Sanitation of Field Borders

Nearly everyone who has read this blog, one of many popular press articles, or any of several periodical publications over the past year or two is aware of the problems many growers in Mississippi have with glyphosate-resistant (GR) Palmer amaranth.  Those who have fields that are infested with GR Palmer amaranth are intimately aware of the challenges that this weed presents.  While the primary focus tends to be on controlling this weed in-crop and preventing yield losses from competition and harvest losses, controlling infestations of this weed in non-crop areas should considered as well.  The photos below provide illustrations of Palmer amaranth growing in ditchbanks immediately adjacent to a cotton field.  While the adjacent cotton field is relatively weed free, the Palmer amaranth growing in the ditchbank will produce unfathomable numbers of seeds and potentially spread pollen to Palmer amaranth plants growing in the cotton field.  The Palmer amaranth growing in the ditch is almost assuredly glyphosate-resistant as nearly all other vegetation is dead due to chemical application. 

Research has demonstrated that glyphosate-resistance can be transferred through pollen.  Any female glyphosate-susceptible Palmer amaranth plants growing in the adjacent field that are fertilized with pollen from the glyphosate-resistant plants will produce seeds, a fraction of which will germinate into GR Palmer amaranth plants.  In more cases than one, fields with no past history GR Palmer amaranth have been infested in this manner. 

Bare ground field borders and/or ditchbanks are not always desirable as problems with wind and water erosion can occur.  However, other methods of controlling vegetation in these areas such as routine mowing can be effective.  Keep in mind that if you are mowing field borders and/or ditchbanks with suspected GR Palmer amaranth, cleaning your mower or other implements prior to moving to other areas of the farm will help prevent further spread as seeds were likely dropped onto equipment during these operations.