Mark Renz, University of Wisconsin extension weed scientist, has received several inquiries about volunteer wheat management in summer alfalfa seedings. "During harvesting of wheat, some seeds fall to the ground and germinate with the alfalfa seed," he says. "Volunteer wheat seedlings have some benefit as they can provide suppression of other weeds, protect alfalfa seedlings from blowing dust and minimize soil erosion. Unfortunately, they also compete with seedling alfalfa plants and can suppress development and reduce establishment." Large infestations have been documented to reduce first-cutting alfalfa yields by 80% the following spring. Dry conditions can cause competition for soil moisture, which also reduces yields.
"While wheat does have good forage value, plants need to be harvested at the boot stage, and this is often not an ideal stage for alfalfa harvest, further reducing yield," Renz notes. "Obviously, the decision to manage volunteer wheat should be dependent upon the density within the field. As a rule of thumb, researchers have recommended that plants be managed if three or four plants are seen per yard."
Volunteer small grains have historically been a problem in fields that are disked, chisel plowed or no-till seeded. They're less likely to germinate and be competitive if fields are moldboard plowed before seeding alfalfa, according to Renz. He suggests that adjusting land preparation, if possible, may be all that is needed. Several herbicides are also available that are effective on volunteer wheat and other small grains.
A summary of options that have been researched and observed to provide control of volunteer wheat in Wisconsin appears online at ipcm.wisc.edu/Portals/0/Blog/Files/17/340/WCM_14(21)a.pdf, or in the 2007 Agronomy Pest Management portion of the Wisconsin Field Crops publication (A3646). Renz suggests producers also read the labels of products they may be using.