This article is the third in a multi-week Agronomy eUpdate series on wheat streak mosaic complex management to address the 2025 outbreak. In week 1, we revisited herbicide recommendations for volunteer wheat. In week 2, we discussed the role of alternate hosts in the landscape. This week, we discuss variety selection as part of an integrated management program for wheat streak mosaic.
- Week 1: (https://bit.ly/4eSVKgP) Wheat-free windows and herbicide recommendations
- Week 2: (https://bit.ly/3GIY2Ta) The role of alternative host crops
- Week 3: Variety selection for wheat streak complex management
Overview
Wheat streak mosaic complex devastated many wheat fields across central and western Kansas in 2025. The conditions that favored this outbreak were covered in a previous eUpdate article: (https://bit.ly/3SwJ7gU). In today’s article, we revisit the concept of wheat-free windows for volunteer management and discuss variety selection for the integrated management of wheat streak.
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 (Aceira tosichella). 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 (such as much of the 2025 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 2026.
In the first article of this series, we shared the recommendation for wheat-free windows (Figure 1). These windows include periods 30 days prior to the start of the optimal winter wheat planting window by zone in Kansas. As the wheat curl mite is a community pest, coordinated breaks in volunteer wheat and other cereals will have the highest likelihood of lowering local and statewide mite levels moving into our 2025 optimal winter wheat planting date periods. Volunteer wheat that emerges after the fall crop is already established poses a lower risk as a green bridge and can be thought of in a similar way as the fall crop. Fall wheat planted early, during wheat-free windows, risks bridging wheat curl mite to the fall-established crop.
Figure 1. Proposed wheat-free windows in different regions of Kansas to reduce the likelihood of a wheat streak mosaic complex outbreak during the subsequent season. Wheat-free windows are defined as the 30-day period prior to the start of the optimal winter wheat planting date for the region.
Here are some important considerations for achieving success with wheat-free windows:
- All volunteer wheat should be terminated and completely dead prior to the start of your regional wheat-free window.
- Where possible, the fall wheat crop should not be planted until the end of the wheat-free window.
- Other winter cereals (such as rye and triticale) should not be planted during this period as they can serve as a “bridge” for the curl mites to move to fall-established wheat.
- A regional “break” in the volunteer wheat green bridge will allow for wheat curl mites to die off prior to the start of the optimal wheat planting window.
- Volunteer wheat that emerges after this period is of less concern, as it will be emerging at a similar time as the fall-established winter wheat crop.
- Success is dependent on coordinated efforts in communities.
Management with genetic resistance: Another tool in the toolbox
In addition to controlling volunteer wheat, genetic resistance is also an important component of a good integrated pest management strategy for wheat streak mosaic complex control. 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,
- 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 (WSMV + TriMV, for example) 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.
When it comes to 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 (https://bookstore.ksre.ksu.edu/pubs/ep145.pdf) or High Plains wheat mosaic virus. In 2025, many mixed infections were detected with more than one of the viruses 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 out of the K-State Manhattan breeding program that is adapted for the central corridor of the state and carries 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.
Kelsey Andersen Onofre, Extension Wheat Pathologist
andresenk@ksu.edu
Sarah Lancaster, Extension Weed Science Specialist
slancaster@ksu.edu
Anthony Zukoff, Extension Entomology
azukoff@ksu.edu
Romulo Lollato, Extension Wheat and Forages Specialist
lollato@ksu.edu
Jeanne Falk Jones, Multi-County Agronomist
jfalkjones@ksu.edu