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Producers in some parts of North Dakota are planning on seeding winter wheat into prevented plant acres this fall. Although these producers may be anxious to get those acres seeded as soon as
possible, the recommended winter wheat planting dates should still be followed. Those recommended planting dates for ND are September 1-15 for the northernhalf of the state, and September 15-30 for the southern half of the state.
Why shouldn’t winter wheat be planted earlier? There are several reasons, but chief among them is to manage
the disease called wheat streak mosaic virus. Wheat streak mosaic virus has been detected across the whole state this year, in winter wheat, spring wheat, and durum. The NDSU diagnostic lab has confirmed this virus
disease in 46 wheat samples from 20 different counties this summer, a much more frequent and widespread detection than normal. In addition, many of these samples also had several other viruses present. Wheat streak
and several other detected viruses are transmitted by wheat curl mites that survive in all wheats, volunteer wheat, green corn, and some grassy weeds. The only way to prevent this disease is to break the “green
bridge” where the mite survives prior to planting the next crop, through tillage or use of burn-down herbicides. This means that volunteers and grassy weeds should be controlled in a field two weeks prior to
planting the next susceptible crop, ie winter wheat this fall. A two-week window of no host present assures that the mite has gone through its life cycle and not found a subsequent host to feed on and transmit the
virus. Even if volunteers within the field to be planted to winter wheat are adequately controlled, planting winter wheat too early exposes the winter wheat crop to higher mite populations from un-harvested, green, and possibly infected tissues. Mites can be blown in from these green fields if they are nearby. It also will allow the mite and
virus numbers to build up to higher levels in the winter wheat crop - prior to freeze-up since the mite reproduces much more rapidly when temperatures are warmer. Seeding winter wheat too early, especially this year
with so much virus and mite populations known to be widespread, may spell trouble for these crops in 2009 and on into 2010.
Source: Marcia McMullen, NDSU Extension Plant Pathologist and Joel Ransom, NDSU Extension Agronomist
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