Avoid ‘green bridge’ from winter wheat wrecks to spring wheat

Manitoba agriculture department staffers report questions coming in about seeding spring wheat in a field where the winter wheat was torn up due to poor emergence or winterkill.

The main disease consideration in this situation is wheat streak mosaic virus (WSMV). This disease is vectored by the wheat curl mite and both the virus and the mite can overwinter on a living host, such as winter wheat.

The main way this disease is managed is by breaking the “green bridge” — a concept that refers to having a period of time (ideally two weeks) where there is no green wheat tissue available on which the mite and virus can survive.

In the fall, this means there should be two weeks from the time the spring wheat ripened to when the winter wheat emerges.

When understanding your risk for WSMV this spring, Manitoba agriculture officials suggest thinking back to what conditions were like last fall: Is your winter wheat bordering a spring wheat field from last year? Is there a chance that the “green bridge” was not broken?

Chances are if you’re tearing up your winter wheat stand because it didn’t emerge last fall, your risk of WSMV overwintering in that crop is slim. That being said, be sure to thoroughly scout your crops, especially along field edges, for WSMV symptoms.

If there is a concern of WSMV, the green bridge can be broken this spring by ensuring two weeks between destroying winter wheat and emergence of this year’s spring wheat crop. — AGCanada.com Network

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