Weeds: Problem Weeds

Weed control in soybeans can be a challenge today. Growers are dealing with a number of weeds that are resistant to some herbicide families or just plain tough to control. This requires growers to adopt a range of tactics and devote extra diligence so they can obtain the level of weed control they experienced when Roundup Ready® soybeans were first introduced and glyphosate was the herbicide of choice.

While herbicide resistance is nothing new, the problem has worsened over the past decade—first with glyphosate-resistant marestail followed by glyphosate-resistant waterhemp and Palmer amaranth. And not far behind are the ragweed species, which are already tough to control. To make matters worse, some of these problem weeds can be resistant to several herbicide chemistries at the same time.

So what is your situation? At the recent Soybean Summit held January 30 in Effingham, Bryan Young, Ph.D, weed scientist at Purdue University and formerly a faculty member at Southern Illinois University in Carbondale, said, “Palmer amaranth and waterhemp resistance to glyphosate continues to spread across Illinois and other Midwestern states. The key aspect to remember is that an effective, preplanned management strategy for these challenging weed species can cost much less than a postemergence rescue attempt.”

So what weeds are impacting your fields and what are you doing to stop the spread to your farm operation?

Young asked the growers who attend his breakout session which resistant weeds were causing the most problems.

• 45% said they had glyphosate-resistant waterhemp.
• 31% said they had waterhemp resistant to glyphosate and a PPO inhibitor.

Answer the ILSoyAdvisor poll question: “Which situation describes the weed control issues you are having with Palmer and waterhemp?”

Drop in a comment below and let us know the toughest weeds you are dealing with and the strategies you are using to control them, or if control is even working.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com.