Wheat streak mosaic (WSM) is a disease caused by the Wheat streak mosaic virus (WSMV). The virus is
vectored by the movement and feeding of the wheat curl mite (Aceria tosichella). Infected plants are
usually stunted and produce fewer seeds, which are often badly shriveled. The earlier the infection, the
greater is the effect on the plant. Plants may die, fail to set seed, be stunted or show little effect
depending on when they were infected.
Most years the virus and vector do not survive winter, so we do not often see early season symptoms in
Alberta wheat fields. The most recent epidemic in Alberta was in 2017. In 2022, more than ten fields
were confirmed in southern Alberta. As of the end of June 2023, close to twenty fields are confirmed.
The area currently reporting symptoms is south of the Red Deer River.
Scout for symptoms
Producers, agronomists, and crop scouts are encouraged to watch for symptoms of WSMV on wheat
(winter, spring, durum), barley, corn and all other cereals and grasses. Wheat is by far the most
susceptible host, followed by barley, so these crops are most likely to have symptoms. Once wheat or
barley becomes infected, symptoms may appear within a few days.