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Taproot of Palmer Amaranth

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

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

  2. 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

  3. What makes Palmer a super weed? • Herbicide resistance? • Growth rate? • Large stature? • Competitive ability? • Reducing harvest efficacy? • Seed production? • Rapid spread?

  4. Number of Seed Produced per PlantGlyphosate-Resistant Weeds in US 450 K 309 K 230 K 28 K 250 Giant ragweed Johnson-grass Horseweed Waterhemp Palmer amaranth 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).

  5. Weakness of a super weed? • Emergence depth! • Seed life longevity? • Light requirement for emergence. Economic survival will depend on managing the seedbank!!!!

  6. Progress during 2009? • Cover crops • Tillage • Tillage + plus cover crops • Herbicides

  7. Palmer requires a significant amount of sunlight to emerge!!

  8. Palmer amaranth response to cover crops. Macon County, GA. 2009. No deep tillage No cover crop No deep tillage Rye cover crop Staple + Reflex + Direx PRE Roundup WMax + Parrlay POST Direx + MSMA Layby

  9. Significant Residue 2009 rye emerging through 2008 rye residue

  10. Management Program? • Cover crops • Tillage • Deep tillage and cover crops?

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

  12. Palmer amaranth seedling density

  13. 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”.

  14. Most Palmer amaranth emerges from top inch

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

  16. Palmer amaranth response to deep tillage. Macon County, GA. 2009. No deep tillage No cover crop Deep tillage No cover crop Staple + Reflex + Direx PRE Roundup WMax + Parrlay POST Direx + MSMA Layby

  17. Management Program? • Cover crops • Tillage • Deep tillage and cover crops?

  18. Most Palmer amaranth emerges from top inch

  19. Palmer amaranth response to deep tillage and cover crops. Macon County, GA. 2009. No deep tillage No cover crop Deep tillage Rye cover crop Staple + Reflex + Direx PRE Roundup WMax + Parrlay POST Direx + MSMA Layby

  20. Reduction in Palmer emergence as affected by deep turning/cover crop residue at 16 DAP. Macon Co., GA 2009. 96 a 94 a percent 65 b 50 c 47 c 46 c Drill Drill Drill Middle Middle Middle Deep turn Rye cover Deep turn + Rye cover Non-treated: 620 plant/m2. No herbicides applied.

  21. GR Palmer amaranth control at harvest with Roundup-based systems. Macon Co., GA 2009. 98 a 80 b 81 b 63 c percent No deep turn No Cover Deep turn No cover No deep turn Rye Cover Deep turn Rye 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.

  22. Seed cotton yield (lb/A) with Roundup-based systems. Macon Co., GA 2009. 2078 a 1627 b 1524 bc 1298 d No deep turn No Cover Deep turn No cover No deep turn Rye Cover Deep turn Rye 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.

  23. Developing Integrated Programs Makes growers nervous Easy to adopt

  24. Potential Benefits • Labor, erosion, etc.. • Prevents GR horseweed • Prevents GR ryegrass • Reduces Palmer 80%+ • Moisture conservation • herbicides overtime • Higher yields??????

  25. Management Program? • Tillage • Cover crops • Deep tillage and cover crops? • Herbicide programs

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

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

  28. No recommendation on handout for RR dryland in conservation tillage? • Run aggressive RR program • Plant rye to produce tremendous cover • Hand weed!!!

  29. Other Information • Burndown • Acetochlor • PPI herbicide applications • Palmer seedbank

  30. Controlling 5 inch Glyphosate-Resistant Palmer amaranth at Burndown. Macon Co., GA 2008.* 94 a 87 b 70 b 58 b 0 c Roundup Parazone 1.33 pt Parazone + 2,4-D (1.5 pt) Parazone + Clarity (8 oz) Parazone + Diuron (1.8 pt)

  31. Palmer control at planting, burndown applied 17 d earlier. Macon Co., GA 2009. 99 a 90 b Direx preplant Valor preplant

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

  33. HOW EFFECTIVE ARE PREPLANT APPLICATIONS?

  34. 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

  35. TREFLAN PRE PPI

  36. REFLEX PRE PPI

  37. Percent GR Palmer amaranth control 28 DAP. Macon Co., GA. 2009. PRE APPLICATIONS 86 a 81 a 51 b 46 b PPI PPI PRE PRE Prowl Treflan RAIN 12 d after planting

  38. Palmer control from acetochlor, S-metolachlor, and metolachlor. Macon Co., GA 2009. 80 a 77 a 50 c acetochlor (1.13 lb) S-metolachlor (Dual Mag, 0.95 lb) metolachlor (Parrlay, 1.3 lb) No Palmer up at time of application. Layby of RU + Direx applied 19 d after POST.

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

  40. 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 1010 seed/A

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

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