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Taproot of Palmer Amaranth Allen 2009 Living with Palmer amaranth in Georgia cotton
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Georgia counties confirmed to be infested with glyphosate-resistant Palmer amaranth. 2004 – 1 county 2005 – 2 counties 2006 – 7 counties 2007 – 10 counties 2008 – 18 counties
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What makes Palmer a super weed? 1. Herbicide resistance? 2. Growth rate? 3. Large stature? 4. Competitive ability? 5. Reducing harvest efficacy? 6. Seed production? 7. Rapid spread?
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230 K 250 28 K 309 K Giant ragweed 450 K Number of Seed Produced per Plant Glyphosate-Resistant Weeds in US Ragweed = Harrison et al. 2001; johnsongrass = Warwick and Black (1983); horseweed = Regehr and Bazzaz (1979); waterhemp = Nordby and Hartzler (2004); Palmer amaranth = Macrae et al (2009). Johnson -grass HorseweedWaterhempPalmer amaranth
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Weakness of a super weed? 1. Emergence depth! 2. Seed life longevity? 3. Light requirement for emergence. Economic survival will depend on managing the seedbank!!!!
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Progress during 2009? 1. Cover crops 2. Tillage 3. Tillage + plus cover crops 4. Herbicides
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Palmer requires a significant amount of sunlight to emerge!!
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Staple + Reflex + Direx PRE Roundup WMax + Parrlay POST Direx + MSMA Layby No deep tillage No cover crop No deep tillage Rye cover crop Palmer amaranth response to cover crops. Macon County, GA. 2009.
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Significant Residue 2009 rye emerging through 2008 rye residue
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Management Program? 1. Cover crops 2. Tillage 3. Deep tillage and cover crops?
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No Deep TillageDeep Turn No Herbicide Treatment Number of Palmer Amaranth Plants During Early Season. Macon Co., Georgia 2008.*
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Palmer amaranth seedling density
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Influence of burial depth on Palmer amaranth emergence Keeley et al. (1987) reported 36-44% emergence at 0-1”, 7% at 2”, and 2% at 3”.
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Most Palmer amaranth emerges from top inch
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Palmer amaranth seed longevity *Data are combined over 4 burial depths: 0.5”, 1”, 4”, 16”
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Staple + Reflex + Direx PRE Roundup WMax + Parrlay POST Direx + MSMA Layby No deep tillage No cover crop Deep tillage No cover crop Palmer amaranth response to deep tillage. Macon County, GA. 2009.
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Management Program? 1. Cover crops 2. Tillage 3. Deep tillage and cover crops?
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Most Palmer amaranth emerges from top inch
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Staple + Reflex + Direx PRE Roundup WMax + Parrlay POST Direx + MSMA Layby No deep tillage No cover crop Deep tillage Rye cover crop Palmer amaranth response to deep tillage and cover crops. Macon County, GA. 2009.
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65 b Drill Middle percent 47 c46 c Reduction in Palmer emergence as affected by deep turning/cover crop residue at 16 DAP. Macon Co., GA 2009. Rye coverDeep turn + Rye cover 96 a 94 a 50 c Deep turn Drill Middle Drill Middle Non-treated: 620 plant/m2. No herbicides applied.
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81 b No deep turn No Cover Deep turn No cover Rye 7 foot when killed, rolled, planted. Deep turn 12 inch in previous fall. Herbicide program: Direx + Reflex + Staple PRE; RU + Parrlay POST, Direx + MSMA at layby. percent 63 c 80 b 98 a GR Palmer amaranth control at harvest with Roundup-based systems. Macon Co., GA 2009. No deep turn Rye Cover Deep turn Rye Cover
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1627 b No deep turn No Cover Deep turn No cover Rye 7 foot when killed, rolled, planted. Deep turn 12 inch in previous fall. Herbicide program: Direx + Reflex + Staple PRE; RU + Parrlay POST, Direx + MSMA at layby. 1298 d 1524 bc 2078 a Seed cotton yield (lb/A) with Roundup-based systems. Macon Co., GA 2009. No deep turn Rye Cover Deep turn Rye Cover
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Developing Integrated Programs Makes growers nervousEasy to adopt
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Potential Benefits 1.Labor, erosion, etc.. 2.Prevents GR horseweed 3.Prevents GR ryegrass 4.Reduces Palmer 80%+ 5.Moisture conservation 6. herbicides overtime 7.Higher yields??????
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Management Program? 1. Tillage 2. Cover crops 3. Deep tillage and cover crops? 4. Herbicide programs
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Dryland Conservation Tillage Prowl + Reflex PRE Roundup + Dual POST Diuron + MSMA PD Prowl + Reflex PRE Ignite + Dual POST Diuron + MSMA PD
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Ignite 23 oz/A APPLY 29 OZ OF IGNITE PRIOR TO 3 INCH PALMER WATER VOLUME AND NOZZLE TYPE IS CRITICAL
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No recommendation on handout for RR dryland in conservation tillage? 1. Run aggressive RR program 2. Plant rye to produce tremendous cover 3. Hand weed!!!
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Other Information 1. Burndown 2. Acetochlor 3. PPI herbicide applications 4. Palmer seedbank
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Controlling 5 inch Glyphosate-Resistant Palmer amaranth at Burndown. Macon Co., GA 2008.* 0 c 87 b 94 a 58 b RoundupParazone 1.33 pt 70 b Parazone + 2,4-D (1.5 pt) Parazone + Clarity (8 oz) Parazone + Diuron (1.8 pt)
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Palmer control at planting, burndown applied 17 d earlier. Macon Co., GA 2009. 90 b Valor preplant Direx preplant 99 a
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Change in Valor Label? 1. Apply Valor and then run strip tillage: 7 day plant back
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HOW EFFECTIVE ARE PREPLANT APPLICATIONS?
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Change in Valor Label? When you have greater than 30% crop residue: 2. Run strip tillage and then spray Valor: Label says 21 day plant back
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TREFLAN PPIPRE
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REFLEX PPIPRE
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Percent GR Palmer amaranth control 28 DAP. Macon Co., GA. 2009. 81 a Prowl 51 b 46 b 86 a Treflan PRE APPLICATIONS RAIN 12 d after planting PRE PPI PRE PPI
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Palmer control from acetochlor, S-metolachlor, and metolachlor. Macon Co., GA 2009. 50 c acetochlor (1.13 lb) 80 a S-metolachlor (Dual Mag, 0.95 lb) metolachlor (Parrlay, 1.3 lb) 77 a No Palmer up at time of application. Layby of RU + Direx applied 19 d after POST.
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Tobacco:Spartan + Yellow 2008 Soybean- Roundup 2008 A.C.York, 2009
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Palmer amaranth seedbank – it is the key! YEAR 1: 5 Palmer females escape Produce 2,000,000 seeds in cotton (50% germ) YEAR 2: Weed program = 99.9% control 1,000 plants per acre left at harvest 400 female plants/A 160,000,000 seeds produced in cotton (50%) YEAR 3: Weed program 99.9% control 80,000 plants per acre left at harvest 32,000 female plants/A = 1.28 X 10 10 seed/A
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Integrating cover crop residue and moldboard plowing into glyphosate-resistant Palmer amaranth management programs will be key! QUESTIONS OR COMMENTS?
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