Wheat Soil Borne Mosaic is a virus transmitted by a soil fungus. For wheat, it mainly exists wheat mosaic and striations mosaic (more widespread in durum wheat).
The first symptoms occur at the end of the winter.
If you want to confirm a suspected disease, you just have to collect the whole plant (about 30 sick plants) in a paper bag and send them at Galys Laboratoire located in Blois.
April and May are the most favorable months for this kind of analysis.
For more information