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Glyphosate-Resistant Palmer Amaranth Has the Potential to Devastate Georgia Agriculture

Stanley Culpepper
University of Georgia
Tifton Campus

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TABLE OF CONTENTS

Glyphosate-Resistant Palmer Amaranth Has the Potential to Devastate Georgia Agriculture Glyphosate-Resistant Palmer Amaranth Photo WeatherMax 22 oz, 2 d after application to 16 inch Palmer Experiment 1: Palmer 3 to 5 inches when treated WeatherMax 33 oz/A WeatherMax 66 oz/A WeatherMax 132 oz/A WeatherMax 198 oz/A WeatherMax 264 oz/A Experiment 2: Materials and Methods Non-treated Control WeatherMax 22 oz WeatherMax 44 oz WeatherMax 88 oz Middle Georgia Cotton Field, July 9, 2006 Why did this happen? Grower Practices Grower Practices Progression of Herbicide Resistance Georgia Counties Roundup Based Program without Resistance Prowl PRE, WMax POST, WMax + Direx Layby Prowl PRE, WMax + Dual Mag. POST, WMax + Direx Layby Prowl + Staple PRE, WMax + Dual Mag. POST, WMax + Direx Layby Prowl + Cotoran PRE, WMax + Dual Mag. POST, WMax + Direx Layby Prowl + Reflex PRE, WMax + Staple POST, WMax + Direx Layby Commonly Used ALS Herbicides 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 RR Cotton System vs Liberty Link Cotton System Palmer Amaranth Field Photo Field Photo Ian Heaps Web Site Herbicide Resistance in Georgia Glyphosate-Resistant Palmer Management Photo

SLIDE CONTENTS

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? % Acres 94% Roundup Ready 44% strip-till Greater than 88% not cultivated 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 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 Male and female plants Forced out crossing Typical 400,000 to 600,000 seed per plant 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 glyphosate buckhorn plantain common ragweed hairy fleabane horseweed goosegrass Italian ryegrass rigid ryegrass Palmer amaranth Herbicide Resistance in Georgia Eric Prostko Glyphosate-Resistant Palmer Management Diversity -herbicide selection -cropping system -cultural practices such as tillage Monitor and be aware! Three to five year plan!!!!