Tim Murray

Following a particularly wet August, Washington farmers are advised to remove volunteer wheat before planting a new crop.

Volunteer wheat is any viable grain that grows at a place and time that wasn’t intended, particularly following harvest, said Tim Murray, a Washington State University professor and extension plant pathologist.  

Volunteer wheat acts as a “green bridge” that allows various insects and diseases to survive from one season’s wheat crop to the next.

Volunteer wheat within a half-mile of a field should be completely dead at least two weeks before planting a new wheat crop, WSU researchers recommend.

It’s a problem every year, to some extent, Murray said.

“We’ve had this abundance of moisture in August that’s a little bit unusual — the amount that we’ve had and how widespread it’s been,” he said. “We expect there’s going to be more volunteer out there.”

Wheat streak mosaic virus has been emerging in the past few years. The virus, and the wheat curl mite that transmits the virus, can also live in corn. The mites can move off sweet corn following harvest into volunteer wheat and start reproducing, as will the virus, Murray said. 

There might have been enough moisture to get the volunteer wheat going, but then the field typically begins to dry, Murray said. As the plants start dying, the mites will move into the new crop seeded nearby. He estimates the mites can travel about half a mile.

“That is probably my primary concern for the volunteer issue,” Murray said. “If you don’t do something about the volunteer, it can cause problems.”

Volunteer wheat can also host Hessian flies and aphids that transmit barley yellow dwarf virus. 

Destroying volunteers after the new wheat emerges is too late, researchers said. Producers should leave enough time to have a second chance if control is incomplete. Tillage and herbicides are the two options available for volunteer control.

There are really no guidelines for how much volunteer wheat is too much, Murray said. 

“After the rains that we’ve had, some of these harvested fields, you’re going to see a green carpet out there,” he said.