JULIA DEBES
Kansas Wheat
Billowing clouds bringing summer showers are a welcome sight for sore eyes following a multi-year drought, but Kansas producers should also keep their eyes on their fields to monitor and control volunteer wheat. Doing so is essential to protecting next summer’s harvest as those sneaky plants harbor the wheat curl mites that carry yield-limiting diseases like Wheat Streak Mosaic Virus (WSMV).
“Now’s the time to be vigilant about volunteer control,” said Kelsey Andersen Onofre, assistant professor of plant pathology at K-State's College of Agriculture. “The best opportunity we have to manage WSMV is by managing our volunteer wheat prior to planting. The situation this past season could lead to heightened risk in 2024-25.”
Onofre explained that a combination of meteorological conditions throughout the growing season led to increased WSMV pressure on the 2024 wheat crop.
“We had volunteer wheat last year because of crop failure due to drought and untimely hail prior to harvest. We even had cases where folks were grazing volunteer wheat because of the drought conditions,” she said. “Then we had good conditions for mite development and reproduction in the fall. All that led to a perfect storm for WSMV last year.”
“This year was a bad year for WSMV, not just in western Kansas, but across the state. We had very severe WSMV across the whole northern tier of counties in Kansas, even in the northeast corner - that’s atypical. In addition, we had higher than usual levels of Triticum mosaic (TriM) come through the K-State Plant Disease Diagnostic Clinic.”
While K-State is still crunching the final yield loss estimates from WSMV for the 2024 harvest, the disease causes an average of $75 million in losses to Kansas wheat farmers every year - with the potential for more than 80 percent yield loss in heavily infected fields.
The virus is spread by the wheat curl mite, which feeds on wheat and other grasses. Wheat curl mites and the virus must have green host tissue to survive on throughout the summer after harvest. They most commonly reside on volunteer wheat that blew out the back of the combine or shattered grain from hailstorms that happened before harvest. The mites move from mature wheat to newly emerged wheat in the summer. Onofre noted there can also be sneaky scenarios where volunteer wheat emerges in double-cropped fields or cover crops.
Fields with WSMV infections last year should be particularly mindful of volunteer management through the summer. While WSMV is not treatable once fields are infected, the disease is preventable - and controlling volunteer wheat is a top priority to do so.
“Managing your volunteer is the absolute best management strategy,” Onofre said, adding that it is recommended that producers terminate volunteer wheat at least two weeks prior to planting wheat to allow enough time to kill all the wheat curl mites present in a field. Ideally, all fields within one to two miles are volunteer-free, but that can be hard to accomplish.
Producers also have the option to select varieties developed with built-in genetic resistance to WSMV - and the list of varieties available with this resistance grows with each year’s releases. However, Onofre cautioned that the genes that provide resistance are not perfect - they’re pressure sensitive, turn off at high temperatures and don’t work against other mite-carried diseases like Triticum mosaic (TriM).
“An uptick in disease emphasizes that you can’t rely on that genetic resistance alone,” she said. “While we do have options and varietal selection is really important, that very first priority has to be controlling that volunteer wheat.”
Onofre also reminded producers that the K-State Plant Disease Diagnostic Clinic can test for WSMV and other wheat viruses to determine the presence of the virus – even as early as this fall. If a producer suspects they have a WSMV or TriM infection, they can work with their local extension office to submit samples to the lab.
Read the latest guidance from K-State Agronomy on WSMV and the importance of controlling volunteer wheat this year at: https://eupdate.agronomy.ksu.edu/.
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