Managing glyphosate-resistant Palmer amaranth in Liberty Link® cotton.

A.W. MacRae1, A.S. Culpepper1, and J.M. Kichler2

1Crop and Soil Sciences DepartmentUniversity of Georgia, Tifton, GA

2Southwest District - CESUniversity of Georgia

Glyphosate-resistant Palmer amaranth

• Glyphosate resistant Palmer amaranth has been found in 4 counties in Georgia.

• There was 144,330 acres planted in these counties in 2005 (Georgia/Publications/County_Estimates/2006/GaCotton.pdf)

• Roundup Ready technology is used on 98% of Georgia’s acreage

WMax 22 oz EPOST, 0.5”

WMax 22 oz MPOST, 3”

WMax 22 oz LPD, 10”

Objective

• Determine the efficacy of Liberty Link cotton weed management systems for control of glyphosate-resistant Palmer amaranth

Experimental Design

• Randomized complete block design with 4 replications.

• Cultivar used: FM 988 LLBR

• 4 row plots– Center two rows used for data collection

• Data collected– Weed efficacy– Cotton yield

Non-treated

Treatments 1st Set1) PRE – Prowl H2O (2 pt/A)

POST – Ignite 280 (23 oz/A), 3 to 4-lf cotton

2) PRE

POST – Ignite 280 (29 oz/A), 3 to 4-lf cotton

POST – Ignite 280 (29 oz/A), 11-lf cotton

3) PRE

POST – Ignite 280 (29 oz/A), 4 to 5-lf cotton

POST – Ignite 280 (29 oz/A), 11-lf cotton

Layby – MSMA (2.7 pt/A) + Direx (2 pt/A) + NIS (0.25% v/v)

Palmer amaranth control (30 DBH)

0102030405060708090

100

Ignite at 4 to 5-lf and11-lf cotton + Layby

Ignite at 3 to 4-lf and11-lf cotton + Layby

PRE = Prowl H2OPOST = Ignite at 3 to 4-

lf cotton + Layby

Pal

mer

am

aran

th c

ontr

ol (%

) 77

Layby = MSMA + Direx + NIS

Ignite (23 oz) at 5 inch

Ignite (23 oz) at 5 inch

Direx + MSMA PD

Ignite (23 oz) at 2 inch

Ignite (23 oz) at 2 inch

Direx + MSMA PD

Prowl PRE

Ignite (23 oz) at 2 inch

Direx + MSMA PD

Seed Cotton Yield

0100200300400500600700800900

1000

Ignite at 4 to 5-lf and11-lf cotton + Layby

Ignite at 3 to 4-lf and11-lf cotton + Layby

PRE = Prowl H20POST = Ignite at 3 to4-lf cotton + Layby

See

d C

ott

on Y

ield

(lb

s/A

) 7

7

Layby = MSMA + Direx + NIS

Treatments 2nd Set1) PRE – Prowl H2O (2 pt/A)

POST – Ignite 280 (29 oz/A), 3 to 4-lf cotton

2) PRE – Prowl H2O (2 pt/A)POST – Ignite 280 (23 oz/A) + Staple LX

(1.7 oz/A), 3 to 4-lf cotton

3) PRE – Prowl H2O (2 pt/A)POST – Ignite 280 (23 oz/A) + Dual Magnum

(1 pt/A), 3 to 4-lf cotton

4) PRE – Prowl H2O (2 pt/A)POST – Ignite 280 (23 oz/A), 3 to 4-lf cottonPOST – Ignite 280 (23 oz/A), 11-lf cotton

Layby – MSMA (2.7 pt/A) + Direx (2 pt/A) + NIS (0.25% v/v)

Palmer amaranth control (30 DBH)

0

10

2030

40

50

60

7080

90

100

Ignite (+ 6 oz) Staple LX Dual Magnum Ignite at 11-lf

Pal

mer

am

aran

th c

ontr

ol (%

) 77

PRE = Prowl H2O

POST = Ignite applied to 3 to 4-lf cotton

Layby = MSMA + Direx + NIS

Prowl PRE

Ignite (23 oz) at 2 inch

Direx + MSMA PD

Prowl PRE

Ignite (29 oz) at 2 inch

Direx + MSMA PD

Prowl PRE

Ignite (23 oz) + Staple at 2 inch

Direx + MSMA PD

Prowl PRE

Ignite (23 oz) + Dual Mag. at 2 inch

Direx + MSMA PD

Prowl PRE

Ignite (23 oz) at 2 inch

Ignite (23 oz) at 2 inch

Direx + MSMA PD

Seed Cotton Yield

0

200

400

600

800

1000

1200

1400

Ignite (+ 6 oz) Staple LX Dual Magnum Ignite 11-lf

See

d C

ott

on Y

ield

(lb

s/A

) 7

7

PRE = Prowl H2O

POST = Ignite applied to 3 to 4-lf cotton

Layby = MSMA + Direx + NIS

Treatments 3rd Set

1) PRE – Prowl H2O (2 pt/A) + Reflex (1 pt/A)POST – Ignite 280 (23 oz/A), 3 to 4-lf cotton

2) PRE – Prowl H2O (2 pt/A) + Reflex (1 pt/A)POST – Ignite 280 (23 oz/A) + Staple LX

(1.7 oz/A), 3 to 4-lf cotton

3) PRE – Prowl H2O (2 pt/A) + Reflex (1 pt/A)POST – Ignite 280 (23 oz/A) + Dual Magnum

(1 pt/A), 3 to 4-lf cotton

Layby – MSMA (2.7 pt/A) + Direx (2 pt/A) + NIS (0.25% v/v)

Palmer amaranth control (30 DBH)

0102030405060708090

100

PRE = Reflex PRE = ReflexPOST=Dual Magnum

PRE = Reflex POST = Staple LX

Pal

mer

am

aran

th c

ontr

ol (%

) 77

PRE = Prowl H2O

POST = Ignite applied to 3 to 4-lf cotton

Layby = MSMA + Direx + NIS

Prowl PRE

Ignite (23 oz) at 2 inch

Direx + MSMA PD

Prowl + Reflex PRE

Ignite (23 oz) at 2 inch

Direx + MSMA PD

Prowl + Reflex PRE

Ignite (23 oz) + Staple at 2 inch

Direx + MSMA PD

Seed Cotton Yield

0

200

400

600

800

1000

1200

1400

PRE = Reflex PRE = ReflexPOST=Dual

Magnum

PRE = Reflex POST = Staple LX

See

d C

ott

on Y

ield

(lb

s/A

) 7

7

PRE = Prowl H2O

POST = Ignite applied to 3 to 4-lf cotton

Layby = MSMA + Direx + NIS

Treatments 4th Set

1) PRE – Prowl H2O (2 pt/A) + Cotoran (2.5 pt/A)POST – Ignite 280 (23 oz/A), 3 to 4-lf cotton

2) PRE – Prowl H2O (2 pt/A) + Cotoran (2.5 pt/A)POST – Ignite 280 (23 oz/A) + Staple LX

(1.7 oz/A), 3 to 4-lf cotton

3) PRE – Prowl H2O (2 pt/A) + Cotoran (2.5 pt/A)POST – Ignite 280 (23 oz/A) + Dual Magnum

(1 pt/A), 3 to 4-lf cotton

Layby – MSMA (2.7 pt/A) + Direx (2 pt/A) + NIS (0.25% v/v)

Palmer amaranth control (30 DBH)

0102030405060708090

100

PRE=Cotoran PRE=Cotoran POST=Dual Magnum

PRE=CotoranPOST=Staple LX

Pal

mer

am

aran

th c

ontr

ol (%

) 77

PRE = Prowl H2O

POST = Ignite applied to 3 to 4-lf cotton

Layby = MSMA + Direx + NIS

Prowl PRE

Ignite (23 oz) at 2 inch

Direx + MSMA PD

Prowl + Cotoran PRE

Ignite (23 oz) at 2 inch

Direx + MSMA PD

Seed Cotton Yield

0

200

400

600

800

1000

1200

1400

PRE=Cotoran PRE=CotoranPOST=Dual Magnum

PRE=CotoranPOST=Staple LX

See

d C

ott

on Y

ield

(lb

s/A

) 7

7

PRE = Prowl H2O

POST = Ignite applied to 3 to 4-lf cotton

Layby = MSMA + Direx + NIS

Summary

1) Timing of Ignite 280 application is more important that rate of Ignite 280 used.

2) Palmer amaranth must not be greater than 2 inches in height to achieve optimum control.

3) Applying Prowl H2O PRE produced 220 lbs more seed cotton than a second application of Ignite 280 with no PRE.

Summary4) The addition of Dual Magnum POST or a

second shot of Ignite 280 provided 11-12% greater Palmer amaranth control (30 DBH) and 350-380 lbs more seed cotton.

5) The addition of Reflex or Cotoran PRE provided 18-22% greater Palmer amaranth control (30 DBH) and 290-320 lbs more seed cotton.

Based on:

PRE = Prowl H2O

POST = Ignite 280 at 2 in Palmer, 3 to 4-lf cotton

LAYBY = MSMA + DIREX + NIS

Summary

6) The addition of Dual Magnum or Staple POST to applications of Prowl H2O + Cotoran or Reflex PRE provided no benefit.

Based on:

PRE = Prowl H2O

POST = Ignite 280 at 2 in Palmer, 3 to 4-lf cotton

LAYBY = MSMA + DIREX + NIS

Conclusions1) Ignite 280 must be applied timely.

2) Preemergencea) Yellow herbicide + Reflexb) Yellow herbicide + Cotoranc) Yellow herbicide + Direx

3) Postemergencea) Ignite + Dual Magnumb) Ignite – 2 applications

4) Layby - MSMA + Direx, Valor, Layby Pro, or Suprend

Prowl PRE, Roundup POST Twice Prowl PRE, Ignite POST Twice

2006 Georgia OVT

0

500

1000

1500

2000

2500

Bainbridge Midville Plains Tifton Average

Trial Location

Cott

on L

int Y

ield

(lb

s/A

)

77

DP 555 BG/RR FM 988 LLBR FM 9166 B2LL

Support for this project and my PAYCHECK has been provided by

Georgia Cotton CommissionCotton Incorporated

BASFBayer

DupontMonsantoSyngenta

Valent

Questions?

Andrew W. MacRae

Post Doctoral Research Associate

Department of Crop and Soil Sciences

University of Georgia, Tifton, GA

UGA Weed Science Website: www.gaweed.com