Blog Post

Three Tips for Effective Weed Management in Iowa

This agronomic image shows soybean plants.

When you come up against prolific seed producers like waterhemp and Palmer amaranth, you can have problems not just this year, but for years to come. At the Traer, Iowa, Grow MoreTM Experience site, we have been conducting a variety of corn and soybean trials to show you effective tools to manage these yield-robbing weed issues.

Based on this year’s weed pressures, there are 3 main takeaways for consideration as you begin planning your 2018 weed management strategies in corn and soybeans:

  1. Use full herbicide rates. Apply PRE and POST herbicides at full, labeled rates and at the correct growth stage for effective control. Lower than recommended application rates can lead to weed outbreaks and eventual resistance.
  2. Strategically plan herbicide timing. Reports this year show growers struggling with their application timing. A common mistake is that they wait for “all” the weeds to emerge before they apply herbicides, which can be a costly decision. Herbicide application must happen before the weed is 4 inches tall or the possibility of control is slim-to-none. The earlier the timing, the better control you will see throughout the growing season. Although the chart below is from a study in Tennessee with Flexstar® herbicide, it’s a good visual for Iowans, too. The chart demonstrates management of Palmer amaranth at various growth stages, showing the importance of getting your herbicides down early.

This agronomic chart shows control of palmer amaranth with Flexstar.

3. Plan for a 2-pass system rather than a 1-pass system. An effective weed management program depends heavily on well-timed herbicide applications in addition to cultural practices. Failing to apply a herbicide at the right time could result in wasted input costs, weed infestations and reduced yield. Growers are reminded to implement a 2-pass system that uses herbicides with multiple,effective modes of action. We recommend Acuron® herbicide followed by Halex® GT herbicide in GT corn and Boundary® 6.5 EC herbicide followed by Prefix® plus glyphosate herbicide in GT soybeans.

By planning ahead and following recommended weed management practices, Iowa corn and soybean growers should see a decrease in weed pressure and overall stronger yield results in 2018.

Submitted by Dean Grossnickle, Syngenta Agronomic Service Representative.

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