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2007 BELTWIDE: Response of Glyphosate-Resistant Palmer Amaranth to Thirteen Residual Herbicides

Jeremy Kichler
University of Georgia

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TABLE OF CONTENTS

Response of Glyphosate-Resistant Palmer Amaranth to Thirteen Residual Herbicides The Objective of this Study was to Determine The Most Effective Residual Herbicides for Use in Cotton Two Locations in 2006 Methods Planting Dates and Rainfall Herbicide Treatments and 1X Rates Data Reporting Percent Palmer Control Averaged Over Herbicide Treatments, 18-26 DAT. Percent Palmer Control Averaged Over Herbicide Treatments, 31-36 DAT. Herbicide Options Percent Palmer Control by PRE Applied Residual Herbicides. 18-26 DAT. Palmer Amaranth Control by PRE Applied Residual Herbicides. 31-36 DAT. Planting Dates and Rainfall Non-treated Reflex vs Staple Prowl vs Caparol Reflex vs Staple Prowl vs Caparol Palmer Amaranth Control by POST Applied Residual Herbicides. 18-26 DAT. Palmer Amaranth Control by POST Applied Residual Herbicides. 31-36 DAT. Stalwart vs Dual Mag. Palmer Amaranth Control by Layby Applied Residual Herbicides. 18-26 DAT. Palmer Amaranth Control by Layby Applied Residual Herbicides. 31-36 DAT. Valor vs Direx Conclusions Conclusions

SLIDE CONTENTS

Response of Glyphosate-Resistant Palmer Amaranth to Thirteen Residual Herbicides Jeremy Kichler The Objective of this Study was to Determine The Most Effective Residual Herbicides for Use in Cotton 1. At planting 2. Postemergence 3. Layby Two Locations in 2006 Macon County, Georgia Robeson County, North Carolina Methods Plot Size – 6 feet by 22-25 feet Conventional Tillage All herbicides applied to soil without debris Planting Dates and Rainfall Planting/Application Dates May 1, 2006 – Macon County, GA May 24, 2006 – Robeson County, NC Factorial treatment 13 herbicides 2 herbicide rates 4 replications Herbicide Treatments and 1X Rates Caparol (2 pt) Cotoran (2 pt) Direx (2 pt) Dual Magnum (1 pt) Envoke (0.1 oz) Layby Pro (2 pt) Linex (2 pt) Prowl H2O (2 pt) Reflex (1 pt) Stalwart (1 pt) Staple LX (1.7 oz) Suprend (1.0 lb) Valor SX (1.5 oz) All treatments were applied at 1X and 1.5X rates Data Reporting Data from both GA and NC reported by location at two evaluation dates Rate main effect significant Herbicide treatment main effect significant Percent Palmer Control Averaged Over Herbicide Treatments, 18-26 DAT. Percent Palmer Control Averaged Over Herbicide Treatments, 31-36 DAT. Herbicide Options Caparol Cotoran Direx Prowl Reflex Staple Direx Layby Pro Linex Suprend Valor SX Dual Mag. Envoke Stalwart Staple At-Planting POST Layby LSD: GA = 6; NC = 6 *Data pooled over two rates. Percent Palmer Control by PRE Applied Residual Herbicides. 18-26 DAT.* *Data pooled over rates. Palmer Amaranth Control by PRE Applied Residual Herbicides. 31-36 DAT.* LSD: GA = 10; NC = 13 Planting Dates and Rainfall Rainfall: GA NC week 1 4.5 in 0.4 in week 2-3 0 in 2.99 in week 4-5 0 in 2.08 in Non-treated GA 115 Reflex Staple GA Prowl Caparol GA 115 Reflex Staple NC Prowl Caparol NC *Data pooled over rates. Palmer Amaranth Control by POST Applied Residual Herbicides. 18-26 DAT.* LSD: GA = 6; NC = 6 *Data pooled over rates. Palmer Amaranth Control by POST Applied Residual Herbicides. 31-36 DAT.* LSD: GA = 10; NC = 13 Stalwart Dual Mag. GA Palmer Amaranth Control by Layby Applied Residual Herbicides. 18-26 DAT.* *Data pooled over rates. LSD: GA = 6; NC = 6 Palmer Amaranth Control by Layby Applied Residual Herbicides. 31-36 DAT.* *Data pooled over rates. LSD: GA = 10; NC = 13 Valor Direx GA Conclusions At-Planting Options -- Reflex or Staple Topical Options -- Staple or Dual Magnum Layby Directed Options -- Suprend or Valor Conclusions Caution with Staple and Suprend due to growing occurrences of ALS inhibitor resistance. In fields without ALS resistance we recommend only 1 application of an ALS herbicide per season.