Palmer amaranth (Amaranthus palmeri) is known by some as “careless weed,” as negligent management quickens its already hasty invasiveness. It can also be incredibly difficult to control — a characteristic that has only worsened in the last few years, as its resistance to multiple-herbicide groups continues to evolve.
According to The International Survey of Herbicide Resistant Weeds, palmer amaranth was first found to have resistance to glyphosate in Georgia in 2005. In 2008, multiple resistance was found in cropland in Mississipi, with plants resistant to both ALS inhibitors and EPSP synthase inhibitors. In 2009, plants with resistance to three herbicide groups (ALS inhibitors, photosystem II inhibitors and HPPD inhibitors) were found in Kansas.
Pamer amaranth paints a painful picture of herbicide resistance for much of the States, but there is still so much we can learn from its invasion as Jason Norsworthy, professor at the University of Arkansas, explains in the following video.