Source: South Dakota State University
Written collaboratively by Anna Hagemann, Madalyn Shires, Clarence Winter, Dalitso Yabwalo, and Connie Strunk.
Wheat Streak Mosaic Virus (WSMV) is a viral disease that infects the Poaceae family, also known as grasses. WSMV has been reported in South Dakota wheat fields and is also a major wheat disease for Great Plains states in 2025. The virus is sweeping across the state and is rampant in winter wheat. There is also risk that the virus will be transferred to spring wheat, which has significantly less resistance to wheat viruses. WSMV is detrimental, as it spreads rapidly and can significantly reduce yield. The virus transmits quickly; therefore, it is essential to diagnose it in a timely manner to manage it properly. Similar diseases, including High Plains Wheat Mosaic Virus, and Triticum Mosaic Virus are associated with WSMV. They are transmitted by the same vector and often co-infect alongside one another.
Transmission
This virus is transmitted by the wheat curl mite called Aceria tosichella. In several cases, WSMV onsets following extensive growth of volunteer wheat. Volunteer wheat from previous harvests is often a result of broken kernels released from hailstorms. The environment provided by this volunteer wheat is the perfect setting for the mite and the virus to thrive. It is important to note that the spread of the disease can occur between overlapping areas of spring and winter wheat as well, moving into different growing seasons. Therefore, early planting can add additional problems, as the virus transfers from the remaining spring wheat to winter wheat in the early fall. The wheat curl mite can overwinter and resides in the crown of the wheat. Cold temperatures slow the development of the disease, but mild winters, like what was seen across South Dakota in 2024/2025, can contribute to disease progression.
Symptoms
WSMV is most common during the early stages of wheat development. However, infection is possible at all stages.
In the beginning of WSMV, plants develop small chlorotic streaks. As the disease intensifies, dark yellow strips take over the surface area of the plant. As the name refers to, mosaics develop, which is alternating patches of green and yellow. The plants become stunted, with large patches of chlorosis, and tiller production significantly reduces.
Prevalence of wheat curl mites determines disease severity. Heightened temperatures also increase disease incidence. Though lower temperatures slow disease activity, WSMV will still persist.
Management
Unfortunately, there are neither preventive nor curative pesticides that can be applied to plants succumbed to WSMV. However, cultural practices can be utilized to reduce disease incidence and occurrence.
- Eradicate and target volunteer wheat and other alternative grass hosts. This can be done through herbicide applications prior to planting.
- Plant in favorable conditions. This will allow for crop development in cooler temperatures.
- Plant varieties of wheat that are resistant to WSMV.
- Avoid the “green bridge” by keeping spring and winter wheats separate. This can be done by delaying fall plantings.
- Avoid planting crops that host the wheat curl mite if WSMV epidemics are an often problem. Rotate crops when possible.
Identification
Correctly identifying this disease or any other fungal, bacterial, or viral disease is extremely important, as it aids in management decisions.
