August 14, 2013

To minimize damage caused by diseases, wheat should be planted at the recommended date for your location. For recommended seeding dates, see this week’s CropWatch article, How Wheat Seeding Date Can Affect Yield, or NebGuide G2056, Seeding Rates for Winter Wheat in Nebraska.

Planting wheat too early can increase the incidence and severity of diseases in several ways.

Wheat streak mosaic, Triticum mosaic, wheat soilborne mosaic, High Plains, and barley yellow dwarf viruses thrive on early planted wheat. By planting wheat early, you provide a longer window for infection in the fall as well as a longer time for diseases caused by these viruses to develop before winter. For wheat streak mosaic, Triticum mosaic, and High Plains viruses, the earlier wheat is planted, the higher the populations of wheat curl mites (which transmit the three viruses) that will move from volunteer wheat onto the fall planted crop. Consequently, heavier infections by these viruses will result.

All of these factors (higher wheat curl mite populations, longer infection window, and longer time for disease development) increase the incidence and severity of disease, as well as the risk of multiple infections by more than one virus.

Infection of wheat by two or more viruses can have a significant negative effect on yield. Research at the Agricultural Research and Development Center near Mead in 2011 and 2012 showed that plots co-infected with wheat streak mosaic and Triticum mosaic viruses yielded 34 and 21 bu/ac less than plots infected with wheat streak and Triticum alone.

Planting early similarly increases the risk of root and crown rot diseases and fall season foliar diseases such as powdery mildew, leaf spots, and leaf rust. These diseases can cause significant damage especially if the fall is wet and the winter is mild.

Stephen Wegulo
Extension Plant Pathologist