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Palmer Amaranth - Update (07/09/15)

There was a concerted effort this past winter meeting season from NDSU Extension specialists and agents to bring the issue to growers of Palmer amaranth movement northward toward North Dakota.

Palmer Amaranth - Update

There was a concerted effort this past winter meeting season from NDSU Extension specialists and agents to bring the issue to growers of Palmer amaranth movement northward toward North Dakota. Excellent identification, biology, and management resources were made available as hand-out material. Information on Palmer amaranth was shown at winter meetings and in pesticide recertification training sessions. Palmer amaranth was designated as “Weed of the Year” again for the second year in a row (2014-2015) because of our objective to quickly identify and kill any infestations that may occur (see pages 128-129 in the 2015 ND Weed Control Guide).

As North Dakota and Minnesota are the last remaining uninfested and unadulterated states in the Midwest, lets summarize where we stand……NO Palmer amaranth yet!

Several folks have sent photos the past couple of weeks for help to accurately ID pigweed species. We have also visited several sites where consultants and agronomist thought that Palmer amaranth have arrived. In all cases, it was waterhemp and not Palmer amaranth. Waterhemp plants in photos had long leaf petioles which caused the confusion – but remember Palmer amaranth has leaf petioles that are longer than the length of the leaf and many times twice as long as the leaf. Plants in photos also showed shiny and narrow leaves which are characteristic of waterhemp. Palmer amaranth has round to oval shaped leaves more similar to redroot pigweed. From now and throughout the rest of the season, Palmer amaranth plants grow quite tall and in addition to long leaf petioles, plants will have 1 to 2 foot long, unbranched, terminal seed heads, and spiny bracts on the stem of female plants. Below are a couple of good web sited with pictures and information:

https://www.extension.purdue.edu/extmedia/WS/WS-51-W.pdf

http://www.extension.iastate.edu/CropNews/2013/0604hartzler.htm

Summary: Be on the lookout – it can show up at most any expected and unexpected place. Contact us if you find this vile, cunning, doppelganger of redroot pigweed and waterhemp.

 

Rich Zollinger

Extension Weed Specialist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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