Soilborne wheat mosaic virus can cause yield loss in winter wheat, especially in cool, wet soils. This virus appears to be transmitted (“vectored”) by a soilborne fungus-like organism, Polymyxa graminis, that occurs in soils.
Winter wheat infected by wheat soilborne mosaic develops a pale-yellow discoloration shortly after breaking dormancy in the spring. The incidence of wheat soilborne mosaic is often greater in low areas of a field, where moist soil conditions favor growth of the protozoa that spread this viral diease. Leaves of infected plants often have a mosaic pattern of dark green blotches on a pale-yellow background. Symptoms normally fade when warm weather slows the viral activity within infected plants.
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