By Scout Nelson
Billowing summer clouds bringing showers are a welcome sight after a multi-year drought, but Kansas producers must also monitor and control volunteer wheat.
These plants harbor wheat curl mites, which spread 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 meteorological conditions throughout the growing season 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 wheat curl mites, which need green host tissue to survive on throughout the summer after harvest. They commonly reside on volunteer wheat from shattered grain before harvest.
The mites move from mature wheat to newly emerged wheat in the summer. Volunteer wheat can also emerge in double-cropped fields or cover crops.
Fields with WSMV infections last year should manage volunteer wheat through the summer. While WSMV is not treatable once fields are infected, the disease is preventable. Managing volunteer wheat is a top priority.
“Managing your volunteer is the absolute best management strategy,” Onofre said, adding that producers should terminate volunteer wheat at least two weeks before planting to kill all wheat curl mites present in a field. Ideally, all fields within one to two miles should be volunteer-free.
Producers can also select varieties developed with genetic resistance to WSMV, though these genes are not perfect and can be pressure sensitive, turning off at high temperatures.
They also 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,” Onofre said. “While we do have options and varietal selection is really important, that very first priority has to be controlling that volunteer wheat.”
Onofre 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.
If a producer suspects a WSMV or TriM infection, they can work with their local extension office to submit samples to the lab.
Photo Credit: istock-ligora
Categories: Kansas, Crops, Wheat