By Brad Haire
University of Georgia
Every peanut farmer in Georgia has heard of it. And this year,
it’s been pretty bad.
“Tomato spotted wilt virus has been very severe across the state
in peanuts,” said Bob Kemerait, a plant pathologist with the
University of Georgia Extension Service.
Not Surprised
The severity of the disease was not unexpected, he said, because
it was bad on tobacco and backyard tomatoes this year, too.
Some fields are 100 percent infected, he said, even in peanut
varieties that are resistant to the virus. But not all fields
have been so severely affected.
“I don’t know that this is the most severe we’ve ever seen,”
Kemerait said. “But it’s certainly the most severe on peanuts in
the past few years.”
The virus didn’t treat peanuts too badly last year.
“I believe many growers began to think we turned the corner on
the disease, so to speak,” he said. “Unfortunately, that was not
the case.”
Management
Some growers this year became a little lax in managing the
disease and didn’t, or were unable to, follow UGA’s TSWV Risk
Index as closely as they might. The index provides guidelines to
reduce risk for the virus.
And TSWV-resistant peanut varieties, like Georgia Green and C99-
R, aren’t totally immune to the virus, especially in years with
a lot of it around.
“Fortunately, newer, more resistant varieties appear to be on
the horizon,” Kemerait said.
Those Thrips
TSWV is spread by small insects known as thrips. Thrips pass the
virus to peanut plants when they feed on them. The virus
reproduces and spreads throughout entire plants. In many cases,
it dwarfs the plants. Yields can be low or nonexistent if the
virus attacks plants early in their growth.
UGA scientists have proven that the date on which peanuts are
planted has a lot to do with the risk of getting the virus.
In the past, planting after May 1 was better. However, this year
it appears, at least from preliminary observations, that the key
was to plant after May 10.
“Peanuts planted before that often, but not always, had more
severe TSWV,” he said.
Research Continues
Plant pathology research has found an association between the
severity of the virus in peanuts and the severity of TSWV in
tobacco and rainfall in the spring. Tobacco is planted before
peanuts.
“Perhaps, the rainfall in the spring affects some aspect of the
insects’ life cycle,” Kemerait said.
To stay ahead of this disease, UGA breeders, researchers and
other specialists keep looking for varieties with improved
resistance. They continue to update the TSWV Risk Index to give
the growers information on steps they can take to reduce the
impact of the disease.
“We’re still growing peanuts and will continue to do so,”
Kemerait said.
Due to recent tropical storms, the harvest of the Georgia peanut
crop is slightly behind the five-year average. As of Sept. 22,
only 29 percent of the peanuts had been dug, and only 18 percent
had been harvested, according to the Georgia Agricultural
Statistics Service.
