TATTNALL COUNTY, Ga. - Despite the early threat of crop-damaging viruses, Georgia's sweet Vidalia onions look good now. There should be plenty to harvest in a few weeks, University of Georgia experts say.
“If the weather stays (springlike) as it has been for the past several weeks, we should have a good crop,” said Reid Torrance, UGA Extension Service coordinator, in late March. Torrance is located in Tattnall County, where farmers plant about half of Georgia’s Vidalia onion crop.
The onions are growing normally, “and we're pleasantly surprised in how good the crop looks,” he says. The quality of Georgia's official vegetable should be top-shelf come harvest time this month.
But a dark, uncertain cloud hovered over the crop this winter, when many onion plants looked really puny, he says. They weren't growing normally, and some were dying in fields.
Torrance believes the early-season onion problems were symptoms of iris yellow spot and tomato spotted wilt, two new viruses discovered in this year's crop.
TSWV has been in Georgia since the early 1990s and has caused problems for other crops like tobacco, peanuts and vegetables. IYSV had never been reported in the state before this year. Both viruses are carried by thrips — small insects that feed on plants.
“Basically, the ill effect of the viruses was a loss of plants in fields early on,” Torrance says. About 25 percent of plants were lost early in the season, he says. Farmers planted about 16,000 acres of onions this year, about 10 percent more than 2003.
There's always some stand loss in any year's onion crop, he says. That's why he believes this year's crop is right on track for an average harvest.
“The onions today look totally different from what they did two months ago,” he says. “I never expected this crop to look this good at this point after looking as poorly as it looked this winter.”
David Langston, a plant pathologist with the UGA Extension Service, agrees. Any damage caused by the new viruses passed, and the pressure from other diseases was light this year.
UGA experts have taken about 4,300 Vidalia onion samples this year. Of these samples, 9.4 percent were infected by IYSV and 7 percent by TSWV.
They also tested weeds around onion fields and found that many were also infected with IYSV. This indicates, Langston says, that IYSV has possibly been in the state a lot longer than just this past winter and spring.
And if IYSV hasn't caused enough onion damage in the past to be noticed, Langston says, there's a good chance it won't in the future.
“We found these viruses this year in onions because this is the first year we've tested onions for these viruses,” Langston says.
IYSV does cause serious problems in other onion-growing regions of the world, such as Peru and parts of the Pacific Northwest.
These regions grow onions in the hot summer. Georgia grows its onions in the cool winter. This could make all the difference in how damaging a virus can be, Langston says.
A lot can happen to an onion crop, he says. And farmers know it. The only way to know for sure if you have a good or bad year is to count the onions when the harvest is over.
About 20 Vidalia onion varieties are grown in Georgia. They're known as short-day onions. They grow to maturity depending on the amount of sunlight they get in a day. Vidalias generally start to bulb when days are about 11 hours long. Harvest runs through June.
Brad Haire is an editor for the University of Georgia Extension Service.