Recent Rains Will Bring on Winter Annual Grass Weeds

Recent rains are likely to result in the germination and emergence of winter annual grass weeds such as downy brome, jointed goatgrass, and feral rye in winter wheat fields throughout Eastern Washington. Many winter wheat growers wait until the spring to apply herbicides to control these weeds. The argument for this approach is that they want to have all their weeds emerged so they can kill them all. They know that they get additional weed emergence over the winter. Despite this argument, fall is the best time to control winter annual grass weeds in winter wheat.

Research has shown that downy brome that emerges within seven to ten days of wheat emergence causes significant yield loss in winter wheat. Downy brome that emerges more than three weeks after winter wheat is much less competitive than earlier emerging downy brome. Growers who delay spraying until spring risk allowing fall-emerged downy brome to compete all winter with wheat. Worse, spring-applied herbicides are often inconsistent in controlling downy brome.

Figure 1

In a summary of 15 years of field data in Eastern Washington, Nevin Lawrence, former Ph.D. weed science student studying under Dr. Ian Burke, found that Outrider, Olympus, and PowerFlex all provided superior downy brome control when applied in the fall rather than the spring (see figure). Downy brome control did not differ for Beyond applied fall or spring. Beyond may only be applied to Clearfield wheat varieties.

What has been reported for downy brome (see figure 1) is likely also true for the other winter annual grass weeds. So whether your problem is with downy brome, jointed goatgrass, or feral rye, the fall is almost always the best time to implement control measures, especially when early fall rains bring these weeds up in September or October.

For more information on controlling downy brome in winter wheat, including herbicide recommendations, see Integrated Management of Downy Brome in Winter Wheat, a Pacific Northwest Extension Publication – PNW668. Similar information is available for jointed goatgrass and feral rye.

For questions or comments, contact Drew Lyon by email at or by phone at 509-335-2961.
Washington State University