F-140: Branching Young Apple Trees with Plant Growth Regulators

Applications where PGR’s can be used to increase branching on apple.

First-leaf apple trees where the leader with no buds broken but just prior to bud swell. For example, newly planted nursery tree “whips.”

1. If dormant buds are present on one-year-old wood: Apply a high rate (5,000 ppm) of MaxCel® or Promalin® mixed in latex paint BEFORE buds break. See product labels for more details and instructions.
2. If buds have broken, and the leaf tissue is showing on one-year-old wood: Mix 400 PPM MaxCel with water, NO SURFACTANT, or 400 PPM Promalin plus a non-ionic surfactant (NIS). Apply by spraying with a back-pack sprayer. Works best when temperatures are warm and there is enough tissue to absorb the PGR. Note: Never add surfactant to a solution of MaxCel as it is already included in the formulated product. Promalin should be combined with a NIS following the label instructions.

Second-leaf apple trees where leaders have “blind wood” with no visible buds or branches.

1. Make a notch with a hacksaw blade (narrow, fine toothed saw, usually used for cutting metal) just above the existing bud scar on the leader then on nonbearing trees, immediately spray the cut with a 1500 PPM solution of MaxCel.

Existing young tall-spindle or vertical-axis apple orchards with limited branching in the tops of the trees: an airblast sprayer application should be considered.

1. If spraying non-bearing trees in second or third leaf, to increase overall branching, apply MaxCel at 200-300 PPM using an airblast sprayer. It is best if lower nozzles are turned off and the spray is targeted to the top 1/3 to 2/3 of the tree where more branching is desired.
2. If spraying bearing trees in second or third leaf to increase overall branching, apply MaxCel at 200 PPM using an air-blast sprayer. It is best if lower nozzles are turned off and the spray is targeted to the top 1/3 to 2/3 of the tree where more branching is desired. Time the application to apply at bloom to petal fall to cover green tissue. This rate will help remove fruit in the top 1/3 of tree, where you do not want to allow the canopy to fill out.

Nursery Trees

1. Apples in a nursery or planted in place can be branched with applications of MaxCel or Promalin at 400 PPM (400 mg. L-1) when leader growth reaches approximately 70 cm. or 28 inches above ground. i.e., the height at which the start of branching is desired. This treatment should be repeated at 7-14 day intervals or every 5-6’’ of leader growth for a total of 4 -5 applications. This rate of terminal growth on the leader will depend on temperature. On the first application date, the central leader shoot tips should be 28 inches above ground. We suggest applying PGR’S to tree leaders with a backpack sprayer. Use a single nozzle (cone jet hollow cone spray tip), calibrated to apply 4 ml of solution per application, and directed over the tip of the leader of each tree. Any hand pump manually operated back pack sprayer can be used but should have the boom modifi ed to have a pressure regulator, and a swivel head attachment for the nozzle head (See Photo) so that the desired amount of spray can be applied to each tree. Parts are available from TeeJet Corporation and Gate Technologies. Note: A complete parts list and instructions can be obtained from the author: Win Cowgill, P.O. Box 143, Baptistown, NJ 08803 USA (wincowgill@ mac.com).

Acknowledgments

This research was partially supported by Valent Bioscience, the International Fruit Tree Association, the Northwest Nursery Improvement Institute, the New Jersey State Horticultural Society, the New Jersey Agricultural Experiment Station, and the University of Massachusetts Agricultural Experiment Station.

We thank Gregory Clarke for technical support and guidance and Mike Beese, Wayne Kessinger, Dave Johnson, Rebecca Magron, and other Rutgers Master Gardeners for support. We also thank John Baugher and Shaun Calahan of Adams County Nursery for their cooperation and support in our research trials that generated the data for these recommendations.

Literature Cited

Terence Robinson, Brent Black, and Win Cowgill. 2014. Use of multiple applications of MaxCel and Promalin to produce feathered trees. Compact Fruit Tree 47(1):23-28.

Duane Greene. 1983. Use of Promalin to increase branching of young trees. Fruit Notes 48(2):20-22.

Win Cowgill, Mike Beese, Rebecca Magron, Wes Autio, Jon Clements, and Terence Robinson. 2014. Studies and recommendations for branching young apple trees. Horticultural News 94(3):1-9.

Issued by University of Massachusetts Extension, Jody Jellison, Director, in furtherance of the acts of May 8 and June 30, 1914. University of Massachusetts Extension offers equal opportunity in programs and employment. F-140:7/17-500