In past years, Georgia farmers had a tough row to hoe in many
crops in fighting the
deadly tomato spotted wilt virus. Now, new technology can give
them an edge in
managing the virus.
For the first time, Georgia scientists can learn in just one day
if insects in the field are
actually transmitting the virus.
“Tomato spotted wilt virus is the No. 1 problem in the state’s
crops,” said Hanu R.
Pappu, a plant pathologist at the Coastal Plain Experiment
Station. “Last year alone, it
caused an average 10 percent loss in many affected crops.”
The three main crops the virus affects are peanuts, tobacco and
tomatoes. But many
others are affected. In these three crops alone, Georgia farmers
lost $63.8 million in
1996. The virus affects the crops differently, but the results
are the same: decreased
yields and crop loss.
Pappu points out, too, that the 10 percent average is just
that. “Some farmers lost only
1 percent or 2 percent,” he said. “Others may have lost close to
50 percent.”
The first problem farmers have with the virus is knowing when
it’s in their fields.
Since it’s a virus, Pappu said, there’s no cure.
“So prevention is extremely important,” he said. “There is no
control, so we’re trying
to get it to a point where we can manage the disease through
other means.”
Viruses rely on carrier insects, he said. The TSWV relies on
tiny insects called thrips
to move from plant to plant and field to field.
But while about a dozen species of thrips live in Georgia, only
two can transmit
TSWV. “And those two species can transmit the virus only when
the insect was
infected as a juvenile,” Pappu said.
Past efforts to control tomato spotted wilt by controlling the
insects didn’t work. “We
just didn’t know at the time that only certain populations were
transmitting,” he said.
Pappu is working with another plant pathologist and an
entomologist at the experiment
station to learn the secrets of the virus that causes tomato
spotted wilt. Once they learn
its secrets, they can use them to fight against the tiny but
destructive organism.
Pappu worked to find the secret of when the thrips can transmit
TSWV. He’s using
new biotech methods to detect specific proteins that appear only
when the insect can
transmit the virus. And they’re doing it quickly.
The method he uses is called TAS ELISA; Triple Antibody
Sandwich, Enzyme-Linked
ImmunoSorbent Assay. It uses virus-specific antibodies that
reveal if viral proteins are
in the insect.
“The presence of the viral protein is a good indication that the
insect was capable of
transmitting the virus,” Pappu said.
Before, scientists needed six to eight weeks to find out if a
thrips population was
transmitting the virus. “Now this technology can tell us in one
to two days,” he said.
Pappu’s goal is to forecast when a transmitting population is
moving into a field.
Armed with that knowledge, farmers can apply pesticides to kill
the insects before they
can transmit the virus into the plants.
“This information will allow them (farmers) to be more precise
in applying chemicals,”
Pappu said. “To be effective with our applications, we needed an
efficient, quick way
to know if the population was transmitting.” Now they have it.
