By Logan Haake

Soybean weed-management for 2019 should be based around three principles: Start clean, stay clean and use multiple modes of action. Over the past decade, the Roundup Ready system gave excellent control with glyphosate herbicide in a wide range of conditions. This program made weed control and management easy for nonresistant weed species. As we look at some of the challenges we are faced with today, such as glyphosate-resistant marestail, waterhemp and palmer amaranth, having a well-rounded weed management program is critical.

Having clean fields starts in the fall after harvest. Winter annuals can emerge in the fall and actively grow until December, depending on weather conditions. The weed will build up a reserve of carbohydrates, which will give the plant a jump-start in the spring. A couple things that can help give control are fall burndown and tillage. A residual can also be added to the burndown to help give longer control through the season.

If fall does not allow for burndown or tillage, a strong and timely weed management program is important. Tillage will control weeds if it significantly disturbs and inverts the soil. This typically does not include vertical tillage. It is still recommended that a residual herbicide be used after the tillage or an early post-application of residual herbicide. If you don’t use tillage, a burndown with multiple modes of action has the best results. Broad-spectrum herbicides such as Roundup, Liberty or Gramoxone paired with 2,4-D, Sharpen and certain labeled dicambas are good options. It is also important to add a residual herbicide to the mix to keep the fields clean. The residual herbicide should also include two modes of action to have the best control to stay clean. It is important to read labels to make sure all tankmixes are on label when making an application.

Remain clean
It is important to stay clean through the growing season. Taking the time to scout fields yourself, or have a professional hired to scout — because it is important to catch break weed emergence early. Spraying weeds before they get bigger than 4 to 6 inches in height will have the best rating on herbicide control. If weeds exceed these heights, a higher-labeled rate would be recommended. With certain weed species, an additional residual post-application of a herbicide would be a good program.

Be sure to continue scouting throughout the growing season. Once soybeans reach canopy, emergence of any new weed typically is low. Check the label if any application is needed when first bloom is reached, and after, too. Scouting is not only a good management practice for the current season, but it is also helpful if you need to make some changes for the coming year. 

Haake is ag products manager for Legacy Farmers Cooperative. Contact him at 419-423-2611 or [email protected].