Good Fruit Grower

December 2011

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Katy Lesser Clowney, while working at the Adams County extension office, found the Darwin at a show in Europe and suggested it be tried out. She has been involved in testing it. DARWIN is evolving M Dave said. He figures he can do five acres a day on the open-vase trees planted on a 12- by 22-foot spacing. Like fingers The strings on the rotating spindle are not really strings, he added. They're more like two-foot-long, soft fingers. While the early models had weed-trimmer-type plastic strings, the newest model's strings are thicker, firmer, and an eighth-inch in diameter. The plastic bends easily but will not wrap around limbs—an important feature that greatly reduces limb damage, Dave said. These fingerlike bristles pene- trate into the canopy, reaching into the fruiting zone, knocking off the blossoms. After using the Darwin, supplemental blossom thinning is done by hand using a brush to remove blossoms. The goal is to blossom-thin everything, but especially all varieties that mature before Redhaven, following up with green fruit as needed. Dave has monitored wear on the Dar- win's strings. After two seasons of use, cov- ering about 100 acres a year, the strings were about four inches shorter than new strings. None had broken off; the wear occurs at the ends from brushing against the limbs, and there is no noticeable thinning of strings as they wear. The ends don't get sharper either. He plans to change them for next spring. Three Springs uses half the number of strings the machine will hold. Instead of six rows of strings, they use three. They move about two miles per hour rotating the spindle about 200 revolutions per minute. The machine mounts easily on the front of a tractor, held by forks used to handle bins. The spindle can be tilted using hydraulic controls, and a digital read-out telling speed and rpms is mounted on the tractor. "We run it, stop, assess what we're doing—looking at Joy Cline manages production of 280 acres of peaches at Bear Mountain, where three Darwin string thinners are used. Bear Mountain Joy Cline, farm manager at Bear Mountain, Aspers, Pennsylvania, said the biggest advantages she sees are more consistent fruit size and a labor savings of at least 40 percent. She manages 1,000 acres of fruit—280 of them peaches—for owners John and Sheila Lott. The com- pany operates a large packing operation, selling its own fruit and that of several other growers. Bear Mountain was an early testing site for the Darwin when Penn State's Extension people in Adams The original Darwin was used to thin apples and worked in this vertical position. Later models could go horizontally across the tops of peach trees. County found out about the European machine and bought one to test. The first one Joy Cline used was the vertical version that would flex somewhat but would not thin in a horizontal position. The orchard has mostly open-vase trees, and the two newer machines work in the horizontal position. "We thin across the top," she said. "We could do it along the sides, but there's no need to do that." Because of the premium that is paid for large peaches, thinning is very important, Cline said, and she's looking for ways to cut labor needs, because of the cost and uncertain availability in the future. The Darwin paid for itself the first year, with a combination of labor savings and improved fruit quality, she said. • how many blossoms are on the ground and how many left in the tree will probably fall off," Dave said. "We have a rope thinner, too," he said, "but we don't use it any more. It beats using nothing, but ropes wrap and damage limbs. That doesn't happen with the Darwin." "For us, it saves a week of green peach thinning by a crew of 12 people." —Dave Wenk att Peters, a sales representa- tive for N.M. Bartlett, Beamsville, Ontario, Canada, says the company has sold about 20 Darwin string thinners this year, bringing the total number of machines in North American orchards to about 50. The company sells two versions of the machine. It builds and sells the original Darwin invented in Germany by Adolf and Seiglinda Betz, and it also sells the PT version, which is built by the couple's company, Fruit- Tec, to specifically address the Amer- ican peach market. The PT runs horizontally over open-vase-style trees. The original Darwin runs vertically along the sides of trees. Peters said the company, and Penn State University, were still mak- ing design modifications that will improve the machine, but these will not be ready for use next year, as had been earlier thought. "We're going to add a few features to make the machine handle better on slopes," Peters said. "Penn State is developing ultrasonic sensors to automatically alter the angle of the spindle and the distance it reaches into the tree canopy." This added control will reduce the need for the operator to manually control the location of the spindle, reducing operator fatigue, increasing accuracy, and increasing ground speed. The Darwin now mounts on the front of a tractor. With the auto- matic features, it can be mounted on the rear of the tractor, and two spin- dles can be used to do two sides of two rows in one pass. The Darwin, which thins blossoms along the sides of trees, sells for about $11,000. The Darwin PT, which does either tops or sides, depending upon the orientation of the rotating spindle, sells for $16,000, Peters said. N.M. Bartlett has developed a sales and service network with deal- ers in Washington State (Blueline Equipment and Manufacturing Company), Virginia (Crown Orchard Company), and Michigan (Louis Gelder and Sons). The company works directly with growers in Penn- sylvania, where the machine was tested and demonstrated extensively and where several peach-growing operations have adopted it. —R. Lehnert GOOD FRUIT GROWER DECEMBER 2011 33 joy cline richard lehnert steve hollabaugh

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