Good Fruit Grower

March 15

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GOOD TO KNOW A research report from Tom Kon, Dr. Jim Schupp, and Edwin Winzeler, Pennsylvania State University. for growers to produce large fruit. However, excessive hand thinning can cause a reduction in yield that diminishes the value of the crop. Pennsylvania fruit grower Dan Boyer of Ridgetop A Orchards, returned from a recent fruit growers' tour with an Equilifruit disk and asked Pennsylvania State Univer- sity researchers to evaluate it as a hand-thinning gauge. The Equilifruit disk was developed by the National Insti- tute for Agricultural Research (INRA) in France. The plastic disk was designed to perform two functions: 1) To provide crop load recommendations for hand thinning, based on the diameter of a limb; and 2) To serve as a pruning gauge in the Solaxe training system. We tested the Equilifruit disk for its potential as a hand-thinning gauge on tall-spindle apple trees. Using Gauging apple pple growers use a variety of untested hand- thinning heuristics (rules of thumb) to adjust final crop load after insufficient chemical thinning. Depending on the cultivar and market, there are often financial incentives crop load The Equilifruit disk uses limb size to estimate the number of fruit that can be best supported by a limb. the Equilifruit for crop load management is a simple process. The worker selects a notch in the disk that fits snugly around a selected limb, and counts the number of fruit on the limb. If the number of fruit is greater than the recommended fruit number (F-value) on the disk that corresponds to the selected notch, then the worker reduces the number of fruit appropriately. When adjusting crop load based on the specifications of the disk, the worker should remove fruit selectively. Fruit should be removed in the following order: 1) dam- aged fruit, 2) small fruit, and 3) clustered fruit. Using the Equilifruit places less emphasis on the spacing of fruit within the canopy, because it uses limb size to estimate bearing surface. Therefore, any major alterations of the bearing surface (i.e., bench cuts) will result in an inaccu- rate estimate of the number of fruit that should remain. This thinning gauge is best suited for trees trained to spindle-type training system with renewal style pruning. The Equilifruit disk was tested for two years as a thinning gauge at Penn State's Fruit Research and Extension Center in Biglerville. When using the Equilifruit, it should fit tightly around the selected limb, about an inch away from the trunk. The F-values on the disk show the recommended number of fruit for limbs of certain diameters. The delta value, also shown on the disk, can be added to or subtracted from the F-value to adjust amount of thinning depending on the variety or tree age, etc. ISOMATE -CM FLEX ® Technolog Sustainable Mating Disruption Technology for Your Growing Needs of 200-400 dispensers per acre 16 MARCH 15, 2012 GOOD FRUIT GROWER courtesy pennsylvania state university

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