Can I re-crop my torn up winter wheat field to spring wheat? What is the risk of WSMV?

 It all depends on whether or not the green bridge was broken! Given the conditions across most of the province last fall the risk for Wheat Streak Mosaic Virus (WSMV) is likely lower than it has been in previous years, but it is not non-existent.

WSMV and its vector, the wheat curl mite, overwinter in Manitoba on host plants. While there are other minor hosts, the major concern for overwintering lies with winter wheat. Knowing this, there are preventative steps that can be taken to lower the risk of overwintering. The virus/mite combination needs green tissue in order to survive, so in the fall growers should ensure the green bridge is broken between the ripening of the spring wheat crop and emergence of the winter wheat. Ideally, this break would be approximately two weeks in length. If this green bridge is not broken, symptoms of WSMV may be observed in the winter wheat crop in the spring once it resumes active growth. If this winter wheat crop is torn up and replanted, it is suggested that the field be re-cropped to something other than spring wheat to prevent this disease cycle from continuing.

In many cases this year the winter wheat field that is being re-cropped did not emerge last fall and germination this spring was poor. If your winter wheat crop only germinated this spring the risk of WSMV overwintering in that field is lowered significantly. However, it is still important to scout for WSMV symptoms as there may have been some plants that germinated in the fall that overwintered the disease/vector or the overwintering may have occurred on one of the more minor hosts. If WSMV is found, the field should be either planted to something other than spring wheat or the green bridge must be broken (ie. two-week period free of green tissue required) to prevent further spread of the disease.

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