By Brad Haire
University of Georgia

Georgia farmers mostly grow seedless watermelons now because
folks don’t like to spit seeds anymore. But this has allowed an
old, deadly plant disease to make a comeback, says a University
of Georgia specialist.

“I think watermelon growers are unfortunately planting
themselves into a corner,” says David Langston, a plant
pathologist with the UGA College of Agricultural and
Environmental Sciences.

The problem is a fungal disease commonly called fusarium wilt
that can live in the soil for years, he said. It’s now popping
up more frequently in Georgia watermelon fields, attacking the
vascular systems of infected melon vines, choking off water and
nutrients and eventually killing the plants.

Some growers have had to destroy entire fields due to the
disease, he said. “Once a melon gets fusarium wilt it can’t be
cured.”

The first documented case of fusarium wilt in watermelons was in
Georgia around the turn of the 20th century. Over the years, the
industry developed varieties with resistance to the disease, he
said. But all of these varieties have seeds. The disease could
still cause isolated problems and was a threat, but it was
controllable.

But watermelon eaters now demand melons without seeds. Seedless
watermelon varieties have been around for many years, but over
the past five years they’ve become the most widely grown melon
type in Georgia and in other watermelon-growing states like
Florida and Texas.

But along with the increase of seedless watermelon growing has
come an increase in fusarium wilt, he said.

“We’ve seen a considerable increase in calls and plant samples
that have been diagnosed as fusarium wilt,” Langston said. “They
come in every day, several times a day. It is always the same
story, only seedless are affected.”

Every watermelon-growing county in Georgia has had reports of
the disease in seedless melons, he said. Most Georgia melons are
grown in the south-central part of the state.

“Growers should be very concerned if they want to grow seedless
melons in the future,” he said. “We haven’t seen any widespread
significant yield losses yet. But we will, as long as we
continue to grow seedless melons with no resistance.”

A few seedless watermelon varieties have resistance to the
disease. But they aren’t popular to grow, he said.

Growers could lower their risk for the disease by planting a
field in watermelons only every eight years. But growers, due to
limited land, usually plant watermelons back to back each year
in the same fields. Or they skip only one year.

This compounds the problem, Langston said, because fusarium wilt
can live and build up in fields that are planted in watermelons
each year.

There is an alternative. In Japan and in some European countries
where land is limited, watermelons are grafted onto squash,
pumpkin and gourd vines which are resistant to fusarium wilt.
But the process is labor-intensive and costly for farmers. It
costs consumers, too. One watermelon in Japan can cost as much
as $25.

Georgia growers will soon start harvesting the first of this
year’s crop. Most Georgia melons are grown to target that
quintessential watermelon-eating holiday: the Fourth of July.

Despite the looming threat of this disease, Georgia’s watermelon
crop is expected to be a good one this year. A dry spring could
hurt overall yields, Langston said, but it has kept other
diseases like gummy stem blight and downy mildew to a minimum.

Georgia is a close second to Florida in overall watermelon
production, growing about 25,000 to 26,000 acres annually.