Buctril/Graminicide Interactions on Annual Grass Species

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Managing Glyphosate-Resistant Palmer Amaranth in
Conventional and Strip-Till Roundup Ready Cotton
Culpepper, Kichler, MacRae, Whitaker, York, Davis
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Management Program For Glyphosate-Resistant
Palmer Amaranth if Things Are Not Perfect
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Strip-Till Cotton Acreage Estimates for Georgia
and North Carolina
Acres
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Conservation Tillage is Very Important To the
Southeast
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2004 Common Horseweed Burndown Program
Photo credit Larry Steckel
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Hypothesis

• Glyphosate-resistant Palmer amaranth will put
  cotton farmers out of conservation tillage
  production?

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2006 Locations

Rocky Mount


Macon Co.
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Materials and Methods
Plot size GA 4 rows by 45 feet NC 4 rows
by 30 feet
Split Plot Design 2 tillage practices 7
herbicide systems
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Herbicide Systems
PRE POST
Prowl Roundup Dual Mag.
Prowl Cotoran Roundup Dual Mag.
Prowl Staple Roundup Dual Mag.
Prowl Reflex Roundup Dual Mag.
Prowl Roundup Staple
Prowl Cotoran Roundup Staple
Prowl Reflex Roundup Staple
Direx MSMA applied at layby for each herbicide
program.
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Herbicides and Rates
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Tillage Systems
Conventional no weeds or residue Strip Tillage
cover controlled several weeks ahead of planting
followed by Gramoxone PRE
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Residues

Rocky Mount
weeds (little residue)


Macon Co.
Thick wheat (heavy cover)
Grazed wheat (little cover)
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(No Transcript)
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Impact of Tillage on Locations with Little Cover
Georgia strip till 67 conven 69
North Carolina strip till 77 conven 74
Averaged over all herbicide systems.
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Percent late-season glyphosate-resistant Palmer
amaranth control. Macon Co., GA. 2006.
95 a
90 ab
84 bc
80 c
80 c
60 d
54 d
Reflex
Prowl
Prowl
Cotoran
Cotoran
Reflex
Staple
WeatherMax Dual
WeatherMax Staple
lt25 resistant
Direx MSMA directed over entire trial area.
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Percent late-season glyphosate-resistant Palmer
amaranth control. Wayne Co, NC. 2006.
94 a
91 a
91 a
93 a
90 a
76 b
69 b
Reflex
Prowl
Prowl
Cotoran
Cotoran
Reflex
Staple
WeatherMax Dual
WeatherMax Staple
lt25 resistant
Direx MSMA directed over entire trial area.
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Seed cotton yield (lb/A). Wayne Co, NC. 2006.
1536 a
1462 a
1420 a
1360 abc
1315 abc
1225 bc
1160 c
Reflex
Prowl
Prowl
Cotoran
Cotoran
Reflex
Staple
WeatherMax Dual
WeatherMax Staple
Direx MSMA directed over entire trial area.
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Residue 9760 lb/A
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Number of plants in the non-treated control at
harvest.
plants per sq. yard
strip till 8 conven 32
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75 Resistant
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Percent glyphosate-resistant Palmer amaranth
control. Macon Co. 2006.
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Glyphosate-resistant Palmer amaranth response to
herbicides and tillage. Macon Co. 2006.
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Prowl Cotoran PRE fb Roundup Staple
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Prowl Cotoran PRE fb Roundup Dual 4 inch fb
Direx MSMA PD
Conv
Strip-Till
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Prowl Reflex PRE fb Roundup Dual 4 inch fb
Direx MSMA PD
Conv
Strip-Till
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Seed cotton yield (lb/A). Macon Co. 2006.






Staple
Prowl
Prowl
Cotoran
Reflex
Cotoran
Reflex
WeatherMax Dual
WeatherMax Staple
Direx MSMA directed over entire trial area.
Asterick denotes similar yield among systems.
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Conclusions

• Low levels of dead residue did not impact
  herbicidal control.
• Heavy residue improved control.
• A. Reduced pigweed emergence
• B. Delayed pigweed emergence and growth
• Heavy residue likely eliminated much of the
  activity of PRE herbicides placing more
  pressure on Staple POST

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2004
0
1.3
5.2
10.2
20.4
2.6
fl oz/A
Staple LX
2006
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2006
0
1.3
5.2
10.2
20.4
2.6
Staple Wmax
fl oz/A
0
3
12
24
48
6
fl oz/A
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