By Brad Haire
University of Georgia

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 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 said. The quality of Georgia’s
official vegetable should be top-shelf come harvesttime in
April.

Winter worry

But a dark, uncertain cloud hovered over the crop this winter,
when many onion plants looked really puny, he said. 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 said.

About 25 percent of plants were lost early in the season, he
said. 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
said. That’s why he believes this year’s crop is right on track
for an average harvest.

Spring surprise

“The onions today look totally different from what they did two
months ago,” he said. “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.

Sampling

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 said,
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 said, 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
said.

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 said.

A lot can happen to an onion crop, he said. 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.