The common link is a soilborne fungus called Polymyxa graminis . The virus is carried into the plant by the zoospores. The fungus can remain in the soil for at least 8 years. The first report of spindle streak mosaic in North America occurred in 1957, right here in Ontario. Fields at risk are those that have had several crops of winter wheat in the past 8-10 years.
Symptoms usually appear early in the spring when growth resumes.
Fields that have had liberal amounts of poultry and livestock manures appear to reduce spindle streak mosaic virus buildup. Keith Reid, Soil Fertility Specialist, Walkerton. Many wheat fields received nitrogen fertilizers over a month ago, and farmers are concerned that the nitrogen will have disappeared. In general, most of the fertilizer will still be in the soil, ready to work as soon as the weather warms up. Most of the nitrogen fertilizer applied to wheat fields is in the form of urea.