Weed of the Month: Palmer Amaranth

Palmer amaranth of the pigweed group is becoming more invasive to the Midwest and causing agronomic issues. With its resistance to glyphosate and other ALS herbicides, this weed has an adaptable nature that continues to challenge farmers across the country.

Palmer Amaranth

  • Common name: Palmer Amaranth
  • Scientific name: Amaranthus palmeri1
  • Have a small hair in leaf tip notch1
  • Long petioles connect the leaf to the main stem1

Fast facts

  • Genetic diversity: Palmer amaranth is a dioecious species, which means that there are separate male and female plants. Dioecious species can increase genetic diversity, making it difficult to control.1
  • Many seeds: Each Palmer amaranth plant can produce at least 100,000 seeds in crop fields and up to a half-million seeds in undisturbed land.1
  • Undisturbed soil: Palmer amaranth thrives in no-till or minimum-till fields because it can emerge from the top few inches of soil.1
  • Extended emergence period: Palmer amaranth must be managed throughout the entire growing season due to its ability to emerge from early May to mid-September.1

Resistance statistics*

  • According to WeedScience.org, herbicide-resistant Palmer amaranth has been discovered in 28 states:* Alabama, Arizona, Arkansas, California, Delaware, Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, Nebraska, New Jersey, New Mexico, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and Wisconsin.
  • Palmer amaranth has developed resistance against numerous herbicide modes of action, including the following: ALS inhibitors (Group 2), dinitroanilines (Group 3), triazines (Group 5), HPPD inhibitors (Group 27), PPO inhibitors (Group 14), long chain fatty acid inhibitors (Group 15), and glyphosate (Group 9).1

*Resistance confirmation does not include all weeds and may vary among different areas of each state.

Identify the differences between common waterhemp and Palmer amaranth

  • Cotyledons of Palmer amaranth are long and narrow, while the cotyledons of waterhemp are not as elongated.2
  • True leaves (the leaves that follow cotyledon leaves) have a small notch, sometimes with a hair, in the tip.2
  • Early identification can allow for early herbicide usage to best control these weeds.2

Corteva Agriscience offers the following weed control solutions:

Corn Herbicides

DuPont Cinch® ATZ herbicide
Durango® DMA® herbicide
Elevore® herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One® herbicide, as part of the Enlist weed control system
FulTime® NXT herbicide
Keystone® LA NXT herbicide
Keystone® NXT herbicide
DuPont Realm® Q herbicide
Resicore® herbicide
SureStart® II herbicide

Soybean Herbicides
Durango® DMA® herbicide
Elevore herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One® herbicide, as part of the Enlist weed control system
DuPont EverpreX® herbicide
FirstRate® herbicide
Sonic® herbicide
Surveil® herbicide
DuPont Trivence® herbicide
DuPontEnlite® herbicide
DuPontAfforia® herbicide
DuPont™ FeXapan™ herbicide Plus VaporGrip® Technology


Sources:

1Legleiter, T., and B. Johnson. 2013. Palmer Amaranth Biology, Identification, and Management. https://www.extension.purdue.edu/extmedia/WS/WS-51-W.pdf
2Jhala, A., 2017. How to Differentiate Common Waterhemp and Palmer Amaranth Seedlings. https://cropwatch.unl.edu/2017/how-differentiate-common-waterhemp-and-palmer-amaranth-seedlings

Afforia, Cinch, DMA, DuPont, Durango, Elevore, Enlist, Enlist Duo, Enlist One, Enlite, EverpreX, FeXapan, FirstRate, FulTime, Keystone, Realm, Resicore, Sonic, SureStart, Surveil and Trivence are trademarks of Dow AgroSciences, DuPont or Pioneer, and their affiliated companies or their respective owners. VaporGrip® is a registered trademark of the Bayer Group. Cinch ATZ, FeXapan herbicide Plus VaporGrip Technology, FulTime NXT, Keystone LA NXT and Keystone NXT are Restricted Use Pesticides. Cinch ATZ, Durango DMA, Elevore, FeXapan herbicide Plus VaporGrip Technology, FulTime NXT, Keystone LA NXT, Realm Q, Resicore, Sonic, SureStart II and Surveil are not registered for sale or use in all states. Keystone NXT is not available for sale, distribution or use in all states. FulTime NXT, Keystone LA NXT, Keystone NXT, Resicore and SureStart II are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. EverpreX is not registered in all states. See your Corteva Agriscience retailer or representative for availability in your state. Enlist Duo and Enlist One herbicides are not registered for sale or use in all states or counties. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your area. Enlist Duo and Enlist One herbicides are the only 2,4-D products authorized for use in Enlist crops. Consult Enlist herbicide labels for weed species controlled. Always read and follow label directions. ©2019 Corteva

FeXapan® herbicide Plus VaporGrip® Technology is a Restricted Use Pesticide. For retail sale to and use only by Certified Applicators and only for those uses covered by the Certified Applicator’s certification. FeXapan herbicide Plus VaporGrip Technology is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions. VaporGrip Technology is a registered trademarks of Monsanto Technology LLC used under license.