Fall is the Time to Protect Winter Wheat From Losses Caused By Downy Brome

While much of the plains wheat was spared from the extreme heat and drought plaguing the late-season crops, the winter wheat area of South Dakota is quite dry going into seeding, and other areas also are short on moisture. Protecting winter wheat from competition for scarce moisture, and using tools that can save time, will be essential this fall.

The winter wheat planted on so many of the prevent-plant acres after the floods of 2011 beat the heat of 2012 and yielded well, says Chad Effertz, herbicide development manager for Arysta LifeScience. “You can’t count on always getting all the acres seeded in the spring, so winter wheat in the crop rotation makes good sense to spread the workload and diversify crop income potential.”

Costly Competition from Downy Brome

As growers begin planting winter wheat across the region, weed scientists remind growers about potential yield losses due to increasing competition from downy brome. This weed, also referred to as cheatgrass, is already well established in Montana’s winter wheat territories and spreading in South Dakota and North Dakota. Downy brome, like Japanese brome, emerges in early fall and spring.

One reason why downy brome is so difficult to control is that it has roughly the same life cycle as winter wheat. It develops and matures more rapidly than winter wheat, and it continues to grow and develop at low temperatures even after the winter wheat crop goes dormant. This gives it a competitive edge when it comes out of dormancy the following spring, and the wheat crop can’t catch up before harvest.

Independent research demonstrates the importance of timely control of downy brome in the fall, Effertz says. “If downy brome emerges with wheat; it is three to six times more yield-reducing and it can produce four times more seed, than if it emerges later,” he says. “You cannot let brome get established in the fall; it will be harder to control and will severely impact yields.”

Urgent to Control Early On

Early weed removal is critical for achieving the highest-yielding crop. If brome grasses emerge within 14 days of a winter wheat crop, they can reduce yield by 15 percent to 22 percent depending on weed density, according to independent research. At 50 bushels per acre and $6 per bushel, that’s equivalent to a loss of up to $65 per acre.

Fall and pre-plant glyphosate applications help suppress downy brome populations. “To be effective, glyphosate applications should be made when the plants are small,” says Kirk Howatt, Ph.D., assistant professor of weed science at North Dakota State University. “My advice to growers is - don’t wait too long. If you don’t get complete control, the plant can still produce enough seed to perpetuate the problem. The brome lifecycle makes it tough to deal with.”

Many growers tank-mix glyphosate with PRE-PARE® Burndown Herbicide to apply in one pass from 10 days before or just after planting, looking to add some residual activity.

“There’s nothing worse than spraying your glyphosate and getting a flush the next day,” Effertz says. By recommending the PRE-PARE/glyphosate tank-mix, “We’re trying to prevent that.”