Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton
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Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton. Culpepper, York, MacRae, Whitaker. Conservation Tillage is Very Important To the Southeast. Objective. Determine the impacts of conservation tillage on the management of glyphosate-resistant Palmer amaranth.

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Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton

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Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Managing glyphosate-resistant Palmer amaranth in conventional and strip-till cotton

Culpepper, York, MacRae, Whitaker


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Conservation Tillage is Very Important To the Southeast


Objective

Objective

  • Determine the impacts of conservation tillage on the management of glyphosate-resistant Palmer amaranth.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Experiment 1: 2006 and 2007 Locations

Mount Olive

*

*

*

*

*

Macon Co.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Materials and Methods

Plot size

GA = 4 rows by 35-45 feet

NC = 4 rows by 25-30 feet

Split Plot/Factorial Design

7 herbicide systems

2 tillage practices


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Herbicide Systems*

*Direx + MSMA applied at layby for each herbicide program.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

PRE

POST

Prowl H20

2.5 pt/A

Dual Mag.

1 pt

WeatherMax

22 oz/A

Cotoran

2 pt/A

Staple LX

1.7 fl oz

Staple LX

1.7 fl oz

Reflex

1 pt/A

Layby

Direx 2 pt + MSMA 2 lb

Herbicides and Rates


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Percent glyphosate-resistant Palmer amaranth control at harvest. Five locations, GA & NC.*

82 a

77 ab

74 ab

70 b

64bc

56

c

40 d

Prowl

Prowl

+Reflex

+Cotoran

+Staple

+Cotoran

+Reflex

WeatherMax + Dual

WeatherMax + Staple

Direx + MSMA directed over entire trial area.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Seed Cotton Yield. Five locations, GA & NC.*

1563 a

1413 a

1416 a

1335 a

1040 b

972 bc

724 c

Prowl

Prowl

+Reflex

+Cotoran

+Staple

+Cotoran

+Reflex

WeatherMax + Dual

WeatherMax + Staple

Direx + MSMA directed over entire trial area.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Tillage Systems

Conventional: no weeds or residue

Strip Tillage: cover controlled several weeks ahead of planting followed by Gramoxone PRE


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Wheat height (inches) at time of burndown.*

32

24

8

4


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Residue= 9760 lb/A


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Percent glyphosate-resistant Palmer amaranth control at harvest. Tillage main effects.*

*

*

*

*An asterisk denotes control greater in strip-till production.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Number of Palmer amaranth (sq yd) infesting the non-treated control 21 to 28 DAP.

*

*

*

*An asterisk denotes less pigweed in strip-till production.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Prowl + Cotoran PRE fb Roundup + Staple


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Prowl + Cotoran PRE fb Roundup + Dual 4 inch fb Direx + MSMA PD

Conv

Strip-Till


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Prowl + Reflex PRE fb Roundup + Dual 4 inch fb Direx + MSMA PD

Conv

Strip-Till


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Seed Cotton Yield as Impacted by Tillage. Georgia and North Carolina. 2006-2007.

*

*

*

*An asterisk denotes significantly higher yields in strip-till production.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Conclusions Experiment 1

  • Heavy residue improved control.

    • A. Reduced pigweed emergence

    • B. Slowed pigweed emergence and growth

  • Heavy residue would likely benefit areas not infested with resistance by reducing selection pressure.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Conclusions Experiment 1

  • 3. Heavy residue would likely put more selection pressure on ALS chemistry (Staple) controlling those plants escaping residual herbicides.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Experiment 2: Materials and Methods

Herbicide systems (1st rainfall 17 DAP)

None or

Prowl + Reflex, RU + Staple, Direx + MSMA

Cover crop options

rye controlled 2 or 4 wk before planting

wheat controlled 2 or 4 wk before planting

no cover


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Materials and Methods

Liter Produced (at planting)

wheat 4 WBP (knee high): 59,895 lb/A of liter

wheat 2 WBP (waist high): 66,429 lb/A of liter

rye 4 WBP (waist high): 68,607 lb/A of liter

rye 2 WBP (head high): 96,921 lb/A of liter


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Percent reduction in Palmer emergence by cover crops without herbicides. 42 DAP.*

57 a

53 ab

40 b

38 b

*Compared to the no cover conventionally tilled system.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Percent Palmer amaranth control at harvest with herbicide programs. Macon County, GA. 2007.

87 a

81 a

79 ab

68 bc

59 c


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Conventional tillage

Prowl + Reflex PRE

RU + Staple POST

Direx + MSMA layby


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Knee high wheat

Prowl + Reflex PRE

RU + Staple POST

Direx + MSMA layby


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Waist high wheat

Prowl + Reflex PRE

RU + Staple POST

Direx + MSMA layby


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Cotton yield as impacted by cover crop residue. Macon County, GA . 2007.*

835 a

820 ab

780 ab

700 b

500 c


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Conclusions Experiment 2

  • Heavy residue improved control.

    • A. Reduced pigweed emergence

    • B. Slowed pigweed emergence and growth

  • Heavy residue would likely put more selection pressure on ALS chemistry (Staple) controlling those plants escaping residual herbicides.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

Palmer amaranth infests strip till cotton.


Managing glyphosate resistant palmer amaranth in conventional and strip till cotton

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