Good Fruit Grower

April 15

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34 APRIL 15, 2015 GOOD FRUIT GROWER A team of university researchers from the Northeast has developed a program that allows orchardists and nurseries to cre- ate highly feathered trees they think are essential in order to reap early profi ts from expensive high-density orchards. The growth regulators can be used either in the nursery or on young trees in the orchard. In the nursery The protocol involves treating the growing tip of young apple trees with multiple sequential applications of either MaxCel (6-benzyladenine or 6-BA) or Promalin (a combination of 6-BA plus gibberellic acid or GA4/7), both products of Valent BioSciences. Treatments begin when trees measure about 38 to 40 inches from the ground to the growing tip. Treatments are applied to the growing tip at every 5 to 7 inches of new growth (about two-week intervals). Each treatment induces buds to break at the point of application, with feathers appearing within two weeks. Win Cowgill, professor and area fruit agent from Rutgers, the State University of New Jersey, presented the recommendations at the Mid-Atlantic Fruit and Vegetable Convention in Hershey, Pennsylvania, in January. Cowgill conducted multiple experiments to deter- mine effectiveness and rates at Adams County Nursery's growing site in Milton, Delaware, working for the past three years in collaboration with other researchers. Similar trials were conducted elsewhere. University of Massachusetts' Wesley Autio and Jon Clements con- ducted similar experiments in Massachusetts, as did Cornell University's Terence Robinson in New York, Washington State, and Chile. The work was supported by the International Fruit Tree Association and Northwest Nursery Improvement Institute. Research began after it became clear that Tiberon (cyclanalide), a plant growth regulator that nurseries began using in 2009, was going to be withdrawn from that market by its manufacturer, Bayer Corporation. In the research, Cowgill applied 4 milliliters (about 1/7 ounce) of liquid to the growing tip of each tree using a backpack sprayer calibrated to deliver that amount. "Both MaxCel and Promalin are very effective in inducing branching on the varieties we tested," Cowgill said. The number of feathers varied with the number of applications. Cowgill believes that fi ve applications would be a suitable number in areas with somewhat longer grow- ing seasons, such as the Mid-Atlantic states, since the trees grow taller. Areas north of there may need fewer applications. In warmer areas, he says, 400 parts per million (ppm) of MaxCel applied four or fi ve times should produce a good quantity of feathers. In cooler areas, 500 ppm may work better. The MaxCel label calls for 500 ppm. Three applications of the MaxCel treatment on Macoun trees produced 15 to 18 branches, he said, compared to 10 to 11 with Tiberon and two to four on untreated trees. On Golden Delicious, either Promalin or MaxCel applied at 500 ppm produced 17 to 20 branches, com- pared to about nine on untreated trees. Untreated tree shoots were longer, about 8 inches, compared to 5 to 6 inches on treated trees. More feathers Treatments with Promalin or MaxCel will put more branches on young apple trees. by Richard Lehnert ONLINE For more details see the two articles from Win Cowgill of Rutgers and Jon Clements of University of Massachusetts in Horticultural News at abcCover94-3.html REBECCA MAGRON Win Cowgill applied plant growth regulators to apple nursery stock at Adams County Nursery's Delaware location in 2012.

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