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1 May 2005 Comparison of Trifloxysulfuron and Pyrithiobac in Glyphosate-Resistant and Bromoxynil-Resistant Cotton
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Field studies were conducted in 2000 and 2001 at Rohwer, AR. Trifloxysulfuron (5.3 and 8 g ai/ha) and pyrithiobac (70 g ai/ha) were applied preemergence (PRE) and postemergence (POST) broadcast at the two- to three-leaf (EP) and three- to four-leaf (MP) cotton growth stages. Both materials were also applied POST in combination with glyphosate at 560 g ae/ha or bromoxynil at 560 g ai/ha at both growth stages. Trifloxysulfuron applied EP or MP at 8 g/ha provided greater control of sicklepod and pitted morningglory 28 d after application (DAA) than trifloxysulfuron at 5.3 g/ha or pyrithiobac at 70 g/ha; however, control of prickly sida was greater with pyrithiobac than with trifloxysulfuron at either rate. Glyphosate alone controlled sicklepod, prickly sida, and pitted morningglory greater than 80%. The addition of trifloxysulfuron at 8 g/ha and pyrithiobac at 70 g/ ha increased control of all species over glyphosate alone 28 DAA. Bromoxynil at 560 g/ha controlled pitted morningglory and hemp sesbania at all application timings; however, sicklepod and Palmer amaranth control was less than 50% with bromoxynil applied alone. When bromoxynil was applied in combination with trifloxysulfuron at either rate, control of sicklepod and Palmer amaranth increased to 80% or greater at all application timings. Trifloxysulfuron has the potential to complement both the glyphosate-resistant and bromoxynil-resistant weed control programs by providing control of less susceptible weeds and by providing residual control to both programs.

Nomenclature: Bromoxynil; glyphosate; pyrithiobac; trifloxysulfuron; hemp sesbania, Sesbania exaltata (Raf.) Rybd. ex A.W. Hill #3 SEBEX; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; sicklepod, Senna obtusifolia L. # CASOB; cotton, Gossypium hirsutum L. # GOSHI.

Additional index words: Application timings, bromoxynil-resistant cotton, glyphosate, glyphosate-resistant cotton, residual herbicides, transgenic cotton, trifloxysulfuron sodium.

Abbreviations: BXN, bromoxynil-resistant; DAA, days after application; EP, early postemergence; MP, mid-postemergence; POST, postemergence over-the-top; PRE, preemergence.

JEFFREY W. BRANSON, KENNETH L. SMITH, and JAMES L. BARRENTINE "Comparison of Trifloxysulfuron and Pyrithiobac in Glyphosate-Resistant and Bromoxynil-Resistant Cotton," Weed Technology 19(2), 404-410, (1 May 2005).
Published: 1 May 2005

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