Fall Weed Control Tips to Protect Fields Before Winter

By Scout Nelson

As harvest season approaches, farmers can reduce weed problems by focusing on two key areas—perimeter weed management and fall weed management. These steps protect crop yields and reduce the spread of resistant weeds.

Perimeter Weed Management
Now is the time to mow weeds along field edges and any non-crop areas inside fields. This prevents weed seeds from entering the combine and spreading across the field. If weed pressure is high near the crop edge, even mowing a small strip of the crop itself can help.

Spray booms often apply less herbicide along field borders, which allows resistant weeds to survive. When combines carry these weeds deeper into the field, they can spread and become harder to control. Mowing before harvest stops this cycle and reduces the chance of resistant weeds moving inward.

Fall Weed Management
Cool-season perennial, biennial, and winter annual weeds are best controlled with herbicide in mid- to late fall, ideally after the first freeze. Key targets include Canada thistle, absinth wormwood, perennial sowthistle, dandelion, and foxtail barley.

Glyphosate is recommended for many of these weeds, with specific rates to ensure control. For example, apply at least 1.125 pounds acid equivalent per acre for Canada thistle and add 2,4-D ester for better dandelion control.

Include ammonium sulfate and the correct surfactant for full effectiveness. Plants should be at least 6–8 inches tall for best results.

For winter annuals like chickweed and shepherd’s-purse, apply glyphosate at 1.0 pound acid equivalent per acre. For horseweed, combine glyphosate with 2,4-D ester.

Fields with heavy wild oat or kochia pressure may benefit from fall applications of Zidua or Valor once soil temperatures stay below 50°F, but follow crop rotation guidelines carefully.

By scouting fields, mowing edges, and timing herbicide treatments correctly, farmers can prevent resistant weeds from spreading and prepare fields for a healthier crop next spring.

Photo Credit: gettyimages-fertnig