UA tests effect of trellises on berries
The summer sun makes blackberries a gamble for farmers in the South, commonly turning the fruit odd shades of red, or white, from overexposure.
Most shoppers won’t see the white ones, because grocers will reject them before they hit stores, said Amanda McWhirt, extension horticulture specialist for the Division of Agriculture at the University of Arkansas.
As a way to encourage sustainable blackberry production and prevent fruit- related diseases or insect damage, McWhirt is researching the effects of rotational trellises on blackberry growth in the Ozark region.
The rotating cross- arm trellis, or RCA, allows blackberries to not just grow vertically, but at an angle or near horizontally as well. This offers full shade coverage for blackberries, solving a significant problem for southern growers.
Originally developed by a horticulturalist in West Virginia in 1992, the RCA trellis was intended to promote blackberry growth in
areas prone to harsh winters. By rotating the blackberry plants so they lie horizontally, growers are able to lay row covers, or blankets, over their crops to help endure frigid climates, McWhirt said.
In Arkansas, farmers face a different dilemma.
“In the South we have an issue with things getting too hot in the summer,” McWhirt said. “So we thought, is there a way to orient the berries so they’re always in the shade?”
Two common diseases brought on from high heat and sun exposure are white drupelet syndrome and red drupelet disorder, which discolor the blackberry drupes — individual parts of the berry — into that particular shade. Sometimes farmers will pick fine blackberries in the fields and once they hit the market or become refrigerated, they’ll turn red or pink, McWhirt said.
“This looks bad and people don’t want to buy them,” she said.
Other issues McWhirt and her colleague Jackie Lee are investigating include whether or not rotational trellises will encourage higher berry yields, and if the plants respond well to lower levels of fungicide and insecticide.
A pest also causing U. S. blackberry damage is the Spotted Wing Drosophila. Originally from Asia, the small fruit fly made its way into America less than ten years ago and has since
caused significant damage to blueberry, strawberry, grape and blackberry crops.
Without adequate control measures, the pests can result in up to $ 500 million in annual losses in Western U. S. production areas, according to a Society of Chemical Industry study.
The Spotted Wing Drosophila tend to hide in the dense canopies of blackberry plants. By rotating berries on their side, McWhirt said that the canopies would be more exposed, allowing easier spray coverage with less insecticide.
While the rotational trellis system has the potential to reduce plant and chemical costs, the system itself is more costly — two to three times the price of a traditional system — and growers may have to hire additional labor for training the blackberries to the trellis.
The rotational trellis system costs growers an estimated $ 3,000-$ 5,000 an acre, according to the Arkansas Division of Agriculture. McWhirt said part of her research would be looking into the economic viability of using rotational trellises over traditional ones.
These systems were installed at the University of Arkansas Division of Agriculture’s Clarksville station in May. Researchers are scheduled to spend the first year getting the plants established, followed by about five years of data collection.
An effect rotational trellises have had on blackberry production nationwide, is
that Arkansas blackberry varieties are able to grow in cooler climates outside of the state.
“Thirty- five years ago, I laughed at it,” said John R. Clark, director of the University of Arkansas System Division of Agriculture fruit breeding program.
He remembered standing next to Fumiomi Takeda, the U. S. Department of Agriculture researcher who refined the rotational trellis years ago, thinking the technology would be too much hassle for growers — training pickers, weaving the plants precisely.
“It was just too much work. But when they started growing Arkansas varieties in cooler climates, I started paying attention,” Clark said.
Fresh blackberry production has spiked in the North because of the rotational trellises, and southern growers have taken to the technology because they swear “the quality is better,” he said.
About 100 miles west of the University of Arkansas lies an Oklahoma farm run by Bill Jacobs, 80, who’s been growing thornless Arkansas blackberries for nearly 20 years. In the last four years, he’s used rotational trellises on about half of his blackberry acreage. He received a grant from the Oklahoma Department of Agriculture to record his own trellis observations.
“It has its pros and cons,” Jacobs said. “It’s pretty labor intensive.”
It takes about 60 hours per week for two of Jacobs’ workers to guide the blackberries
through the trellis frame, he said.
At Jacobs’ U- pick operation, he said maneuvering the berries to one side has given him more control over his crop and made picking faster and easier for customers.
“There’s no hunting. Every berry is hanging free and exposed,” Jacobs said.
His observations also matched McWhirt’s hypothesis, that the rotational trellis influenced the yield of berries with white or red drupelets and insect problems.
“They’re completely eliminated,” Jacobs said.