Recent symptoms in some Ontario soybean fields have raised concerns about a new virus that may be in Ontario.  Soybean Vein Necrosis Virus (SVNV) is a relatively new disease to northern US soybean growing areas. 

SVNV is common in the southern US soybean growing areas.  Symptoms typically start around the midvein of the soybean leaf and spread across leaves following the veins.  Thrips carry the virus from plant to plant while feeding.  Areas around the midvein first appear light green to yellow, turning red prior to necrosis (browning or cell death).  SVNV typically moves slowly within the plant and progresses through the canopy.

SVNV symptoms look very similar to ACCase herbicide (Assure® II) damage.  High rates of Assure® II can also cause areas around the midvein to turn pale yellow followed by red.  The key difference between the two issues is the progression of the symptoms.  Over time, SVNV spreads across leaves and up the plant.  However, ACCase herbicide injury remains on the leaves emerged when the herbicide application was made (i.e. new growth is unaffected). 

Robust management strategies of SVNV have yet to be established.  Weekly scouting in the field will help when identifying the cause of symptoms. 

Shawn Winter, CCA-ON, Maizex Seeds Product Development Manager
Twitter: @SWinter_Maiz 

Pictured: Symptoms from an ACCase application.