Soilborne wheat mosaic virus (SBWMV) was recently detected on winter wheat in another new location in Grant County near Ephrata, Washington, north of Highway 2. This is the second year in a row when we’ve marked a new location for this disease and we encourage growers to be on the lookout.
Winter wheat from an irrigated field was submitted to the WSU Pullman Diagnostic Clinic in late April with symptoms of virus infection. The field was described as having random patches of affected wheat with no pattern. Wheat within these patches was stunted, with older leaves yellowish in color and purple tips. The newer leaves were a little lighter in color with yellowish blotches. Symptoms were not observed by the grower last fall. As is typical of SBWMV, symptoms appear in late winter to early spring while temperatures are still cold and plants appear to improve as temperatures increase; however, damage remains, and yield is reduced in the symptomatic patches.
With warming temperatures, symptoms of SBWMV are likely to be waning and not easily detectable now. However, because the virus is transmitted by a soilborne fungus-like organism, symptoms will appear in the same patches in future years. Patches will also enlarge over time as infested soil is moved by tillage resulting in larger infested areas that will develop symptoms when conditions favor the disease. 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 occurred in one of your fields, consider 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. Information about variety resistance to SBWMV is available in the Variety Characteristics table. Finally, you can submit a sample to the Plant Pest Diagnostic Clinic if you suspect plants have SBWMV.
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.