Soybean Vein Necrosis Virus Confirmed in DE, MD and VA

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Soybean vein necrosis virus was confirmed this week by Dr. Yannis Tzanetakis, Department of Plant Pathology at the University of Arkansas. So the symptoms that we have been seeing and sharing with concerned growers are due to this new virus disease. Although I say it is new, some of the first symptoms were seen in 2008 in Tennessee and Arkansas. The subsequent work by the researchers at Arkansas discovered the new virus. They were able to report that this new virus disease, soybean vein necrosis virus (SVNV), belongs to a group of thrips-transmitted viruses. This group called the tospo viruses includes several that we see in greenhouse production in the region and in the field occasionally, namely tomato spotted wilt virus and impatiens necrotic spot virus.

 Early symptoms of soybean vein necrosis virus (SVNV) from DE

This group of viruses are acquired by thrips feeding on infected plants and once acquired then the virus can be transmitted by the thrips for the rest of its life. We call this a persistent virus in the vector and this may allow us to control SVNV by controlling thrips. This is very preliminary and much work is being done in the Midwest to identify the thrips vectors and possible other hosts of the virus that may harbor it and allow thrips feeding to move it to soybeans. It is too early to know if that strategy will work practically. 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 some yield effects are possible. But we have some time to go before maturity, so the jury is still out on the yield effects here in the Mid-Atlantic. Fortunately this group of viruses is not known to be seed-transmitted and that is being addressed by these researchers.

The researchers from Arkansas have noted that often a single virus infection may not have much of an effect but multiple infections with other viruses may increase yield loss potential. We have occasional outbreaks of bean pod mottle virus and we have seen soybean mosaic virus and peanut stunt virus in soybeans in the region, so the potential is here for multiple infections. We do not have much information about the extent of other virus diseases in soybeans.

The other avenue of control is identifying sources of resistance and evaluating current soybean varieties for resistance. Ideally identifying sources of genetic resistance that are incorporated into good varieties will be best control strategy. That work is ongoing as well. It is too early to be making recommendations but growers need to be aware of this disease and know that work is being conducted to answer some of these pressing questions.

Also, do not ignore soybean cyst nematode. Soil sampling after harvest before any fall tillage is recommended for fields to be planted next season to soybeans following this year’s crop. Do not plant SCN susceptible varieties without soil testing first. Soil sample bags are available from the county Extension offices for $10/ sample bag.

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