Palmer amaranth update – it is not good news

You may be sick of hearing about Palmer amaranth already but get used to it.  Mark Loux, OSU Weed Science Specialist shares a few things to be aware of right now:

There appears to be somewhat of an epicenter of new Palmer amaranth infestations in an area southwest of Columbus, bordered roughly by Midway on the north and Washington CH on the south.  There is a dairy in the area that has been using cottonseed products for feed and a local grower has been transporting these products to the dairy from somewhere in the south.  There are Palmer amaranth plants in a number of fields in the area and also on the grounds of the dairy.  One grower contacted us after finding it in his field, and has since been busy digging out and removing plants.  If you farm in this area, be sure to take some time to scout fields and roadsides now for Palmer amaranth and take appropriate action as necessary.  Palmer amaranth is a prohibited noxious weed in Ohio.

The Palmer amaranth plants we have found so far do not appear to have formed mature seed yet, which would be indicated by the presence of small black seeds.  We’re not sure why but one hypothesis is that the residual from pre-emergence herbicides prevented the early flushes of Palmer amaranth, and the later-emerging plants are still reaching maturity.  This means that there is still time to dig up or chop down plants, and ideally also remove them from the field.  Once mature seed has formed, the strategy changes from plant removal to isolation and remediation of infestations.

The OSU weed science website (agcrops.osu.edu/specialists/weeds) has information on Palmer amaranth, including a short video on identification and a new 11-minute video that explains the risk from this weed.  Similar information can be found on the Purdue weed science website.  If you find plants that you believe to be Palmer amaranth, please contact us to confirm identification, and at that point we can also offer more guidance for management of new infestations.

For more detailed information, visit the Darke County OSU Extension web site at www.darke.osu.edu, the OSU Extension Darke County Facebook page or contact Sam Custer, at 937.548.5215.