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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. - PowerPoint PPT Presentation
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Taproot ofPalmer Amaranth
Allen 2009
Living with Palmer amaranth in Georgia cotton
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
What makes Palmer a super weed?
1. Herbicide resistance?
2. Growth rate?
3. Large stature?
4. Competitive ability?
5. Reducing harvest efficacy?
6. Seed production?
7. Rapid spread?
0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
400,000
450,000
500,000
230 K
25028 K
309 K
Giant ragweed
450 K
Number of Seed Produced per PlantNumber of Seed Produced per Plant Glyphosate-Resistant Weeds in USGlyphosate-Resistant Weeds in US
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).
Johnson-grass
Horseweed Waterhemp Palmer amaranth
Weakness of a super weed?
1. Emergence depth!
2. Seed life longevity?
3. Light requirement for emergence.
Economic survival will depend on managing the seedbank!!!!
Progress during 2009?
1. Cover crops
2. Tillage
3. Tillage + plus cover crops
4. Herbicides
Palmer requires a significant amount of sunlight to emerge!!
Staple + Reflex + Direx PRE
Roundup WMax + Parrlay POST
Direx + MSMA Layby
No deep tillage
No cover crop
No deep tillage
Rye cover crop
Palmer amaranth response to cover crops. Macon County, GA. 2009.
Significant Residue
2009 rye emerging through 2008 rye residue
Management Program?
1. Cover crops
2. Tillage
3. Deep tillage and cover crops?
No Deep Tillage Deep Turn
No Herbicide Treatment
Number of Palmer Amaranth Plants During Early Season. Macon Co., Georgia 2008.*
Palmer amaranth seedling density
Treatments
No-Break Break
AM
AP
A d
ens
ity/m
2 to
a d
ep
th o
f 5 c
m
0
2000
4000
6000
8000
10000
12000
14000
Influence of burial depth on Palmer amaranth emergence
Depth of burial (inches)
0.5" 1" 4" 16"
Pe
rce
nt (
%)
em
erg
en
ce
0
10
20
30
40
50S-Palmer amaranthR-Palmer amaranth
Keeley et al. (1987) reported 36-44% emergence at 0-1”, 7% at 2”, and 2% at 3”.
Most Palmer amaranth emerges from top inch
Palmer amaranth seed longevity
Length of burial (months)
0 3 6 9 12 18Per
cent
(%
) of
rec
over
ed s
eed
40
50
60
70
80
90
100 SusceptibleResistant
*Data are combined over 4 burial depths: 0.5”, 1”, 4”, 16”
Staple + Reflex + Direx PRE
Roundup WMax + Parrlay POST
Direx + MSMA Layby
No deep tillage
No cover crop
Deep tillage
No cover crop
Palmer amaranth response to deep tillage. Macon County, GA. 2009.
Management Program?
1. Cover crops
2. Tillage
3. Deep tillage and cover crops?
Most Palmer amaranth emerges from top inch
Staple + Reflex + Direx PRE
Roundup WMax + Parrlay POST
Direx + MSMA Layby
No deep tillage
No cover crop
Deep tillage
Rye cover crop
Palmer amaranth response to deep tillage and cover crops. Macon County, GA. 2009.
0
20
40
60
80
100
65 b
Drill Middle
per
cen
t
47 c 46 c
Reduction in Palmer emergence as affected by deep turning/cover crop residue at 16 DAP.
Macon Co., GA 2009.
Rye cover Deep turn
+ Rye cover
96 a94 a
50 c
Deep turn
Drill MiddleDrill Middle
Non-treated: 620 plant/m2.
No herbicides applied.
0
20
40
60
80
100
81 b
No deep turn
No Cover
Deep turn
No 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.
per
cen
t
63 c
80 b
98 a
GR Palmer amaranth control at harvest with Roundup-based systems. Macon Co., GA 2009.
No deep turn
Rye Cover
Deep turn
Rye Cover
0
700
1400
2100
1627 b
No deep turn
No Cover
Deep turn
No 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.
1298 d1524 bc
2078 a
Seed cotton yield (lb/A) with Roundup-based systems. Macon Co., GA 2009.
No deep turn
Rye Cover
Deep turn
Rye Cover
Developing Integrated Programs
Makes growers nervous Easy to adopt
Potential Benefits
1.Labor, erosion, etc..
2.Prevents GR horseweed
3.Prevents GR ryegrass
4.Reduces Palmer 80%+
5.Moisture conservation
6. herbicides overtime
7.Higher yields??????
Management Program?
1. Tillage
2. Cover crops
3. Deep tillage and cover crops?
4. Herbicide programs
Dryland Conservation Tillage
Prowl + Reflex PRE
Roundup + Dual POST
Diuron + MSMA PD
Prowl + Reflex PRE
Ignite + Dual POST
Diuron + MSMA PD
Ignite 23 oz/A
APPLY 29 OZ OF IGNITE PRIOR TO 3 INCH PALMER
WATER VOLUME AND NOZZLE TYPE IS CRITICAL
No recommendation on handout for
RR dryland in conservation tillage?
1. Run aggressive RR program
2. Plant rye to produce tremendous cover
3. Hand weed!!!
Other Information
1. Burndown
2. Acetochlor
3. PPI herbicide applications
4. Palmer seedbank
Controlling 5 inch Glyphosate-Resistant Palmer amaranth at Burndown. Macon Co., GA 2008.*
0
20
40
60
80
100
0 c
87 b94 a
58 b
Roundup Parazone
1.33 pt
70 b
Parazone +
2,4-D (1.5 pt)
Parazone +
Clarity (8 oz)
Parazone +
Diuron (1.8 pt)
Palmer control at planting, burndown applied 17 d earlier. Macon Co., GA 2009.
0
20
40
60
80
100
90 b
Valor preplant
Direx preplant
99 a
Change in Valor Label?
1. Apply Valor and then run strip tillage:
7 day plant back
HOW EFFECTIVE ARE PREPLANT APPLICATIONS?
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
TREFLAN
PPIPRE
REFLEX
PPIPRE
Percent GR Palmer amaranth control 28 DAP. Macon Co., GA. 2009.
0
20
40
60
80
100
81 a
Prowl
51 b 46 b
86 a
Treflan
PRE APPLICATIONS
RAIN 12 d after planting
PRE PPI PRE PPI
Palmer control from acetochlor, S-metolachlor, and metolachlor. Macon Co., GA 2009.
0
20
40
60
80
100
50 c
acetochlor
(1.13 lb)
80 a
S-metolachlor
(Dual Mag, 0.95 lb)
metolachlor
(Parrlay, 1.3 lb)
77 a
No Palmer up at time of application. Layby of RU + Direx applied 19 d after POST.
Tobacco:Spartan + Yellow 2008
Soybean- Roundup 2008
A.C.York, 2009
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
Integrating cover crop residue and moldboard plowing into glyphosate-resistant Palmer
amaranth management programs will be key!
QUESTIONS OR COMMENTS?
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