By Elliott Minor
The Associated Press

ALBANY, Ga. - Researchers are scrambling to identify a mystery disease that has emerged for the first time as a threat to Georgia's $75 million crop of Vidalia sweet onions.

Tests are being conducted on lesions that have started appearing on the leaves of onion plants in seed beds. Scientists are trying to find out whether they have a unique cause or are related to tomato spotted wilt virus, which has plagued Georgia peanuts and tobacco, or iris yellow spot virus, which has damaged onion crops in South America and the northwestern United States.

"This is the first year it's come to our attention," said Reid Torrance, a University of Georgia extension coordinator in Tattnall County, the state's largest Vidalia-producing county. "It's also the first year we've tested for it."

Onion seeds are planted in beds starting in September. When the plants are large enough, usually in November and December, they are replanted in fields.

Georgia's 134 registered Vidalia growers harvested 12,500 acres of onions last year. There are no official estimates yet for this year's crop, but experts think that it could be larger than in 2003.

The disease does not appear to be any of the typical bacterial or fungal diseases that attack onions, Torrance said Monday.

Glennville grower Delbert Bland, who had to replant 200 acres because of the problem, believes a virus is to blame.

"It's one of those things that, if you ignore it, you can have a crisis," he said. "If you go out there and treat it and do a good job, you can overcome it."

Vidalia onions are available in May and June. Some onions are stashed in atmosphere-controlled warehouses to extend the season through October. During the off season, some growers import sweet onions from Peru and other Latin American countries so they can market onions year-round.

Farmer Moses Coleman started Georgia's onion industry near Vidalia in 1931 when he noticed that his first crop was unusually mild.