Palmer amaranth (Amaranthus palmeri) collected in a cotton field in Concordia Parish, La., has been confirmed as resistant to glyphosate.

The data indicates that 50% of the Palmer amaranth population at this site is approximately 54 times less sensitive to glyphosate compared to the susceptible standard.

Unfortunately, LSU AgCenter weed scientists are following up on many other locations throughout Louisiana where Palmer amaranth or waterhemp, another Amaranthus species, have not been effectively controlled by glyphosate.

Any producer or consultant in Louisiana should be aware of the potentially devastating effect herbicide-resistant weeds can have on their crop.  If you suspect that a weed population is resistant to a herbicide (not just glyphosate, ANY herbicide), please contact your local LSU AgCenter county agent.  LSU AgCenter personnel need to know of these issues so we can help you avoid or mitigate weeds resistance from spreading throughout Louisiana.

If you have any questions, please me at call me at (318) 308-7225 or email me at dstephenson@agcenter.lsu.edu.