Wheat Streak Mosaic Virus Confirmed in Minnesota

The diversity of diseases on spring wheat is increasing in the Red River Valley.  On July 15, Ardell Knudsvig, Plant pest surveyor with the Minn. Dept. of Agriculture sampled symptomatic plants from a flowering wheat field in Roseau County.  Disease symptoms included longitudinal striping of leaves typical of those caused by wheat streak mosaic virus (WSMV).  Presence of the virus was confirmed using immunosorbent electron microscopy (ISEM).  This is the first confirmed plant sample with WSMV during the 2008 growing season in Minnesota. 

The virus is spread to hosts by wheat curl mites (Figure 1).  For more information about the biology of these tiny vectors and the environment that supports their growth and lifecycle go to:

http://www.extension.umn.edu/cropEnews/2006/06MNCN38.htm

Disease spread is known to occur more often during dry weather.  Recent wet weather will help to contain the vectors and limit additional spread of the disease.  It is possible that the virus may currently exist in northern Minnesota on other crops (winter wheat, corn) or grass plants.  Alternatively, mite vectors may have blown into the State on winds from infested locations in North Dakota.  Wheat streak mosaic virus was confirmed in that state in winter wheat plant tissues that were collected during the last week of May. 

This disease requires a “green bridge”.  If continuously green host plants are present in an area, mite feeding and virus transfer are supported.  Producers wanting to grow winter wheat in NW Minnesota this year are urged to control volunteer wheat at least two weeks prior to planting winter wheat to break the vector’s lifecycle.  Delaying winter wheat planting as long as possible may also prove beneficial.  Planting near corn crops should be avoided as that crop stays green late into the fall. 

Fungicide application will not manage this disease.  If plants become diseased, there is little one can do.  Crop losses are variable but depend on variety, environment, and time of infection (early infection causes most severe losses).

Charla Hollingsworth, Extension plant pathologist, NWROC

Bob Koch, Research Scientist, Plant Protection Division,
MN Dept Agriculture

Ben Lockhart, Virologist, UM Dept. of Plant Pathology

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