Issue link: https://read.dmtmag.com/i/57720
Mechanical thinning of cherries Handheld thinners expand the tools available to growers for managing the crop. by Geraldine Warner A T fter success with mechanical thinning of stone fruit, researchers have turned their attention to cherries and are experimenting with several tools to help cherry growers reduce the crop load and increase fruit size. Karen Lewis, Washington State University extension specialist, has been running trials. Two years ago, she began trials in cherries with the Fruit-Tec Darwin thinner, which has a single spindle with cords that can be operated horizontally or vertically, and the Bonner thinner, from the University of Bonn in Germany, which has three independent spindles. Lewis did bud-removal trials during the dormant season (mid- February or mid-March) in Rainier, Early Robin, and Santina cherries. The dormant treatment reduced fruit set by 23 to 49 percent, with the March treatment thinning the most. Lewis said more research needs to be done on mechanized dormant bud removal. She also tested the thinners during bloom in Sweetheart and Selah o see photos and videos of the Electroflor, go to www.infaco- usa.com. cherries. One of the goals was to determine the most effective spindle rotation speed, and she tested a range of revolutions per minute from 275 to 350. The ground speed was kept at a constant three miles per hour, a speed that Lewis thinks is necessary for treating large, western orchards. Bloom treatments gave 29 to 52 percent reductions in fruit set. More flowers were removed at the lower spindle speeds. Problems resulting from the Darwin bloom treatments included overthinning, blind wood, and leaf damage. Lewis said thinning cherries is different from thinning peaches and apricots, because cherries have leaves during bloom that can be ripped up by the thinner, whereas other stone fruits do not. The Bonner thinning results clearly reflected the limited cord-to-bloom contact, which is directly related to tree architecture, Lewis said. One of the big issues with these two mechanical thinners is that the tree fruit indus- try in the Pacific Northwest has what Lewis calls four-dimensional trees. They are three dimensional, and the fourth dimension is the variability from row to row and tree to tree. Trees can have different bloom intensity and different thinning requirements. Handheld mechanical thinners allow a more targeted thinning approach to suit each individual tree and crop load goals or strategy. They can be used from the ground or from a platform. NEW FOR 2012 FirmYield Pollen's IMPROVED Lightweight ATV Pollen Applicator The Electroflor looked promising for mechanically thinning cherries in tests that Karen Lewis, WSU extension specialist, conducted. WSU has been working on a handheld thinner that was adapted from commercial weed trimmers. The first prototype had a gasoline engine on the pole, but it proved to be too heavy and noisy. It also would power up or down, depending on the load, and might come to a stop when it reached a tight cluster, Lewis said. WSU agricultural engineers developed a version with a battery on the pole, but the tool lacked power and didn't work very well, she said. A later version had two batteries in CONTROLLED POLLINATION HIGH QUALITY POLLEN and the Means to Apply It! for… • Apples • Pears • Cherries • Apricots • Plums •Increases the rate of pollen germination. •Increases honeybee activity •Effective with ATV pollen application or BeeBoster pollen inserts. WASHINGTON WASHINGTON D&M Chemical Wilson Irrigation Michael Ellingson 509.678.5750 509.453.9983 14 MARCH 15, 2012 GOOD FRUIT GROWER CALIFORNIA Tom Majors Central Valley, CA 559.287.8900 OREGON Tim Polehn The Dalles, OR 541.340.9238 Phone 509/453-4656 • Fax: 509/469-3689 www.firmyieldpollen.com OREGON Blue Mountain Growers Dennis Burkes 541.938.3391 509.520.0686 MICHIGAN Alpers Tree Sales Suttons Bay, MI 231.633.8358 N. EUROPE Fruit Consult Jan Peeters 0031.653.410.921 www.goodfruit.com geraldine warner