Reducing blackberry sun-scald

Research that had its genesis in an effort to address freeze damage to blackberries in the Midwest could also help protect blackberries in California from the state’s searing summer sun.

A trellis system that permits berry canes to be attached to a rotating cross arm could be a key to solving both challenges, and it’s being tested at the University of California Kearney Agricultural Research and Extension Center in Parlier, Calif.

“Right now, in blackberries there are heavy losses due to sun-scald,” said Manuel Jimenez, University of California Cooperative Extension farm advisor for Tulare County. So far growers may have already lost 60 percent of their 2009 crop due to a brief, but searing hot spell in May.

“It’s beautiful fruit, very sweet due to our weather. But the sun cooks it; it’s like using a magnifying glass.”

Trellis research by Fumiomi Takeda caught the eye of Jimenez, who believes the work by the research horticulturist with the U.S. Department of Agriculture could address the sun-scald issue in the San Joaquin Valley.

Takeda is lead scientist with the Appalachian Fruit Research Station of the Agricultural Research Service in Kearneysville, W. Va., 70 miles west of Washington, D.C.

Takeda, who grew up in Fresno, Calif., was among speakers at a blackberry and blueberry field day at Kearney.

He explained how the rotating trellis was developed to “reduce winter injury” in places where temperatures often drop into single digits. The system does not merely rely on the mechanics of a trellis arm that rotates. It also depends on training of floricanes, primocanes and lateral canes.

One result is that fruit appears on one side of a row, simplifying harvest. Another feature is that the arm can be dropped downward to permit use of a row cover – instead of a high tunnel – to offer freeze protection.

The rotating crossarm is hoisted into position twice each year.

Takeda said use of the system has expanded commercial growing of blackberries into states that include Indiana, Ohio, Pennsylvania, and New York. He believes the system reduces harvest and pesticide costs.

Richard Barnes, owner of Trellis Growing Systems in Fort Wayne, Ind., said he has worked with the USDA to design and make the trellis system, including the experimental one at Kearney.

“We’ve been in the development stages for almost two years, but we’re not yet at commercialization of the product,” he said.

His prototype would cost about $2.50 a row foot to commercialize. Barnes has manufacturers in California with hope of developing lower cost hardware.

“The product at Kearney is fiberglass, stainless steel and aluminum,” he said. “It doesn’t corrode and it rotates smoothly, but it’s probably more product than is needed for California.”

Barnes said the state’s arid climate could mean that alternative, less expensive materials would stand up well and cost less.

“You can get at least a 50 percent, if not a 200 percent to 300 percent increase in the amount of [marketable] berries.” This would go a long way to recover the $10,000 per acre cost of the trellising system.

Barnes said USDA efforts to use mechanical harvesting with the system have not been successful to this point. “They couldn’t get consistent quality; there was bruising,” he said.

Barnes said scientists at Kearney are now doing research on semi-erect blackberry trellising.

Richard Collins, president of California Vegetable Specialties in the Sacramento Valley, is already experimenting with his own rotating trellis system on two acres near Davis, Calif. By 11 a.m., in the heat of the day,” Collins said, his berries are “essentially shaded.”

Before bloom, he said, the rotating arm is down. Once a crop is set, he said, “it’s shifted to let them ripen. We’re still tweaking it, but it’s a divine concept.”

His system costs $5,000 to $6,000 per acre. “It’s easier to pick and it should increase yields,” he said. “This year will be the first test.”

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