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Agronomic Crops Network

Ohio State University Extension


Screening conservation cover seed for the presence of Palmer amaranth - be informed before you plant

The three primary sources of new Palmer amaranth infestations in Ohio so far have been:  1) presence of Palmer seed in the cotton-based feeds that are brought here from the south; 2) movement of contaminated combines from Palmer-infested areas of the south to Ohio; and 3) presence of Palmer seed in seed for conservation plantings (cover crop/CRP/wildlife/pollinator), which comes from states farther west such as Texas and Kansas.  The latter mechanism has gained some notoriety lately in Iowa, where Palmer amaranth was found in conservation plantings in four counties due to the planting of a likely contaminated seed mix.  We currently know of at least two sites here in Ohio where Palmer was introduced this way, one of which resulted in the contamination of several large fields along the Scioto river, and the other where the producer chose to destroy an extensive new conservation planting rather than risk spread to his crop fields.

Knowing what the sources of palmer amaranth are in theory means that we should be able prevent any additional new infestations.  Wishful thinking, to some degree at least.  Among other things, this would require that every grain or animal producer, feed dealer, and equipment dealer be well-informed enough about this problem to take the appropriate steps: 1) stop importing combines from Palmer-infested areas; 2) stop using cotton-based feed products from these areas; and 3) test all cover crop seed for the presence of Palmer amaranth seed prior to planting.  All of us who provide information know the challenges of getting it to everyone that needs it, not the least of which is refusal of some growers to actually read vehicles such as C.O.R.N.  We can hope that we continue to work toward these solutions before the state gets overrun with Palmer amaranth, but in the meantime here is your chance to be part of the solution now if you are making conservation plantings (assuming that you are one of the informed). 

OSU, NRCS, and ODA all highly recommend that you take advantage of a free service that ODA is providing to have any seed intended for conservation plantings tested for the presence of palmer amaranth seed at no charge.  That’s right – absolutely free, but the process requires an ODA representative to come to the site of seed storage and take an official sample (rather than sending seed directly to ODA).  Contact David Simmons at ODA for more information at 614-728-6410 or  In addition, we suggest thorough scouting of recently established conservation plantings for the presence of Palmer amaranth.  Any plants found should be cut off below soil line, removed from the area, and composted or burned.  Repeated mowing of infested areas between now and frost can also greatly reduce seed production.  Be aware however that where plants are already producing mature seed (small black seed), mowing will cause further dissemination of seed and the possibility of a more widespread  infestation next year, especially where the cover crops do not completely shade the ground.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.