NDSU Extension Service - Stark & Billings County

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Be on the Lookout for Wheat Streak Mosaic Virus

The virus, it's symptoms, management

An extended warm fall, mild winter and an insulating snow layer have provided suitable conditions for survival of winter wheat, small grain volunteers and grassy weeds. These conditions have also increased the risk for Wheat Streak Mosaic Virus (WSMV). With planting season around the corner, here is a brief review of the disease.

Virus and Vector:
WSMV is vectored (spread) by a tiny wingless mite known as the wheat curl mite (WCM). WSMV and WCM can only survive on a living host and overwinter on winter wheat, surviving small grain volunteers and grassy weeds. WCM can also vector Wheat Mosaic Virus (formerly known as High Plains Virus), but WSMV tends to be more common in North Dakota.

Symptoms:
Characteristic symptoms of WSMV include stunting, yellowing, and streaking of leaves (mosaic pattern). Symptoms tend to progress from field edges or first start in pockets in a field. There are several mimics (environmental stressors, nutrient disorders, etc.) of WSMV and positive identification can be achieved by submitting samples to a Plant Diagnostic Lab. Since risk for WSMV will be high in some areas, county agents in southwest North Dakota will facilitate sample submission to the NDSU Plant Diagnostic Lab for a reduced fee.

Next Step:
Assess each field situation separately and submit samples suspected to be WSMV. If winter wheat was seeded early in the fall and the green bridge was not broken, incidence of both WSMV and WCM will likely be high in those fields. For fields dedicated to small grains this spring, eliminate all small grain volunteers and grassy weeds for two weeks before planting. This will reduce the risk of mites spreading the virus from overwintering hosts to the small grain crop.

Management:
Breaking the green bridge is essential for management of this disease and it is important to eliminate volunteers and grassy weeds before planting. Planting spring small grains early will also reduce risk of WSMV occurrence. WCM activity is reduced in temperatures below 70 F limiting the spread of WSMV. Miticides and insecticides do not adequately manage the mite and are not recommended.

For more information on WSMV and WCM, please contact the local County Extension office.




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