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Glufosinate resistant palmer amaranth confirmed in Missouri

Glufosinate resistant palmer amaranth has been found in the Missouri bootheel.

University of Missouri Integrated Pest Management Coordinator Mandy Bish tells Brownfield the discovery is frustrating, but not surprising.

“We have a limited number of post-emergent herbicide options for control of pigweeds like palmer amaranth and waterhamp. As Dr. Bradley, our state weed scientist, has said multiple times if we are overusing them then we are going to break the system, so it seems we have officially broken glufosinate in at least one palmer population in Missouri.”

This marks the fourth confirmed herbicide family that palmer amaranth has shown resistance to in Missouri crops; ALS inhibitors (group 2), PPO inhibitors (group 14), ESPS inhibitors (group 9) and now glutamine synthetase inhibitors (group 10). Outside of Missouri palmer amaranth has confirmed resistance to nine different classes of herbicides (2, 3, 4, 5, 9, 10, 14, 15 and 27).

MU Extension Weed Scientist Dr. Kevin Bradley encourages growers to use herbicides with multiple modes of action and to consider cultural practices for weed control like narrow row spacing and cover crops.