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.
Nomenclature: Bromoxynil; fluometuron; MSMA; pyrithiobac; trifluralin; common lambsquarters, Chenopodium album L. #3 CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; eclipta, Eclipta prostrata L. # ECLAL; entireleaf morningglory, Ipomoea hederaceae var. integriuscula Gray # IPOHG; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. IPOHE; pitted morningglory, Ipomoea lacunosa L. # IPOLA; peanut, Arachis hypogaea L.; prickly sida, Sida spinosa L. # SIDSP; redroot pigweed, Amaranthus retroflexus L. # AMARE; smooth pigweed, Amaranthus hybridus L. # AMACH; spurred anoda, Anoda cristata (L.) Schlecht. # ANVCR; tall morningglory, Ipomoea purpurea (L.) Roth. # PHBPU; cotton, Gossypium hirsutum L., ‘BXN 47’, ‘BXN 57’.
Additional index words: Cotton yield, crop tolerance, cyanazine, herbicide-resistant crops.
Abbreviations: DAT, days after treatment; fb, followed by; PDS, postemergence directed; POST, postemergence; PPI, preplant incorporated; PRE, preemergence.