Field studies were conducted to determine the tolerance of bromoxynil (3,5-dibromo-4- hydroxybenzonitrile)-resistant cotton (Gossypium hirsutum L. 'BXN 57') and weed control with pyrithiobac {2-chloro-6-[(4,6-dimethoxy-2- pyrimidinyl)thio]benzoic acid}, bromoxynil, pyrithiobac plus MSMA (monosodium methylarsonate), and bromoxynil plus MSMA applied post-emergence to one- to three-leaf cotton. MSMA at 0.6 to 0.8 kg a.i. ha-1 added to pyrithiobac at 70 g a.i. ha-1 or bromoxynil at 0.6 kg a.i. ha-1 increased control of sicklepod [Senna obtusifolia (L.) H. S. Irwin & Barneby], yellow nutsedge (Cyperus esculentus L.), and purple nutsedge (Cyperus rotundus L.) compared with pyrithiobac or bromoxynil applied alone without adversely affecting cotton yield. MSMA did not improve prickly sida (Sida spinosa L.) control by pyrithiobac or bromoxynil.
