Soilborne wheat mosaic virus (SBWMV) was first detected on winter wheat in Washington State in 2007 and has been detected in new locations in Eastern Washington over the past two years. We encourage growers to be on the lookout for this disease again this spring. Symptoms typically appear in late winter or early spring when temperatures are cool. Symptoms of SBWMV started appearing in some areas of Southeastern Washington near Walla Walla as early as December 2023, after a brief warm-up during this mild winter. More fields near Walla Walla have been showing symptoms this past month.
Symptoms often appear first in patches within a field, especially in areas with cool wet soil conditions. Wheat within these patches is stunted, and the foliage appears mottled with white to dark green streaks that are parallel with the leaf veins–a symptom known as a mosaic. The mosaic can range from a light green to a more severe yellowing, sometimes with older leaves going purple at the tips. The symptoms may fade as temperatures increase; however, damage remains, and yield is reduced in the symptomatic patches.
Because the virus is transmitted by a soilborne fungus-like organism, symptoms will appear in the same patches in future years when winter wheat is grown and weather is conducive for infection. SBWMV is spread by cultivation, wind, water, and other factors that disperse infested soil, like moving equipment. Consequently, patches will enlarge over time as infested soil is spread resulting in larger infested areas and eventually the entire field becomes infested. Soil fumigation is not biologically or cost effective for control of SBWMV; however, winter wheat varieties with effective resistance to SBWMV are available and very effective in reducing yield loss.
If you suspect SBWMV is present in one of your fields, consider submitting a sample to the Plant Pest Diagnostic Clinic for confirmation and planting a resistant variety the next time winter wheat is grown in that field.
For more information including photos of infected plants and a description of the disease cycle, see the article on Soilborne wheat mosaic virus in the Disease Resources section of the Wheat & Small Grains website. Likewise, information about variety resistance to SBWMV is available in the Variety Characteristics table on the same website. Finally, you can submit a sample to the Plant Pest Diagnostic Clinic if you suspect plants have SBWMV and help us track the spread of this disease.
For questions or comments, contact Rachel via email at rachel.wieme@wsu.edu.
For questions or comments, contact Tim Murray via email at tim.murray@wsu.edu, via phone at (509) 335-7515, or by following him on Twitter @WSUWheatDoc.