Palmer amaranth in Iowa, but not officially

Rich Keller, 01/10/2013


It is stranger than strange that there is no official confirmation that Palmer amaranth is present in Iowa, especially since at least one Extension weed management specialist admits to identifying the weed in Southwest Iowa 15 years ago.

Palmer amaranth has been confirmed in Wisconsin, Illinois, Missouri, Kansas, Nebraska, Indiana, Ohio and Southern Michigan. That leaves Iowa as a hole in the middle of the northern Palmer amaranth presence map.

Bob Hartlzer, Iowa State University Extension weed management specialist, told Tim Hoskins of Iowa Farmer Today that his identification 15 years ago for a local agronomist didn’t seem that important, and at the time, he thought the weed had officially been identified in Iowa and listed by the proper officials.

The weed is in the pigweed family and a cousin to waterhemp. It has really become a problem in Southern states where glyphosate-resistant plants have exploded. The weed, up until now, has been best suited for rapidly reproducing in midsouth and southern climates.

Mike Owen, ISU Extension weed management specialist, agrees with Hartlzer that Palmer amaranth is almost for sure in some fields of the state each spring and summer, Hoskins discovered.

To set the state record straight, Owen is asking anyone finding a weed that doesn’t appear to match waterhemp or another pigweed species to send a one-plant sample of the weed they find to him this spring or summer. It would probably be best express mailed to Michael D.K. Owen, 3218 Agronomy Hall, Ames, IA 50011 with contact information of the person sending it and site information where the weed was found.

Hartlzer said Palmer amaranth resembles waterhemp. “However, the seed heads are very sharp and could puncture skin,” Hartlzer told Hoskins. Read the Iowa State University pigweed identification brochure.




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