Waterhemp peeking above a soybean crop

As the end of the season nears and focus shifts to 2020, it’s key to consider your weed management plans. Due to this season’s weather conditions, there is wide mix of how weeds are appearing in fields. Some unplanted fields are riddled with weeds, while other planted fields didn’t have timely herbicide application, and weeds are starting to pop up.

Weeds that go to seed this season will likely need to be managed next season, particularly when you consider how many seeds these yield-robbing weeds produce, including:

• Marestail can produce up to 200,000 seeds per plant, which are highly mobile and easily spread to new areas.
• Not only can waterhemp produce up to 1 million seeds per plant, its seeds can also survive in the soil for 7 to 10 years.
• Capable of producing up to 600,000 seeds per plant, Palmer amaranth remains viable in the seed bank for up to 6 years.

On recent episodes of the AgriTalk Podcast, Syngenta Agronomy Service Managers Mike Leetch and Leon Hunter shared their tips on managing the weed seed bank. Take the opportunity to look at your weed situation while harvesting this fall and make a plan for how to take back control. Two important elements to keep in mind are:

• Minimize deposits in the soil seed bank. The best way to prevent future weed issues is by stopping them from going to seed.
• Choose herbicides with multiple effective sites of action for the best weed control.

For unplanted fields overrun with weeds, tillage may be needed to take down existing weeds. Incorporating the weeds into the soil can bury seed heads and minimize the ability for some weeds to germinate next season. However, keep in mind that tillage may also help other weed seeds resurface to germinate this fall.

You can manage against fall weed growth by planting a winter cover crop, or monitor for weed emergence in both tilled and harvested fields. Apply an appropriate herbicide with multiple effective sites of action that allows you to rotate to your intended crop next spring.

A Look Ahead

With some fields likely facing heavy weed challenges in 2020, preemergence herbicides will be a critical component to regaining control of weeds while also fighting resistance development. To minimize heavy weed pressure:

• For corn, Syngenta recommends using Acuron® The herbicide can be applied in 2 ways – up to 28 days preemergence (including burndown) at the full, labeled rate, or in a split-shot application with half of the full rate applied preemergence and half mixed with glyphosate and applied post-emergence up to 12″ corn. Trials show Acuron can deliver 5-15 more bu/A than other corn herbicides*.
• In soybeans, use Boundary® 6.5 EC, BroadAxe® XC or Prefix® herbicide preemergence. Use Tavium® Plus VaporGrip® Technology herbicide on dicamba-tolerant varieties post-emergence, the first dicamba herbicide premix. Combining dicamba with S-metolochlor expands control to both pre- and post-emergent weeds for up to 3 weeks longer than dicamba alone.

Discuss weed management plans with your retailer or Syngenta sales representative to find the product best suited for your farm and ensure strong weed control. Listen to more of what our agronomic service managers have to say about managing the weed seed bank.

Mike Leetch, agronomy service manager for the western Midwest.

Leon Hunter, agronomy service manager for the eastern Midwest.

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