I have been getting more phone calls this year than normal about wheat fields being infected with Wheat Streak Mosaic Virus (WSMV).
As a reminder volunteer wheat ideally needs to be completely dead/killed two weeks before wheat is drilled in the Fall. Volunteer wheat, or wheat leftover from past crops, houses the wheat curl mite. Mite populations, ultimately, depend on the amount of volunteer wheat within an area. If you had some wheat in a neighboring field that survived after harvest, or maybe it was hidden in some double crop field nearby, that's where those curl mites survive. They can then blow into your field or a neighbor’s field in either the fall or the early spring and that's typically when you start to see damage.
You can get wheat samples tested for WSMV at the K-State plant pathology lab, just to confirm it. You can contact your local Extension Office to bring in your sample.
You get kind of a fan appearance, so it is worse on the edge of the field and gets progressively better as you move towards the center of the field.
Warm weather conditions induce the appearance of wheat streak mosaic within fields. While plants may be infected during the winter and times of cold, hot temperatures activate the viruses’ symptoms. “Usually, you don't see that streaking symptom until the weather starts to warm, so we can have some infection cooking there over the winter”, says K-State wheat disease specialist Kelsey Anderson Onofre.
Increased moisture and other weather events during the 2023 harvest contributed to more volunteer wheat and desirable conditions for the wheat streak mosaic virus to thrive in the current growing season.
One last note or observation from my experience is that in the spring when volunteer wheat gets terminated either with tillage or herbicide. If there is nearby wheat it will get WSMV. Because the curl mite must have green and living tissue to survive on. Once the wheat is dying or killed, the mite will leave the plants using the wind because they do not have wings. They will then infest other nearby healthy fields with the wheat curl mite and thus WSMV.
For further information about WSMV just search on-line for Wheat Streak Mosaic, KSU. If you have any questions give me a call at 785-628-9430.
Stacy Campbell is a Crop Production Extension agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact him by e-mail at [email protected] or by calling 785-628-9430.