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Palmer Amaranth – A Plant Form of Cancer (07/23/15)

In the very small chance that readers have not heard of Palmer amaranth nor heard of the devastation it can inflict, here is a summary:

Palmer Amaranth – A Plant Form of Cancer

In the very small chance that readers have not heard of Palmer amaranth nor heard of the devastation it can inflict, here is a summary:

Palmer amaranth is a C-4 carbon assimilating species, thrives in hot environments, and can survive, establish, and spread in the northern latitude of the U.S., including the northern plains. It was introduced to some areas (e.g. Michigan) through the spread of manure from dairy cows that were fed cotton-seed screening that included Palmer amaranth seed as a feed supplement.

Palmer amaranth seed could easily be brought into ND through various ways including:

  1. Custom combines moving south to north into ND.
  2. Contaminated crop seed used for seeding.
  3. Transportation of contaminated hay and forage across state borders.
  4. Food source for birds and bird migration. Watch for amaranth plants under power lines and anywhere birds might land.
  5. Water flow - Palmer amaranth seed is small, light, and floats in water which makes water movement a primary source of spread. Waterhemp, another pigweed species, has spread in ND through water flow, especially in drown-out areas where no crop competition allows weeds to grow uninhibited.

 Below are reasons why it is being called “Satan” and why growers should quickly destroy any plants found.

  1. Biotypes of this weed are resistant to one or more of the following herbicide site of action groups:        ALS (2), atrazine (5), glyphosate (9), and HPPD inhibitor (27) herbicides, leaving very few herbicide options available for management.
  2. One of the fastest weed growth rates known - >2 inches/day.
  3. Long emergence pattern from mid-May through August.
  4. Can exploit even slight canopy openings.
  5. Produces from 1 to 1.8 million seeds/plant.
  6. Seed is short-lived and only 2% of seed is viable after 6 years but the sheer number of seeds produced by a female plant makes eradication difficult once established.
  7. Female plants can grow to more than 10 feet tall with a 5-6 inch stem girth and seed heads more than 1 foot in length. Male plants are small and generally non-competitive.
  8. Can cause 78% yield loss in soybean, 91% in corn.

 Palmer amaranth’s prolonged emergence period, rapid growth rate, prolific seed production, and propensity to evolve herbicide resistance quickly makes this the most pernicious, noxious, and serious weed threat that ND farmers have ever faced.

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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