(Wines&Vines) - California grapegrowers whose vineyards are affected by the Grapevine Red Blotch-associated Virus may be eligible for financial aid to replace infected vines under a relatively new program attached to the 2014 Farm Bill. The aim is to ameliorate the affects and limit the spread of the still-mysterious red blotch virus in many of the state’s major grape-producing counties.

The aid comes under the Farm Bill’s Tree Assistance Program (TAP), which provides financial assistance to growers whose vines are damaged by “natural disasters.” First emerging as an important issue in California vineyards in 2011, the vectors of red blotch have yet to be determined. The new malady is not caused by known viruses or other plant diseases, researchers said. It can cause major damage to grape crops by causing the fruit to not fully ripen.

Agri-Analysis LLC, approved by the California Department of Food and Agriculture (CDFA) to diagnose vine disease, continues to encourage growers to be vigorous in testing new planting materials so as to prevent any infected vines from being planted in new vineyards.

“In other crops, viruses of the geminiviridae family are known to be transmitted by whiteflies and leafhoppers feeding on plant phloem fluids,” according to Agri-Analysis. The company gives a status report and list of red blotch-related events here. “Some research suggests that the global climate change is causing the virus to migrate from tropical climates to new areas. However, it is too early to tell exactly what vectors harbor and transmit this virus in grapevines. Pest management guidelines are not yet available.”

Tales from the field

Speakers at the 2014 Unified Grape & Wine Symposium shared tales of red blotch, with Peter Opatz of Silverado Winegrowers describing a “nightmare” situation in a 40-acre Alexander Valley vineyard. “It was a great site, and it wasn’t until the third leaf that we found a problem with red blotch. The symptoms we noted could almost be attributed to deficiencies with phosphorus or potassium at first.” The vines had many red and pink leaves, and the grapes stopped accumulating sugar at 19º Brix.

After Jim Wolpert from the University of California, Davis, confirmed the culprit was red blotch, the grower sold off the grapes to a winery that then paid for Mega Purple flavoring and concentrate to make them usable.