Caused by a virus transmitted by Polymyxa graminis (Led.), a common soilborne fungus that attacks wheat roots during cool, wet periods of the fall and early spring. Symptoms include a light green to yellow mosaic discoloration of leaf and leaf sheath tissue, and general stunting. Symptoms can occur uniformly across a field, but are often patterned to match wet, low-lying areas that favor activity of the P. graminis vector. Very susceptible varieties develop plants with shortened bluish green leaves and tillers that remain in a rosette condition. Symptoms from fall infections are most prominent in early spring when temperatures are ideal (50 to 68 F) for disease development. Disease progression is halted and symptoms often disappear at temperatures warmer than 68 F. Spring infections are though to have little or no effect on wheat yields. Vector and virus are spread by any means of dispersing soil from infested fields.