Soybean vein necrosis virus, a new disease in Indiana soybeans, was confirmed earlier this month, says Kiersten Wise, a Purdue Extension plant pathologist. A soybean sample exhibiting symptoms of the virus, also known as SVNV, was sent to Purdue's Plant and Pest Diagnostic Laboratory. The laboratory sent the plant sample to Agdia Inc. for further testing. Molecular test results confirmed the presence of a tospo virus, or a disease causing cell death, in the sample.
"SVNV is one of our newer viruses that we've confirmed in soybeans," says Wise. "This is the first year we've confirmed it in Indiana, although we've seen suspect symptoms in the past."
While the disease doesn't appear to affect yield, it does cause foliar symptoms similar to herbicide injury, including yellowing in or near plant veins and light green patches or mottled green and brown speckled areas associated with veins. Leaves will show a blotchier, scorched appearance in shades of orange and yellow. As the season progresses, Wise says the virus could cause tissue death, which can leave a scorched appearance on severely affected plants.
Since the discovery of SVNV by a University of Arkansas professor in 2008, the virus had been reported in 12 states: Arkansas, Delaware, Kentucky, Kansas, Illinois, Maryland, Missouri, Mississippi, New York, Pennsylvania, Tennessee and Virginia.
The virus is spread by thrips, insects that infest a variety of plant species.
"When those insects are feeding on the soybeans, they may be transmitting this virus as well," Wise says. "We suspect that's why we're seeing more symptoms this year, because we've had more thrips damage in soybeans."
Calling the virus an "oddity," she says farmers are seeing more of it this year than ever before.
"It's all across Indiana from the Kentucky border all the way up to the Michigan border. And growers are concerned about what these blotches are on their soybeans," Wise says.
But even with the high incidence of SVNV, she doesn't recommend any treatment.
"We are still learning more about this virus, and we're going to continue to monitor it in the future," she says. "But at this point in time we wouldn't recommend any changes in production practices."
Wise encourages growers and crop consultants to inspect any still-green soybean plants for symptoms of soybean vein necrosis and email images of possible cases to firstname.lastname@example.org.