Posts Tagged: Grapes
Will machines replace the romance of the hand-cultivated wine grape vineyard? A “touchless” vineyard was among the latest research on labor shortages, weeds and pest management by UC Cooperative Extension scientists discussed at Grape Day at the UC Davis Oakville Station, located in the epicenter of California wine country, on June 6.
About 200 wine grape growers, vineyard consultants and other industry people attended to learn about the latest UC Cooperative Extension research. Vineyard managers from boutique wineries such as Fork in the Road to Pine Ridge Vineyards to the Fortune 500 wine company Constellation Brands gathered at the research station's experimental vineyard. Several vineyard equipment representatives brought their machines to the field to demonstrate their weeding, pruning and canopy management capabilities.
Addressing labor shortages
To help growers attract and retain farm workers, Monica Cooper, UC Cooperative Extension advisor for Napa County and her research assistant, Malcolm Hobbs, are conducting a survey of agricultural workers to determine the factors that affect job satisfaction. They found the number of female workers in Napa County has increased rapidly since 2013. “Women may be moving into the labor pool to fill vacancies caused by the decline in the number of male workers migrating to the U.S. for agricultural work,” Cooper said.
They plan to provide participating companies with custom recommendations for recruiting and retaining workers.
“We will also be generating a generic summary that will be widely shared with participants and non-participants at the close of the study. For now, we cannot make any general conclusions or recommendations because data collection is ongoing,” Cooper said. “We are aiming to distribute our final report this winter, so stay tuned.”
To help growers reduce their need for hand labor, UC Cooperative Extension viticulture specialist Kaan Kurtural designed a “touchless” demonstration vineyard that is mechanically managed. The mechanized vineyard is one of six trellis systems he is studying for water use, nitrogen use efficiency, yield and fruit quality of the wine grapes.
“We're always looking for ways to improve yield, quality and to reduce cost,” said Francisco Araujo, director of viticulture for Atlas Vineyard Management. “In light of the labor shortage we're facing right now, Kaan is exploring new production systems that include new trellises, mechanization, different types of mechanization from pruning to shoot thinning and trunk suckering. He's obtaining information about how these new trellis systems that he is investigating are going to play with yield and quality.”
The touchless vineyard experiment started out as a demonstration at first, but with grower interest, it turned into a full-blown research project.
“It started as way of saving labor costs, but when we started looking at the physiological aspects of how these plants grow, we saw the benefits from the quality point of view in addition to the labor savings,” said Kurtural, who is based in the Department of Viticulture and Enology at UC Davis.
A traditional vineyard in the Napa area is about a meter or 36 inches above the vineyard floor with vertical shoots held up with wires, which are moved by hand.
“We said, ‘Why don't we turn the system upside down?' Grow a tall trunk then put the bilateral cordon about 62 inches above the vineyard floor, that way we can push the rows a lot closer,” said Kurtural, who oversees the 40-acre Oakville experimental vineyard. The leaves grow down to generate the same leaf area as a traditional vineyard, but the leaves in the mechanized vineyard use water more efficiently so the no-touch vineyard requires less water compared to traditional vineyard systems.
“This is a dense system, this is 1.5 meters by 2 meters, roughly 1,340 plants per acre – we're getting by here on a third to quarter acre foot of water,” Kurtural said.
“It costs us roughly about a dollar in labor operation costs to manage each plant in a traditionally farmed vineyard of roughly about 1,300 plants per acre on the North Coast now,” Kurtural said. “The no-touch plants are costing us about 7 cents in labor operations costs.”
“The biggest expense is pruning, after that we go through what they call trunk suckering, which is also done mechanically here, and after that they will do shoot removal to open up the canopy. That's also done mechanically. After that, if there's need, they will do leaf removal, that's also done mechanically. And one last resort, if there's too much crop here, they will shake off excess berries with a harvester.”
The conventional system yields up to 5 to 6 tons per acre whereas the mechanized vineyard yields 7 to 8 tons per acre.
“These clusters set far fewer berries than a traditionally managed vineyard, but the berry size is also very small, which is what the winemakers like,” he said.
During harvest, grapes picked by machine are sorted on board the harvester so they go into the winery in uniform sizes, whereas hand-harvested grapes have to be sorted on a tray before they are put into the press tank.
“We made wines from these last year and compared to our traditionally farmed vineyards. Until we tell people what it is, they cannot distinguish the quality of the fruit or the wine.”
Weed and pest management
John Roncoroni, UCCE weed science farm advisor in Napa County, discussed options for weed control among young grape vines.
In the past, many vineyards were fumigated before planting for disease control, but it also provided weed control for young vines.
“With the loss of most fumigants for use in vineyards, hand-weeding was often used to accomplish this task,” Roncoroni said. “Increased costs and decreased labor force have made hand weeding impractical. Mechanical cultivation, at this point, is too imprecise – either leaving weeds close to young vines or causing damage by being too close.”
Covers on young vines allow the use of many post-emergence herbicides to control weeds, but Roncoroni cautioned that application of post-emergence herbicides on vines that aren't protected by mature bark may damage or even kill the vine.
“Herbicide use on vines less than 3 years old is a risky endeavor,” Roncoroni said. “Follow all label requirements, paying special attention to soil and irrigation recommendations.”
Lynn Wunderlich, UC Cooperative Extension advisor for the Central Sierra, and Franz Niederholzer, UC Cooperative Extension advisor for Colusa, Sutter and Yuba counties, demonstrated how to calibrate sprayers and to get uniform coverage when spraying fungicides.
In 2016, UC Davis researchers identified the three-cornered alfalfa hopper, Spissistilus festinus, as a vector of grapevine red blotch virus. Cindy Preto, a Ph.D candidate in the UC Davis Department of Entomology who is assisting UC scientists studying the three-cornered alfalfa hopper's biology and host plants, provided an update on their research.
Araujo, the viticulture consultant, said he and his colleagues value the university's research. “Napa Valley is a place where quality is paramount yet more and more we have labor shortage, we have inflation, production costs are going up,” he said. “Finding a way to get maximum quality along with yield levels that will pay for the increasing costs of production is the only way we'll be sustainable now and in the future.”
Excitement over the new Sunpreme raisins was evident at UC Kearney Grape Day Aug. 8, 2017. As soon as the tram stopped, dozens of farmers and other industry professionals rushed over to the vineyard to take a close look and sample the fruit. Raisins pulled from the vine were meaty with very little residual seed. The flavor was a deep, sweet floral with a muscat note.
Sunpreme raisins, bred by now-retired USDA breeder David Ramming, promise a nearly labor-free raisin production system. Traditionally, raisins are picked and placed on paper trays on the vineyard floor to dry. The development of dried-on-the-vine varieties opened the door to greater mechanization. Workers would cut the stems above clusters of grapes, which then dry out in the canopy and are harvested mechanically. The new wrinkle with Sunpreme is that grapes ripen and then start to dry on their own - no cane cutting needed.
UC Cooperative Extension viticulture specialist Matthew Fidelibus and UCCE viticulture advisor George Zhuang are now studying the performance of Sunpreme grapes on different rootstocks and trellis systems at the UC Kearney Agricultural Research and Extension Center.
"We didn't know a lot about this variety," Fidelibus said. "We've found it to be very vigorous."
Fidelibus said the raisins take about a month to dry, and one challenge is the tendency for dried raisins to drop off the vine.
"We want to keep the self drying and stop self dropping," he said.
Ramming discovered the Sunpreme variety in a Thompson seedless table grape variety trial in the mid-1990s. He was going down the row, saw clusters of raisins and screeched to a stop. He had discovered Sunpreme. The variety is not yet available for commercial production.
Fighting nematodes with new solutions
Also during Grape Day 2017, UC Cooperative Extension nemotology specialist Andreas Westphal outlined research underway to keep nematodes at bay.
"There's no methyl bromide in commercial planting," Westphal said. The very effective fumigant was banned because of it's tendency to deplete ozone in the atmosphere and the risk to human health because of its toxicity. Many farmers have turned to Telone as an alternative, however it is expensive and its use is limited by a township cap.
Westphal is comparing alternative treatments for clearing the soil of the tiny worms that feed on vine roots and inhibit vineyard productivity.
"Some companies are coming up with new chemistry," Westphal said. "Our challenge in the perennial world is that the roots go so deep."
Seven new products and Telon were drenched in different replicated research plots. Some areas were left alone to serve as control. Three times the number of Sauvignon Blanc vines were planted in the plots compared to a typical vineyard so researchers could take out plants twice and examine the roots for evidence of pests.
"We are excited to see significant growth differences among the treatments," Westphal said, pointing out a row that was visibly shorter and less vigorous. "It amazed me. Three years after treatment, and it never grew back out of it."
Work is still ongoing, but Westphal said he believes some chemical treatment could be available in the future to help reduce nematode pressure.
To deal with nematode populations, Westphal encouraged growers to sample soil and communicate with the diagnostic laboratory to determine what pest nematodes are in their vineyards, and then use that information for root stock selection.
"Growers should not forget the value of nematode-resistant rootstocks," he said. "Plant material needs to be chosen very carefully when different species of nematodes are present."
When consumers are asked in surveys whether they would buy genetically engineered (GE) produce such as fruit, most say they would not buy GE produce unless there were a direct benefit to them, such as greater nutritional value.
Yet with continuing invasions and spread of exotic insects and diseases for which there is no known control, the potential importance of trees or vines with some form of genetically engineered resistance is on the rise. In California, such diseases include Pierce's disease in grapes, crown gall disease in walnuts, and the invasive citrus greening (huanglongbing or HLB) in citrus.
"These are potentially devastating diseases to California growers, who produce 70 percent of the fresh fruit and nuts for the entire United States," notes Victor Haroldsen, scientific analyst at Morrison and Foerster, in the current California Agriculture. "They are also a mainstay of the California economy. Fruit and nut tree crops accounted for one-third of the state's total cash farm receipts, or $13.2 billion in 2010."
Now, however, Haroldsen reports that there may be a way to satisfy both consumers and growers — called "transgrafting."
"In transgrafting the genetically engineered rootstock can potentially confer the whole plant with resistance to disease. Yet the rootstock does not transfer the modified genes to the fruits or nuts produced," said Haroldsen.
Although over 10 years old, transgrafting technology is just now nearing commercialization, partly due to the long generation times of most trees and vines. Two such transgrafting applications are: a crown gall-resistant walnut rootstock, and a grape rootstock that confers moderate resistance to Pierce's disease.
"The key advantage of transgrafting is that the plant's vascular system can selectively transport across graft junctions the proteins, hormones, metabolites and vitamins from the roots without changing the heritable genes or DNA sequence in the fruit or nut." says Haroldsen.
In recent research at UC Davis, Haroldsen (a former graduate student) and his colleagues confirmed that modified DNA and full-length RNA from the rootstock does not cross the "graft union" into the scion, in the walnut and grape applications, or in a tomato model of these two systems.
"These current GE applications address root or xylem pests and diseases, but future applications will likely target traits aimed at consumer needs such as increased nutritional value or improved flavor," said Haroldsen. "If perceived risks to personal health and the environment could be reduced, genetic engineering could benefit not only growers but Californians around the state," he adds.
A new federal voucher that gives low-income women access to a range of fruits and vegetables could provide unique new marketing opportunities for California growers.
In 2009, the federal Special Supplemental Nutrition Program for Women, Infants and Children (WIC) began distributing monthly cash vouchers to low-income women with children to buy fruits and vegetables. The program reaches almost half of the infants and one-quarter of children under 5 years old in the United States.
A team of UC Cooperative Extension (UCCE) researchers and nutrition advisors has been exploring the possibility of developing a farm-to-WIC program that would link these low-income consumers with local growers. The purpose of such a program would be to increase the consumption of a wide variety of fresh produce, with a focus on locally grown produce when available.
UCCE conducted a survey of produce preferences and buying habits among WIC participants in Tulare, Alameda and Riverside counties in 2010. The full study is published in the January-March 2012 issue of California Agriculture journal.
Based on the results, the UCCE team developed a list of 19 produce items to promote in a possible new farm-to-WIC program. They are:
Although mustard greens and collards were not popular across all sites, the advisors gauged a potential market in Alameda County, so these were retained. Based on write-in responses, oranges were also added.
In California, which has the nation's largest WIC program, 82 local agencies serve about 1.43 million participants at 623 local centers, and WIC participants can redeem their monthly vouchers at 4,000 grocery stores statewide. About 40 percent shop at WIC-only stores, which stock and sell only WIC-authorized foods.
Stocking produce is relatively new to WIC-only stores; before rollout of new WIC food packages in October 2009, these stores were only required to stock limited amounts of fresh carrots. In the survey, most WIC participants (58 percent to 72.3 percent) responded that their preferred stores offered many choices, but fewer participants (18.5 percent to 41 percent) rated the produce quality as “excellent.” Key factors determining purchase decisions were produce quality and freshness, and nutrient value (vitamins and minerals). Cost was relatively less important, possibly because WIC participants procure the produce with the vouchers.
The list has served as a starting point for discussions with growers and WIC vendors.
“The survey showed that WIC participants were interested in purchasing fresh produce with better quality and more variety,” wrote lead author Lucia L. Kaiser, Cooperative Extension specialist in the UC Davis Department of Nutrition, and co-authors, in California Agriculture. “Some WIC participants that we surveyed said they avoided shopping at WIC-only stores in part because these interests were not met.”
A dish made with nopales (cactus pads).