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Glyphosate-resistant Palmer amaranth

Stanley Culpepper
Extension Weed Specialist
University of Georgia
Tifton, GA

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TABLE OF CONTENTS

Glyphosate-resistant Palmer amaranth Georgia counties confirmed to be infested with glyphosate-resistant Palmer amaranth Palmer amaranth In-field pollen movement Number of Seed Produced per Plant - Glyphosate-Resistant Weeds in US 2 Plants per 20 Row Feet = 23% Yield Loss Tactics for Control Tillage No Deep Tillage vs Deep Turn No Deep Tillage vs Deep Turn Depth Most if not all Palmer emerges from top 1 inch Influence of burial depth on Palmer amaranth emergence R-Palmer amaranth seed longevity Prowl H20 PRE vs Treflan Incorporated Late-season Glyphosate-Resistant Palmer amaranth Control. Cultivation Roundup 88 oz; Staple LX 10 oz Tactics for Control Cover crops Cover crops Tactics for Control Dryland Conservation Tillage Glyphosate-Resistant Palmer amaranth Infesting Dryland or Irrigated LL Corn Palmer amaranth Ignite 23 oz/A Palmer amaranth Ignite 23 oz/A Glyphosate-Resistant Palmer amaranth Infesting Dryland Conservation Tillage RR Cotton Glyphosate-Resistant Palmer amaranth Infesting Dryland ConventionalTillage RR Cotton Glyphosate-Resistant Palmer amaranth Infesting Irrigated RR Cotton Prevention Programs for Controlling Sensitive Palmer amaranth Populations in RR Cotton Monsanto's Roundup Ready Cotton Performance for Roundup Ready and Roundup Ready Flex Cotton How effective are preplant applications? Preplant application Must apply pre application Control of glyphosate-resistant Palmer amaranth if management tactics are not aggressive and timely

SLIDE CONTENTS

Glyphosate-resistant Palmer amaranth Georgia counties confirmed to be infested with glyphosate-resistant Palmer amaranth. 2004 – 1 county 2005 – 2 counties 2006 – 7 counties 2007 – 10 counties 2008 – 6 so far 1-28-09 In-field pollen movement 230 K 250 28 K 309 K Giant ragweed 450 K Number of Seed Produced per Plant Glyphosate-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 WeatherMax 33 oz/A 2 Plants Per 20 Row Feet = 23% Yield Loss Tactics For Control Deep Tillage Incorporating yellow herbicide Cultivation No Deep Tillage Deep Turn No Herbicide Treatment No Deep Tillage Deep Turned Prowl H20 + Reflex PRE; WeatherMax + Dual Magnum POST; Direx + MSMA Layby Most if not all Palmer emerges from top 1 inch Influence of burial depth on Palmer amaranth emergence Keeley et al. (1987) reported 36-44% emergence at 0-1”, 7% at 2”, and 2% at 3”. R-Palmer amaranth seed longevity Prowl H20 PRE Treflan Incorporated Reflex PRE; WeatherMax + Dual Magnum POST; Direx + MSMA Layby DRYLAND PRODUCTION Late-season Glyphosate-Resistant Palmer amaranth Control. Macon Co., Georgia 2008.* *All programs received Reflex preemergence; Roundup + Dual Magnum POST; Direx + MSMA at layby. 91 a 98 a 94 a 80 b % Roundup 88 oz Staple LX 10 oz Tactics For Control Deep Tillage Incorporating yellow herbicide Cultivation Cover Crops Tactics For Control Deep Tillage Incorporating yellow herbicide Cultivation Cover Crops Herbicide system Dryland Conservation Tillage Prowl + Reflex PRE Roundup + Dual POST Direx + MSMA PD Prowl + Reflex PRE Ignite + Dual POST Direx + MSMA PD Glyphosate-Resistant Palmer amaranth Infesting Dryland or Irrigated Liberty Link Cotton. *Add paraquat in with PRE application! Ignite 23 oz/A Ignite 23 oz/A APPLY 29 OZ OF IGNITE PRIOR TO 3 INCH PALMER Glyphosate-Resistant Palmer Infesting Dryland CONSERVATION Tillage Roundup Ready Cotton. NO UGA RECOMMENDATION in fields with significant resistant populations Glyphosate-Resistant Palmer Infesting Dryland CONVENTIONAL Tillage Roundup Ready Cotton. *Add paraquat in with PRE application! *Add paraquat in with PRE application! Glyphosate-Resistant Palmer amaranth Infesting Irrigated Roundup Ready Cotton. Prevention Programs For Controlling Sensitive Palmer amaranth Populations in Roundup Ready Cotton. Monsanto’s Roundup Ready Cotton Performance for Roundup Ready and Roundup Ready Flex Cotton *Seeding rate will influence value of rebate to each grower HOW EFFECTIVE ARE PREPLANT APPLICATIONS? MUST APPLY PRE APPLICATION!!!!!!!!! Control of glyphosate-resistant Palmer amaranth if management tactics are not aggressive and timely! Only 1 application of Valor or Reflex per year Only 1 application of Staple, Envoke, or Suprend per year COMMENTS OR QUESTIONS????