Bob Hartzler Describes Palmer Amaranth

Stopping the Spread of Palmer Amaranth, an Aggressive, Competitive Weed

August 15th, 2016

AMES, Iowa — Palmer amaranth is an invasive weed that is native to the southwestern United States. Over the last three years, however, the weed has made its way into Iowa and has been identified in at least nine counties, most recently in Madison, Clayton, Washington and Crawford Counties.

Palmer amaranth is related to waterhemp, a common weed found across Iowa. In addition to traditional weedy traits, the characteristic that makes those two weeds unique, and hard to manage, is their ability to evolve resistance to herbicides, according to Bob Hartzler, professor of agronomy and extension weed specialist at Iowa State University.

“Both weeds are adapted to a production system that relies on herbicides,” said Hartzler. “Waterhemp is a relatively non-competitive weed so many farmers have learned to accept lower levels of weed control. If Palmer amaranth spreads across the state and farmers try to manage it like they do waterhemp, it will have a huge negative economic impact.”

The known cases of Palmer amaranth in the state are isolated right now, and keeping it from spreading is the immediate need.

“Palmer amaranth built its reputation on how it devastated the cotton industry in the south after the near complete reliance on glyphosate in Roundup Ready cotton,” Hartzler said. “The best way to manage it is to slow its spread into and within the state. This is a highly competitive weed that has adapted to our current management system for corn and soybean crops.”

For more go to: http://www.cals.iastate.edu/news/releases/stopping-spread-palmer-amaranth-aggressive-competitive-weed

Contact Bob Hartzler if you think you've identified a Palmer Amaranth weed in Iowa at (515) 294-1164, [email protected].