Glyphosate Resistant Palmer Amaranth on Delmarva

Barbara Scott, Research Associate; bascott@udel.edu & Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Glyphosate-resistant Palmer amaranth has been confirmed on Delmarva. There has been suspicion of glyphosate-resistance in the region, but this is the first year of confirmed resistance. This discovery is not surprising since Palmer amaranth has a tendency to develop resistance. Fields with Palmer amaranth (or suspected Palmer amaranth) should not be treated with glyphosate alone. In soybeans glyphosate should be tank-mixed with an ALS inhibiting herbicide (group 2) or PPO herbicide (group 9).

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