Good Fruit Grower

March 15

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Call us FIRST for the largest selection of trees and rootstocks available Future contracts for cherries, pears, & apples; ALL ROOTSTOCKS. NEW APPLE rootstock! 1-800-421-4001 Phone: 503-538-2131 Fax: 503-538-7616 E-mail: Web: INC. Representing Over 30 Leading Nurseries in the U.S. and Europe From the breeders of Bud 9: • Vigor between M-9 T337 and M-9 Pajam®2 • Yield efficiency similar to M-9 T337 • Dwarfing • Cold hardy • Disease resistant • Fireblight tolerant B10 ® cv. Mich 96 USPP 21,223 Services are FREE TO GROWERS! • Impressive coverage with a CHINOOK Blade • Protect Over 15 Acres • Powerful V10 Engine with or without catalytic converter Toll Free: 855-855-0318 • We've got you COVERED! Introducing our newest dealer: Windworx, LLC Wind Machine Sales and Service Mechanical thinning can damage spurs and leaf tissue as well as flowers. by Geraldine Warner M echanical thinning looks like a promising tech- nique for reducing the amount of labor-intensive hand thinning required in order to grow a good crop of nice-sized apples. That's the conclusion reached by a team of research- ers from around the country who worked on a major project to evaluate mechanical thinning. For their proj- ect, they tested a couple of thinning machines—the Darwin and the Uni Bonn string thinners, both of which originated in Europe. The machines, which have rotating spindles with ropes or strings attached, are designed to knock flowers off the trees, but they can also remove spurs and damage leaf tissue. This got Tory Schmidt, research associate with the Washington Tree Fruit Research Commission, wonder- ing how mechanical thinning might affect a tree's fruit production in the long term. "We know we get good thinning with the Darwin, but if you continue to beat up the canopy and knock off the spurs every year, does that have a long-term detrimental effect on the bearing surface?" he wondered. "I had always been bothered by seeing all the spurs left on the ground after a mechanized thinner goes through," he said. "It's always been a question that was nagging me." So, three seasons ago, Schmidt began a project in a block of Granny Smith apples at Washington State Uni- versity's Sunrise research orchard near Wenatchee, to find the answer. Three treatments He's comparing three different treatments: —The standard chemical thinning program of two applications of fish oil and lime sulfur during bloom fol- lowed by one application of a bloom thinner —Mechanical thinning with the Darwin —Chemical thinning and mechanical thinning on alternate years (beginning with mechanical in the first year of the trial) Schmidt wants to see two to three more years of data, but early indications are that potential yields in the mechanically thinned block have dropped off. Bloom density decreased from 9.2 flower clusters per square centimeter of trunk cross-sectional area the first year to 6.0 the second year, and only 2.7 in the spring of 2013. In comparison, bloom density in the chemical treat- ment went from 8.9 clusters per square centimeter the first year, to 2.5 the second year, but up to 3.9 clusters last year. In the alternating treatment, the flower clusters went from 6.3 to 4.1 to 4.0. "In the mechanized thinning treatment, we're con- cerned that the bloom density has gone down every year," he said. Schmidt said it remains to be seen if this is a trend or just a temporary downtick. • Mechanical thinning effects studied GOOD FRUIT GROWER MARCH 15, 2014 29

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