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Improper HPPD Chemistry Usage May Increase Herbicide Resistance

September 27, 2019

Bare ground trials demonstrate the impact of applying Acuron® corn herbicide, used both pre- and post-emergence, at Rend Lake, IL.

Growers have experienced significant financial challenges this season, and cutting back on weed management may be tempting. However, when cutting back turns into cutting corners, herbicide resistance can become much more difficult to fight.

This season, a trial at the Rend Lake, IL, Grow More™ Experience site showed the risk of herbicide resistance. In bare ground trials of various corn herbicides that use HPPD chemistry, including Acuron®, Halex® GT and Capreno® herbicides, post-emergence-only treatments struggled to combat both Palmer amaranth and waterhemp. Applications leaving the weeds only burned, not killed, allow the survivors to develop resistance to the HPPD chemistry and pass on this trait to future generations. Importantly, all HPPD herbicides use the same sites of action (SOA) for post-emergence treatments, so switching brands will not suffice to combat resistance.

Results from post-emergence bare ground trials     Results from post-emergence bare ground trials

Results from post-emergence bare ground trials of Halex GT (left) and Capreno (right) at the Rend Lake, IL, Grow More Experience site.

Weeds like Palmer amaranth and waterhemp can survive HPPD herbicides when applications are made using lower-than-recommended rates, which can occur if you only make 1 pass instead of a 2-pass system. Even at recommended rates, applications that occur too late or that use too few SOAs can fail to kill larger weeds, allowing them to develop and pass on resistance to future applications.

To tackle Palmer amaranth and waterhemp in corn while defending against resistance, we recommend a burndown application of Gramoxone® SL 2.0 herbicide followed by:

  • A 2-pass system of Acuron or Acuron Flexi herbicides followed by Halex GT plus atrazine or dicamba brand. All of these corn herbicides contain multiple effective SOAs for built-in resistance management and provide long-lasting residual control when used in a 2-pass system.

Contact your Syngenta sales representative for help identifying the right weed management plan for your area.

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