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Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton

Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton. Culpepper, York, MacRae, Whitaker. Conservation Tillage is Very Important To the Southeast. Objective. Determine the impacts of conservation tillage on the management of glyphosate-resistant Palmer amaranth.

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Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton

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  1. Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton Culpepper, York, MacRae, Whitaker

  2. Conservation Tillage is Very Important To the Southeast

  3. Objective • Determine the impacts of conservation tillage on the management of glyphosate-resistant Palmer amaranth.

  4. Experiment 1: 2006 and 2007 Locations Mount Olive * * * * * Macon Co.

  5. Materials and Methods Plot size GA = 4 rows by 35-45 feet NC = 4 rows by 25-30 feet Split Plot/Factorial Design 7 herbicide systems 2 tillage practices

  6. Herbicide Systems* *Direx + MSMA applied at layby for each herbicide program.

  7. PRE POST Prowl H20 2.5 pt/A Dual Mag. 1 pt WeatherMax 22 oz/A Cotoran 2 pt/A Staple LX 1.7 fl oz Staple LX 1.7 fl oz Reflex 1 pt/A Layby Direx 2 pt + MSMA 2 lb Herbicides and Rates

  8. Percent glyphosate-resistant Palmer amaranth control at harvest. Five locations, GA & NC.* 82 a 77 ab 74 ab 70 b 64bc 56 c 40 d Prowl Prowl +Reflex +Cotoran +Staple +Cotoran +Reflex WeatherMax + Dual WeatherMax + Staple Direx + MSMA directed over entire trial area.

  9. Seed Cotton Yield. Five locations, GA & NC.* 1563 a 1413 a 1416 a 1335 a 1040 b 972 bc 724 c Prowl Prowl +Reflex +Cotoran +Staple +Cotoran +Reflex WeatherMax + Dual WeatherMax + Staple Direx + MSMA directed over entire trial area.

  10. Tillage Systems Conventional: no weeds or residue Strip Tillage: cover controlled several weeks ahead of planting followed by Gramoxone PRE

  11. Wheat height (inches) at time of burndown.* 32 24 8 4

  12. Residue= 9760 lb/A

  13. Percent glyphosate-resistant Palmer amaranth control at harvest. Tillage main effects.* * * * *An asterisk denotes control greater in strip-till production.

  14. Number of Palmer amaranth (sq yd) infesting the non-treated control 21 to 28 DAP. * * * *An asterisk denotes less pigweed in strip-till production.

  15. Prowl + Cotoran PRE fb Roundup + Staple

  16. Prowl + Cotoran PRE fb Roundup + Dual 4 inch fb Direx + MSMA PD Conv Strip-Till

  17. Prowl + Reflex PRE fb Roundup + Dual 4 inch fb Direx + MSMA PD Conv Strip-Till

  18. Seed Cotton Yield as Impacted by Tillage. Georgia and North Carolina. 2006-2007. * * * *An asterisk denotes significantly higher yields in strip-till production.

  19. Conclusions Experiment 1 • Heavy residue improved control. • A. Reduced pigweed emergence • B. Slowed pigweed emergence and growth • Heavy residue would likely benefit areas not infested with resistance by reducing selection pressure.

  20. Conclusions Experiment 1 • 3. Heavy residue would likely put more selection pressure on ALS chemistry (Staple) controlling those plants escaping residual herbicides.

  21. Experiment 2: Materials and Methods Herbicide systems (1st rainfall 17 DAP) None or Prowl + Reflex, RU + Staple, Direx + MSMA Cover crop options rye controlled 2 or 4 wk before planting wheat controlled 2 or 4 wk before planting no cover

  22. Materials and Methods Liter Produced (at planting) wheat 4 WBP (knee high): 59,895 lb/A of liter wheat 2 WBP (waist high): 66,429 lb/A of liter rye 4 WBP (waist high): 68,607 lb/A of liter rye 2 WBP (head high): 96,921 lb/A of liter

  23. Percent reduction in Palmer emergence by cover crops without herbicides. 42 DAP.* 57 a 53 ab 40 b 38 b *Compared to the no cover conventionally tilled system.

  24. Percent Palmer amaranth control at harvest with herbicide programs. Macon County, GA. 2007. 87 a 81 a 79 ab 68 bc 59 c

  25. Conventional tillage Prowl + Reflex PRE RU + Staple POST Direx + MSMA layby

  26. Knee high wheat Prowl + Reflex PRE RU + Staple POST Direx + MSMA layby

  27. Waist high wheat Prowl + Reflex PRE RU + Staple POST Direx + MSMA layby

  28. Cotton yield as impacted by cover crop residue. Macon County, GA . 2007.* 835 a 820 ab 780 ab 700 b 500 c

  29. Conclusions Experiment 2 • Heavy residue improved control. • A. Reduced pigweed emergence • B. Slowed pigweed emergence and growth • Heavy residue would likely put more selection pressure on ALS chemistry (Staple) controlling those plants escaping residual herbicides.

  30. Palmer amaranth infests strip till cotton.

  31. Comments

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