycrisp’, and ‘Suncrisp’. Response with ‘Gala’ varied depending on the temperature range. Multiple sprays of Gibberellins (GA4+7, or GA3) at 250 mg·L−1 applied to nursery trees in the late summer inhibited flower bud development and flowering in the orchard the next year. This reduces the risk of fire blight infection in newly planted trees.
This research was partially supported by the International Fruit Tree Association, the Northwest Nursery Improvement Institute, the New Jersey State Horticultural Society, and the New Jersey Agricultural Experiment Station, with additional support from the Utah Agricultural Experiment Station (Journal paper #8959).
We thank John Baugher, Taun Beddes, Mike Beese, Shaun Calahan, Ricardo Chalhub Z., Gregory Clarke, Bill Howell, Dave Johnson, Wayne Kessinger, Bill Lawler, Rebecca Magron, and JD Obermiller for technical support and guidance. We also thank the cooperating nurseries Adams County, C&O, Univiveros, VanWell, and Willow Drive.
The authors have declared that no competing interests exist.
JacynaT.BarnardJ.2008Modification of branching behavior in apical-dominant apple trees with plant growth regulators and their residual effects on tree growth after transplantingJ. Amer. Pomol. Soc.624160172
Jacyna,T.Barnard,J.2008Modification of branching behavior in apical-dominant apple trees with plant growth regulators and their residual effects on tree growth after transplanting624160172)| false
JaumienF.CzarneckiB.PoniedzialekW.MitrutT.1993Very similar effects of a mixture of GA3 and BA (6-benzylaminopurine) and of GA4+7 and BA on branching of some apple cultivars in nurseryActa Hort.3293542
Jaumien,F.Czarnecki,B.Poniedzialek,W.Mitrut,T.1993Very similar effects of a mixture of GA3 and BA (6-benzylaminopurine) and of GA4+7 and BA on branching of some apple cultivars in nursery3293542)| false
McArtneyS.ObermillerJ.D.2015Effect of notching, 6-benzyladenine, and 6-benzyladenine plus gibberellin A4 + A7 on budbreak and shoot development from paradormant buds on the leader of young apple treesHortTechnology25233237
McArtney,S.Obermiller,J.D.2015Effect of notching, 6-benzyladenine, and 6-benzyladenine plus gibberellin A4 + A7 on budbreak and shoot development from paradormant buds on the leader of young apple trees25233237)| false