Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton
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Transcript of Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton
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Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton
Culpepper, York, MacRae, Whitaker
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Conservation Tillage is Very Important To the Southeast
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Objective
Determine the impacts of conservation tillage on the management of glyphosate-resistant Palmer amaranth.
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Experiment 1: 2006 and 2007 Locations
Mount Olive
*
Macon Co.***
*
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Materials and Methods
Split Plot/Factorial Design
7 herbicide systems
2 tillage practices
Plot size
GA = 4 rows by 35-45 feet
NC = 4 rows by 25-30 feet
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Herbicide Systems*
PRE POSTProwl
Roundup + Dual Mag.Prowl + CotoranProwl + StapleProwl + ReflexProwl
Roundup + StapleProwl + CotoranProwl + Reflex
*Direx + MSMA applied at layby for each herbicide program.
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Herbicides and Rates
2.5 pt/AProwl H20
2 pt/ACotoran
1.7 fl ozStaple LX
1 pt/AReflex
22 oz/AWeatherMax
1 ptDual Mag.
1.7 fl ozStaple LX
PRE POST
Layby
Direx 2 pt + MSMA 2 lb
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Direx + MSMA directed over entire trial area.
Percent glyphosate-resistant Palmer amaranth control at harvest. Five locations, GA & NC.*
0
20
40
60
80
100
77 ab
+Cotoran +Reflex +Cotoran +Reflex+Staple
74 ab
WeatherMax + Dual
40 d
56
c
70 b 64
bc
82 a
WeatherMax + Staple
Prowl Prowl
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Direx + MSMA directed over entire trial area.
Seed Cotton Yield. Five locations, GA & NC.*
0
400
800
1200
1600
1413 a
+Cotoran +Reflex +Cotoran +Reflex+Staple
1416 a
WeatherMax + Dual
724 c
972 bc
1335 a
1040 b
1563 a
WeatherMax + Staple
Prowl Prowl
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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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Wheat height (inches) at time of burndown.*
0
11
22
33
NC 06 GA1 06 NC 07 GA 07 GA2 06
4
32
24
8
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Residue= 9760 lb/A
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Percent glyphosate-resistant Palmer amaranth control at harvest. Tillage main effects.*
0
20
40
60
80
100
NC 06 GA1 06 NC 07 GA 07 GA2 06
Conv. Strip
*
* *
*An asterisk denotes control greater in strip-till production.
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Number of Palmer amaranth (sq yd) infesting the non-treated control 21 to 28 DAP.
0
20
40
60
80
100
120
GA1 06 NC 07 GA 07 GA2 06
Conv. Strip
* *
*An asterisk denotes less pigweed in strip-till production.
*
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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 as Impacted by Tillage. Georgia and North Carolina. 2006-2007.
0
600
1200
1800
2400
3000
GA1 06 NC 07 GA 07 GA2 06
Conv. Strip
*
*
*An asterisk denotes significantly higher yields in strip-till production.
*
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Conclusions Experiment 1
1. Heavy residue improved control.
A. Reduced pigweed emergence
B. Slowed pigweed emergence and growth
2. Heavy residue would likely benefit areas not infested with resistance by reducing selection pressure.
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Conclusions Experiment 1
3. Heavy residue would likely put more selection pressure on ALS chemistry (Staple) controlling those plants escaping residual herbicides.
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Experiment 2: Materials and Methods
Cover crop options
rye controlled 2 or 4 wk before planting
wheat controlled 2 or 4 wk before planting
no cover
Herbicide systems (1st rainfall 17 DAP)
None or
Prowl + Reflex, RU + Staple, Direx + MSMA
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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
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Percent reduction in Palmer emergence by cover crops without herbicides. 42 DAP.*
0
20
40
60
80
100
wheat 4 WBP wheat 2 WBP rye 4 WBP rye 2 WBP
*Compared to the no cover conventionally tilled system.
38 b
53 ab40 b
57 a
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Percent Palmer amaranth control at harvest with herbicide programs. Macon County, GA. 2007.
0
20
40
60
80
100
wheat 4WBP
wheat 2WBP
rye 4WBP
rye 2WBP
Conv.
68 bc79 ab81 a
59 c
87 a
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Conventional tillage
Prowl + Reflex PRE
RU + Staple POST
Direx + MSMA layby
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Knee high wheat
Prowl + Reflex PRE
RU + Staple POST
Direx + MSMA layby
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Waist high wheat
Prowl + Reflex PRE
RU + Staple POST
Direx + MSMA layby
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Cotton yield as impacted by cover crop residue. Macon County, GA . 2007.*
0
300
600
900
wheat 4WBP
wheat 2WBP
rye 4WBP
rye 2WBP
Conv.
700 b780 ab
835 a
500 c
820 ab
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Conclusions Experiment 2
1. Heavy residue improved control.
A. Reduced pigweed emergence
B. Slowed pigweed emergence and growth
2. Heavy residue would likely put more selection pressure on ALS chemistry (Staple) controlling those plants escaping residual herbicides.
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Palmer amaranth infests strip till cotton.
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