Weed management in bromoxynil-resistant Gossypium hirsutum

An experiment was conducted at two locations in Georgia and two locations i n North Carolina during 1994 and 1995 to evaluate weed management in conven tional-tillage bromoxynil-resistant Gossypium hirsutum L. (cotton). The wee d management systems evaluated included different combinations of fluometur on preemergence (PRE), bromoxynil or bromoxynil plus MSMA early post emerge nce (EPOST), bromoxynil postemergence (POST), and cyanazine plus MSMA late post-directed (LAYBY). Fluometuron PRE improved control of Acanthospermum h ispidium DC. (bristly starbur), Cassia occidentalis L. (coffee senna), Chen opodium album L. (common lambsquarters), Desmodium tortuosum (Sw.) DC. (Flo rida beggarweed), Sida spinosa L. (prickly sida), Jacquemontia tamnifolia ( L.) Griseb. (smallflower morningglory), and Anoda cristata (L.) Schlecht. ( spurred anoda), compared to systems that did not use fluometuron PRE. It al so improved G. hirsutum yields at three of four locations. Bromoxynil-conta ining systems provided better weed control and higher G. hirsutum yields th an systems without bromoxynil. Bromoxynil EPOST controlled A. hispidium, C. occidentalis, C. album, D. tortuosum, S. spinosa, J. tamnifolia, and A. cr istata. Control of these species was frequently improved by a second applic ation of bromoxynil POST. Bromoxynil EPOST, POST, or EPOST plus POST did no r control Senna obtusifolia (L.) Irwin and Barneby (sicklepod), but the add ition of MSMA to bromoxynil EPOST improved S, obtusifolia control. Control of all dicotyledonous weeds was improved by a LAYBY treatment of cyanazine plus MSMA, and yields were improved at three of four locations with this tr eatment. Gossypium hirsutum was nor injured by POST treatments of bromoxyni l, and only temporary injury resulted from POST treatments of MSMA.