The wheat disease, soilborne wheat mosaic virus, has made itself known this spring in parts of the Walla Walla Valley in southern Washington and northeastern Oregon. This is the second time it has appeared, but this time it is more noticeable and wider spread than 2 years ago according to local crop consultant Jerry Zahl of Walla Walla. Two years ago affected areas were small and limited to low lying areas. This time around more fields are affected and larger areas are showing symptoms. Spofford area near Milton-Freewater, Oregon and in the Mill Creek and Russell Creek areas east of Walla Walla, Washington are again seeing the disease.
The impact of the virus on the affected areas is unknown at this time and will be determined largely by the weather and related growing conditions this coming spring.
The diseased wheat foliage exhibits mosaic symptoms similar to wheat streak mosaic, which is already known to occur in the region, but wheat streak mosaic is expressed later in the growing season.
| Soilbourne Wheat Mosaic |
In Oregon, this virus was first detected in winter wheat in the Willamette Valley in 1994 and in winter wheat in western Umatilla County in 2005 and 2006. The disease is transmitted from root to root by the fungus Polymyxa graminis. It is a virus that is only moved by soil, and likely to be a problem in years when cool moist conditions occur in the fall after seeding as moisture is needed for the infection to take place.
