1. Management Systems for Glyphosate-Resistant Palmer Amaranth
J.R. Whitaker, A.C. York, and A.S. Culpepper

2. Palmer Amaranth

3. Back: untreated
Front: glyphosate-only program

4. Weathermax 22 oz POST-1
Weathermax 22 oz POST-2
Weathermax 22 oz POST-3

5. Glyphosate-resistant Palmer amaranth has been documented in several cotton-producing states
North Carolina
Tennessee
South Carolina
Arkansas
Georgia

6. No PRE
POST 1 (1-2-leaf): WM 22 oz/A+ Dual Magnum 1 pt/A
POST 2 (6-leaf): WM + Staple 1.8 oz/A
Lay-by: WM + Valor 1 oz/A

7. Experiment 1 (Materials and Methods)
Conventional tillage
Study site: Mt. Olive, NC in 2007
Treatments differed only in PRE application
RCBD w/ 4 replications
Means from weed control and yield were separated by Fisher’s Protected LSD (p=0.05)

8. Mt. Olive Location High PA infestation ~1/3 Pop GR-resistant
Non-treated Check
WM 22 oz/A
Mt. Olive Location
High PA infestation
150/yd2
~1/3 Pop GR-resistant
No Staple resistance
WM 22 oz/A oz/A Staple LX

9. Experiment 1 (Treatments)
5 preemergence herbicides alone:
Cotoran 2 pt/A
Prowl H2O 2.1 pt/A
Reflex 1 pt/A
Reflex 1.5 pt/A
Direx 1.6 pt/A
Staple 1.8 oz/A
No PRE

10. PRE Combinations Reflex 1 pt/A + Prowl H2O 2.1pt/A + Direx 1.6 pt/A
+ Cotoran 2 pt/A
+ Staple 1.8 oz/A
Direx 1.6 pt/A + Prowl H2O 2.1pt/A
+ Reflex 1 pt/A
Staple 1.8 oz/A + Direx 1.6 pt/A

11. Experiment 1 (Treatments)
All plots received same herbicide regiment for remainder of season:
Post 1 (2-leaf cotton):
Sequence 2.5 pt/A (glyphosate + s-metolachlor)
Post 2 (5-leaf cotton):
Touchdown Total 34 oz/A
Lay-by (12” cotton):
Suprend 1.25 lb/A + MSMA pt/A

12. Palmer amaranth control (Individual herbicides)AB BC 90 CD D 84 78 71 68 E
% Control E 51 44
No PRE
Cotoran
Prowl
Reflex
1 pt.
Direx
Reflex
1.5 pt.
Staple
60 days after Layby

13. Palmer Amaranth control (Direx combinations)BC 95 BC C 85 78 70
% Control
Direx
Direx +
Prowl
Direx +
Reflex
Direx +
Staple
60 days after Layby

14. Palmer amaranth control (Reflex combinations)
BCD BC 95 DE E 88 84 85 76 71
% Control
Reflex
1 pt.
Reflex
1.5 pt.
Reflex1 +
Cotoran
Reflex1 +
Direx
Reflex1 +
Prowl
Reflex1 +
Staple
60 days after Layby
1Reflex 1 pt/A

15. Palmer amaranth control (Staple Combinations)95 95 90
% Control
Staple
Staple +
Direx
Staple +
Reflex
60 days after Layby

16. Cotton in Mt. Olive on August 2, 2007

17. Yield (Individual herbicides)
+94% A A A A
+70%
+60%
+60%
+60%
+61% B
Seed Cotton Yield lb/A
670
lbs No
PRE
Direx
Staple
Prowl
Cotoran
Reflex
1 pt.
Reflex
1.5 pt.

18. Yield (Direx combinations)
+ 33% B B B
1040
lbs
+ 0%
Seed Cotton Yield lb/A
- 12%
Direx
Direx +
Prowl
Direx +
Reflex
Direx +
Staple

19. Yield (Reflex combinations)AB AB AB
1290
lbs AB R1
+ 12%
R1.5
+ 0% R1
+ 2%
R1.5
- 10%
1030
lbs B R1
- 7%
R1.5
- 18% R1
- 21%
R1.5
- 31%
Seed Cotton Yield lb/A
Reflex
1 pt.
Reflex
1.5 pt.
Reflex1 +
Cotoran
Reflex1 +
Direx
Reflex1 +
Staple
Reflex1 +
Prowl
1Reflex 1 pt/A

20. Yield (Staple Combinations)AB
+ 31 % B
+ 8 %
1060
lbs
Seed Cotton Yield lb/ A
Staple
Staple +
Reflex
Staple +
Direx

21. Experiment 2 Management systems in no-till cotton
Study conducted during
2007 in Mt. Olive, NC
Treatments in factorial
arrangement (RCBD)
with 3 replications

22. Factorial Arrangement of Treatments
2 Preplant options (26 days before planting):
Roundup Weathermax (WM) 22 oz/A + 2,4-D 0.5 pt/A
WM + 2,4-D 0.5 pt/A + Valor SX 2 oz/A
2 PRE options: WM
WM + Reflex 1 pt/A
3 Early POST options (2-leaf cotton):
WM + Dual Magnum 1 pt/A
WM + Staple LX 2.5 oz/A

23. Materials and Methods All plots received: WM 22 oz/A (6-leaf cotton)
Lay-by application of Direx 2 pt/A + MSMA pt/A (12” cotton)
Weed control data arcsine square root transformed and subjected to ANOVA with partitioning appropriate for factorial treatment design (p=0.05)
Means for main effects and interactions were separated with Fisher’s Protected LSD (p=0.05)

24. Palmer amaranth control 14 Days After Planting (Pre-plant
Palmer amaranth control 14 Days After Planting (Pre-plant*PRE interaction) A B C 97 93 81
% Control D WM
WM +
Reflex WM
WM +
Reflex
PRE:
Preplant:
WM + 2,4-D
WM + 2,4-D + Valor

25. Palmer amaranth control (30 Days After Lay-by)96 93
% Control
WM + 2,4-D
WM + 2,4-D +
Valor
Pre-plant Main Effect

26. Control 30 Days After Layby (PRE*Early POST)99 99 96 95 92 85
% Control WM WM WM +
Dual WM +
Staple WM +
Dual WM +
Staple
Early POST
PRE WM
WM + Reflex

27. Yield (Pre-plant main effect)B
+ 15 %
1530
lbs
Seed Cotton Yield (lb/A)
WM + 2,4-D +
Valor
WM + 2,4-D

28. Palmer amaranth control (30 Days After Lay-by)96 93
% Control
WM + 2,4-D
WM + 2,4-D +
Valor
Pre-plant Main Effect

29. Palmer amaranth control 14 Days After Planting (Pre-plant
Palmer amaranth control 14 Days After Planting (Pre-plant*PRE interaction) A B C 97 93 81
% Control D WM
WM +
Reflex WM
WM +
Reflex
PRE:
Preplant:
WM + 2,4-D
WM + 2,4-D + Valor

30. Yield (Pre-plant main effect)B
+ 15 %
1530
lbs
Seed Cotton Yield (lb/A)
WM + 2,4-D +
Valor
WM + 2,4-D

31. Yield (Preemergence Main Effect )B
+ 9 %
1580
lbs
Seed Cotton Yield (lb/A) WM
WM + Reflex

32. Yield (Early POST Main Effect )AB B
+ 16 %
+ 7 %
1530
lbs
Seed Cotton Yield (lb/A) WM
WM + Dual
WM + Staple

33. Conclusions (1st Experiment)
Any PRE better than nothing
Most effective individual PREs were Direx, Staple, and Reflex
Combinations of Staple + Direx or Staple + Reflex are best PRE options

34. Conclusions (2nd Experiment)
Applied alone, Reflex more effective that Valor, both are best
Staple POST somewhat better than Dual Magnum (if no ALS resistance)
The most effective system was:
Valor preplant,
fb Reflex PRE,
fb WM + Staple POST,
and residual Lay-by

35. Other Systems Preplant PRE POST Lay-by Valor Direx WM + Staple LX
Residual Lay-by
None
Reflex 1.5 pt/A
WM + Dual Magnum
Reflex 1 pt/A + Direx
Reflex 1 pt/A + Staple
Staple + Direx