It’s a virus, it’s incurable and it has cost Georgia peanut
farmers more than $50 million
in just the past two years.
But farmers now have a new tool to assess their crop’s risk for
the deadly tomato
spotted wilt virus. Now they can learn how to reduce that
risk.
“There isn’t anything farmers can do for their crop once it’s
infected,” said Steve L.
Brown, an entomologist with the University of Georgia Extension
Service. “We have to
avoid high-risk situations.”
Tomato spotted wilt is a viral disease that can wipe out a
peanut crop.
Albert Culbreath, a plant pathologist with the UGA Coastal Plain
Experiment Station,
said the virus attacks the plant, interfering with peanut
production. Instead of growing
leaves and peanuts, the plant begins making more viral cells.
It also makes the plant more susceptible to other diseases and
more sensitive to
environmental stress, including drought, excess moisture and
insects.
In the past they’ve tried to control its spread by controlling
the thrips that carry it from
field to field. Those efforts have proven nearly worthless. By
the time farmers spray to
control the tiny insects, the plants are already infected.
But they can change some practices that affect the disease’s
severity.
Research in the UGA College of Agricultural and Environmental
Sciences shows that
many factors affect whether and how severely TSW will infect a
field.
Brown said no single factor effectively controls the disease.
But together they can
change how TSW affects peanut yields.
“Peanut variety, planting date, plant population, virus history
in the field and
at-planting insect control all affect how likely the virus is to
cause problems,” he said.
In 1996, the scientists created a simple-to-use index of those
risk factors. Farmers now
can use the index to lower their risk of getting TSW in their
peanut fields.
Tomato spotted wilt virus struck fast and hard in nearly all of
Georgia’s 533,000
peanut acres in 1996. “We saw a higher incidence of it in 1996
than in 1995,” Brown
said. “But yield losses were greater in 1995.”
The disease struck later in the season in 1996. The later it
infests a field, the lower its
impact on yields.
The disease has infected Georgia peanuts only in the past 10
years. But it has become
more important every year since it was found in 1986.
TSW cost peanut farmers as much as $33 million in 1995 — about
8 percent of the
crop’s total value.
“Losses due to tomato spotted wilt were estimated to be greater
than any other disease
in 1995,” Brown said. “You can’t cure it, but farmers can change
their management
practices to reduce the damage TSW can do.”
Worth County peanut farmer Johnny Cochran said TSW “nearly wiped
out my 1995
irrigated peanut crop — I had to do something!” Cochran figures
he lost about 1,000
pounds per acre.
Cochran used the risk index in 1996 and decided to change his
peanut variety, his
planting dates and how he treated for insect control.
“We’ve got to approach this problem from several different
directions to conquer it,”
he said.
Georgia peanut farmers send about half their crop, nearly 700
million pounds, to
peanut butter factories.
In fact, about half the peanut butter produced in the U.S. is
made from Georgia
peanuts. The average American eats about 3.3 pounds of peanut
butter every year.
Brown said the risk index is a unique way to manage a
pest. “This is the first risk index
that I know of,” he said.
Since there is no cure for TSW, prevention is everything — and
the only thing — that
can make a difference.
“This isn’t the perfect answer to tomato spotted wilt,” Brown
said. “But it’s a good
first step at dealing with the problem.”
