Will D. Duffie1, A. S. Culpepper2, A. C. York3, A. MacRae2, P. Roberts2 and P. H. Jost4

1University of Georgia, Waynesboro, GA 2University of Georgia, Tifton, GA

3North Carolina State University, Raleigh, NC 4University of Georgia, Statesboro, GA

1-11-06

4:30 pm

Grand Ballroom C

Assessing Roundup Flex Cotton Tolerance to Over-the-top Applications of Glyphosate, Dual

Magnum, Staple, PGR’s and Insecticides

Background

• Transgenic Technology (RR Flex Cotton)

• Weed Resistance

• Residual Herbicides (POT)

• Seed Treatments

planting harvest4 leaf Layby 60% open bolls

Roundup Ready® Flex Cotton

In-season; emergence to 60% open

4.5 lb a.e. total in-crop Max of 1.13 lb a.e. per application

Maximum of 4.5 lb ae/A from emergence to 60% open, or 128 oz W.Max or O.Max

Maximum of 1.13 lb a.e. per application, or 32 oz W.Max or O.Max

Maximum of 1.5 lb a.e. (44 oz W.Max or O.Max) from layby to 60% open

No restrictions on timing of sequential applications

Maximum of 1.5 lb a.e. (44 oz W.Max or O.Max) from 60% open till 7 days preharvest

1.5 lb a.e.

7 days

Preharvest

Herbicide Resistant Palmer Amaranth in Georgia

ALS

Glyphosate

ALS or glyphosate

Glyphosate-resistant Palmer control by residual POST cotton herbicides.

31 DAT. GA, 2006.

83

53

73

87

67

0

20

40

60

80

100

Dual Mag 1 pt

Stalwart 1 pt

Stalwart 1.5 pt

Staple 1.7 fl oz

Envoke 0.1 oz

%

ab

d

bc

a

c

Seed Treatments

Thrips Control

Seed treatments typically supply thrips control for 3 weeks.

Temik normally provides 3+ weeks, and is rate dependent.

0

20

40

60

80

100

2WAP 3WAP 4WAP

Perc

ent

Contr

ol

Temik 3.5 lbTemik 5 lbCruiser

These factors warrant studying cotton plant response to post-over-top (POT) herbicide

applications mixed with insecticides or plant growth regulators.

Materials & Methods

Location Year Planting Seed Rate Application Dates

Cultivar Date (seed/30 cm) 1 to 3-lf 7 to 9-lf

Midville, GA 2005 ST 4554 B2RF May 11 3 May 25 June 16

2006 ST 4554 B2RF May 5 3 June 6 June 22

Tifton, GA 2005 475 WRF May 3 3 May 20 June 4

2006 ST 6565 B2RF April 27 3 May 24 June 9

Rocky Mount, NC 2005 ST Flex Undesignated May 12 3 June 7 June 27

2006 ST 4357 B2RF May 2 3.5 May 31 June 19

Table 1. Field trial location, planting, and application information.

Treatment List

• glyphosate*

• glyphosate

+ Dual Magnum

• glyphosate

+ Staple

• None• Orthene• Bidrin• Dimethoate• Mustang Max

• Pentia (GA Only)

* Roundup WeatherMax

Ratings taken:1) % visual injury (after each application)

• Rated from 0-100 • 2-5 DAT

2) Yield

Materials & Methods

Cotton injury, no insecticide tank-mix partner

Herbicide treatment Cotton injury (1 to 3-lf application)

Tifton, GA Rocky Mount, NC Midville, GA

2005 2006 2005 2006 2005 2006

------------------------------ % ------------------------------

1) Glyphosate 0 0 0 0 7 8

2) Glyphosate + Dual Magnum 14 8 8 2 15 35

3) Glyphosate + Staple 11 17 8 11 7 22

Herbicide treatment Cotton injury (7 to 9-lf application)

Tifton, GA Rocky Mount, NC Midville, GA

2005 2006 2005 2006 2005 2006

------------------------------ % ------------------------------

1) Glyphosate 0 0 0 0 0 0

2) Glyphosate + Dual Magnum 13 1 0 11 6 0

3) Glyphosate + Staple 23 1 0 16 0 37

No Injury

Leaf Burn

Chlorosis

Percent cotton injury following 1- to 3-leaf applications. Tifton, GA 2005. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

no insecticide

Orthene

Mustang Max

Dimethoate

Bidrin

* **

*

*denotes significantly different from the herbicide treatment without the insecticide.

Percent cotton injury following 1- to 3-leaf applications. Tifton, GA 2006. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

no insecticide

Orthene

Mustang Max

Dimethoate

Bidrin

*

**

**

*denotes significantly different from the herbicide treatment without the insecticide.

*

Percent cotton injury following 1- to 3-leaf applications. Midville, GA 2005. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

no insecticide

Orthene

Mustang Max

Dimethoate

Bidrin*

*denotes significantly different from the herbicide treatment without the insecticide.

Percent cotton injury following 1- to 3-leaf applications. Midville, GA 2006. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

no insecticide

Orthene

Mustang Max

Dimethoate

Bidrin

*denotes significantly different from the herbicide treatment without the insecticide.

Percent cotton injury following 1- to 3-leaf applications. Rocky Mount, NC 2005. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

no insecticide

Orthene

Mustang Max

Dimethoate

Bidrin

*

*denotes significantly different from the herbicide treatment without the insecticide.

Percent cotton injury following 1- to 3-leaf applications. Rocky Mount, NC 2006. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

no insecticide

Orthene

Mustang Max

Dimethoate

Bidrin

*denotes significantly different from the herbicide treatment without the insecticide.

*

Percent cotton injury following 7- to 9-leaf applications. Tifton, GA 2005. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

no insecticide

Orthene

Mustang Max

Dimethoate

Bidrin

* *

*

*

*denotes significantly different from the herbicide treatment without the insecticide.

Percent cotton injury following 7- to 9-leaf applications. Tifton, GA 2005. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

No Pentia

Pentia

*denotes significantly different from the herbicide treatment without the insecticide.

*

Percent cotton injury following 7- to 9-leaf applications. Midville, GA 2005. 3DAT.

0

10

20

30

40

50

glyphosate + Dual Mgn + Staple

No Pentia

Pentia

*denotes significantly different from the herbicide treatment without the insecticide.

*

Results

• Dual Magnum & Staple increased plant injury when tank-mixed with glyphosate.

• Orthene & Pentia slightly increased injury • EC formulated insecticides (Dimethoate, Bidrin)

tended to cause the highest levels of injury• No yield differences observed.

Conclusion• With the exception of Orthene, adding

insecticides with glyphosate plus Dual or Staple mixtures will likely increase visual cotton injury.

• Environment will affect injury• Injury transient, no lasting adverse effect• Glyphosate/Dual or Staple/insecticide mixtures

acceptable• Glyphosate/Dual or Staple/Pentia mixtures

acceptable