By Mark Loux, Extension Weed Specialist
Palmer amaranth has to date been found in about 11 Ohio counties. Infestations within a county can range from one or more fields or other areas with just a few plants or patches of plants, to the presence of one or more fields with dense populations.
There isn’t any real pattern to the distribution of counties where Palmer has been found. Palmer seed has entered the state via contaminated CREP or wildlife seed that comes from farther west, and via the cotton feed products that are shipped from the south and used in animal operations.
The latter has been the source of our most recent and most severe infestations that occurred in 2015 in northeastern Ohio. While some animal operations are aware of this problem and have stopped using these types of feed products, it’s likely that many other operations or feed dealers have not received information about this issue or modified their practices.
The current Palmer amaranth situation is summarized in a brief video and presentation that can be found on the OSU weed science website – http://u.osu.edu/osuweeds.
We have also posted several fact sheets there that summarize the Palmer problem and current distribution, and provide tools for pigweed identification.