What is in this article?:
- New disease, insects threaten Virginia soybeans
- Symptoms found in mid-July
• A new disease to Virginia, soybean vein necrosis virus (SVNV), has spread into soybean fields and may cause a problem for growers in the 2012 season.
• This year Virginia soybean growers will likely see kudzu bugs in large numbers.
• Each of these pests are a threat to soybean yields and to profitability of the crop in Virginia.
SYMPTOMS of soybean vein necrosis virus.
Virginia soybean growers got their first taste of brown marmorated stink bugs last year and just a glimpse of a new soybean disease called soybean vein necrosis virus.
This year they will likely see kudzu bugs in large numbers.
Each of these pests are a threat to soybean yields and to profitability of the crop in Virginia.
Soybean prices are likely to remain high for the 2012 crop and acreage across the Southeast is likely to react to price. Virginia Tech Soybean Specialist David Holshouser says in some areas of the state input costs are already pushing $10 a bushel, and the prospect of dealing with new pests is almost certainly going to push these costs higher.
A new disease to Virginia, soybean vein necrosis virus (SVNV), has spread into soybean fields and may cause a problem for growers in the 2012 season.
This disease is transmitted by thrips in much the same was as tomato spotted wilt virus is transmitted.
The record warm winter of 2011-2012 and other factors indicates a heavier than usual thrips flights. If infestations are heavy in the later part of the thrips season, it would bode well for transmittal of SVNV.
Soybean vein necrosis virus belongs to a group of thrips-transmitted viruses called the tospo viruses. The most common and damaging of these viruses in row crops in the Southeast is tomato spotted wilt virus.
Pat Phipps, long-time Virginia Tech plant pathologist, says SVNV showed up for the first time in Virginia soybeans last year. The disease causes yellow blotches initially and as they start to darken, yellowing in the vein of the plant develops.
How much yield damage this disease can cause in soybeans in the Upper Southeast isn’t known. It has been found sporadically in Kentucky, Tennessee and Arkansas since 2008, but it is so new to Virginia and the Upper Southeast that researchers have not had time to determine how much of a threat it may be to soybeans there.
Phillip Sylvester, an Extension agent in Kent County, Del., says the disease showed up for the first time in 2011 in his state. “The question we all have is: will it reduce yield here or affect seed quality? So far I have not seen enough leaf loss to imply that yield losses are likely,” he says.
Determining yield loss from SVNV is going to be difficult because the disease often occurs in combination with other diseases, like cercospora blight. Symptoms from the two diseases and other commonly occurring diseases in soybeans are similar.
Phipps says the new disease was widespread in Virginia last year, though most growers didn’t know it even existed.
“We didn’t see the symptoms expressed until July, and then symptoms became more and more prevalent later in the growing season,” Phipps explains.