Wheat streak mosaic virus (WSMV)

Written by: Diego Gutierrez Castillo
Posted: December 28, 2023

Disease symptoms

Wheat streak mosaic virus (WSMV) disease was first reported in the United States in 1922. Since its initial description in Nebraska, it has been found in throughout North America, Europe, and Australia. It is one of the most important and damaging wheat viruses in North America.

WSMV disease develops as mosaic, chlorotic lesions or yellow streaks on wheat leaves, which lead to decreased growth and reduced yield (Figure 1). WSMV often co-infects plants with Triticum mosaic virus (TriMV) and/or High plains wheat mosaic virus (HPWMoV), which together cause wheat mosaic virus disease, and are all transmitted by the wheat curl mite (Aceria tosichella). WSMV, TriMV, and HPWMoV symptoms appear very similar, and it is not possible to reliably distinguish these viruses from symptoms alone. Laboratory tests must be implemented to determine and diagnose which viruses are present and causing the symptoms. The Colorado State University Plant Diagnostic Clinic accepts plant samples for disease diagnostics, including viruses.

Quick Facts

  • Disease symptoms include chlorotic spots or yellow streaks on leaves, stunted plants, and reduced yield.
  • The virus is transmitted by the wheat curl mite (Aceria tosichella).
  • Wheat streak mosaic virus infects wheat, barley, maize, and other cereal grasses.
  • This virus is commonly found in wheat plants co-infected with Triticum mosaic virus (TriMV).
  • The disease can lead to high yield losses.
WSMV symptoms

Wheat streak mosaic virus (WSMV) symptoms on a wheat plant. Image credit: Emmanuel Byamukama, SDSU, Bugwood.org.

Wheat streak mosaic virus symptoms on leaf

Symptoms of wheat streak mosaic virus on wheat leaf. Image credit: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org 

Wheat streak mosaic virus symptoms

Comparison of wheat inoculated with WSMV (left) and healthy wheat (right). Image credit: Mary Burrows, Montana State University, Bugwood.org 

Pathogen life cycle

The wheat curl mite spreads WSMV to new wheat plants during feeding, and can also spread WSMV to other grain crops, including barley, corn, and cereal grasses. Over the winter, the wheat curl mite feeds on volunteer wheat that emerges between fall harvest and planting, and the infected volunteers serve as a virus reservoir and mite habitat over the winter. Mites transmit the virus from infected volunteers to newly emerged plants, spreading the virus. The mosaic virus disease progresses during spring and the summer, causing increasingly larger and more severe leaf symptoms. In the summer, during wheat harvest, the mites can spread to corn or other grasses and survive there until new wheat plants emerge in the fall, serving as an additional virus reservoir. This creates a ‘green bridge’ that allows the virus to survive over the winter and continuously infect new wheat.

Disease management

Viral diseases can be mitigated through controlled farming practices and cultural methods that reduce or eliminate the ‘green bridge,’ which are overwintering opportunities for mites viruses. First, it is important to control volunteer wheat that emerges between harvest and planting. This may be done using herbicide applications and/or rouging. Second, shifting planting to later in the season after summer crops (such as maize) have dried down reduces possible virus reservoirs. However, this must be balanced with other farming impacts such as weather and variety.

The development of cultivars resistant to WSMV has been a target of wheat breeding programs for decades. Three types of resistance (Wsm1, Wsm2, and Wsm3) have been introduced into several wheat varieties that are now grown commercially. In Colorado, Wsm2 is broadly used, and some examples of WSMV-resistant varieties include Guardian, Canvas, Whistler and Thunder CL (Plainsgold, 2020). Similarly, resistance to the wheat curl mite (Cmc1 and Cmc4) can help control the spread of the virus through vectors. However, all types of WSMV resistance have decreased effectiveness at higher temperatures, so proper farming practices to reduce the ‘green bridge’ should still be followed. Additionally, Wsm2 is not effective against TriMV or HPWMoV, so controlling volunteers in conjunction with WSMV resistance is the best way to control mosaic virus disease.


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