Most of Washington’s vineyards are first-generation plantings. But as the state’s wine industry matures and pressures mount from pests and market changes, growers must decide when it’s time to pull an aging block and how best to replant.
Planting in new ground and replanting pose very different challenges and considerations. Pest pressure from nematodes or phylloxera, disease pressure from adjacent blocks and nutrient stress from decades of farming all build and can overwhelm young vines, said Michelle Moyer, extension viticulturist for Washington State University.
“The only thing that replanting and planting have in common is that they both cost money,” Moyer said. “Young vines can’t handle a lot of stress, but you are adding all the stresses that have accumulated to the new vineyard.”
She spoke about replanting at a session about vineyard renovation at the Washington Winegrowers’ annual meeting in March, along with vineyard managers Joe Cotta and Brad Sorensen, who shared their experiences with deciding when a vineyard needed to go and what should replace it.
“It’s part of the natural cycle of a vineyard,” said Sorensen, the vineyard manager for Les Collines in Walla Walla. He recently moved to Washington after years in Sonoma and Napa, California, where replanting due to virus issues was just part of the management plan.
Deciding to replant
Vineyard renovation starts with evaluating the health and bottom line of aging blocks, said Cotta, manager of Ste. Michelle Wine Estates’ Cold Creek Vineyard. You never want to pull a block your winemakers still love. But other times, if it is clear you have lost a roguing battle against leafroll virus, the block — or a subsection thereof — needs to go to protect the rest of the vineyard, he said.
Roguing involves removing vines that test positive for a disease or virus.
“The possibility of eradicating the virus once that block is 25 percent infected, that’s a difficult challenge,” he said. Actually, if your roguing strategy calls for removing several vines on either side of each vine that is symptomatic or tests positive, it takes a far lower infection rate to remove 25 percent of the block, he added.
“You have to decide on your roguing methodology and know that it’s working,” he said. “You don’t want to spend money farming a block when the quality isn’t going to be there.”
Moyer said that roguing is only a reliable strategy when no vectors for the disease are present, as is the case with red blotch in Washington, or when you catch a vectored disease such as leafroll very early. Otherwise, you need a more aggressive response that removes several adjacent vines.
Cotta also shared some strategies to maintain older vineyards, such as training extensions to fill gaps. Replanting new vines into an existing block poses challenges, but if you try it, you need to adjust your irrigation strategies, Cotta said. Transplants need slower and more frequent irrigation to get established, but that may be more water than you want on the rest of the block.
“When profits are down, lowering your costs by removing vineyards can be wise when there are areas in your vineyard with long-term quality problems,” he said.
Once the decision has been made to pull a block, then comes the decision about what to replant. In today’s market, it’s more important than ever to plant under contract with a winery, Sorensen said. He recommended using what you’ve learned from the first planting to guide the second: Understanding the regional climate and microclimate, frost risk and growing season length, you should have a good idea of the best-suited variety.
The method of removal depends on whether you want to keep your trellis. “It’s a lot faster to remove a block with a bulldozer than vine by vine,” he said.
Design the system for how you plan to manage it, with a focus on mechanization-friendly design, if you plan to manage it that way, and general “farmability,” Sorensen said. He gave the example of a long skinny block where he opted to run several long, east-west oriented rows rather than lots of little rows at the typical north-south orientation. That will save his tractor driver a lot of turning around.
He also recommended evaluating the soil health before planting.
“Do you have nematodes? Do you have phylloxera? It’s certainly worth a look before you commit to own-rooting,” Sorensen said.
When it comes to nematodes, the pressure can catch growers off-guard when they replant, Moyer said. Established vines can withstand the feeding from even high populations of root knot nematodes, but when baby vines are suddenly planted in the same soil, the damage can overwhelm them and stunt their growth.
Fumigation, which growers would like to think leaves a clean slate for replants, doesn’t provide as long-lasting or as consistent of an effect. In her nematode trials, she found that after two years, root knot nematode pressure was actually higher in fumigated blocks, because the process likely wiped out the good soil microorganisms as well, giving the nematodes a competitive advantage when they came back. The aim of fumigation is to give young vines a head start, but that head start doesn’t seem to be enough, she said.
Replanting and shifting the row spacing can help growers avoid the root-feeding nematodes, which are found directly in the root zone, Moyer said. Otherwise, there are resistant rootstocks to try.
“Rootstocks are going to be an extremely important tool for managing nematodes and other replant situations,” including phylloxera, she said.
Many Washington growers believed relatively sandy soils prevented phylloxera establishment, but they may find that the management steps taken to boost soil organic matter over the years made the soils more hospitable to phylloxera. During the first-generation planting, phylloxera didn’t pose a risk, but cold damage did, so it made sense to plant own-rooted. Now, in some locations, the risk calculus looks different, Moyer said.
“Some areas will be able to stay own-rooted; others won’t,” she said. “It’s a farming decision. We solved the phylloxera problem, we solved it over 100 years ago, and if you are in an infested area, you might need to use them.” •
—by Kate Prengaman