Preparing an effective strategy for controlling early emerging weeds is key for successful corn and soybean crops.
Giant ragweed, lambsquarters and Canada thistle are three of the most resilient early-season weeds to prepare for, points out Scott Pringnitz, market development specialist, Corteva Agriscience.
These species can begin emerging at temperatures as low as the mid-40s, grow fast and quickly outcompete corn and soybean seedlings, so waiting to craft a control plan can limit yield.
“Weeds that germinate early in the season have the greatest opportunity to compete with the crop for nutrients, soil moisture and sunlight,” Pringnitz says. “They also can be harder to control if they reach a larger size or more advanced growth stages.” He offers these reminders:
- Start with a clean seedbed. It’s important that weeds don’t have a head start on corn or soybeans as the crops are getting established. A clean seedbed also provides a more ideal environment for seed-to-soil contact, consistent emergence and an even stand — contributing to top yield potential and uniform crop moisture at harvest.
- Scout and prioritize. Prompt scouting is important not only to determine the size and type of weeds present before herbicide applications are made but also to keep records throughout the year of the fields most impacted by early emerging weeds. Knowing where the high-priority fields are to start scouting enables effective and well-timed herbicide applications.
- Investigate new options. When choosing herbicides, it’s important to balance what has worked well in the past with new tools or combinations that improve weed control and manage weed resistance. “Although manufacturers are working to develop new modes of action, it’s much faster for them to develop new premixes of existing herbicides,” Pringnitz says.
- Choose multiple modes of action (MOA). The best herbicide programs use multiple, effective modes of action to control the spectrum of existing weeds. Using products with as many as three modes of action pays off in the short term with more-effective weed control and in the long run by maintaining viable herbicide options. “Weeds try to metabolize individual herbicide applications, but it’s more difficult for them to overcome two or three at the same time — especially when the herbicides attack the weeds in different ways,” Pringnitz says. “Everyone recognizes weed resistance is increasing. It’s critical that multiple modes of action are used to prevent or delay resistance from developing.”
- Keep season-long control top of mind. Time is precious, and spring weather can delay postemergence applications — giving weeds an upper hand. When choosing corn and soybean herbicides for an initial application, consider the benefit of extended residual control to keep subsequent weed populations at bay as the crop becomes established. Some of the newest herbicide combinations may offer as much as eight weeks of residual control.
- Remember crop safety. Controlling larger weeds in an established crop can present challenges that may be difficult to overcome without using herbicide mixes and/or adjuvants that are more likely to result in crop response.
- Waiting can be costly. Decisions that save money now, but lower yield potential, may lower profitability. “Avoid the temptation to reduce costs before compromising short- or long-term weed control practices. Weeds that are not well-controlled are more likely to impact yield. They’re also prone to regrow and produce seed, which can increase weed control challenges in future growing seasons,” Pringnitz adds.
Corteva Agriscience has a robust portfolio of corn and soybean herbicides available for early and season-long weed control. Consult your local Corteva Agriscience representative for information.
