Published online by Cambridge University Press: 20 January 2017
An experiment was conducted at four locations in North Carolina in 1996 and 1997 to evaluate weed control and cotton response in conventional-tillage bromoxynil-resistant cotton. Weed management systems evaluated included a factorial arrangement of bromoxynil postemergence (POST) at 0, 0.28, 0.42, or 0.56 kg ai/ha in mixture with pyrithiobac POST at 0, 0.018, 0.032, or 0.072 kg ai/ha. Additional treatments evaluated included trifluralin preplant-incorporated (PPI) plus fluometuron preemergence (PRE). All systems received a postemergence-directed (PDS) treatment of fluometuron plus MSMA. Bromoxynil at 0.42 kg/ha POST followed by (fb) fluometuron plus MSMA PDS controlled common lambsquarters, common ragweed, eclipta, prickly sida, redroot pigweed, spurred anoda; and entireleaf, ivyleaf, pitted, and tall morningglory at least 93%, whereas smooth pigweed and volunteer peanut were controlled 73 and 86%, respectively. Pyrithiobac at 0.036 kg/ha POST fb fluometuron plus MSMA PDS controlled eclipta, common ragweed, prickly sida, redroot, and smooth pigweed, and spurred anoda at least 94%. Volunteer peanut was controlled 84% by pyrithiobac at 0.032 kg/ha, whereas pitted, ivyleaf, and entireleaf morningglory were controlled by 63, 78, and 83%, respectively. Pyrithiobac at 0.072 kg/ha fb fluometuron plus MSMA PDS controlled common lambsquarters 48%. Cotton yield with bromoxynil plus pyrithiobac POST mixtures were equivalent to trifluralin PPI plus fluometuron PRE at three locations and better at the fourth location. Bromoxynil-resistant cotton ‘47’ and ‘57’ had excellent tolerance to all POST herbicide treatments.