Published on 03/29/07

Treatment could stop wine grape killer

By Stephanie Schupska
University of Georgia

At a test plot, Phil Brannen injects a grape vine with a bacterium similar to a deadly grape disease. If he pokes the needle into just the right spot, the vines xylem, or central vein, will suck the bacterium right up, possibly giving the vine protection against the disease.

“It’s very experimental,” said Brannen, a plant pathologist with the University of Georgia College of Agricultural and Environmental Sciences.

Working with University of Florida plant pathologist Don Hopkins, Brannen is testing this inoculation, or cross protection, process in Georgia. It’s another step in the search for better ways to manage Pierce’s disease, a vine-destroying disease Georgia growers have battled for years.

Hopkins and Brannen are injecting both wine grape seedlings and older plants. According to Brannen, Hopkins has vinifera wine grapes in Florida that have survived 10 years thanks to cross protection.

“In Florida, vinifera grapes would normally die within a year from Pierce’s disease,” Brannen said.

To fight the disease, wine grape growers must either replant vines periodically to replace the diseased vines to keep their businesses going.

Wine grape production is a rapidly growing industry in north Georgia, where grape vines add a bit of a Napa Valley feel to the rolling hills. In 1999, Georgia grape production, which includes muscadines, was valued at about $4 million. By 2005, the value had almost doubled. Vineyards now cover about 1,700 acres.

The biggest battle in growing vinifera grapes in Georgia continues to be Pierce’s disease, primarily because Georgia doesn’t have much suitable land high enough in elevation to prevent or slow down its spread.

For wine grapes to grow well, Brannen said, vines should be planted at an elevation of 1,300 feet or higher.

“In the past, several vineyards have been decimated at lower elevations,” he said. “Plus, warmer winters over the last few years may have resulted in a shift in the Pierce’s disease safe zone.”

The shift has alerted the industry, he said. It could be a chronic problem related to changing winter temperatures.

But cross protection could help.

“Even if this technology continues to show promise in the field, it is unlikely that this method will allow for a major expansion of the vinifera range, though this is a possible outcome,” Brannen said.

The technology is likely to be more valuable during warmer winters, he said. It could reduce epidemics on the edge of the Pierce’s disease safe zone.

Cross protection is very expensive and takes a lot time and effort.

“But if it works right now, we’d be golden,” Brannen said.

(Stephanie Schupska is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

Stephanie Schupska is the communications coordinator with the University of Georgia Honors College.