Early sowing of wheat can lead to several problems, from increased chances of insect- or mite-transmitted viral diseases to decreased emergence due to high temperatures and its consequences on wheat germination of particular varieties and reduced coleoptile length.
Ideally, growers should consider planting around the optimum window; but, if planting early due to moisture availability or a dual-purpose system, growers should consider selecting wheat varieties with tolerance to major yield-reducing factors in their respective region. Kansas growers should also strongly consider a seed treatment with both fungicides and insecticides if planting wheat early.
Wheat streak mosaic virus causes considerable damage to the Kansas wheat crop each year, primarily in the western portion of the state. In 2017, this disease caused a conservative $76.8 million in direct losses to wheat farmers, a loss of 19.2 million bushels of wheat. The 2017 loss was a 5.6% yield loss, up from an average 1.5% loss. For this past growing season, however, tests show the disease showed up not only in western Kansas but also in central Kansas.
Wheat curl mites that spread WSMV and other diseases survive the summer on volunteer wheat and certain other grasses. As those plants die off, the wheat curl mites leave in search of new plants to feed on. Early planted wheat is likely to become infested and thus become infected with wheat streak mosaic virus, high plains virus and Triticum mosaic virus. The wheat curl mites are moved by wind and can be carried a mile or more before dying, so if wheat is planted early, make sure all volunteer wheat within a mile is completely dead at least two weeks before planting. For growers considering planting early, a good management consideration would be to select wheat varieties with resistance to the wheat streak mosaic virus and/or tolerance to the wheat curl mite, especially in the western portions of the state.
For more information on this devastating disease, download a packet of information at https://kswheat.com/wsmvpacket or request a printed copy from Kansas Wheat, 1990 Kimball Ave., Manhattan, KS 66502.
As farmers begin making plans to drill winter wheat, we must stop the spread of wheat streak mosaic virus and related diseases. There are no effective ways to treat, so the only way to stop it is to prevent it through one or more of the following three ways.
Control volunteer wheat
The best way to prevent the spread of the wheat streak mosaic virus is to remove volunteer wheat and other grassy weeds. Volunteer wheat must be completely dead and dry for two weeks before planting a new wheat crop. Volunteer wheat and other grassy weeds can be removed with herbicides or tillage, but it’s absolutely essential to allow time for herbicides to work.
Avoid early planting
Avoid early planting; plant after the best pest management planting date, or BPMP (formerly known as the “Hessian fly-free”) date. By avoiding early planting, Kansas wheat farmers can avoid times when wheat mite populations are the highest in late summer and decrease the interval between planting and fall freeze events.
Plant resistant varieties
Plant varieties with moderate or high levels of resistance to WSMV. “Wheat Variety Selection” is a new publication in the Kansas Wheat Rx Series and addresses steps to ensure a successful variety selection.
These ratings have been compiled from multiple sources, including company websites, screening tests by John Fellers, USDA-Manhattan and Wheat Varieties for Kansas and the Great Plains datasheets. It is very difficult to rate varieties for WSMV. There are three separate virus diseases in the Central Plains that can all occur, separately or in combination: WSMV, High Plains Virus and triticum mosaic virus. They have similar symptoms and are vectored by the wheat curl mite. If two or more of these diseases occur together, all wheat varieties become susceptible. These ratings are for WSMV only and this list is not all-inclusive.
At this point, there are no chemical options such as insecticides or pesticides that are effective at controlling the wheat curl mite. The best way to stop the spread of WSMV is to control volunteer wheat at least two weeks prior to planting a new crop.
