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Grape field day hightlights research

Growers seek ways to keep vineyard costs down with no-prune methods and field grafting.

Field grafting wine grapes, minimally-pruned juice grapes, a new fruit juice concentrate and by-products production facility, and viticulture research updates from WSU scientists were the highlights of the Washington State University’s viticulture and enology field day held in mid-August at the Irrigated Agriculture and Research Center in Prosser. The field day, sponsored by the Washington State Grape Society, has become an annual event, bringing industry and WSU scientists and graduate students together to share the latest in research.

Field grafting

Grandview, Washington grape grower Dick Boushey of Boushey Vineyards shared his successful and not-so successful field grafting experiences, showing field day attendees a small, two-acre block of Semillon grapes planted in 2003 that were grafted earlier this spring to Sauvignon Blanc.
Though Boushey had a better grafting take in a small block several years ago, his most recent experience—with 60 to 70 percent take—was borderline successful, he said. He used the cleft graft technique, employing a commercial grafting company from California.
He thinks this year’s cool spring weather limited his success and he should have waited a few more weeks for temperatures to warm up before grafting. When done successfully, grafting can save time and money, he said, getting the block back into production by the following year.

Minimal pruning

Keith Oliver, manager at Olsen Brothers Farms, a diversified family farming operation in Prosser that includes tree fruit, juice and wine grapes, blueberries, wheat, and hops, uses minimal pruning to keep labor costs down in both juice and wine grapes. Since 1993, when Olsen Brothers first began using mechanical pruning in their Concord vineyards, they have now transitioned to what Oliver calls “minimal or almost no pruning” in nearly all of their juice and some wine grapes.

For minimal pruning, they use a sickle-hedge style pruner with two angled sickle bars that trim the canopy skirt bottom. A hand crew follows the pruner, making one pass to prune any straggler canes that are hanging to the ground. “We tell the crew, ‘don’t stop walking’ as they pass through.”

In tracking yields through the years between minimal pruned and mechanically pruned vineyards, Oliver said that over time, they haven’t seen yield differences. And with the new mechanical harvesters, the crop is picked clean and “material other than grapes,” known in the industry as MOG, is not an issue.

He encouraged growers to transition slowly to minimal pruning, shifting a portion of their acreage to minimal pruning each year. Getting high enough sugar (Brix) in juice grapes can be a problem in the first year or so. “If you stretch it out over several years, you’ll have other portions of the vineyard to blend with to raise your sugar levels.”

WSU research

Dr. Joan Davenport, WSU soil scientist, is completing the final year of a four-year study to quantify nutrient deficiencies in wine grapes in the Pacific Northwest. For the last four years, she has grown Semillon and Cabernet Sauvignon vines in five-gallon buckets of sand, adding back essential nutrients when the vines show deficient symptoms. Information collected will help her determine the low end of nutrient levels needed for vine health as well as the impact that deficiencies can have on other nutrients.

“Nutrient deficiencies in white grapes tend to make the vine look hungry, while in reds, there’s more discoloration symptoms,” she said during the WSU show and tell session. Often, it took two years of withholding a specific nutrient to observe any symptoms, she added.
Davenport will compile her report and develop information, including photos of nutrient deficiency symptoms, in the coming months in a format that’s usable for growers.

Drs. Markus Keller and Bhaskar Bondada, along with WSU viticulture graduate students, are working to unravel the mysteries of berry shrivel, a common disorder in the Pacific Northwest that sporadically hits red and white wine grapes, especially the varieties Cabernet Sauvignon, Semillon, Sauvignon Blanc, and Petite Syrah. In some blocks, up to 40 percent of the clusters have been damaged by shrivel.
Berry shrivel is not to be confused with sunburn or bunch stem necrosis, said Keller. So far, scientists have learned that in berries suffering from the disorder, sugar accumulation has stopped, acids have begun degradation, and the rachis and phloem have died. “We don’t know what kills the phloem or what’s causing the symptoms, so we can’t develop practical solutions,” he said. “Every time we come up with a hypothesis, a graduate student finds out that it’s not the answer.”

Shrivel rarely returns in the same vine year after year, but often jumps around within a vineyard, said Bondada. “We spend hours tagging affected vines, and then the next year the vine is healthy, but if you go a few rows over, you’ll find shrivel.”

The WSU researchers continue to look for answers, and urge growers who observe berry shrivel in their vineyards to contact them so that they can visit the vineyard and learn more about the disorder.

Keller can be reached at mkeller@wsu.edu and Bondada at: bbondada@wsu.edu.