This article is the fourth and final one in a multi-week series on wheat streak mosaic complex management. This week, we discuss variety selection as part of an integrated management program for wheat streak mosaic.
Overview - wheat streak mosaic complex devastated many wheat fields across central and western Kansas in 2025 and problematic again in 2026. As a reminder, wheat streak mosaic is a complex of three viruses: wheat streak mosaic virus, Triticum mosaic virus, and High Plains wheat mosaic virus. The wheat streak mosaic complex of viruses is vectored by the tiny wheat curl mite. The highest risk place for curl mites to survive the summer is volunteer wheat. Conditions that favor grain shattering, such as preharvest hail or harvest delays due to windy storms (as in much of the 2026 Kansas wheat harvest), can increase the presence of pre-harvest volunteer wheat. If mites are allowed to survive on this volunteer wheat or alternative hosts until the fall established wheat crop is planted, there is a high likelihood of another outbreak in 2027.
Management with Genetic Resistance: Another Tool in the Toolbox - in addition to controlling volunteer wheat, genetic resistance is an important component of a good integrated pest management strategy for controlling the wheat streak mosaic complex. It’s important to note that while some varieties provide partial protection against the wheat streak complex, there is no silver bullet variety that will work in all scenarios. That is, all commercial varieties will be symptomatic under some conditions, but the degree of yield loss to the virus complex will vary between varieties.
As a reminder, yield loss to wheat streak complex is highly influenced by: timing of infection, composition of viruses, and variety choice.
We know that fall infections and infections that occur in earlier stages of wheat development (prior to jointing) can result in the highest levels of yield loss. Infections that occur after the flag leaf and booting growth stages generally result in lower levels of yield loss. It should be noted that infections can occur in the fall and remain “dormant” in the plants until the weather warms in the spring. This is why we can sometimes see symptoms come on suddenly when the weather warms in the spring.
In addition to the timing of infection, the composition of viruses in a given field can impact final yield losses. Infections with more than one virus (e.g., WSMV + TriMV) can result in synergistic yield losses. It was common to see infections with two or more viruses in Kansas in 2025.
When we think about variety resistance in the context of wheat streak mosaic complex, there are two main types: resistance to the virus and resistance to the mite.
Regarding resistance to the virus, several genes have been described (wsm1, wsm2, and wsm3). The gene wsm2 is most widely available in Kansas varieties, including KS Territory (red), KS Mako (red), KS Bill Snyder (red), KS Dallas (red), KS Hamilton (red), Guardian (red), Oakley CL (red), Joe (white), and KS Big Bow (white). This resistance gene can help with severe wheat streak mosaic virus infections, but has key limitations. For example:
· This gene is effective against wheat streak mosaic virus but not against Triticum mosaic virus or High Plains wheat mosaic virus. In 2025, many mixed infections were detected, with more than one virus in the complex. So, it was not uncommon to see a variety with wsm2 appear symptomatic in the field. In many of these cases, Triticum mosaic virus was detected in the sample.
· The resistance conferred by wsm2 can also become less effective at high temperatures, although resistance in KS Dallas and KS Hamilton seems to endure greater temperatures before breaking down (~ 70º F). The resistance is much less effective if wheat is planted too early for grazing or if high temperatures persist into October. KS Silverado (white) also has temperature-sensitive resistance to wheat streak mosaic, although from a different source than wsm2.
In addition, there are a handful of varieties with resistance to the wheat curl mite (cmc4), including Guardian, Canvas, TAM 112, Byrd, Avery, Langin, Kivari AX, KS Western Star, Whistler, Crescent AX, Incline AX, Fortify SF, TAM 115, TAM 204, and T158. These varieties remain susceptible to viral diseases, but they generally slow the development of the mite populations in the fall. This resistance can help reduce the risk of severe disease, but will not provide enough protection if wheat is planted in close proximity to volunteer wheat or other hosts infested with large populations of the curl mites and virus.
Central Versus Western Kansas: Location Matters - unfortunately, many of these varieties are adapted to Western Kansas and may not be the best options for production systems in the central corridor. Some central Kansas-adapted varieties, including Rockstar, AP Prolific, SY Wolverine, LCS Photon AX, LCS Helix AX, and LCS Julep, tolerate WSMV infection better than others. It should be noted that, for all the reasons mentioned above, these varieties will still appear symptomatic under high disease pressure. KS Mako is a new release from the K-State Manhattan breeding program, adapted for the central corridor of the state and carrying the wsm2 gene. These varieties will still show symptoms of WSMV but may yield better than other varieties that are more susceptible.
More information on variety selection can be found here: MF991 Wheat Variety Disease and Insect Ratings https://bookstore.ksre.ksu.edu/pubs/MF991.pdf. A newer version of this publication will be released in the coming weeks.
Stacy Campbell is a Crop Production Extension agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Extension. You can contact him by e-mail at scampbel@ksu.edu or by calling 785-628-9430.