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Weeds Waking Up: Palmer Amaranth

April 9, 2019

As the last featured weed in our Weeds Waking Up series, Palmer amaranth typically emerges well into the season, sometimes even after harvest has concluded, as seeds typically germinate close to the soil surface.

Palmer amaranth’s reputation as a difficult-to-control weed often precedes its arrival. After working its way through the South, Palmer amaranth is now moving into the Midwest. In 2018, Syngenta weed scientists noted that Palmer amaranth had been reported as far north as MN.

A small-seeded broadleaf weed, Palmer amaranth produces thousands of seeds that are well adapted to today’s minimum- and no-till practices. Worse still, many populations have developed resistance to glyphosate, ALS and HPPD inhibitors, with some exhibiting resistance to multiple sites of action. Because Palmer amaranth can cross-pollinate with other weeds in the amaranthus family, resistant populations can spread rapidly, overtaking entire geographic areas.

Palmer amaranth facts:

  • Produces up to 100,000 seeds per plant and germinates throughout the season.
  • Aggressively competes with corn and soybeans, growing up to 3” per day and reaching up to 8’ in height.
  • When allowed to compete throughout the growing season, it can create yield losses up to 91% in corn and 79% in soybeans.

Learn more about how to identify and manage Palmer amaranth.

Despite its tough reputation, Palmer amaranth is manageable with a start clean, stay clean approach to weed control that incorporates multiple, effective sites of action. Syngenta recommends Acuron® corn herbicide, which has 3 effective sites of action (Groups 5, 15 and 27) and Acuron Flexi corn herbicide, which has 2 (Groups 15 and 27). For optimal control of Palmer amaranth, these brands should be applied before it emerges. Acuron and Acuron Flexi can be applied alone or pre-emergence followed by a post-emergence application of Halex® GT corn herbicide (Groups 9, 15 and 27) plus AAtrex® 4L corn herbicide (Group 5).

Syngenta also offers an effective weed management program in soybeans that starts with BroadAxe® XC herbicide (Groups 14 and 15) or Boundary® 6.5 EC (Groups 5 and 15) herbicide. These herbicides provide for pre-emergence weed control of Palmer amaranth with long-lasting residual and multiple sites of action. A post-emergence application of Flexstar® GT 3.5 (Groups 9 and 14) delivers 2 different sites of action to control glyphosate and ALS resistance.

If you would like input in developing a herbicide program for 2019 based on the specific weed pressures in your field, contact your Syngenta retailer, local Syngenta sales rep or visit www.ResistanceFighter.com.

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