Figure 1. Foliar symptoms of SVNV on soybean
Soybean vein necrosis virus (SVNV) was first confirmed in Iowa last season. Last year we did not see SVNV until August.
This past week we identified SVNV in several locations in Iowa. It is not known yet if earlier symptoms may increase chances of yield loss. We will continue to monitor and provide updates.
The virus belongs to the tospovirus group, which is vectored by thrips and possibly other insects.
Symptoms often begin as chlorotic (light green to yellow) patches near the main veins, which may enlarge eventually becoming necrotic (brown) areas (Figure 1). The veins may appear clear, yellow or dark brown.
Figure 2. Browning of the veins on the lower leaf surface
The browning of the veins may be especially noticeable on the lower leaf surface (Figure 2), but this may not always occur.
Currently, there are no management recommendations for this disease. Other pathosystems that include thrips and tospoviruses, including tomato spotted wilt virus, focus on resistance and management of the vector.
Because of the newness of this disease, there are no known sources of resistance. Insecticide application only should be considered in fields with a known risk of yield loss.