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Mid-Season Tough Weed: Palmer Amaranth

June 5, 2017
This agronomic photo shows the weed palmer amaranth.

Caption: Palmer Amaranth

Out of a number of problematic weeds to watch for, Palmer amaranth remains a top threat across most soybean- and corn-producing regions.

Purdue University characterizes Palmer amaranth as a particularly problematic weed because of its ability to produce 100,000 to 1/2 million seeds per plant, easily disperse its seeds and compete aggressively with crops by growing 2 to 3 inches per day.

Palmer amaranth is unpredictable – it can emerge at any point in the season. Because of its erratic nature, growers should begin scouting for this weed now and continuously to do so throughout the season.


  • Diamond-shaped leaves varying from green to pink
  • Seed heads grow up to 30 inches long
  • Could have white, V-shaped markings on the leaves

Palmer amaranth is best controlled before it reaches 4 inches in height. Because of its ability to quickly adapt and spread herbicide-resistant genes, it is essential that growers select a proven treatment containing multiple modes of action.

Syngenta recommends growers consider using herbicides, such as Acuron®, Acuron® Flexi or Halex® GT for corn. For soybeans, growers should apply Flexstar® GT 3.5 herbicide to takedown an aggressive weed like Palmer amaranth.

In preparation for scouting, take the Resistance Fighter® Weed IQ Quiz to test your weed identification knowledge.

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All photos are the property of Syngenta or are used with permission.

Syngenta hereby disclaims liability for third party websites.

Photo resized. Photo credit: Joseph M. DiTomaso, University of California – Davis, Bugwood.org

©2017 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties. Please check with your local extension service to ensure registration status. Acuron is a Restricted Use Pesticide. Acuron®, Boundary®, Flexstar®, Halex®, Resistance Fighter® and the Syngenta logo are registered trademarks of a Syngenta Group Company. BroadAxe® is a registered trademark of FMC Corporation.