Palmer Amaranth Breaking Through Crop Canopies
LARRY STECKEL
JACKSON, TENNESSEE
Questions continue on what to do with late season pigweed breaking through the crop canopy. Most questions have been in cotton where escaped pigweed are more visible. More questions recently have been in soybean as escapes are poking up through the canopy (picture 1).
In cotton the best recommendation has been to use a cultivator or a hooded application of paraquat to try to take out Palmer amaranth between the rows. In narrow row soybean there is really no good answer.
Escaped pigweed at this point cannot be controlled with any POST applied herbicide. This in part due to the Palmer amaranth in these fields often having some level of resistance to dicamba and glufosinate. Even if the Palmer amaranth is susceptible to glufosinate or dicamba it has become too large to be controlled. Moreover, R4 and R5 glufosinate applications are not labeled and may injure the soybean crop.
At this point it is best to wait until soybean desiccation time and apply paraquat as a harvest aid to dry down the pigweed and help mitigate Palmer amaranth seed production. In fields heavily infested with pigweed this year consider rotating to corn next year. ∆
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LARRY STECKEL
UNIVERSITY OF TENNESSEE
Picture 1. Palmer amaranth breaks through soybean canopy
LINK: https://news.utcrops.com/2026/07/palmer-amaranth-breaking-through-crop-canopies/
