10-05-2025
Kansas wheat farmers facing worst Wheat Streak Mosaic Virus outbreak since 2017
KANSAS CITY, Mo. — Wheat farmers in Kansas are facing one of the worst Wheat Streak Mosaic Virus (WSMV) outbreaks in years.
The wheat curl mite is a small but mighty adversary of Kansas wheat producers as the vector for WSMV, Triticum mosaic virus (TriMV) and High Plains Mosaic Virus.
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Experts with Kansas Wheat said producers across the state appear to be losing the battle against these tiny critters and the diseases they carry in what could be the worst WSMV outbreak since 2017.
'We have some fields that are close to total losses,' said Kelsey Andersen Onofre, K-State assistant professor of plant pathology, who has been across the state scouting fields. 'It's hard to walk in a wheat field in Kansas right now and not find at least low-level, trace-level symptoms of WSMV—and that's pretty unusual.'
Andersen Onofre explained that symptoms of WSMV – symptomatic leaves with dark green coloring and light-yellow discolorations or stunted plants with a distinct yellow discoloration – are showing up more clearly over the past few weeks as temperatures warm up.
Experts suspect that a high population of mites from this past summer managed to survive the mild winter and disperse over long distances up to one or two miles away.
There are now concerning levels of the diseases they carry across the state, Kansas Wheat said in a news release.
'If we have an extended, warm fall, like we did in 2024, it's a perfect storm for mite populations to stay at high levels and increase later in the season,' Andersen Onofre said. 'The more populations increase, the higher the chance they will be blown by wind into neighboring fields. If the weather stays warm, we can see this spread continue over long distances.'
The group said this is certainly the case in Saline County, where more diverse cropping systems are making it an emerging issue where it hasn't traditionally been found.
'This is by far the worst year I've seen for impact of wheat streak mosaic virus in our area,' said Gypsum farmer Justin Knopf. 'Many fields have been affected with a high level of presence of the virus. Some fields…right next to a field where the source was have significant impact.'
Producers with infected fields should expect yield loss, especially in fields where the flag leaf has already turned yellow, experts warned.
'Unless we have a significant weather event such as hail or excessive heat during grain fill, wheat streak mosaic virus is likely to be the number one cause of yield loss in this area,' Knopf said.
Unfortunately, there is no effective treatment for WSMV once the infection has occurred.
Kansas Wheat said in its news release that producers must balance estimated yield loss, requirements for crop insurance and the economics behind terminating the most severely infected fields in favor of planting a summer crop.
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'Unfortunately, there is not much to do at this point in the season if you have a field that has severe WSMV infection,' Andersen Onofre said. 'These fields are likely not good candidates for a fungicide application. Fungicides will have no effect on wheat streak, and it will be difficult to recover yield losses from foliar diseases if yield potential is already reduced by wheat streak.
'We do not recommend spraying insecticides or miticides. There is no immediate action you can take to slow down the spread of WSMV or preserve yield in affected fields.'
Knopf attributed the widespread infection this year to three really dry falls and winters in a row, more hail in the area in 2024 (areas with hail are virus hot spots) and more diverse cropping systems, including warm season cover crops and double cropping.
For more advice on how to deal with WSMV, click here. You can read more about the virus at
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