Good Fruit Grower

May 15

Issue link:

Contents of this Issue


Page 7 of 55

8 MAY 15, 2014 GOOD FRUIT GROWER Art to Science 5 Thinning apples with MORE CONFIDENCE Duane Greene's key contribution to fruit thinning was the discovering that apples that will drop can be identified very early, helping growers know what to do early in the thinning window. O ver the last few years, apple growers should have gained confidence that they can chemically thin their apples and achieve pretty good results. The gains have come through increased understanding of tree fruit physiology—how trees shed excess fruit and why. There have been few breakthroughs in new chemistry (although some are on the horizon). The plant growth regulators now used to thin apples were discovered more than 40 years ago, and the newest, BA (benzyladenine), was introduced as a thinner in the 1990s. There have been several key players in developing an understanding of how to effectively use thinners. One is Dr. Duane Greene at the University of Massachusetts. Greene was one of a half-dozen tree fruit physiologists who spoke during the Cornell University In-Depth Fruit School early this spring. The school's intent was to recognize the contributions of those who have devoted their careers to discovering why fruit trees act the way they do. Greene was selected to speak based on his long career studying plant growth regula- tors. Over the years, he has appeared frequently in the pages of Good Fruit Grower, most recently for his development of a way to determine how well thinners already applied have worked so that additional thinning can be done if needed—without danger of overthinning. Quite simply, Greene's "fruitlet model" involves accurately measuring the growth of selected fruit. Greene found that apples growing at half the rate, or less, of fruit that persist to harvest will fall off, and that the growth rate of apples that will fall off begins to slow down as soon as three or four days after a thinner has been applied. He measures the diameter of selected fruits three or four days after thinners are applied, and again three or four days later. Greene collaborated with other researchers, Drs. Terence Robinson and Alan Lakso at Cornell University and Phil Schwallier at Michigan State University, in developing the fruitlet model. They were working together to develop a carbohydrate model for predicting when apples could be thinned most effectively. "Chemical thinning is a process that by its very nature provides different opportunities." —Dr. Duane Greene Apple thinning gets more predictable as scientists gain understanding. by Richard Lehnert

Articles in this issue

Links on this page

Archives of this issue

view archives of Good Fruit Grower - May 15