At a recent growers' conference in Napa, viticulture expert Professor Andy Walker, of the University of California, Davis, pulled out his crystal ball to consider the likely challenges that lie ahead for this premium wine growing region.
No. 1. Phylloxera:
The University of California, Davis made a slip-up by advising growers to use the rootstock AXR1, which left the Napa Valley reeling from a devastating outbreak of phylloxera in the late 1980's and early 1990's.
Recently, there have been reports of phylloxera outbreaks on the root stock 101–14, but Walker, a root stock expert, isn't convinced it is to blame and advises a more diverse approach to planting. “101–14 has been mentioned as maybe a bad idea but actually it's appropriate for the right sites," he says. "But using the same root stock across the entire valley is not such a good idea, so we want to diversify.”
No. 2. A killer fungus:
Most vines in Napa live for between 25 and 30 years, although at the Haynes Vineyard in Coombsville, some zinfandel vines are more than a century old. The reason most vines don't make it to a grand old age is a wood-rotting fungus, says Walker. “It's probably the major problem that faces viticulture ... There are no obvious solutions.”
No. 3. Don't rely on cabernet:
Napa Valley has become synonymous with age-worthy cabernet sauvignon and its popularity means acreage is on the up in the region. Relying on a single varietal hasn't caused too many problems for Chablis or the Mosel Valley, but there are voices in Napa who are concerned about relying too heavily on a single varietal, fearing it will fall out of fashion and become the next Australian chardonnay. Walker says this is an important issue for Napa.
There is also concern that climate change – whether it makes the region hotter, colder or simply more unpredictable – could cause problems for the region. "If it does get a whole lot hotter, it's going to be hard to make as much high-quality cabernet as we do now. If the fogs come in more intensively than they do already and rush up the Carneros into Napa and Oakville, it's going to be more difficult to make cabernet, as it will be too cold."
No. 4. The blotch blight:
Walker's ears have been burning: he has answered as many as 2,000 phone calls in the past year on Red Blotch disease, after using DNA sequencing to identify the virus that discolors grape leaves in the fall and lowers sugar levels in grapes. The disease isn't new, but scientists simply didn't know what it was until 2012. While it can now be detected, there's still no way to eradicate it.
Walker says: “We don't know what the hosts are yet and they have vectors and that's going to be a big problem in how we control it. It's going to be tricky and you are going to be hearing a lot about it.”
No. 5. The Pierce fear:
There's still no real solution to Pierce's disease, a bacterium that kills vines within one to five years of infection. It has had devastating effects for some producers in North America – 25 percent of the Temecula Valley in the South Coast region of California had to be replanted after an outbreak in 1999. It could hit Napa at any time.
“It's episodic; it always has been episodic and we don't know when it's coming next. Is it going to come back?” asks Walker. Climate change could also make the region more susceptible to the malady. “Pierce's is more severe in drier climates than wetter climates. If we get a warmer climate in California, Pierce's could be more intense.”
Scientists are currently working on breeding resistant varieties, crossing Vitis vinifera stock with resistant vines from Mexico.
No. 6. Middle Eastern influence:
Lamb tagine with old Napa cabernet sounds like a delicious combination, but how about Napa cabernet that actually contains Middle Eastern vine stock? It could be coming to a vineyard near you. Researchers are working on crossing the usual suspects with 10 Middle Eastern varieties that are resistant to powdery mildew, which should lead to the launch of new varieties.
Walker predicts these will be released in the not-too-distant future. The result would be that vines wouldn't have to be sprayed with sulfur. “It's important to get ahead of the curve, to make wines sustainable.”
No. 7. Attack of the clones:
There's an entire industry based on creating new clones for wine producers looking to get an advantage over their rivals. Do they really make all the difference? “Yes," says Walker, "but they are massively overshadowed by soil, climate and winemaking, and yet we depend upon clones as our savior.”
He also suggests that the clones which are seen as the solution to all problems may in fact be diseased. “The horrible truth about clones is that we can't get them through the certification process quickly enough to make sure they are virus-free ... We have to get them out while they are still popular.” His suggestion? Try a different variety instead of a clone to achieve greater diversity.
No. 8. Dry times:
Water is an issue for wine producers around the world, not simply Napa. “Water is critical," says Walker. "It's the most important thing that's going to face all of us through our lifetime. The next 25 to 50 years, it will be critical. Drinking water, bathing water, irrigation water, how we allocate that water will be key, because we are a semi-dry climate.”