2011 Beltwide: Managing glyphosate-resistant Palmer amaranth using 2,4-D systems in Dow AgroSciences Herbicide Trait Technology (DHT) Cotton In GA, NC, and TN. Culpepper, Steckel, York (UGA, UT, NCSU) Braxton and Richburg (Dow AgroSciences)

York 2010 Hand Weeding

York 2010 Hand Weeding

DHT Cotton In Development by Dow AgroSciences DHT 2,4-D tolerant cotton 2,4-D sensitive cotton

Objective Determine the most effective 2,4-D weed management systems for glyphosate- resistant Palmer amaranth in DHT cotton.

Amaranthus rudis Amaranthus palmeri Tennessee Missouri Illinois Mississippi Georgia S Carolina N Carolina Alabama Louisiana Arkansas Glyphosate-Resistant Pigweed Species Steckel 2010

Tennessee Missouri Illinois Mississippi Georgia S Carolina N Carolina Alabama Louisiana Arkansas Experimental Locations GA Locations: completely resistant populations; NC and TN: mixed population.

Experimental Treatments POST 1 (2-3“ Palmer) 2,4-D 2,4-D + Ignite ® Ignite ® Durango ® 2,4-D + Durango ® POST 2 (4-9” Palmer) 2,4-D 2,4-D + Ignite ® Ignite ® Durango ® 2,4-D + Durango ® Total POST programs Direx ® + MSMA directed to all systems. 2,4-D = Weedar ® 34 oz/A; Ignite ® 29 oz/A; Direx ® 2 pt/A; MSMA 2 lb ai/A. A non-treated control was included. TRT Durango ® - Dow AgroSciences, LLC Direx ® - Dupont Crop Protection Ignite ® - Bayer Crop Sciences LP

Experimental Treatments POST 1 (2-3“ Palmer) 2,4-D 2,4-D + Ignite 2,4-D + Durango POST 2 (4-8” Palmer) 2,4-D 2,4-D + Ignite 2,4-D + Durango Prowl ® and Reflex ® (SE) or Cotoran ® (TN) PRE Direx + MSMA directed to all systems. 2,4-D 34 oz/A; Ignite 29 oz/A; Direx and Cotoran 2 pt/A; MSMA 2 lb ai/A; Prowl H oz. TRT Prowl® BASF Corporation Reflex® Syngenta Crop Protection, Inc.Cotoran® MANA - Makhteshim Agan of North America, Inc.

Planting Dates: May 1 to May 6 First Activating Rainfall: GA1 = 2 d; GA 2 = 11 d; NC: 11 d; TN = 6 d Crop tolerance data not reported as technology still being developed.

Percent Palmer amaranth control just prior to layby. GA1, GA2, TN, NC c 85 b 43 d 86 b 93 a 99 a 2,4-D Dur. + D Durango Ignite Prowl POT 1 POT 2 IG + D 97 a 2,4-D Dur. + D IG + D

Percent Palmer amaranth control just prior to layby in residual systems. GA1, GA2, TN, NC b 99 a Prowl POT 1 POT 2 2,4-D Dur. + D IG + D Reflex or Cotoran 92 b93 b Reflex or Cotoran 93 b 99 a

Durango fb Durango Palmer amaranth control just prior to layby. Macon Co., 2010.

2,4-D fb 2,4-D 2,4-D + Ignite fb 2,4-D + Ignite Palmer amaranth control just prior to layby. Macon Co., 2010.

Prowl fb 2,4-D twice Prowl fb 2,4-D + Ignite twice Palmer amaranth control just prior to layby. Macon Co., 2010.

Percent Palmer amaranth control during late season. GA1, GA2, and NC d 84 c 28 e 90 bc 95 ab 98 a 2,4-D Dur. + D Durango Ignite Prowl POT 1 POT 2 IG + D 97 a Direx + MSMA directed to all systems. 2,4-D Dur. + D IG + D

Percent Palmer amaranth control just prior to layby in residual systems. GA1, GA2, NC Prowl POT 1 POT 2 Direx + MSMA directed to all systems. 2,4-D Dur. + D IG + D Reflex 9695 Reflex 97 98

Seed Cotton Yield. GA1 and GA2, b 855 b 242 c 876 b 1170 a 1115 a 1205 a 2,4-D Dur. + D Durango Ignite Prowl POT 1 POT 2 IG + D 1230 a Direx + MSMA directed to all systems. 2,4-D Dur. + D IG + D

Prowl POT 1 POT 2 Direx + MSMA directed to all systems. 2,4-D Dur. + D IG + D Reflex Reflex Seed Cotton Yield. GA1 and GA2, 2010.

Summary  In total POST sequential systems: Ignite + 2,4-D > Dur. + 2,4-D > 2,4-D > Ignite > Dur.  In 2,4-D systems, residual applications of Prowl were as effective as Reflex or Cotoran. All programs provided at least 93% control.  Control of 99% only noted with systems including sequential Ignite + 2,4-D applications.  Cotton yields greater with residual systems and in the total POST system with Ignite + 2,4-D.

Conclusion Numerous weed management systems in DHT Cotton will effectively manage glyphosate-resistant Palmer amaranth

Concerns  Making it to 2015 or when commercialized?  Sustainability of Ignite?  Off target movement of 2,4-D research to address this concern is in progress

2,4-D Ester 2,4-D Amine New Formulation N

S SESW EW N NENW Potted cotton plants placed in all 5, 10, 20, 40, 80 and 160 ft 4 plants per station Volatility distance – (plants placed in field after drift pots were removed)

Temperature (F) Sept 9-11 Application

Visual Injury 27 DAA from 2,4-D Volatility, October 6, 2010 Error bar is 1 Std error of mean Averaged across directions Entire 48 hrs

Volatility Injury to Cotton: Tunnel/Dome Data John Richburg 2010 Project Review November, 2010

Visual Injury 27 DAA from 2,4-D Volatility under Tunnels (October 6, 2010) Entire = 48 hrs T1 = 1 st 24 hrs T2 = 2 nd 24 hrs

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