Palmer Amaranth found in South Dakota

BROOKINGS — SDSU weed science team confirms the finding of Palmer Amaranth (Amaranthus palmeri) in South Dakota. The Palmer Amaranth plants were found in a sunflower field in Buffalo County next to the Missouri River in central South Dakota.

“Palmer Amaranth is a vigorous weed that is a member of the pigweed family that also includes common waterhemp, redroot pigweed, prostrate pigweed and others,” said Paul O. Johnson, SDSU Extension Weed Science Coordinator.

He explained that Palmer Amaranth is native to the southwestern United States. It is an annual and only reproduces by seed however, it is not known if South Dakota has a long enough growing season for Palmer Amaranth to produce viable seed in South Dakota. “If seed is produced, it is not known if the seed will be able to overwinter this far north, although plants have established in Pennsylvania, Iowa, and Michigan,” Johnson said. “The area it was found, next to the Missouri River, may provide a favorable microclimate for overwintering.”

A major concern is that Palmer Amaranth in other states has shown resistance to several different mode-of-action herbicides.

The SDSU weed science team will continue to monitor the state for more reports of Palmer Amaranth to better understand this weed’s distribution and determine the extent and consequences of this weed problem in South Dakota. The SDSU weed science team is made up of Dr. Sharon Clay Professor of Plant Science, Dr. Gary Larson Professor of Natural Resource Management, Darrell Deneke, SDSU Extension IPM Coordinator, and Paul O. Johnson SDSU Extension Weed Science Coordinator.

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