Taproot of Palmer Amaranth Allen 2009 Living with Palmer amaranth in Georgia cotton

Georgia counties confirmed to be infested with glyphosate-resistant Palmer amaranth – 1 county 2005 – 2 counties 2006 – 7 counties 2007 – 10 counties 2008 – 18 counties

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?

230 K 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

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!!!!

Progress during 2009? 1. Cover crops 2. Tillage 3. Tillage + plus cover crops 4. Herbicides

Palmer requires a significant amount of sunlight to emerge!!

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

Significant Residue 2009 rye emerging through 2008 rye residue

Management Program? 1. Cover crops 2. Tillage 3. Deep tillage and cover crops?

No Deep TillageDeep Turn No Herbicide Treatment Number of Palmer Amaranth Plants During Early Season. Macon Co., Georgia 2008.*

Palmer amaranth seedling density

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”.

Most Palmer amaranth emerges from top inch

Palmer amaranth seed longevity *Data are combined over 4 burial depths: 0.5”, 1”, 4”, 16”

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

Management Program? 1. Cover crops 2. Tillage 3. Deep tillage and cover crops?

Most Palmer amaranth emerges from top inch

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

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 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.

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 No deep turn Rye Cover Deep turn Rye Cover

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 d 1524 bc 2078 a Seed cotton yield (lb/A) with Roundup-based systems. Macon Co., GA No deep turn Rye Cover Deep turn Rye Cover

Developing Integrated Programs Makes growers nervousEasy to adopt

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??????

Management Program? 1. Tillage 2. Cover crops 3. Deep tillage and cover crops? 4. Herbicide programs

Dryland Conservation Tillage Prowl + Reflex PRE Roundup + Dual POST Diuron + MSMA PD Prowl + Reflex PRE Ignite + Dual POST Diuron + MSMA PD

Ignite 23 oz/A APPLY 29 OZ OF IGNITE PRIOR TO 3 INCH PALMER WATER VOLUME AND NOZZLE TYPE IS CRITICAL

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!!!

Other Information 1. Burndown 2. Acetochlor 3. PPI herbicide applications 4. Palmer seedbank

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)

Palmer control at planting, burndown applied 17 d earlier. Macon Co., GA b Valor preplant Direx preplant 99 a

Change in Valor Label? 1. Apply Valor and then run strip tillage: 7 day plant back

HOW EFFECTIVE ARE PREPLANT APPLICATIONS?

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

TREFLAN PPIPRE

REFLEX PPIPRE

Percent GR Palmer amaranth control 28 DAP. Macon Co., GA a Prowl 51 b 46 b 86 a Treflan PRE APPLICATIONS RAIN 12 d after planting PRE PPI PRE PPI

Palmer control from acetochlor, S-metolachlor, and metolachlor. Macon Co., GA 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.

Tobacco:Spartan + Yellow 2008 Soybean- Roundup 2008 A.C.York, 2009

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 seed/A

Integrating cover crop residue and moldboard plowing into glyphosate-resistant Palmer amaranth management programs will be key! QUESTIONS OR COMMENTS?