Weed Management in Transgenic and Non-Transgenic Cottom (Gossypium hirsutum) in the Texas High Plains

B. Scott Asher, J. Wayne Keeling, Peter A. Dotray

Abstract


Field experiments conducted at the Texas Agricultural Experiment Station near Lubbock in 1996 and 1997 evaluated Palmer amaranth (carelessweed), devil’s-claw, and barnyardgrass control in cotton.  Weed management systems included the following soil-applied treatments:  Treflan (trifluralin) preplant incorporated (PPI), Caparol (prometryn) preemergence (PRE), or Treflan followed-by (fb) Caparol.  Foliar treatments included Roundup Ultra (glyphosate) postemergence (POST) and postemergence-directed (PDIR) in Roundup Ready (Roundup-tolerant) cotton, Buctril (bromoxynil) POST in BXN (Buctril-tolerant) cotton, and Staple (pyrithiobac) POST in conventional (non-transgenic) cotton.  Each of these foliar treatments was also used following the soil-applied treatments.  In 1996, Roundup Ultra following any soil-applied herbicide treatment provided season-long Palmer amaranth control.  Due to multiple Palmer amaranth flushes in 1997, two Roundup Ultra applications were required for control similar to 1996 in all Roundup Ultra-treated plots except for Treflan fb Caparol fb Roundup Ultra, which required only one Roundup Ultra application.  Staple following any soil applied herbicide treatment controlled Palmer amaranth at least 96% at the end of the season in 1996, but control was only 75 to 94% at the end of the season in 1997.  Neither Buctril nor Staple applied alone controlled Palmer amaranth, but when applied following soil-applied herbicides, control was at least 72% at the end of the season each year.  Roundup Ultra or Buctril applied alone controlled devil’s-claw at least 92% in both years.  Staple applied alone controlled devil’s-claw 70% and 92% in 1996 and 1997, respectively.  Roundup Ultra was the only POST herbicide that controlled barnyardgrass and was the most consistent POST herbicide in both years.  All POST herbicides improved weed control as compared to soil-applied herbicides used alone.  Plots treated with Roundup Ultra alone yielded more than plots that received a soil-applied only treatment and yielded similar to plots that received a soil-applied fb foliar treatment.

Keywords


barnyardgrass; Buctril; BXN cotton; Caparol; Devil's-claw; Palmer amaranth; Roundup Ultra; Roundup Ready cotton; staple; Treflan

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