glyphosate-resistant palmer amaranth has the potential to devastate georgia agriculture a. stanley...
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Glyphosate-Resistant Palmer Amaranth Has the Potential to Devastate Georgia Agriculture
A. Stanley Culpepper
University of Georgia
Tifton Campus
Glyphosate-Resistant Palmer Amaranth
1) Glyphosate-resistant Palmer amaranth confirmed in GA.
2) Why are we having this problem?
3) How widespread?
4) How much of a management nightmare are we facing?
5) Other resistant weeds?
WeatherMax 22 oz, 2 d after application to 16 inch Palmer
Experiment 1: Palmer 3 to 5 inches when treated. Dual Magnum applied over entire trial to eliminate continual emergence.
WeatherMax
33 oz
66 oz
132 oz
198 oz
264 oz
WeatherMax 33 oz/A
WeatherMax 66 oz/A
WeatherMax 132 oz/A
WeatherMax 198 oz/A
WeatherMax 264 oz/A
Application Timings
EPOST: 0.5” Palmer
MPOST: 3” Palmer
LPD: 10” Palmer
0.5” at application
3” at application
Field Experiment 2: Materials and Methods
Non-treated Control
WMax 22 oz EPOST, 0.5”
WMax 22 oz MPOST, 3”
WMax 22 oz LPD, 10”
WMax 44 oz EPOST, 0.5”
WMax 44 oz MPOST, 3”
WMax 44 oz LPD, 10”
WMax 88 oz EPOST, 0.5”
WMax 88 oz MPOST, 3”
WMax 88 oz LPD, 10”
Middle Georgia Cotton Field, July 9 2006
Why did this happen?
0
25
50
75
100
1997 2000 2003 2005
RR cottonStrip till
% A
cres
1) 94% Roundup Ready
2) 44% strip-till
3) Greater than 88% not cultivated
4) Trends away from effective residual herbicides
Grower Practices
Numerous applications of Roundup have replaced conventional chemistry and many tillage practices, year after year after year.
Grower Practices
Progression of
Herbicide Resistance
Year 1
Year 2
Year 5
Year 3
Year 4
Alan York, NCSU
Roundup Based Program without resistance
Prowl PRE,
WMax POST,
WMax + Direx Layby
Glyphosate-resistant Palmer response to common programs.
Prowl PRE,
WMax + Dual Mag. POST,
WMax + Direx Layby
Glyphosate-resistant Palmer response to common programs.
Prowl + Staple PRE,
WMax + Dual Mag. POST,
WMax + Direx Layby
Glyphosate-resistant Palmer response to common programs.
Prowl + Cotoran PRE,
WMax + Dual Mag. POST,
WMax + Direx Layby
Glyphosate-resistant Palmer response to common programs.
Prowl + Reflex PRE,
WMax + Staple POST,
WMax + Direx Layby
Glyphosate-resistant Palmer response to common programs.
Commonly Used ALS Herbicides
• Accent
• Ally
• Beacon
• Cadre
• Classic
• Envoke
• Exceed
• Express
• Finesse
• FirstRate • Harmony Extra • Osprey• Peak• Permit/Sandea• Pursuit• Python• Scepter• Staple• Strongarm
All have the same mode of action!!!!!!!Eric Prostko
WMax 22 oz; Palmer 4” when treated
WMax 22 oz + Staple LX 1.7 oz; Palmer 4” when treated
WMax 22 oz + Staple LX 2.55 oz; Palmer 4” when treated
WMax 22 oz + Staple LX 1.7 oz; Palmer 0.5” when treated
WMax 22 oz + Staple LX 2.55 oz; Palmer 0.5 “ when treated
Prowl PRE, Roundup POST Twice
(RR cotton)
Prowl PRE, Ignite POST Twice
(Liberty Link cotton)
Palmer Amaranth
1. Male and female plants
2. Forced out crossing
3. Typical 400,000 to 600,000 seed per plant
4. Resistance is carried through pollen
(>50% offspring resistant in initial work)
Ian Heaps Web Site (www.weedscience.org/in.asp)
182 species resistant to herbicides in the world
8 species resistant to glyphosatebuckhorn plantain
common ragweed
hairy fleabane
horseweed
goosegrass
Italian ryegrass
rigid ryegrass
Palmer amaranth
Herbicide Resistance in Georgia
Weed Year Herbicide Location
goosegrass 1992 DNA East GA
Prickly sida 1993 IMI ?
Italian ryegrass
1995 Hoelon Peach Co. Hart Co.
Palmer amaranth
2000 2005
SU/IMI glyphosate
Burke Co. Central GA
Eric Prostko
Glyphosate-Resistant Palmer Management
1. Diversity
-herbicide selection
-cropping system
-cultural practices such as tillage
2. Monitor and be aware!
3. Three to five year plan!!!!
