Management of Palmer Amaranth in Cotton Using Cover Crops and Herbicides

Glyphosate-resistant (GR) weeds continue to be the most problematic weeds to control in most cropping systems in the Mid-South region of the United States.  There are now no less than ten GR weed species in the Mid-South and no less than six confirmed species GR species in Tennessee. Of these, Palmer amaranth (Amaranthus palmeri S. Wats) is the most difficult of to control.  Successful management schemes for controlling GR weeds include the use of PRE-emergence (PRE) herbicides, overlaying residual chemistries, making timely applications of POST-emergence (POST) herbicides and integrating cultural control methods. Unfortunately, rainfall to activate PRE’s and residual herbicides can be sporadic at best in Tennessee.  Therefore, timely applications of POST herbicides are essential for many producers to grow a profitable crop.  This heavy reliance on POST herbicide applications increases selection pressure and the possibility of herbicide resistance.  Integrating cultural control methods, such as cover crops, is a viable option available for area producers to reduce selection pressure and gain early season weed control.  Unfortunately, research on integrating herbicides with a cover crop system is limited.  Therefore, this trial was conducted to evaluate the effectiveness of integrating high residue cover crops in to a glyphosate and glufosinate based weed control system in cotton.