Cause A virus, wheat soilborne mosaic virus, transmitted by a soilborne fungus-like organism, Polymyxa graminis. In 1993, the disease was first found west of the Rocky Mountains, in Washington and in Columbia County, Oregon. The disease tends to be in wetter areas of the field, following the distribution of its fungal vector.
Symptoms A pale green to bright yellow mosaic on wheat leaves. Infected wheat does not show mosaic symptoms until spring. Effects on yield in Oregon are unknown, but stunted plants and partly filled kernels are evident on infected plants. Resting spores of P. graminis are evident on roots but also may be on plants not infected with the virus. Because the fungus tends to be in wetter areas, the disease may be misdiagnosed as nitrogen leaching.
Cultural control
- Do not move soil by any means from infected sites, if possible.
- In the Eastern and Central United States, resistant varieties offer practical control. Resistance levels in Pacific Northwest varieties are not known.
- Late planting and long rotations out of cereals are helpful but usually not good enough for commercial control.
Reference Murray, T.D., Pappu, H.R., and Smiley, R.W. 2009. First report of soilborne wheat mosaic virus on Triticum aestivum in Washington state. Online. Plant Health Progress doi:10.1094/PHP-2009-1204-01-BR.