Syrah decline increasing?

Wines & Vines, April, 2005 by Larry Walker, California

In 1999, growers on the Central Coast of California noticed problems with Syrah vines in some vineyards. Mark Battany, UC extension farm advisor in San Luis Obispo and Santa Barbara counties, noted that symptoms included early reddening of the leaves, grapes not reaching ripeness and poor juice color, leading to lower yields and a decline in grape quality.

Viticulturists knew that a similar but not identical condition had been seen for several years in France, which the French called Syrah decline. The California version was named "Syrah disorder" to distinguish it from the French version. One key difference is that California vines seemed to decline faster than those in France.

When Dr. Deborah Golino, director of Foundation Plant Services at UC Davis, conducted a survey in 2002 of California vineyards in Calaveras, El Dorado, Madera, Merced, Napa, Sacramento, San Joaquin, San Luis Obispo, Sonoma and Stanislaus counties, she turned up symptoms of Syrah disorder. The vineyards surveyed included 12 clones, seven field selections and 12 rootstocks. No pattern was found, although at the time Golino thought symptoms might be traced to frost damage on young vines as well as water stress.

Wines & Vines contacted Mark Battany following the 2004 harvest to get an update on conditions on the Central Coast. He replied by e-mail:

"We are still seeing a variety of symptoms, and not all plantings show the same mix. This has led us to think that there are a variety of issues affecting the vines. In the simplest case, spring growth is normal ... sometime in late July or early August, the leaves gradually take on a splotchy red color. Around harvest, the leaves scorch over a period of one or two days. The fruit on affected vines doesn't ripen well, has low sugars and very poor color development," he wrote.

He observed, however, that some plantings show the red leaves but not the scorching, and the fruit quality is not as poor. "Other symptoms that we are seeing include unexplained wounds in the trunk and poor scion-rootstock connections; again, these symptoms are not always present in the 'simple' case presented above." He added that vine death is not common in the early stages, but has been seen.

Asked if the condition is being seen on vines other than Syrah, he said similar symptoms have been noted in Mourvedre and Zinfandel vineyards.

Battany said that he has not seen any patterns with respect to clones or rootstocks. He added that reduced water stress through an increase in irrigation has led to decreased red leaf symptoms. Studies in both France and California have found no direct correlation between soil type and Syrah decline/disorder.

Asked if the problem appeared to be spreading on the Central Coast, Battany said he heard fewer complaints in 2004 than in 2003.

Dr. Andrew Walker, in the department of enology and viticulture at UC Davis, said Syrah decline/disorder is being seen throughout the state. "It is most common on shallow soils with low rainfall where the vines are stressed," he told Wines & Vines.

Walker said it has been seen on all clonal selections except those from Australia. "It typically shows up in three to five years, leading to fairly quick death of the vine," he said. Walker said planting on richer soils and applying more water and fertilizer usually eliminate the symptoms. "But then you are no longer making good Syrah," he added.

Walker said the situation in France is much different than in California. "Typically, there the vineyards are multi-aged. As old vines die or become diseased, they are replaced one by one. They are willing to put up with some loss of vines."

However, that doesn't mean the French are not aware of the problem. It was first noticed in the early 1990s, when vines with swollen and cracked graft unions as well as the red leaves were observed, with the plant usually dying within 10 years. In 2000, a national committee was formed to coordinate research into the problem.

(In some parts of Languedoc and Roussillon, growers are resisting pressure from appellation authorities to plant more Syrah to blend with the traditional Grenache and Carignane of the regions, fearing that Syrah decline could spread to other vines.)

As in California, the French believe that a number of separate factors could play a part in Syrah decline, with vine stress perhaps the key.