Darwin used on perpendicular vee peach orchard in California (Family Tree Farms).

Researchers who studied the Darwin string thinner found it does a good job on peaches, saving growers time and labor and generating high-quality, valuable fruit. So, the next step for peach growers is to adopt the machine and put it to use, while researchers move on to testing it in apples, sweet cherries, apricots, and pears.

Matt Peters, sales representative for N.M. Bartlett in Beamsville, Ontario, Canada, said his company sold 15 units to growers in Canada and the United States just in December and January.

That brings to about 40 the total number now in the field in North America. Karen Lewis, the Washington State University Extension specialist who has participated in the research, said she learned on a recent trip that 49 are in use in Italy.  There are 350 machines total in use in Europe with 90 percent used for conventional production and the remainder for organics, Peters said. The machine was invented 20 years ago in Germany by organic apple grower Herman Gessler, but commercial production and worldwide sales began in 2006 when the company Fruit-Tec partnered with Gessler.

Extremely happy

Kevin Bittner at Singer Farms in Appleton, New York, bought one and reported he is extremely happy with it. So did Maurice Tougas in Northborough, Massachusetts, and Ed Rankin in Pennsylvania, all of whom spoke up at a meeting in Hershey, Pennsylvania, in early February.

The project to research and evaluate the Darwin was backed by a federal $1-million Specialty Crops Initiative grant and required matching money, part of which came in cash from California and part from growers who allowed research to be done in their orchards.

In an interview with Good Fruit Grower, Peters said it appears the adoption curve is on track. Some growers, like Doug Lott in Pennsylvania, imported a machine from Germany when they first saw a picture of it—before research even started. Others bought early. More take a wait-and-see attitude, Peters said, but the research project has been so well publicized, every grower knows about the machine. “It’s been in growers’ faces for four or five years,” he said.

The story at N.M. Bartlett is also one of love at first sight. “We first saw the data coming out of the research performed by Penn State,” Peters said. “The researchers there found it and brought a machine to the United States. I saw it and said, ‘We’ve got to get this thing.”

Penn State researchers assembled a team under the banner of the Pennsylvania Ag Innovations Initiative, and then collaborated with researchers in California and Washington and with other universities. That team includes Adams County tree fruit educator Dr. Tara Baugher, horticulturist Dr. Jim Schupp, ag engineer Dr. Paul Heinemann, ag innovations and specialty crop educator Dr. Katie Ellis, and others.

Matt Peters and his father, Don, flew to Berlin, Germany, and met with Adolf and Sieglinde Betz, owners of Fruit-Tec. “We bought two of the machines, a PT (which stands for Peach Thinner) and a Darwin 250, to try them and gauge grower interest. The Betzes came to Ontario and spent ten days with us. With the help of Ken Slingerland at the Ontario Ministry of Agriculture, Food, and Rural Affairs, we ran fifteen trials in ten days, and we got good response—from the trees and from the growers who watched the ­demonstrations.”

Bartlett immediately began importing the machines and also building them. They now sell two ­versions—the Darwin, which Bartlett manufactures in Ontario, and the PT, which is currently built by Fruit-Tec  in  Germany.

Interestingly, Peters said, the PT was made by Fruit-Tec in response to the demands of the North American peach market. The original Darwin was invented to blossom-thin organic apples. The PT mounts on a forklift or front-end loader, and rotates up to 180˚ (from 135˚ to 315˚). It can be positioned horizontally to knock blossoms off the top of open-vase-style trees as well as vertically to thin the sides. The Darwin can be adjusted up to 90˚ (from 45˚ to 135˚), but basically it remains vertical and is best adapted to a fruiting wall system such as the perpendicular V in peaches or the super spindle system in apples, Peters said.

For many years, some growers have used the rope thinner manufactured by Phil Brown Welding in Conklin, Michigan, Peters said. “Some of these growers with open-vase trees  are using the rope thinner to do tree centers and the Darwin to do the edges.  This way, they can purchase the lower-cost Darwin and still make use of the rope thinner they already own and are comfortable with.  So, there are several options.”

However growers choose to do it, Peters said, most feedback is the same.  At the end of the year, growers are saving 40 to 50 percent of their hand-thinning labor bill, and their packouts are showing larger fruit and higher yield.

The two-foot-long strings take off a third to a half of the blossoms in the outer two feet on both sides of the tree, where most of the bloom is. “We know that the earlier you remove fruits or flowers, the more carbohydrate you have to make the remaining fruit larger,” Peters said. “Hand thinning lets you make great choices on which flowers or fruit to remove, but it takes so long.”

Growers who use the string thinner follow up with hand thinning, but much of the work has already been done. “The workers seem to enjoy the Darwin-treated blocks as they can move through much faster, and hand thinning becomes a much more pleasant task,” Peters said.

The Bartlett company

The N.M. Bartlett company was started by Norman Millet Bartlett in 1912 and is still family-owned. Peters is a great-grandson of the founder. The company has 45 employees, and is both a manufacturer and distributor. It sells crop protection chemicals, VanWamel orchard mowers, Greefa grading lines, ­custom-made packing house equipment, and other products.

Peters said he has no idea how many of the thinners will ultimately be sold. Some growers, especially in California, saw the Darwin and decided to make new plantings in a style that best fit the machine, anticipating they would use it, Peters said. They’ll buy machines when the time is right.

In Ontario, he said, growers are trying to adjust their labor force and the work flow to fit. The Darwin may reduce the size of the work force needed. In northern stone-fruit production in Ontario, growers typically bring in offshore help in late spring and start to prune late, right through bloom, to avoid problems with bacterial canker, then prepare for thinning. Pruned trees thin better with the Darwin, Peters said, so they are now adjusting their pruning schedule to prune early blooming varieties first and ­continue pruning later varieties while the Darwin is thinning the early ones. Spreading out the pruning season and using the mechanical thinner will require fewer workers.