Home 5 Ag Stories Weed Scientists Have Discovered Palmer Amaranth Lurking in Iowa

Weed Scientists Have Discovered Palmer Amaranth Lurking in Iowa

by Whitney Flach

This summer, Palmer amaranth infestations have been identified in two Iowa counties, Muscatine and Madison. Both infestations were found in Conservation Reserve Program acres that were newly seeded this spring with a diverse mix of forbs and grasses, according to an Iowa State University bulletin.

Known as Palmer amaranth or pigweed, the plant is a legitimate threat in the Midwest. Aaron Hager, weed scientist from the University of Illinois says, “While most concern focuses on Palmer amaranth in agronomic cropping systems, keep in mind that Palmer amaranth also can become established in non-crop areas,” Hager cautioned in a recent news release. He added, “It’s a tough situation, but by keeping an eye on these plantings, the risks can be minimized.” Pigweed populations that set seed in non-crop environments can easily find their way into production fields. Palmer amaranth grows fast and is extremely competitive within Midwest cropping systems. Soybean yield losses approaching 80%, and corn yield losses exceeding 90% have been reported in the peer-reviewed scientific literature. Earlier Midwest Palmer amaranth infestations, are believed to have been introduced from cottonseed used for animal feed, commercial grain transportation or machinery. Iowa State agronomists said, they’ve found no evidence that cover crop seed has been the source of Palmer amaranth infestations.

The location in Muscatine County, was seeded to a wildlife habitat mix, and the Madison County site was seeded to pollinator habitat. Individuals made both discoveries with significant experience working with and identifying weeds. A release stated, “We are confident that the Palmer amaranth was not in these fields prior to this year due to the low plant numbers and the random distribution of plants, rather than occurring in patches.”

“Regardless of how and where a Palmer amaranth population becomes established, it remains critically important to take all appropriate steps to prevent established Palmer amaranth plants from producing seed,” Hager said. If Palmer amaranth is identified, please take steps to remove these plants before viable seeds are produced on the female plants. Plants should be severed at or below the soil surface and carried out of the field. Severed plants can root at the stem if left on the soil surface, and plants can regenerate from stems severed above the soil surface. Scouting new plantings should be a standard practice, especially in mid-late summer when it will be easier to identify the obnoxious intruder.

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